Nickel coatings are widely employed in industrial applications due to their excellent corrosion resistance and high-temperature stability. Among thermal spray techniques, cold spraying is increasingly preferred for its high deposition rate and ability to produce thick, dense coatings with low porosity while avoiding phase transformations. The corrosion performance of cold-sprayed coatings is primarily governed by inter-splat bonding, which plays a more critical role than the intrinsic properties of the feedstock material. Insufficient inter-splat bonding permits the ingress of corrosive media, leading to localized attack at splat boundaries. Additionally, the microstructure of the coating influences the formation and protective nature of the native oxide layer. This study investigates the effect of initial feedstock condition, specifically grain size variations produced via different atomization techniques, on cold-sprayed nickel coatings' deposition characteristics and corrosion behavior. Microstructural evolution during spraying and subsequent heat treatment was characterized using electron backscatter diffraction (EBSD), and corrosion performance was evaluated by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in a 3.5

The present study aims to extend the life of tungsten carbide (WC) cutting tools utilized in face milling operations of Ti-6Al-4V by applying hard protective coatings developed using the cathodic-arc physical vapor deposition (CAPVD) technique. Box-Behnken design with 15 experimental runs and response surface methodology were used to mathematically model the relationships between input parameters and output responses to determine the optimal cutting parameters resulting in maximum material removal rate and minimum tool wear. Additionally, the performance of uncoated and coated carbide tools was assessed under dry and wet conditions to identify the best machining conditions. Intriguingly, the tool life of an uncoated WC tool in dry conditions was up to threefold more than that in wet conditions. The tool life of the coated tools was 33% to 166% longer than that of their uncoated counterparts. An analysis of their performance revealed an inverse relationship between the amount of Al in the coating and the tool life. The results from sliding wear tests suggest that Al-deficient coatings have a low coefficient of friction. This study sheds light on the effectiveness of CAPVD-coated carbide tools for improving the tool life during face milling of Ti-6Al-4V.

Deposition of Ni-Cr through cold spraying has potential implications in power sector as a potential candidate for high temperature oxidation and corrosion resistance coating. In this work, cold spray deposition of Ni-Cr at different stagnation temperatures varying from 600 degrees C to 800 degrees C using air as process gas instead of expensive nitrogen and helium gases is realised. The bonding state at the inter-splat boundaries was simulated and the same was correlated with the results obtained from mechanical and thermal cycling studies. Coatings deposited at higher temperature exhibit superior performance due to the formation of strong inter-splat boundaries, thus reflected in porosity and oxidation resistance. Deposition conditions (V-P / V-Cr) used in this study meets the requirement for inter-splat bonding. The fraction of bonded inter-splat boundaries achieved at 20 bar 800 degrees C was estimated to be similar to 100 % thus reflects in functional properties such as porosity, microstructure, superior oxidation and spallation resistances.

Cold spray bonding mechanism is often correlated with adiabatic shear instability and jetting at inter-splat boundaries. In this work, the role of in-flight temperature on the deposition characteristics is synergistically addressed with the in-flight velocity of the impacting powders. The fraction of inter-splat bonding and the properties of the coatings are correlated as a function of total energy of the powder upon impact rather than inflight velocity alone. Fraction of inter-splat bonding is used to obtain normalised electrical conductivity and normalised elastic modulus for variety of materials ranging from low melting point zinc (Zn) to high melting point tungsten (W). Onset of deposition is characterized with the dimension less parameter estimated by normalising the total energy of the impacting powder with the Ebond (critical energy). The data is correlated with the experimental results. For instance, the critical velocity (VCr) and critical energy (Ebond) for bonding of copper are estimated to be 451 m/s and 27.25 & mu;J respectively. One can tailor the process condition to deposit the metallic powder in cold spraying by selecting either in-flight velocity or in-flight temperature. The synergistic effect of velocity and temperature can be corroborated with the bonding state in cold sprayed coatings.

