ObjectivesPolycrystalline diamond (PCD) blades are widely used in precision machining and high-speed machining. However, as a high-hardness and brittle material, PCD has a more complex material removal mechanism compared to other materials, making it prone to surface defects and edge chipping during the grinding process. These defects increase the cutting force and cutting deformation of PCD blades. Furthermore, these defects are geometrically replicated on the machined surface, thereby affecting the machining accuracy of the workpiece and shortening the blade's service life. This paper aims to improve grinding quality by investigating the optimal process parameters for grinding PCD blades.MethodsBased on the floating grinding process, the orthogonal experimental method is employed to investigate the influence of diamond grinding wheels, PCD diamond particle size, grinding wheel speed, and table tuning pressure on the workpiece grinding quality. The cutting edge radius, cutting edge defect, and flank roughness are used as evaluation indicators for the PCD tool grinding quality to optimize the grinding process parameters. High-definition microscopy, scanning electron microscopy, and surface profilometry are utilized to observe the PCD tools and conduct an in-depth study of the material removal mechanism.ResultsConclusions are derived through meticulous analysis of the experiments, which reveals that the PCD composite flake particle size exerts a substantial influence on the flank roughness, cutting edge radius, and cutting edge defect of PCD blades. Furthermore, the cutting edge defect and flank roughness of PCD blades are found to be significantly influenced by the use of diamond grinding wheels. Additionally, the table tuning pressure is found to have a substantial impact on the cutting edge radius. The removal mechanism of PCD blades is principally based on brittle removal, with plastic removal playing a supplementary role. The process of brittle removal in PCD blades encompasses a variety of mechanisms, including crushing along the crystal, through the crystal, deconstruction, and scaling removal.ConclusionsBy combining the influence patterns of grinding process parameters on tool grinding quality, the optimal process parameters are obtained. Under the conditions of a 6/8 metal-based grinding wheel, CMX850 composite sheet, a grinding wheel speed of 1 000 r/min, and a table tuning pressure of 151 N, the blade's cutting edge defect is 2.45 μm, the cutting edge radius is 3.28 μm, and the flank roughness is 0.015 μm. Moreover, under these conditions, the proportion of material undergoing plastic removal is significantly higher than under other process conditions, and the resulting surface quality of the PCD tool is relatively smooth.
ObjectivesTo address the low drilling efficiency and frequent "bit balling" or slipping issues encountered by conventional impregnated diamond bits when drilling through hard, dense, and weakly abrasive formations characterized by rock Mohs hardness exceeding 7 in a major hydropower project exploration area in Tibet, this study aims to design an innovative impregnated diamond bit featuring a multi-stage matrix block with helical distribution structure. The core objective is to enhance the proportion of volumetric rock fragmentation by modifying the bit-rock interaction mechanism, thereby improving the rate of penetration and drilling efficiency in such challenging formations. The research focuses on elucidating the rock fragmentation mechanism of the novel bit and optimizing its key structural parameters through finite element simulation, providing a new technical approach for drilling difficulties in these formations.MethodsFirstly, based on the rock fragmentation principle of impregnated diamond bits, a bit with a multi-stage helically distributed matrix block structure was designed from the perspective of increasing rock fracture free surfaces and inducing volumetric fragmentation. The innovation lies in the bit face configuration, where wear-resistant spiral matrix blocks and weakened ordinary matrix are alternately arranged, forming a unique helical pattern. Additionally, annular gauge blocks are set at the inner and outer diameters of the bit to ensure drilling stability. Based on theoretical analysis of its rock fragmentation mechanism including ridge formation, increased free surfaces, and radial thrust action, finite element simulation using Abaqus software was employed to optimize the bit structural parameters. The Drucker-Prager model was selected as the rock constitutive model to simulate elastoplastic deformation and progressive damage failure processes of rock. Taking the block-to-slot ratio (the ratio of spiral block thickness to inter-block slot width) as the key variable, the force and torque characteristics of five bit types with block-to-slot ratios of 1∶0, 1∶1, 1∶2, 1∶3, and 1∶4 were comparatively analyzed under fixed conditions of 1.5 mm block thickness, 6 mm/s penetration rate, and 6 r/s rotational speed. Based on this, internal and external gauge structures were further introduced to comparatively analyze the mechanical responses of bits with different gauge parameters, determining the optimal bit face structure combination.ResultsThe simulation results indicate that: (1) Without gauge structure, the reaction force on the bit in the z-axis (drilling direction) decreases as the block-to-slot ratio reduces, being maximum at 1∶0 and minimum at 1∶4, with no significant differences among the reaction forces at ratios of 1∶2, 1∶3, and 1∶4. (2) Regarding torque, the z-axis torque on the bit is maximum at a block-to-slot ratio of 1∶1 and minimum at 1∶2; the z-axis torques on bits with ratios of 1∶2, 1∶3, and 1∶4 are all lower than those on bits with ratios of 1∶0 and 1∶1, with no significant differences among the three. (3) All helically arranged bits exhibit significant eccentric forces and eccentric torques in the x and y axes directions, while such eccentric phenomena are not pronounced for the flat-bottom bit with a ratio of 1∶0. (4) The addition of gauge structures increases the bit face area, leading to a certain increase in z-axis reaction force, but shows no significant effect on z-axis torque. However, the incorporation of gauge structures significantly reduces the eccentric forces and eccentric torques on the bit in the x and y axes directions, effectively enhancing drilling stability.ConclusionsThis study has successfully designed an impregnated diamond bit with multi-stage helically distributed matrix blocks, and verified through simulation its feasibility for application in hard, dense, and weakly abrasive formations. The research reveals the mechanism by which the helical arrangement structure enhances rock fragmentation efficiency through inducing ridge formation and volumetric fragmentation. The optimal bit face structural parameters are determined as follows: spiral block thickness of 1.5 mm, inter-block slot spacing of 4.5 mm (corresponding to a block-to-slot ratio of 1∶2) or 4.0 mm, and gauge block thickness of 1.5 mm. This parameter combination can reduce the reaction force and torque required for drilling while effectively controlling eccentric loads, achieving a balance between drilling efficiency and stability. The innovation of this study lies in introducing the helical distribution concept into the matrix block design of impregnated diamond bits, addressing the hard rock slipping problem by altering the bottom-hole stress field and increasing volumetric fragmentation, rather than simply relying on contact area reduction.
Objectives:Diamond,renowned for its exceptional hardness,high thermal conductivity,remarkable wear resistance,and chemical inertness,has become indispensable in the cutting of semiconductor materials such as silicon carbide(SiC),sapphire,and gallium nitride.As demand for these advanced materials grows in the electronics and optoelectronics industries,the performance requirements for cutting tools become increasingly stringent.This paper aims to provide a systematic review of the current state of three primary diamond wire saw preparation technologies:electroplating,resin bonding,and brazing.The objective is to critically analyze and compare these fabrication methods,elucidating their respective principles,advantages,limitations,and influence on cutting performance across different applications.Furthermore,by identifying key technical challenges,this review proposes viable directions for future research and process optimization to enhance the comprehensive performance of diamond wire saws.Methods:This study undertakes a thorough review of existing literature,encompassing key research findings from both domestic and international academic sources.The methodology involves a structured comparative analysis of the three preparation technologies,examining their specific technical characteristics,including base wire materials,bonding mechanisms between diamond abrasives and the substrate,diamond grit properties(size,shape,concentration,and surface condition),preparation apparatus,and critical process parameters.Beyond technical description,this review analyzes the performance of the resulting wire saws during actual cutting operations,evaluating key indicators such as cutting efficiency,surface quality of sliced wafers,tool wear mechanisms,lifespan,and cutting stability.By correlating manufacturing parameters with performance outcomes,the primary factors influencing the efficacy of each wire saw type are identified and discussed.Results:Electroplated diamond wire saws,owing to their mature and well-established preparation process achieve large-scale industrial application in cutting materials such as photovoltaic silicon crystals,sapphire,and marble.However,a significant limitation lies in the relatively low bonding strength between the diamond grits and the substrate,which restricts the tool's lifespan and cutting efficiency when processing high-hardness materials like silicon carbide(SiC)and sapphire.Nevertheless,their inadequate heat resistance and wear resistance constrain their applicability in high-speed cutting scenarios.In contrast,brazed diamond wire saws achieve substantially enhanced bonding strength through a metallurgical bond between the diamond and the matrix.This results in superior cutting performance and durability compared to the other two technologies.Despite these advantages,the brazing process itself presents technical bottlenecks,notably thermal damage to the diamond grits,such as graphitization,and a decline in the mechanical properties of the base wire,necessitating further research and process optimization.Conclusions:Diamond wire saw technology evolves along three distinct paths,each offering unique advantages and limitations that determine suitability for specific cutting tasks.Electroplated saws dominate current industrial practice due to maturity and low cost but are performance-limited by low bond strength for ultra-hard materials.Resin-bonded saws provide flexibility and good surface finish but are constrained by poor thermal stability.Brazed saws offer the highest theoretical performance due to superior metallurgical bonding but face challenges related to thermal damage to both the diamond and the wire substrate.Future research should focus on overcoming these barriers:for brazed wires,developing novel filler alloys with lower melting points to mitigate thermal damage and implementing advanced thermal management strategies;for electroplated and resin-bonded wires,exploring composite matrices and modified resins with enhanced thermal conductivity.Through these targeted improvements,the comprehensive performance of diamond wire saws can be significantly elevated to meet the increasing demands of advanced material processing industries.
