This study fabricated three biomimetic structures (cicada wing, shark skin, and moth eye) on TA1 titanium with wire electrical discharge machining (WEDM) and coated them with ZrN. ZrN coating increased static contact angles, which reduced microbial adhesion. The moth-eye structure showed the highest contact angle (136.94 degrees +/- 1.1 degrees), achieving 99.0 % antibacterial rate, which outperformed unstructured pure titanium with ZrN (39.52 %). The TA1-Moth-Eye-ZrN structure improved antibacterial performance and corrosion resistance, demonstrating good biocompatibility and potential applications in orthodontic treatment.

Nowadays,various compositions of Al2O3-based ceramic coatings have been studied and applied.Among these,Al2O3-Cr2O3 coatings have attracted attention due to their excellent comprehensive performance.Graphene possesses outstanding hydrophobicity,self-lubricating properties,and corrosion resistance,and has been widely used to enhance the corrosion resistance of organic coatings.Researchers have found that the addition of graphene to Al2O3 bulk materials and coatings can improve their mechanical properties and wear resistance.However,the effect of graphene nanosheets on the corrosion behavior of Al2O3-based coatings has not yet been fully revealed.Therefore,studying the corrosion behavior of graphene-modified Al2O3-Cr2O3 coatings is of great significance.Nanostructured Al2O3-Cr2O3 powders with varying contents of graphene nanosheets were firstly prepared using traditional ball milling and spray granulation.Atmospheric plasma spraying(APS)technology was employed to deposit double-layer coatings on 45#steel substrates.NiCrAlY was used as the bond coating,while the top coatings were Al2O3-Cr2O3 with different graphene nanosheet contents.The morphologies and compositions of the powders and coatings were characterized using SEM and EDS.The corrosion resistance of the coatings was evaluated through electrochemical and immersion tests.The macro-and microstructures of corroded coatings were observed,and the corrosion products were analyzed using SEM,XRD,and Raman spectroscopy to reveal the corrosion mechanisms.Spherical Al2O3-Cr2O3 powders,both with and without graphene,were successfully prepared.However,the powder morphology became irregular when the graphene content increased to 6％.Test results showed that the corrosion resistance of the coatings initially increased and then decreased as the graphene content rose,even though coating porosity increased almost linearly.The self-corrosion potential(Ecorr)firstly increased and then decreased with increasing graphene content,while the self-corrosion current density(Icorr)exhibited an opposite trend.The coating with 1％graphene(AC-1)showed excellent corrosion resistance,with its Ecorr increasing by 89 mV and Icorr decreasing by 26％compared to the coating without graphene.Additionally,the polarization resistance of the AC-1 coating was approximately twice that of the unmodified coating.Pore resistance decreased with increasing graphene content,likely due to higher porosity.The immersion corrosion rate curves fluctuated over time,but the AC-1 coating maintained a relatively low corrosion rate compared to other coatings,decreasing by up to 29％relative to the unmodified coating.In contrast,the coating with 6％graphene(AC-6)exhibited the poorest corrosion resistance.Immersion in NaCl solution led to severe corrosion of the steel substrate,with noticeable rust on the coatings.The number of pores and lamellar interfaces increased after immersion,and corrosion products accumulated at pore edges.Corrosion mainly occurred at the interface between the substrate and the bond coating.The primary corrosion products were iron oxides,iron hydroxides,and FeOOH,with a small amount of Cl-containing products also detected.The effects of graphene on coating porosity and the diffusion of corrosive media determined the variations in corrosion rates.The addition of graphene to Al2O3-Cr2O3 coatings inhibited the diffusion of corrosive media into pores due to its hydrophobicity,thereby improving corrosion resistance.However,excessive graphene increased coating porosity—owing to its high melting point—thus deteriorating corrosion resistance.This study clarifies the influence of graphene nanosheets on the corrosion resistance of Al2O3-Cr2O3 coatings and provides a theoretical basis for preparing high-performance Al2O3-based ceramic coatings.

Scratching behavior and abrasion wear resistance of E690 claddings with different contents of TiC were studied in this paper. Nano-indentation tests were conducted to study the elastic-plastic deformation ability of the claddings. Scratch tests under constant and increased normal load modes and two-body abrasion wear tests for the claddings were performed by a scratch tester and a self-made abrasion wear tester. The morphology and size parameters of scratch and wear tracks were observed and measured. The results showed that the cladding with 1 % TiC (LC-1) possessed higher resistance to plastic deformation and scratch resistance than other claddings. The load leading to serious scratch damage for LC-1 cladding was higher than 30N. The area of pile-up, scratch area, scratch depth and scratch width of LC-1 cladding decreased by 33 %, 62 %, 47 % and 27 % compared with those of the cladding without TiC under a load of 30N. TiC addition improved the abrasion wear resistance of the cladding. The variation trend of wear mass loss of the claddings changed with the normal load increased. The claddings with 5 % and 1 % TiC had better wear resistance than other claddings when the loads were 5N and 20N respectively, the wear mass losses of which decreased by 30 % and 32.4 % compared with those of the cladding without TiC. The excellent abrasion wear resistance of the cladding could be attributed to its high scratch resistance and high mechanical properties endowed by TiC when the load was high. The main abrasion wear mechanism of the claddings was ploughing accompanied by tearing.