Component reclamation and additive manufacturing using cold spray technique is gaining attention in various industrial sectors as one of the cheapest alternative. Depositing super alloys (IN625 and IN718) using air as a process gas (As against Nitrogen or Helium) further reduces the deposition cost. In this work, inter-splat bonding states at the impacting interfaces of IN625 and IN718 in cold spraying are studied through Finite Element Modelling (FEM) studies and the bonding fraction is correlated with the microstructure, and performance of the coatings. The role of process temperature along with the impact velocity of the powder particle is considered rather than impact velocity alone to estimate the bonding state. This synergistic effect upon impact paves a way to successfully deposit high temperature structural materials such as Inconel using air as a process gas. The inter-splat bonding state for the coatings deposited at different process conditions, correlates well with the mechanical and corrosion performance of the coatings.

The study of residual stresses induced during machining is of considerable importance due to their effect on fatigue life of machined components. The metallurgical changes occurred due to thermo-mechanical phenomenon in cutting process affects the distribution of residual stress in machined components. Ultrasonic vibration assisted turning (UVAT) is effective machining process for low thermal conductivity materials like Ti6Al4V alloy and improves the surface characteristics by reducing cutting force and cutting temperature. In this paper, experimental and finite element (FE) studies are conducted to study the circumferential and axial residual stress distribution in UVAT of Ti6Al4V alloy. FE model is developed to study the effect of vibrating parameter (ultrasonic power intensity) and cutting parameters (cutting speed, feed rate, and depth of cut) on the residual stress profiles of machined surface. The FE simulation results of cutting force and cutting temperature are validated with experimental results. The circumferential and axial surface residual stresses obtained from FE simulation are also compared with experimental results using X-ray diffraction method. The effect of thermo-mechanical loading on residual stress distribution is analyzed with respect to force components (cutting force and feed force) and cutting temperature. Finally, the effect of each cutting parameter on subsurface layer of machined component is analyzed.

The performance of the machining process depends on the time of contact of the cutting tool with the workpiece. In this work, the effect of vibrating and cutting parameters on tool-work contact ratio (TWCR) in ultrasonic vibration-assisted turning (UVAT) is evaluated. Machining performance is measured in terms of average cutting force, cutting temperature, and average surface roughness. Full factorial experiments are conducted on a Ti6Al4V alloy to evaluate the performance of the UVAT process in terms of TWCR. The performance of the UVAT process is analyzed and compared with the conventional turning process at various conditions, such as intensity of ultrasonic power (80, 90, and 100 %), cutting speed (10, 30, and 50 m/min), feed rate (0.055, 0.103, and 0.161 mm/rev), and depth of cut (0.1, 0.3, and 0.5 mm). The cutting force, cutting temperature, and surface roughness are decreased with the increase in percentage intensity of ultrasonic power. The effectiveness of UVAT process is greater at higher levels of vibrating parameters and lower levels of cutting parameters in the selected range. Finally, it is concluded that the maximum benefit from the UVAT process is obtained at TWCR of 0.136 and its effect is dominant at lower levels of cutting conditions. However, the effect of thermal loading is dominant at higher levels of cutting conditions in the selected range.

The effect of the machining process has been expanding step by step to fulfil the needs of the current mechanical insurgency. The current enterprises are zeroing in streamlining materials wastage and the machine tools. In this work, the principle center is around enhancing the cutting conditions and the surface nature of workpiece material while machining aluminium alloy AA6063 utilizing physical vapour deposition (PVD) carbide inserts and uncoated carbide inserts. The examinations were done based on L9 orthogonal array utilizing taguchi method. Additionally, the examination was finished utilizing analysis of variance (ANOVA) and the combined effect of parameters are analysed utilizing multiple regression (MR) examination. The test results were contrasted and anticipated qualities and the ideal tests were gotten independently with TiCN coating PVD coated and uncoated carbide inserts. From the outcomes acquired by examination of analysis of variance, it was observed that the influence of feed (84%) is more on surface roughness compared to speed (2%) and depth of cut (13%), the depth of cut influenced (79%) more on cutting force compared to speed 8% and feed (5%), the speed (68%) influenced more on temperature compared to feed (6%) and depth of cut (21%). It was seen that machining with PVD coated carbide inserts delivered 11% better surface roughness, 10% less power and 12% lower temperature contrasted with uncoated carbide inserts during the machining of aluminium alloy AA6063. In light of the conclusive outcomes got, the utilization of PVD coated carbide inserts can give better machining execution of AA6063 contrast with uncoated carbide inserts.