SignificanceCutting tools are indispensable key instruments in the manufacturing industry, whose performance status directly affects machining quality, production efficiency, and equipment safety. Accurate prediction of the remaining useful life (RUL) of tools not only enables the intelligent transition from "scheduled replacement" to "condition-based replacement" but also significantly reduces resource waste caused by premature tool changes, workpiece scrapping and even equipment damage risks due to delayed replacement. With the deep integration of industrial automation, digitalization, and smart manufacturing, tool RUL prediction has become one of the core technologies in intelligent manufacturing and predictive maintenance, holding substantial engineering application value and theoretical research significance for enhancing the overall competitiveness of the manufacturing industry.ProgressThis paper systematically reviews the research progress in methods for predicting the remaining useful life of cutting tools. Based on their prediction principles, these methods are categorized into four main types, and their modeling ideas, applicable scenarios, advantages, and disadvantages are analyzed in depth. (1) Physics-based model prediction methods: These methods start from the physical mechanisms of tool wear, constructing mathematical models to describe the wear process, such as wear mechanism models, cutting force coefficient models, and finite element models. Their advantage lies in having clear physical significance and strong interpretability, making them particularly suitable for stable machining processes with well-understood mechanisms. However, these methods rely on accurate modeling of multiple physical fields in complex machining environments, face difficulties in parameter identification, and exhibit weak adaptability to dynamically changing working conditions. (2) Data-driven statistical model prediction methods: These methods do not rely on physical mechanisms but instead analyze historical monitoring data to build RUL prediction models using statistical laws. They mainly include empirical wear models (e.g., Taylor's formula and its extended forms) and stochastic process models (e.g., Wiener process, Gamma process, inverse Gaussian process). Such methods demonstrate good fitting capability when data is sufficient and can quantify prediction uncertainty, but their performance is limited by data quality and quantity, and their generalization ability is usually weak. (3) Artificial intelligence-based prediction methods: With the advancement of big data and computing power, artificial intelligence methods represented by machine learning and deep learning show great potential in tool RUL prediction. Machine learning models (e.g., SVM, RVM, AR, HMM) are adept at handling small-sample and nonlinear problems; deep learning models (e.g., RNN, LSTM, CNN, DBN) can automatically extract deep features from raw sensor data and possess stronger capabilities for temporal modeling and pattern recognition. Although AI methods offer high prediction accuracy and strong adaptability, their "black-box" nature leads to poor interpretability, and they require large volumes of high-quality labeled data. (4) Hybrid model prediction methods: To compensate for the limitations of single-method approaches, researchers in recent years tend to construct hybrid models that integrate the advantages of physics-based knowledge, data statistics, and artificial intelligence. For example, combining physical models with data-driven methods, or introducing stochastic modeling of the degradation process into the AI framework, to balance prediction accuracy and model reliability. Through multi-source information fusion and complementarity, hybrid models significantly enhance RUL prediction capability under complex working conditions, representing a current hot research direction.Conclusions and ProspectsThrough a systematic review of existing research, it can be concluded that tool RUL prediction methods evolve from single models to multi-method fusion, and from offline analysis to online intelligent diagnosis. However, this field still faces the following major challenges. (1) Reliability of machining signal acquisition and processing: Industrial field data is often plagued by noise interference and incomplete sampling. There is an urgent need to develop more robust feature extraction and signal denoising methods, and to explore real-time data acquisition technologies based on new sensing methods such as intelligent tool holders. (2) Effective fusion of multi-sensor data: Effectively integrating multi-source heterogeneous information (e.g., force, vibration, acoustic emission) and extracting common features strongly correlated with tool degradation from them are key to enhancing model robustness. (3) Balancing model accuracy and generalization ability: Most current models perform well under specific conditions but are prone to performance degradation in application scenarios with varying tool materials and machining parameters. Future research needs to explore cross-condition, adaptive, and lightweight model architectures. (4) Improving the interpretability of hybrid models: Although hybrid models have advantages in accuracy, their decision-making processes often lack transparency. Enhancing model interpretability so that their predictions can be understood and trusted by engineers is a crucial link in promoting technology implementation.
ObjectivesAt present, China's oil and gas exploration and development are gradually advancing towards deep and ultra-deep well fields, which have the characteristics of high environmental temperature, high rock strength, and complex formations. Therefore, higher requirements are put forward for the long-term and efficient performances of rock-breaking tools. Polycrystalline diamond compact (PDC) cutting cutter are formed by combining artificial diamond micro-powder with a tungsten carbide matrix through high-temperature and high-pressure sintering technology. They possess the high hardness, high wear resistance, and high thermal conductivity of diamond, as well as the high strength and good impact toughness of tungsten carbide, and are essential core materials and tools for oil and gas exploration and development. The content of metal phases such as Co and W in the polycrystalline diamond (PCD) layer has a decisive influence on the synthesis and performance of PDC cutting cutters. The study of metallic phases can provide an in-depth understanding of the performance, the microstructure and the failure mechanism of PDC cutting cutters.MethodsIn the research and development of PDC cutting cutters, Co removal technology, composite doping technology, and structural design technology have been widely applied and have achieved excellent drilling results. For example, the wear resistance and thermal stability of PDC cutters can be enhanced by reducing the metal content in the PCD layer, and the impact toughness of PDC cutters can be enhanced by adding WC-Co metal. However, the research on the influence mechanism of metal content on the performance of PDC cutters is relatively scarce. Therefore, three types of PDC cutting cutters with different WC-Co contents were prepared using the high-temperature and high-pressure method and a uniform powder mixing process. The distribution of metallic phases and microscopic morphology characteristics in PDC are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the wear resistance and impact resistance are compared and tested using a vertical turret lathe and a drop hammer impact tester. Meanwhile, the microstructure of the grinding section and impact fracture surface after performance testing of PDC cutting cutters are observed to further explore the influence of metal content in PCD on the mechanical properties and failure mechanism of PDC cutting cutters.ResultsThree types of PDC cutters with different WC-Co contents, namely cutter #1, cutter #2, and cutter #3, are prepared using the uniform powder mixing method and cobalt removal treatment. The PCD layers are uniform, and the metal phase content gradually increases from cutter #1 to cutter #3. All three types of PDC cutters are well sintered, and the addition of WC-Co metal phase reduces the number of D-D bonds in the PCD layer. The removal of Co improves the wear resistance of PDC cutters, while the metal phase content is negatively correlated with the wear resistance of PDC cutters. As the WC-Co content increases, the roughness of the worn surfaces of PDC cutters increase, and the number of intergranular microcrack fractures at the grinding mouth increases. At the same time, the increase in metal phase content significantly improves the impact resistance of PDC cutters. The impact resistance of cutter #3 is much higher than that of cutter #1 and cutter #2. The reason is that the metallic phase in the PCD layer plays a key role in hindering the propagation of microcracks.ConclusionsAn increase in the content of metallic phases will microscopically change the bonding degree of the diamond skeleton, the morphology of the ground surface and the fracture mode of microcracks, and will macroscopically directly affect the mechanical properties of PDC cutters. That is, changes in the microstructure of PDC cutters directly affect the quality of their macroscopic properties.
ObjectivesThe preparation of precursor powders for high-entropy alloys (HEA) typically employs the mechanical alloying (MA) method. The composite powder obtained after MA possesses high energy and is prone to spontaneous combustion. To facilitate handling in air, the powder is water-cooled, followed by sintering into blocks via spark plasma sintering (SPS). This study investigates the effects of water-cooling time on the microstructure and properties of the CoCrNiCuFe high-entropy alloy.MethodsWater-cooled MA is used to prepare HEA composite powder, and SPS technology is used to sinter the composite powder. The sintered body is subjected to rough grinding, fine grinding, and polishing to prepare a bright and scratch-free sample. X-ray diffraction (XRD) is used to detect the phases of the powder and sintered body; scanning electron microscope (SEM) is used to detect the element distribution and morphology of the powder and sintered body; a visible porosity and bulk density tester is used to test the apparent porosity of the sintered body; a Vickers hardness tester is used to measure the microhardness of the sintered body; a universal testing machine is used to test the compressive performance of the sintered body; and a synchronous thermal analyzer is used to test the thermal stability of the sintered body. The composition, morphology, and properties of the water-cooled sample are systematically analyzed.ResultsThe powders cooled for 2, 4, and 6 h all have a Ni rich FCC structure phase and a Cr-rich BCC structure phase, and the sintered body contains FCC1 phase, FCC2 phase, and Cr2O3 phase. The average grain sizes of the FCC1 phase in the sintered bodies after 2, 4, and 6 h of water-cooling are 69.1, 58.7, and 59.8 nm, respectively. The average grain sizes of the FCC2 phase are 62.7, 56.9, and 57.8 nm, respectively. The average grain sizes of the Cr2O3 phase were 50.3, 42.7, and 44.2 nm, respectively. Water-cooling reduces the agglomeration of CoCrNiCuFe powder and refines the microstructure and grain size. After 4 h of water-cooling, the scanning morphology of the powder shows slight clumping, with a large amount of powder in the form of thin flakes and a small amount in the form of fragments. However, the distribution of the 5 types of powder is uniform, indicating that CoCrNiCuFe powder is MA in air and has a low degree of oxidation. After water-cooling, a thin oxide film adheres to the surface of the powder, which prevents spontaneous combustion of the material during air exposure and achieves a passivation effect. In addition, the surface structure of the sintered body after 4 h of water-cooling is uniform, without obvious pores, and the high-entropy alloy phase is circular in shape, while the Cu-rich phase is irregular in shape. Through analysis of the point scan results at point 1, the five elements Co, Cr, Ni, Cu, and Fe are evenly distributed without precipitation or enrichment, indicating that these five metal elements are well dissolved together to form a high-entropy alloy phase. A high content of Cu element appears at point 2, indicating segregation of Cu (bright green area), and the enrichment of Cu element surrounds the HEA phase. The black spot at point 3 corresponds to a localized enrichment zone of Cr element, indicating that Cr is not fully dissolved in the matrix and forms an enrichment zone at the grain boundary during the sintering process. The grain structure between CoCrNiCuFe high-entropy alloy phases is an equiaxed dendritic structure, while the grain structure between Cu-rich phases is an irregular dendritic structure. The eutectic structure of FCC1 phase, FCC2 phase, and oxide phase can be attributed to the hysteresis diffusion effect of HEA. Meanwhile, the sintered body after 4 h of water-cooling has a density of 94.6%, a hardness of 460 HV0.5, and a compressive strength of 1 388 MPa. Thermal analysis tests show that the initial oxidation temperature of the sintered body is 1 082.9 ℃, and the final oxidation temperature is 1 152.3 ℃, resulting in a 28.4% increase in oxidation mass.Conclusions(1) Water-cooling refines the grain size of CoCrNiCuFe HEA, inhibits secondary dendrite growth, and reduces powder agglomeration of HEA. (2) The physical properties of CoCrNiCuFe HEA after 4 h of cooling are excellent, with density, hardness, and compressive strength reaching 94.6%, 460 HV0.5, and 1 388 MPa, respectively. (3) CoCrNiCuFe HEA has excellent oxidation resistance after 4 h of cooling, with an initial oxidation temperature of 1 082.9 ℃ and a final oxidation temperature of 1 152.3 ℃. The oxidation mass increases by 28.4%, which is due to the selective oxidation behavior of the HEA and the dense oxide film protection formed by Cr element oxidation.
ObjectivesPolycrystalline diamond prepared by chemical vapor deposition exhibits excellent mechanical, thermal, optical, and electrical properties. The application of diamond crystals in fields such as optics and electronics requires stringent uniformity in the large-area growth achieved by microwave plasma chemical vapor deposition. To address this, the present work focuses on the homogeneous deposition of polycrystalline diamond over large areas.MethodsBy employing a 915 MHz microwave plasma reactor and utilizing plasma spectral analysis, this study optimizes both the plasma conditions and growth parameters. First, the spatial distribution of the plasma discharge region is quantified using Hα spectral imaging profile analysis. Then, a microwave plasma reactor operating at a microwave power of 80% is used to grow polycrystalline diamond thick films. Finally, the thickness distribution, crystal orientation distribution, crystalline quality distribution, and microstructural morphology of the resulting polycrystalline diamond are characterized. This approach establishes a clear correlation between plasma distribution and diamond growth uniformity.ResultsThe results indicate that a high-density plasma with a radial dimension exceeding 180 mm is achieved at a microwave power greater than 27 kW and a pressure of 100-120 Torr. Hα exhibits a linear relationship with both power and pressure, whereas C2 shows a linear dependence on power and an exponential dependence on pressure. The C2/Hα ratio follows an "M"-shaped profile along the radial direction of the plasma, and increasing pressure significantly reduces the uniformity of the C2/Hα distribution. Using the optimized plasma control strategy, a polycrystalline diamond with a diameter of 150 mm and a thickness of 1 mm is fabricated, demonstrating good crystalline quality and growth uniformity. The crystal orientations are predominantly〈111〉and〈311〉, with a Raman FWHM of 4.2-5.5 cm-1. Compressive stress on the nucleation side and tensile stress on the growth side result in a deformation of 122 µm. A higher C2/Hα ratio promotes〈400〉-oriented growth, which leads to increased thickness but a decline in crystal quality.ConclusionsQuantifying plasma characteristics and establishing the relationship between the chemical vapor deposition environment of diamond and the quality of crystal growth are challenging research topics. Optical emission spectroscopy is an effective means of characterizing the spatial distribution of the plasma. By detecting the spectral intensities of Hα and C2 along the radial distribution of the plasma, it is possible to quantitatively analyze the size of the plasma discharge region, the average microwave power density, and the distribution of plasma species. This allows the establishment of how the distribution of plasma active species varies with microwave input power and gas pressure, thereby optimizing the key factors influencing the uniform growth of polycrystalline diamond.