High cutting temperatures developed during machining of Ti6Al4V alloy diminish the tool life by rapid increase in rate of tool wear. The high cutting temperatures increase the chemical reactivity of the workpiece with tool material and form the localized temperature zones at the vicinity of cutting tool edge. Ultrasonic vibration-assisted turning (UVAT) is an effective cutting technique in which tangential vibrations are provided to the cutting tool. The reduced cutting force and temperature improve the tool life in the UVAT process. In the present study, flank wear of the uncoated carbide cutting tool has been studied in UVAT processes at various cutting speeds (90, 120, and 150 m/min) and ultrasonic powers (80, 90, and 100 %). The flank wear of the tool is measured with a scanning electron microscope, and it is observed that tool wear is low in UVAT compared with the conventional turning (CT) process. Fracture of the cutting edge of the tool is observed in CT because of high compressive stresses with the high cutting temperature, which did not occur in the UVAT process. The growth of average and maximum flank wear with cutting velocity is low in UVAT, whereas rapid growth is observed in the CT process. From the experimental results, tool life improvement is observed in UVAT compared with CT at an average flank wear of 300 mu m; however, this improvement is decreased with an increase in cutting speed in the order of 62, 53.2, and 32 % for 90, 120, and 150 m/min, respectively, at 100 % ultrasonic power. Similarly, tool life is improved with an increase in ultrasonic power in the order of 18, 55, and 62 % for 80, 90, and 100 % ultrasonic power, respectively, at 90 m/min cutting speed.

Providing advanced coating solutions for high-speed dry machining applications is gaining importance by the day especially with the increasing employment of difficult-to-machine materials in niche areas. Taking into account the recent demands in developing such coatings, in the present study, a novel low-friction coefficient nanocomposite coating: CrAlSiN/gradient (G)-CrAlSiCN was developed which can be used in high-speed or dry machining applications. Initially, CrAlSiN nanocomposite coating and carbon incorporated CrAlSiN coating were deposited separately using the cylindrical cathodic arc physical vapor deposition (PVD) technique. The as-deposited films were comprehensively analyzed to determine their adhesion strength, phase composition, sliding wear properties (friction coefficient), hardness, and tool life. Preliminary observations revealed that the films did not show evidence of diamond-like carbon (DLC) formation (from Raman analysis). Further, an increase in the carbon content led to a steep decrease in the adhesion strength. This result persuaded a study on developing a novel coating with gradient carbon architecture that would retain the properties of a nanocomposite whilst supporting the nanocomposite underlayer by reducing the coefficient of friction. In comparison with the CrAlSiN nanocomposite coating and a standard DLC coating, the novel gradient carbon coating showed superior tribological properties along with better tool life. This study marks the first such attempt at studying the influence of carbon incorporation to the CrAlSiN nanocomposite coating on improving the overall mechanical and tribological properties of the coating architecture (CrAlSiN/G-CrAlSiCN) for dry machining applications.

The accuracy of numerical modeling of a machining process largely depends on material model constants. The Johnson-Cook (J-C) material model constants, i.e., A, B, C, n, and m, describe deformation behavior of material under thermomechanical loading. This paper considers an equivalent strain hardening exponent neq in place of ‘n’ in the J-C constitutive law for accurate prediction of material model constants at near orthogonal machining conditions. The effect of strain on the secondary deformation zone, i.e., the tool-chip interface, is also considered for accurate prediction of material parameters. In the present work, a machining approach based on response surface methodology and particle swarm optimization technique are used to identify J-C material model constants for the Ti6Al4V alloy. The cutting force, feed force, and chip thickness obtained from orthogonal experiments are used to evaluate the physical quantities of Oxley’s extension theory at different rake angles. It is noted that J-C constants determined from the present approach at a 7° rake angle are more accurate in predicting flow stress than J-C constants determined from other methods. J-C constants identified from a machining approach show less deviation from the measured equivalent flow stresses obtained at similar machining conditions.