ObjectivesDiamond wire saw cutting stone has the advantages of narrow cutting seams, low production of stone powder, and a high yield rate. It can reduce the amount of stone powder generated in stone processing from the source and is a new processing technology that promotes the green and sustainable development of the stone industry. In view of the current problems in the stone industry, where electroplated diamond wire saws are prone to wear and consume a large amount of wire when cutting large-sized and heterogeneous stones with multiple wires, the idea of using a brazing method instead of the traditional electroplating method to solidify diamond abrasive particles is proposed to prepare wire saw tools and process large stone slabs.MethodsUnder the same processing conditions, the process of cutting stone by self-developed brazed diamond wire saws and commercially available electroplated diamond wire saws is monitored. As a flexible cutting tool, the wire saw undergoes significant macroscopic deformation during the cutting process, resulting in a wire bow angle, which is an important parameter for measuring the sawing ability of the wire saw. Sawing force is the parameter most closely related to the sharpness and wear resistance of the wire saw, while the force ratio could reflect the difficulty of the wire saw cutting into the workpiece. The sawing force generated by the wire saw during the stone cutting process is examined from normal and tangential directions. The tangential force is along the direction of the saw's movement, while the normal force is along the cutting direction of the workpiece. At the end of cutting, the rapid lifting method is used to obtain the precise normal force. The tangential force, due to its obvious periodicity, is obtained through data analysis. The service life of a wire saw is a key factor in ensuring the continuity of the cutting process and the flatness of the stone surface after cutting. It is also a basic requirement for preventing the saw seam from expanding and saving costs. The wire bow angle, cutting force and wire saw life of the two types of wire saws during the sandstone sawing process are measured, and the cutting area and the cutting time under extreme conditions are obtained by cutting harder granite. The sawing processing efficiency and the wear morphology of the two types of wire saws are obtained to comprehensively compare the sawing performance of brazed diamond wire saws and electroplated diamond wire saws.ResultsWhen cutting sandstone, the wire bow angles of both types of wire saws show an upward trend, but the wire bow angles of brazed diamond wire saws are smaller than those of electroplated diamond wire saws. When the cutting depth of the sandstone is 4 mm, the wire bow angle of the brazed diamond wire saw is only 20% of that of the electroplated diamond wire saw. At this point, the tangential and normal forces of the brazed diamond wire saw are only 38% and 32% of those of the electroplated diamond wire saw, respectively. The cutting force ratio of the brazed diamond wire saw is smaller than that of the electroplated diamond wire saw. When cutting harder granite, the electroplated diamond wire saw experiences wire breakage after cutting for 22 min of cutting on the machine, and the effective cutting area of the workpiece is about 440 mm2. The brazed wire saw experiences wire breakage at the 28 min of cutting, and the effective cutting area of the workpiece is approximately 670 mm2. In terms of cutting time, the cutting life of the brazed diamond wire saw is slightly longer than that of the electroplated diamond wire saw, about 6 min longer. Therefore, the cutting efficiency and tool life of brazed diamond wire saws are significantly higher than those of electroplated diamond wire saws. At the same time, the wear morphology before and after wire saw cutting shows that the wear behavior of abrasive particles during the processing of brazed and electroplated diamond wire saws is significantly different.ConclusionsThrough experimental comparison, it is found that under the working conditions of stone cutting, the comprehensive sawing ability of brazed diamond wire saws is stronger than that of electroplated diamond wire saws, as reflected in the improvement of cutting efficiency, tool life, and wear resistance.
ObjectivesTA16 titanium alloy slender tubes are widely used in critical components such as cooling systems, heat exchangers, and electrode systems within nuclear power plants due to their excellent corrosion resistance, high strength, and good machinability. Under the demanding service conditions of the nuclear industry, the surface quality of the inner wall of slender tubes not only affects fluid flow efficiency but also directly influences the occurrence of tip discharge effects. Excessive surface roughness on the inner wall can cause protruding microscopic peaks to concentrate discharges, leading to localized corrosion or thermal stress, thereby reducing equipment lifespan and reliability. However, the structural characteristics of TA16 slender tubes—high aspect ratio and small inner diameter—make it difficult for traditional machining methods to access the interior for effective finishing. Additionally, the high hardness and chemical reactivity of titanium alloy materials make them prone to defects such as microcracks, scratches, and oxide layers during machining. Therefore, there is an urgent need to develop an efficient, precision finishing process suitable for the inner walls of TA16 slender tubes to enhance their surface quality and meet the high safety and long-life requirements of nuclear power equipment.MethodsTo address the aforementioned issues, this paper proposes a magnetic particle grinding and finishing process utilizing segmented magnetic field assistance. This process involves placing auxiliary magnetic poles saturated with magnetic abrasive inside the slender tube, while dynamically rotating external magnetic poles are positioned outside. Magnetic forces drive the internal auxiliary poles to adhere to the tube wall and rotate with the external poles, thereby generating relative motion between the abrasive and the tube wall to remove surface defects. To address the tendency of slender tubes to develop eccentricity and vibration during high-speed rotation, a center support is employed in experiments, alongside a segmented machining strategy. Simultaneously, to enhance magnetic field strength and increase grinding pressure, a magnetic pole arrangement pattern with a 120° angle is designed. The effectiveness of this design is validated through simulation comparisons of magnetic field distributions before and after improvement using Maxwell software. Regarding process parameter optimization, three key influencing factors are selected: the relative rotational speed between the slender tube and external magnetic poles, the axial feed rate, and the average particle size of the magnetic abrasive. Using the surface roughness Ra of the slender tube's inner wall as the evaluation metric, a three-factor, three-level experiment is designed using response surface methodology (RSM). A second-order regression prediction model for surface roughness is established and validated for significance and goodness-of-fit via F-tests. Subsequently, a genetic algorithm (GA) is employed for global optimization of process parameters to obtain the optimal parameter combination and the lowest predicted surface roughness value. Surface roughness measurement instruments and a super-depth-of-field 3D microscope are used to inspect and characterize the tube wall surface morphology before and after machining.ResultsSimulation results indicate that the 120° pole arrangement pattern generates an average magnetic flux density of approximately 0.80 T on the outer surface of the auxiliary poles. This represents a 45% increase compared to the 0.55 T achieved by the single magnet arrangement pattern, significantly enhancing grinding pressure and improving machining efficiency. Segmented machining uniformity validation tests reveal that after 1 h and 2 h of processing, the maximum differences in surface roughness reduction across five inspection zones at the pipe joint sections are 0.101 8 μm and 0.137 4 μm, respectively—both below 0.2 μm. This confirms that the segmented machining method effectively ensures uniform material removal from the pipe wall, preventing localized machining inconsistencies. The surface roughness prediction model established via response surface methodology exhibits high significance (model F-value254.34, P-value ＜0.000 1, with insignificant deviance), indicating excellent model fit and high reliability. The order of significance for factors influencing surface roughness is: relative rotational speed ＞ feed rate ＞ average abrasive particle size. Response surface analysis reveals that surface roughness exhibits a decreasing-then-increasing trend with changes in all three factors, indicating the existence of optimal parameter ranges. Interaction analysis shows significant interactions between relative rotational speed and average abrasive particle size, as well as between feed rate and average abrasive particle size: parameters outside narrow ranges can lead to under-machining or "over-grinding", adversely affecting surface quality. Through genetic algorithm optimization (population size 50, crossover probability 0.7, mutation probability 0.05, 73 iterations), the optimal process parameter combination is determined: relative rotational speed 2 247.95 r/min, feed rate 3.46 mm/s, and average abrasive particle size 234.16 μm. Under these conditions, the predicted surface roughness value is 0.29 μm. Validation tests using rounded optimized parameters (2 250 r/min, 3.5 mm/s, 250 μm) yield an actual surface roughness of 0.28 μm. The absolute relative error between measured and predicted values is 3.57%, confirming the prediction model's accuracy and the effectiveness of the optimized parameters. Three-dimensional topography reconstruction reveals significant surface undulations on the tube wall prior to machining (maximum peak-to-valley difference approximately 60 μm). Post-machining, the surface becomes smooth with uniformly distributed fine scratches (peak-to-valley difference approximately 5 μm), indicating effective removal of original defects.ConclusionsThe segmented magnetic field-assisted magnetic particle grinding process proposed in this paper effectively achieves high-quality finishing of the inner walls of slender TA16 titanium alloy tubes. Optimized magnetic pole structures significantly enhance magnetic field strength and processing capacity. The segmented processing strategy resolves challenges in machining long, slender tubes while ensuring uniformity at segment boundaries. The response surface method-based predictive model accurately reflects the relationship between process parameters and surface roughness, while genetic algorithms achieve efficient global optimization of multiple parameters. Under the optimal parameter combination, the inner wall surface roughness of the slender tube can be reduced from an initial high level to 0.28 μm, significantly improving surface quality and meeting the high-precision inner wall requirements for nuclear power engineering. This research provides a theoretical foundation and technical reference for the efficient precision machining of slender titanium alloy tubes.
Significance: Diamond composites exhibit exceptional properties, including ultra-high hardness, superior wear resistance, and outstanding thermal conductivity, making them indispensable for advanced applications in tool manufacturing, thermal management, and biomedical science. However, traditional fabrication techniques (such as high-pressure high-temperature synthesis and powder metallurgy) face significant limitations: they struggle to produce complex geometries, optimize performance gradients, and achieve efficient material utilization, thereby restricting design flexibility and application scope. To overcome these challenges, 3D printing technology has emerged as a transformative approach, offering unparalleled capabilities for geometric freedom, waste reduction, and rapid customization. By systematically evaluating the research progress and unresolved challenges of diamond composite materials in 3D printing, this work aims to accelerate the exploration of diamond composite materials in 3D printing and establish core technical theories for industrial implementation. Progress: This review systematically examines five principal 3D printing technologies—SL, SLS, SLM, LMD, and FDMS—for manufacturing diamond composites, critically assessing their respective advantages and limitations in processing these materials. SL and SLS exhibit advantages in handling polymer-based diamond composites due to their low processing temperature, which minimizes diamond thermal damage, while SLM and LMD excel in metal matrix composites by achieving high densification through precise laser energy control, though challenges remain in balancing diamond retention and matrix bonding. FDMS, on the other hand, offers unique capabilities in manufacturing thin-walled structures with uniform diamond distribution, albeit with higher equipment complexity. Significant application advances are highlighted across key domains. Firstly, in the realm of tool making, 3D printing has overcome the long-standing limitations of traditional processes, and the enhanced structure of 3D-printed diamonds significantly improves the cutting performance and durability. By using SLM's high precision in constructing complex lattice structures, grid-structure diamond drill bits have achieved a 67% increase in specific pressure and 40% longer lifespan in hard rock drilling, attributed to optimized stress distribution enabled by tailored porosity. Similarly, porous diamond grinding wheels fabricated via SLM-Al composite processing, through meticulous adjustment of laser parameters to balance porosity and mechanical strength, reached 246 MPa bending strength while maintaining a grinding speed of 12 m/s—performance metrics unattainable with conventional casting methods. FDMS further extended tool capabilities by producing ultrathin diamond saw blades that eliminate thermal damage during cutting, a breakthrough enabled by its ability to control diamond-matrix interface integrity at microscale. Secondly, for thermal management materials, 3D-printed composites achieve substantially enhanced thermal conductivity and tailored thermal expansion properties. For Cu-coated diamond/Cu systems processed by SLM, strategic optimization of diamond-to-copper ratio and coating thickness enhanced interfacial bonding, resulting in thermal conductivity of 300 W/(m·K). This approach was extended to Diamond/SiC composites via SL, where particle gradation optimization combined with laser energy density control yielded 245.68 W/(m·K) thermal conductivity, demonstrating the scalability of 3D printing in high-performance thermal materials. Polymer-diamond coils, fabricated using SL process, leveraged precise control over diamond dispersion to reduce coolant temperature from 39 ℃ to 25 ℃, highlighting the technology's versatility across material systems. Finally, biomedical science applications have similarly benefited from the synergy between diamond's intrinsic properties and 3D printing's design flexibility. LMD-fabricated Ti-diamond scaffolds, through careful tuning of laser power and deposition thickness to achieve optimal porosity, enhanced osteoblast viability by 30% while reducing bacterial adhesion—key metrics for bone tissue engineering. SLM produced Ti implants coated with PCD, engineered to 65.7 nm nanoroughness via controlled laser surface modification, significantly improved bone integration compared to polished surfaces. Utilizing the LMD process to print Ti-diamond composite hybrid electrodes and evaluate their feasibility for neuron interface applications, further expanding the potential of 3D-printed diamond composites in the biomedical field. These advancements collectively demonstrate how 3D printing enables the tailored design of diamond composite structures to meet the stringent requirements of biomedical environments. Conclusions and Prospects: Future research will focus on material innovations including nano-reinforced metal matrices (such as Ti/Cr-doped materials) and functionally graded designs to enhance interfacial bonding and multifunctional integration. Precision manufacturing requires AI-driven parameter optimization and multi-laser synchronous scanning SLM platforms to improve production efficiency while minimizing energy consumption. For biomedical science fields, developing diamond composites with controlled porosity and sp3-rich surfaces is critical to advance osseointegration and long-term implant stability. Industrial scalability necessitates cost reduction strategies such as reusable diamond feedstocks and domestic production of 3D printing systems (such as continuous fiber-reinforced 3D printing). Interdisciplinary integration with emerging techniques like laser ablation and shockwave-assisted sintering will enable next-generation components with synergistic functionalities. Addressing these priorities will promote the translation of laboratory innovations into industrial and clinical applications.
Objectives:Metal-bonded diamond cutting tools are extensively utilized in industrial applications such as stone cutting,metal processing,and mining due to their superior hardness and wear resistance.However,the use of metallic elements in diamond tools presents certain limitations.Specifically,poor wetting of diamond at elevated temperatures results in inadequate adhesion,while elemental powders can adversely affect the surface morphology of diamond at lower temperature conditions.This study aims to investigate the effects of pre-alloyed powders under various hot pressing conditions on the performance of diamond tools,with a particular emphasis on compressive strength,surface morphology,and Raman spectroscopy analysis.Additionally,the influence of different alloy powders on the mechanical properties of diamond tools is explored,with the objective of understanding how alloy composition and sintering temperature impact their structural integrity and performance under high-temperature conditions.Methods:In this experiment,diamond samples are prepared using nickel-based,copper-based,and iron-based pre-alloyed powders.These materials are selected due to their potential influence on the interaction between the binder and the diamond matrix during the sintering process.The choice of these alloys is based on their anticipated effects on diamond behavior,particularly regarding high-temperature stability and corrosion resistance.The diamonds are hot-pressed and sintered at various temperatures to assess the impact of temperature and alloy composition on diamond properties.After sintering,compressive strength is measured through single particle testing,and surface morphology is analyzed using scanning electron microscopy(SEM).Additionally,Raman spectroscopy is employed to investigate structural changes,particularly those associated with graphitization and high-temperature exposure.Results:The sintering temperature significantly impacts the performance of diamond tools.An increase in temperature leads to intensified corrosion of the diamond surface,resulting in a decrease in compressive strength.At 900℃,the compressive strength of a single particle decreases to 97.2 N,indicating substantial degradation of the diamond structure at elevated temperatures.This suggests that higher sintering temperatures can damage diamond materials and reduce tool effectiveness.In addition to temperature,the composition of pre-alloyed powder plays a crucial role in determining the mechanical properties of diamonds.Nickel-based pre-alloyed powders containing Cr promote the formation of chromium carbide(Cr3C2)at high temperatures,which further weakens the structural integrity of diamonds.In contrast,copper-based powders exhibit a protective effect,maintaining the mechanical properties of diamonds at elevated temperatures.Raman spectroscopy further confirms that Co exerts a stronger graphitization effect on diamonds,compromising their structural stability.Conclusions:The sintering temperature and the composition of pre-alloyed metal powder are key factors affecting the performance of diamonds.High sintering temperature can cause significant degradation of diamonds,while alloy composition can alleviate or exacerbate this effect.The Cu element in iron-based pre-alloys has a protective effect on diamond,to some extent protecting the corrosion from Fe element on the surface of diamond.Due to its similar unit cell constant to diamond,Co is more likely to promote the conversion of diamond to graphite at high temperatures.The Cr element in nickel-based pre-alloys reacts with diamond,resulting in a significant decrease in the compressive strength of diamond at higher temperatures.These findings emphasize the importance of selecting the optimal alloy composition and sintering conditions to improve the performance of diamond tools,especially in high-temperature applications in industrial environments.In addition,alloy selection plays a crucial role in maintaining the mechanical integrity of diamond tools during usage.Future research can explore more alloy powders and deepen our understanding of their interaction with diamond,in order to further optimize the performance of diamond tools in various industrial applications.