Inconel 718 alloy is, in exacting superalloy, used extensively in the most sophisticated application such as aerospace, chemical, marine and high-speed racing cars. However, the characteristics of this material make it difficult to machine due to poor thermal conductivity (11 W/mK) and work hardening. The turning process is classified as a process that produces continuous chips and experiences elevated temperatures. With emerging new and efficient MQL delivery systems, the industry has shown drift from flood and dry lubrications towards MQL. Having this in mind, to further improve the cutting fluids, a novel hybrid nanocomposite of Cu–Zn was developed in situ with mechanical alloying. Cu–Zn/vegetable oil (groundnut oil) hybrid nanofluids were prepared by dispersing the synthesized nanocomposite powder in vegetable oil. A unist MQL system combined with a compressor is used to supply nanofluid mist to the cutting zone. The inserts used were TiAlN coated beyond blast insert from Kennametal with ISO designation CNGG 120408. The insert holder used was from Kennametal beyond blast with ISO designation MCLNL 2525 M12BB. The intent of this work is to haul out the effect of cutting parameters like speed, feed, depth of cut, volume of fluid and air pressure, when machined under dry, MQL/vegetable oil and MQL/nanofluid conditions. The results were compared while machining with dry and Veg/MQL lubricating conditions. A 39% reduction in surface roughness was obtained when compared to dry machining.

In this study, Taguchi-based analysis of variance (ANOVA) is adopted for optimization of lower-frequency vibration-assisted turning (LVAT) process parameters such as cutting speed, frequency, amplitude, and feed rate. Machining parameters are analyzed by evaluating maximum cutting force and tensile maximum circumferential residual stress (MCRS) in VAT of Ti6Al4V alloy. Finite element simulations are performed in ABAQUS according to L27 orthogonal array to find the optimum condition for maximum cutting force and MCRS (tensile). Results show that the vibrating parameters, frequency, and amplitude are most significant for maximum cutting force and MCRS (tensile), respectively. The optimum condition is obtained at 30 m/min of cutting speed, 150 μm of amplitude, 600 Hz of frequency, and 0.05 mm/rev of feed rate for cutting force while the optimum condition for MCRS (tensile) is 45 m/min of cutting speed, 50 μm of amplitude, 200 Hz of frequency, and 0.15 mm/rev of feed rate.

Metal matrix composites (MMC) have found wide applications in the transportation sector. But, the presence of hard particles in the MMCs causes catastrophic tool failures. The current study presents a method to select process parameters to increase the material removal rate in finish turning of Al-MMC (Al 6061, 5% SiC, 3% C) using TiN coated carbide inserts. The key aspects of the method are (a) Using the fractional factorial method for performing experiments economically (b) Using radial force instead of cutting force (c) Using frame statistics and linear spectrum of the radial cutting force signal to select process parameters. The experiments were conducted on a precision lathe. A 6-component piezoelectric dynamometer was used to measure the cutting force.

Sensors have become an integral part of the current manufacturing systems. However, gaining insight into the data collected from sensors is a complex task. The current paper presents an approach to identify stable machining parameters by applying frame statistics and kurtosis to cutting force signal. The approach is presented in finish turning of aluminum metal matrix composites (Al-MMC) using coated carbide inserts. It was found that the process parameters suitable for finish turning Al-MMC are 80 m/min cutting speed, 0.103 mm/rev feed and 0.1 mm depth of cut. The approach presented can be applied to other machining processes, and as it is computationally efficient, it can be used in online monitoring systems.

The main objective of this work is to assess the performance of graphene nanoplatelets–based cutting fluid in minimum quantity lubrication grinding of Inconel 718. Nanocutting fluids with varying concentrations and different specific surface areas of graphene nanoplatelets were developed, and basic properties like viscosity and thermal conductivity were evaluated at different temperatures. The role of graphene nanoplatelets concentration and specific surface area is investigated by comparing force generated during grinding, surface roughness, grinding temperature, grinding coefficient and specific grinding energy. The experimental results show that graphene nanoplatelets significantly lower the grinding force, temperature, specific grinding energy and roughness of the finished surface. Nanocutting fluid with 0.3 wt% graphene nanoplatelets and 750 mm2/g was found effectively improved the surface quality of the Inconel 718 compared to dry grinding and minimum quantity lubrication grinding with soluble oil.