SignificanceDiamond tools are irreplaceable advanced processing tools with ultra-high hardness, excellent wear resistance, high-temperature resistance, and corrosion resistance, which are widely used in machining hard-to-cut materials such as optical glass, engineering ceramics, and titanium alloys. High-quality bondings between diamond grits and matrix, as well as between diamond segments and steel substrates, are critical to exert the superior performances of diamond tools. As a key technology to realize high-strength metallurgical or mechanical joining, welding plays an indispensable role in the manufacturing of diamond tools, which directly determines the structural stability, service life, and machining accuracy of diamond tools. This work aims to clarify the fundamental principles of mainstream welding technologies of diamond tools, summarizes their technical characteristics and influencing parameters, and highlights their typical applications in high-end manufacturing fields, therefor providing theoretical and technical references for the performance optimization and engineering applications of diamond tools.ProgressThis work systematically reviews three typical welding technologies of diamond tools: high-frequency welding, laser welding, and brazing. Introduces their working principles, characteristics, process parameters, and application boundaries. High-frequency welding realizes rapid heating and joining based on electromagnetic induction and skin effect, featuring high efficiency, low equipment cost, and suitability for mass production of large-size tools, but with relatively lower joint strength and a larger heat-affected zone compared to laser welding. Laser welding employs a high-energy-density laser beam as a heat source to form small-hole deep-penetration welding, with advantages of high bonding strength, small heat damage, high precision, and strong impact resistance, which is suitable for high-precision and thin-wall diamond tools, yet its equipment and maintenance costs are high. Brazing uses active filler metals containing Cr, Ti, Zr, and other elements to achieve chemical metallurgical bonding between diamond and matrix, which greatly improves the holding force to diamond grits and enables high protrusion height and good self-sharpening ability, making it ideal for grinding wheels and dressing tools. In addition, emerging technologies, including ultrasonic-assisted brazing and additive manufacturing, have effectively improved wettability, refined microstructures, and reduced thermal damage. This paper also summarizes the applications of welded diamond tools in aerospace, semiconductor, new energy, medical treatment, rail transit, and bearing machining. Analyzes the effects of welding and processing parameters on joint strength, surface quality, and tool wear mechanism.Conclusions and ProspectsWelding technologies significantly enhance the interfacial bonding strength and service performance of diamond tools. Reasonable selection of welding methods and optimization of process parameters can effectively reduce thermal damage, improve joint quality, and extend tool life. Welded diamond tools have become core of processing equipment in aerospace, semiconductor, new energy, and other high-end manufacturing fields, showing unique advantages in high-efficiency and high-precision machining of hard and brittle materials. Future research priorities include developing new filler metals matching with diamond and matrix to relieve residual stress, preparing fine-grained, low-melting-point, and high-sintering-activity pre-alloyed powders to suppress graphitization of diamond, developing multi-layer diamond tools with functional gradient design via integrating powder metallurgy, brazing, and additive manufacturing, and promoting intelligent, green, and low-carbon welding processes to meet the requirements of extreme working conditions and sustainable development.
ObjectivesWith the rapid development of microelectronics technology, the high power density and high integration of electronic devices have led to increasingly prominent heat dissipation problems, and it is necessary to develop composite materials with high thermal conductivity. Diamond/copper composite materials have become a research hotspot due to their excellent thermal conductivity, but the poor interfacial affinity between diamond and copper limits their performance. The aim of this study is to systematically analyze the properties of the interfaces between diamond (100) and (111) crystal faces/copper composite materials using first principles calculations, and to explore the improvement mechanism of titanium coating on the interface properties, providing a theoretical basis for optimizing composite material design.MethodsUsing the first-principle calculation method based on density functional theory (DFT), the CASTEP module of Materials Studio software is used to construct 4 interface models of diamond (100) and (111) crystal faces with copper and titanium (111) faces, respectively. Through structural optimization, energy calculation, electron state density analysis, Mallikan population analysis, and phonon density of states calculation, the binding energy, electronic structure, and heat conduction characteristics of the interfaces are studied. The calculation parameters include a truncation energy of 500 eV, a k-point grid of 14×14×2, and a vacuum layer of 15 Å to ensure calculation accuracy. At the same time, the interface adhesion work is determined by the universal binding energy relation (UBER), and the phonon thermal resistance is quantitatively analyzed by the atomic Green's function (AGF) method.ResultsThe diamond (100) interface has a stronger binding force, and the binding force of diamond (100)/titanium is significantly higher than that of diamond (100)/copper. The adhesion energy of the diamond (100)/titanium interface is 7.875 J/m2, which is approximately 88% higher than that of the diamond (100)/copper interface and 216% higher than that of the diamond (111)/copper interface. By analyzing the electronic state density and Marckensheimer occupation number of the 4 different interfaces, it is found that the diamond (100) interface exhibits a higher density of p-orbital electronic states near the Fermi level and stronger bonding, which are beneficial for electron conduction and chemical reactions. The electron distribution on the (111) crystal surface is more uniform, and the chemical stability is higher than that on the diamond (100) surface. At the same time, the charge change between the first-layer titanium atoms and the carbon atoms at the diamond (100) interface is more significant, while the charge redistribution at the diamond (111) interface is more uniform, and the interfacial stress is lower, which is conducive to the formation of uniform and stable bonds. In addition, the phonon spectrum matching of diamond (100)/copper and diamond (100)/titanium is better, and the interfacial thermal resistance is lower. The phonon spectra of diamond (111)/titanium and diamond (111)/copper overlap less, resulting in higher thermal resistance.ConclusionsOverall, the interface structure between diamond and titanium is superior to that between diamond and copper in terms of interfacial bonding performance, stability, and phonon coupling. The diamond/copper composite material prepared with a titanium coating shows better performance on the diamond (100) surface than on the diamond (111) surface. Therefore, when designing diamond/copper composite materials for thermal conductivity applications, adding a titanium coatings and selecting the diamond (100) crystal face are better choices.
ObjectivesTo explore methods for ultra-precise and high-efficiency processing of quartz glass, the influence of the oxidant H2O2 on the dispersion of the mixed abrasive particles is studied, and the material removal mechanism by the oxidant H2O2 and mixed abrasive particles during chemical mechanical polishing (CMP) processing of quartz glass is clarified.MethodsFirstly, the influence law of the oxidant H2O2 content on the dispersion performance of mixed abrasive particles in the polishing solution is analyzed. Then, the effects of H2O2 content and the ratio of mixed abrasive particles on surface processing morphology and removal rate during CMP processing of quartz glass are discussed. Finally, the material removal mechanism at the microscopic scale during CMP is also expounded.ResultsWhen 4% H2O2 solution with a mass fraction is added to the polishing solution, the static stability and spatial steric hindrance between the mixed abrasive particles result in a minimum average particle size (294.1 nm), and the absolute value of the zeta potential increases to a higher value (31.8 mV). The improved dispersion of the mixed abrasive particles reduces the surface roughness Ra of quartz glass to a minimum value (1.12 nm), and the material removal rate reaches 970.45 nm/h. When the ratio of mixed abrasive particles in the polishing solution changes, the material removal rate of quartz glass decreases from 1 455.67 nm/h to 1 238.87 nm/h. When the ratio of mixed abrasive particles in the polishing solution is 1:4, the alternating scratches on the processed surface of quartz glass gradually disappear, and the synergistic effect of the mixed abrasive particles enhances the material removal rate.ConclusionsMixed abrasive particles adsorb OH- groups on their surfaces to form a protective layer. This protective layer reduces the van der Waals forces and Coulombic forces between the mixed abrasive particles, resulting in high dispersion stability of the polishing solution. The synergistic effect of the mixed abrasive particles enhances their bonding and detachment behavior and optimizes both the material removal rate and surface accuracy.
Objectives:SiCf/SiC ceramic matrix composites were continuous fiber-reinforced materials that had attracted extensive attention and application in fields such as automotive and aerospace due to its high strength,high hardness and high-temperature resistance.However,the difficult machinability makes it challenging to investigate the micro-scale material removal characteristics and mechanisms using traditional methods.To reveal the processing mechanism of spherical grinding heads milling SiCf/SiC ceramic matrix composites,a more approximate woven composite model was established for simulation and investigation.Methods:The milling simulation of SiCf/SiC adopts a more approximate woven body model.Considering that the overlapping area of fiber filaments is prone to burrs during processing,the microstructure of the woven ceramic composite material's latitude and longitude boundary area is modeled.The upper and lower layers of fibers in the model are vertically interwoven at a 90°angle.Finite element simulation is conducted to simulate the milling process of a single abrasive grain on a spherical grinding head.The variation laws of single abrasive grain grinding force,grinding temperature,and grinding force ratio of SiCf/SiC ceramic composite materials under different processing parameters and fiber orientations,as well as the changes in material removal characteristics,are studied.Finally,the single abrasive grain scratch experiment is conducted to verify the results.Results:In the simulation of SiCf/SiC material machining,when other machining parameters remain unchanged and only the grinding depth ap increases from 5 µm to 20 µm,the grinding force significantly rises.The normal grinding force Fn increases by 90%,the grinding temperature T rises by 25.4%,and the grinding force ratio decreases by 22.0%.Additionally,the increase in ap has a substantial impact on the variation of each parameter.When the grinding speed Vs increased from 12 000 r/min to 18 000 r/min,the grinding force exhibited minor changes.Fn decreased by 5.9%,T increased by 10.4%,and the grinding force ratio rose by 1.1%.Thus,both the increase in ap and Vs lead to an increase in T,but the effect of ap is greater than that of Vs.Additionally,changes in ap have a more significant impact on grinding force variations than changes in Vs.When the grinding angle θ increases from 0° to 45°,Fn decreases by 54.7%,T decreases by 7.7%,and the grinding force ratio decreases by 66.8%.When θ increases further from 45° to 75°,Ff increases by 100.3%,T increases by 5.9%,and the grinding force ratio increases by 112.4%.When only changing the fiber direction of the material when the abrasive grain feed is changed,the grinding force generated by processing along the fiber axis is greater than that generated by processing along the fiber longitudinal direction,generally increasing by about 35%.Therefore,when the angle between the grinding heads is smaller,the grinding force is concentrated and Fn is larger;When the angle is larger,the grinding force becomes more dispersed and the material becomes more difficult to process.When only the material fiber orientation relative to the abrasive feed direction is changed,the grinding force generated along the fiber axial direction is greater than that along the fiber longitudinal direction,with an overall increase of about 35%.Therefore,when the grinding head angle is smaller,the grinding force becomes more concentrated and Fn is larger.When the angle increases,the grinding force becomes more dispersed,and the material becomes more difficult to machine.Conclusions:In SiCf/SiC materials,the interface between fibers and matrix is the preferred path for crack propagation,and fibers can change the crack propagation path.At the intersections of the warp and weft fiber yarns,crack growth can be effectively inhibited.When the grinding force ratio is relatively small,there are more burrs,cracks,and debris generated on the grinding surface of composite ceramic materials.In order to obtain a better machining surface without significantly affecting machining efficiency,a smaller ap should be preferred,followed by a larger Vs.In order to maximize the flexibility of spherical grinding head processing,it is recommended to maintain a small θ when the grinding head angle deviates.When processing along the longitudinal direction of the fiber,the failure mode of the fiber is mostly fracture.In this case,the matrix mainly supports the fiber,and cracks mainly appear at the interface between the matrix and the fiber,leading to fiber pull-out and exposure.When machining along the axial direction of the fiber,the main forms of fiber failure are compression and stretching,with some fibers being pulled out and then fractured along the interface to form fragments.At the same time,the experiment also verified the fracture characteristics of SiCf/SiC composite ceramic materials,which are consistent with the simulation results.
Objectives:With the wire line coring being widely used in deep rock core drilling,the drilling efficiency of diamond bits directly affects the efficiency of drilling projects.In view of the problem that diamonds are easily dislodged from the commonly used WC-Cu-based diamond bits when drilling in hard rock formations,resulting in low drilling efficiency,the effect of adding pre-alloyed powder brazing material on the properties and microstructure of WC-Cu based drill bits is investigated.Methods:Specimens and diamond composite specimens,containing 0-12%pre-alloyed brazing material and using 63#formulation as the base formulation,are prepared by hot press sintering method.The specimens are subjected to mechanical tests,wear ratio tests and XRD tests.In order to investigate the mechanism of action of pre-alloyed brazing material to improve matrix performance,the fracture of the specimen is observed with a scanning electron microscope.Drill bits are made with the ordinary matrix formula and the formula with the greatest increase in performance.Drilling tests are conducted to calculate rate of penetration and the wear of the working layer per unit footage to assess the application value of adding this brazing material.In order to study the changes in the wear condition of the matrix caused by the addition of pre-alloyed material,the morphology of the wear surface of the drill bit is observed with a body-view microscope and the number of diamonds was counted for each wear condition.Results:Mechanical property tests show that the addition of pre-alloyed powder to WC-Cu-based matrix can improve the mechanical properties of specimens.FCu14 and FAg737 additions at 8%resulted in the greatest enhancement of the mechanical properties of the specimens,with the highest rise in flexural strength of the matrix of 4.9%and the diamond composite specimens having an elevated wear ratio of 44.5%.The results of the XRD tests show that the pre-alloyed brazing material do not react with the constituents in the matrix to generate a new physical phase.Micro-morphological characterisation show that the addition of pre-alloyed powder brazing material is able to reduce the pores of the matrix.The pre-alloyed brazing material could achieve liquid-phase sintering and fill the gaps between the WC particles,which led to stronger toughness of the matrix.FAg737 pre-alloyed brazing material increases the hardness of the matrix through grain refinement.In the diamond composite material,the addition of pre-alloyed brazing material can make the diamond combine with the matrix more closely,and improve the mechanical holding force of the matrix on the diamond.The results of drilling test show that in hard granite formation,the rate of penetration of the drill bit with added pre-alloyed brazing material is increased by 98.4%and 97.3%,which is close to two times of the drilling speed of 63#formula drill bit.Observation of the wear surface of the drill bit shows that in the drill bit with pre-alloyed brazing material,the matrix supports the diamond in a tadpole shape,which results in a stronger holding force of the matrix on the diamond.On the cutting surface of the drill bit with pre-alloyed brazing material,the diamond spalling pits are obviously reduced,and the proportion of diamond that can play a role in cutting is larger,which effectively improves the drilling efficiency and makes the bit more difficult to slip.Conclusions:The addition of pre-alloyed brazing material to the WC-Cu-based matrix lead to liquid-phase sintering,which can fill the gaps between the WC particles and between the diamond and the matrix,thus increasing the toughness of the matrix and improving the mechanical holding power,which is reflected in the significant increase in the abrasion ratio of diamond composite specimens.The increase in matrix holding force contributes to the reduction of diamond shedding during the drilling process,and the diamond is able to perform more cutting,thus improving the drilling efficiency.
ObjectivesTo improve the grinding efficiency and quality of DD6 single crystal high-temperature alloy, the influence of ultrasonic vibration-assisted grinding on material removal is analyzed.MethodsConventional grinding (CG) and ultrasonic vibration-assisted grinding (UVAG) are performed perpendicular to the casting axis of the single crystal superalloy material. The influence laws of amplitude and grinding parameters on indicators such as grinding force and surface roughness are analyzed. Additionally, the influence of UVAG on the material removal process is examined in combination with grinding temperatures, grinding forces, and surface morphologies.ResultsThe results show that normal and tangential forces of UVAG are smaller than the ordinary grinding forces under the same parameters. In most cases, UVAG can reduce the surface roughness of the workpiece to different degrees. UVAG can reduce the risk of grinding burns. In the ordinary grinding process, the abrasive particles are in continuous contact with the workpiece, and continuous grinding marks can be obviously seen on the surface of the workpiece. In the condition of ultrasonic vibration, the surface of the workpiece can be found with obvious periodic short grinding marks. When the grinding depth ap＝0.5 mm, the workpiece feeding speed vw＝100 mm/min, and the grinding speed vs ＝30 m/s, the normal force Fn and tangential force Ft under ultrasonic vibration assisted state are about 60% smaller than that of ordinary grinding. The roughness decreases the most when ap＝0.5 mm, vw＝150 mm/min, vs＝30 m/s, and the maximum value is equal to 30%. When ap＝1.0 mm, vw＝100 mm/min, vs＝30 m/s, the UVAG temperature is still lower than the maximum applicable temperature of DD6, while the CG temperature exceeds the maximum applicable temperature of DD6, indicating that the UVAG can improve the material removal efficiency of DD6.ConclusionsHigh-frequency vibration optimizes the material removal mechanism which reduces the abrasive contact ratio and grinding forces during material removal by promoting the periodic "contact-separation-contact-separation" intermittent cutting behavior between abrasive particles and workpiece. At the same time, ultrasonic vibration improves the cooling conditions and helps the coolant to penetrate, allowing the coolant to enter the grinding area more efficiently and carry heat away. The temperatures of ultrasonic grinding are lower than that of traditional grinding. Ultrasonic vibration infuses the grinding process with a pulsating impact, transitioning the interaction between the abrasive particles and the workpiece from a state of constant contact to a pattern of intermittent engagement. This shift diminishes friction and wear at the interface, as well as curtails the adherence of material to the workpiece surface. Ultrasonic vibration effectively reduces grinding forces and grinding temperatures through intermittent cutting mechanism, lowers the difficulty of material removal, and ultimately improves the processing efficiency and surface quality of DD6 single crystal superalloy.