The machining of Ti6Al4V alloy with vibration assisted turning (VAT) is an effective consideration to control the surface integrity of machined components. The effect of cutting and vibrating parameters in a VAT on cutting force, cutting temperature, equivalent stress and compressive maximum circumferential residual stress (MCRS) was studied in the present work. The parameter optimisation of a VAT of Ti6Al4V alloy was achieved with Taguchi based analysis of variance (ANOVA) and grey relational analysis (GRA). The input parameters considered for optimisation of VAT process are cutting speed, feed rate, frequency and amplitude. The finite element (FE) simulations were performed with commercial FE code, ABAQUS. The result shows that the vibrating parameters (frequency and amplitude) play a significant role than cutting parameters (speed and feed rate) in VAT process. The optimum condition for each output response was determined from ANOVA. The optimum condition obtained at 30 m/min of cutting speed, 150 μm of amplitude, 600 Hz of frequency and 0.05 mm/rev of feed rate for cutting force, cutting temperature and MCRS (compressive) while the optimum condition for equivalent stress is 30 m/min of cutting speed, 100 μm of amplitude, 600 Hz of frequency and 0.05 mm/rev of feed rate. The GRA suggests the combination of process parameters 30 m/min of cutting speed, 150 μm of amplitude, 600 Hz of frequency and 0.05 mm/rev of feed rate provides the optimum response.

Cutting tool micro-geometry and surface integrity have been critical aspects to be considered for successful application of PVD thin films for cutting tool life enhancement. The present study examines in detail the role of pre-coating surface preparation (micro-blasting and drag finishing) on the tool life of coated cutting tools. TiN coating was deposited on different kinds of pre-treated (Micro blasting, Edge rounding and a combination of both) HSS and WC drills using cylindrical cathodic arc deposition method. They were subsequently characterized for surface roughness (Ra), adhesion strength and machining performance on EN 24 material. Pre-coating surface roughness (developed due to pretreatment) has a major influence on the adhesion strength of the coating. A lower pre-coating surface roughness with optimized edge rounding led to higher adhesion and edge strength which in turn resulted in a notable increase in tool life. Further underlining the importance of the present study, commercial TiN coatings deposited on HSS substrates were tested. The tool life obtained in the current study prolonged the tool life by a factor of 3 in comparison to the commercially available tools in the present day market.

CrAlSiN nanocomposite thin films with varying film chemistry were developed on tungsten carbide (WC) specimens using cylindrical cathodic arc physical vapor deposition (c-CAPVD) technique. The physical, mechanical, and tribological properties of all the films were comprehensively investigated for arriving at the film chemistry leading to the best properties with respect to mechanical applications. The best tribo-mechanical properties were obtained in films with Cr/(Al_Si) ratio of 1.2. This coating with best properties was translated on to WC drill bits for machining tests. The Al and Si content has shown major influence on the adhesion strength and phase constitution of the films, with a considerable change in residual stress too. The superior properties achieved could be attributed to the formation of a near-perfect nanocomposite structure, with the crystalline CrAlN phase surrounded by an amorphous Si3N4 phase. The tool life of the coated CrAlSiN tools was investigated during dry machining of EN 24 material. In comparison to the tool life of an uncoated tool and a TiAlSiN-coated tool, the best CrAlSiN coatings synthesized in this study performed exceedingly well. The present study clearly demonstrates the advantages of CrAlSiN over other existing similar coatings for high-speed machining.

With the development of biodegradable cutting fluids for manufacturing systems, the need for enhancement of the heat transfer capabilities of cutting fluids has increased. In this contest, the viscosities of the cutting fluids are studied experimentally and theoretically. Cu-Zn hybrid nano-particles with combinations (0:100, 75:25, 50:50, 25:75, and 100:0) were used to prepare nano-fluids by dispersing them into vegetable oils. The results showed increase in viscosity of nano-fluids with increase hybrid particle loading and decrease in viscosity with rise in temperature. Neural network models were proposed to represent the viscosity as a function of the temperature, nano-particle concentration, diameter of nano-particle and the viscosity of the base fluids and compared to the existing theoretical models. Regression model with ANN the predicted output has 0.999% confident levels. In addition, the measured values of the viscosity of nano-fluids are found to be underestimated by classical models.