ObjectivesThe S-shaped internal cooling channels of turbine blades, typically manufactured via the lost foam casting process, are prone to the formation of residual deposits. These residues increase the surface roughness of the flow passages, subsequently restricting airflow and compromising cooling efficiency. Abrasive flow machining (AFM) is a viable post-processing technique to address this. However, the complex S-shaped geometry of these channels results in an unclear understanding of the material removal characteristics of adherent deposits during AFM, posing significant challenges for effective polishing. This study aims to investigate the processing characteristics of simulated powder adhesive residues within S-shaped channels during AFM. The primary objectives are to elucidate the material removal behavior at different locations of the channel and to develop a predictive model for the removal amount.MethodsTo simulate the adherent powder residues found in actual channels, small cylindrical platform were added at various strategic locations along an S-shaped channel. Computational simulations were employed to predict the material removal amount on the curved surfaces of these cylindrical platform during the AFM process. Subsequently, a mathematical model for material removal in the finishing of S-shaped channels was established. The influence of different parameters on the removal amount was analyzed by substituting them into this predictive model. Furthermore, to validate the theoretical findings, experimental tests were conducted. The material removal amounts from the small cylindrical platform obtained through experiments were compared and analyzed against the simulation predictions.ResultsThe results revealed a non-uniform material removal distribution along the S-shaped channel. The material removal on the circular platform was found to be greater at the inlet and outlet sections of the channel. Notably, the removal amount increased abruptly within the curved sections, especially at the first bend. At this first bend, the diameter and height reduction of the cylindrical platform were 44.1% and 43.3% greater, respectively, compared to the straight sections preceding and following the bend. The theoretical predictions for both diameter and height reduction showed a consistent trend with the experimental measurements, despite observable quantitative differences. The deviation between theoretical and experimental values for diameter and height removal was 21.43% and 24.79%, respectively. This indicates that the model possesses a preliminary capability to predict the removal amount at different locations within the channel.ConclusionsThis study demonstrates that material removal in AFM for S-shaped channels is highly location-dependent, with curved sections experiencing significantly enhanced removal. The established model, incorporating single abrasive particle dynamics analysis and material removal prediction, shows a consistent trend with experimental data, confirming its fundamental utility. The deviations between theoretical and experimental values highlight areas for future refinement, potentially involving more complex rheological models of the abrasive medium or finer meshing in simulations. Nevertheless, the developed model provides a powerful and valuable tool for determining material removal in AFM processes, offering significant guidance for optimizing the polishing parameters of complex internal channels like those in turbine blades. Future work should focus on model refinement and exploring its application to other complex channel geometries.
ObjectivesAiming at the problems faced in the precision grinding of aero-engine blisks, such as the difficulty in ensuring profile consistency during batch production processing and improving the surface grinding quality and efficiency, a robotic abrasive-belt flexible high-efficiency grinding method for blisks is proposed.MethodsThis article analyzes the flexible grinding process of a blisk using an abrasive belt. An independently designed robotic flexible grinding tool platform (with a drive spindle + floating mechanism + flexible abrasive belt) is adopted, and grinding verification experiments and surface quality inspections (grinding effect, morphology, roughness and surface profile) are conducted after grinding.ResultsAfter robotic abrasive-belt flexible grinding of the blisk, the grinding time is reduced from the previous manual grinding time of about 75 min to 32 min (including rough and fine grinding), and the efficiency is increased by 57.3%. The surface texture of the blisk is fine and uniform, the difference between concave and convex points is decreased from 6.9 μm to 4.0 μm, a reduction of 42.0%, the scratch type is single and the curvature jump is suppressed, resulting in a more uniform and stable surface morphology. The leaf basin surface roughness Ra is decreased from (0.82±0.11) μm to (0.31±0.05) μm, a reduction of 62.2%. The profile allowance is reduced from 0.224 1 mm to 0.050 1 mm, a decrease of 77.7%, the distribution of the profile allowance is more uniform, and the contour after grinding has a higher degree of overlap with the ideal contour.ConclusionsThe adoption of an independently designed flexible grinding tool platform dedicated to robots can achieve efficient and high-quality processing of blisks, and the quality after processing meets the requirement that the surface roughness of the blisk is less than 0.4 μm. In the future, by optimizing the force/position control method for robotic abrasive-belt grinding, the surface integrity of the titanium alloy blisk can be further improved.
ObjectivesWith the rapid development of the semiconductor and related industries, the power density and heat generation per unit area of electronic devices have increased dramatically. To solve the increasingly serious thermal problems of electronic components, researchers have focused on advanced thermal management materials. Diamond/Al composites have become a research hotspot for the new generation of thermal management materials due to their advantages of high thermal conductivity, low thermal expansion coefficient, and light weight. How to effectively reduce the interfacial thermal resistance is the key to fully leveraging the thermal conductivity enhancement provided by the diamond reinforcement.MethodsIn this paper, diamond particles are modified with Ti nanolayers (40, 80, and 160 nm) and Ti-Al double-nanolayers (Ti80 nm-Al60 nm) with controllable thicknesses by single-target and dual-target magnetron sputtering strategies, respectively. The rotating vibration platform used in the magnetron sputtering process controls the thickness of the layers at the nanoscale while ensuring uniform thickness. The diamond/Al composites are then fabricated by gas pressure infiltration technology, and the theoretical thermal conductivities of the composites are predicted using a combined differential effective medium and acoustic mismatch model. The influences of Ti nanolayers and Ti-Al double-nanolayers on the microstructures and thermo-physical properties of the composites are investigated.ResultsThe results show that the Ti nanolayers react with diamond to form TiC interfacial layers during the fabrication process of diamond-Ti/Al composites, which significantly enhances the interfacial bonding of the composites. By optimizong the thickness of the Ti nanolayers, a TC of 598.6 W/(m·K) is achieved at a justified TiC nanolayer thickness of 80 nm, which is about 81.08% of the theoretical value. Based on this optimized thickness of the Ti nanolayers, diamond particles with Ti-Al double-nanolayers (Ti80 nm-Al60 nm) are prepared using a dual-target sputtering strategy. After introducing the Al layer, the composites form a Diamond/TiC/TiAl3/Al gradient interface, and the thermal conductivity increases to 640.1 W/(m·K), which is 89.13 % of the theoretical value. Infrared thermography test is used to visually verify the thermal response of the composites over 0～10 s. The heating rate VDia-(Ti80 nm-Al60 nm)/Al＝2.46 ℃/s, VUncoated dia/Al＝1.53 ℃/s, and Vpure Al＝0.91 ℃/s. The heating rate of diamond-(Ti80 nm-Al60 nm)/Al is 1.6 times higher than that of uncoated diamond/Al and 2.7 times higher than that of pure Al, and the results of the infrared thermography tests correspond well with the thermal conductivity of the composites. The diamond/Al composite with Ti-Al double-nanolayers is subjected to a thermal cycling test from －50 ℃ to 150 ℃ for 100 thermal cycles, and the thermal conductivity declines by just 3.06%, indicating the excellent thermal cycling stability.ConclusionsThe formation of the Diamond/TiC/TiAl3/Al gradient interface not only benefits the improvement of the interfacial bonding, but also effectively reduces the difference in Debye temperature between the diamond reinforcement and the Al matrix. Therefore, the acoustic velocity mismatch between the diamond and the Al matrix is reduced, and the thermal conductivity of the composite is effectively improved. Compared with the single Ti nanolayer strategy, the Ti-Al double-nanolayers strategy provides new insights into the preparation of high thermal conductivity diamond/Al composites.