With the increased use of antimicrobial drugs, the threat of antimicrobial resistance is becoming a thorny problem. Preparing silver (Ag) based coatings with a certain antimicrobial property on the implants has emerged as an alternative strategy to reduce the use of antibiotics. However, how to prepare antimicrobial Ag-based coatings with good durability simply and efficiently is still an urgent problem to be resolved. In this research, a novel preparation method of Ag-based coating using traditional electrical spark discharge (ESD) deposition technique was proposed. Silver nitrate solution instead of traditional ESD working media and a flexible titanium brush electrode instead of silver brush electrode were used to prepare the Ag-based coating. Besides, a microcolumn array structure was fabricated on the substrate to improve the antimicrobial efficacy and durability of the coating. The experimental results showed that a relatively complete Ag-based coating was prepared successfully on the micro-column textured surface of titanium alloy substrate. Antimicrobial tests showed that the antimicrobial efficacy of the coating sample with micro-column array against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coil) increased by more than 95 %. The ultrasonic vibration tests and wear tests confirmed that the coating sample with micro-column array possessed good adhesion ability and durability. The deposition of Ag in the coating can be attributed to the decomposition of AgNO3 during the electrical spark discharge process.

A hybrid laser–GMAW-based directed energy deposition (DED) was developed to stabilise the cathode jet and droplet transfer in DED of Ti alloy. High-speed photography, spectroscopic diagnostic, theoretical calculation, and numerical simulation were employed to investigate the stabilising mechanisms. At a high laser energy density, the highest temperature of the molten pool was located in the laser-irradiated zone, generating a stable cathode jet. Ti atoms easily ionised into Ti ions at high temperatures (>8200 K); therefore, the cathode jet was primarily composed of Ti ions. The laser-induced metal vapour attracted and contracted the arc, resulting in an increase in the arc temperature, and strong evaporation near the wire during the peak-current stage. Therefore, the distribution areas of Ti I and Ti II were enlarged. Introducing the laser inhibited the obstructive effect of the cathode jet on the droplet, thereby enhancing the stability of droplet transfer.

In this study, plasma-sprayed Al2O3-Cr2O3 coatings with different contents of graphene nanosheets were prepared for investigating effects of the graphene on microstructure, mechanical properties, and wear behavior of the coating. The experimental results showed that graphene increased the porosity and the microhardness of the coating. But excessive graphene decreased the microhardness remarkably. Besides, the anti-crack initiation and propagation abilities of the coatings with graphene improved significantly. The wear rate of the coatings decreased first, and then increased with increasing the graphene content. Impressively, the wear rates of the coating with 2.9% graphene decreased by 33.5% and 36.7%, compared with those of the coating without graphene under normal loads of 5 and 15 N, respectively. The main wear mechanisms of the coatings with and without graphene are brittle fracture and abrasive wear.

To improve the sliding wear resistance of plasma sprayed Mo coating, Mo–SiC and MoO3–Al–SiC composite powders were used to prepare Mo composite coatings by plasma spraying. The results show that the introduction of SiC improved the mechanical properties and sliding wear resistance of plasma sprayed Mo coating. The reactivity of Mo and SiC was low during plasma spraying Mo–SiC composite powder. The thermite reaction for MoO3 and Al was not conducive to the densification of the composite coating prepared by MoO3–Al–SiC composite powder, but improved the reactivity of in-situ generated Mo and SiC, and the Nowotny phase Mo4.8Si3C0.6 was observed in the coating. The coating prepared by Mo–SiC composite powder displayed better mechanical properties and sliding wear resistance than that of the coating prepared by plasma spraying MoO3–Al–SiC composite powder. The coating obtained by Mo–SiC composite powder revealed a combination of adhesive wear, abrasive wear and oxidation wear.

A ZrC-ZrSi2-Al2O3 coating system was designed and prepared by atmospheric plasma spraying. Densely packed whisker microstructure and alumina-zirconia hypoeutectic were found in the as-prepared coating. The surface oxidation behavior of this composite coating under plasma torch ablation was fully revealed based on the characterizations from macroscopic to microscopic perspectives. After 20 s ablation, the major phases on the coating surface are t-ZrO2, Al2O3, SiO2, ZrSiO4, and ZrSi2. ZrC-ZrSi2 whiskers showed good integrity during the ablation process and finally, a dense Zr-Si-O layer was formed in the whisker area. Good coordination between alumina and zirconia is obtained by forming the solid solution and eutectic on the after-ablation coating surface. The as-prepared coating showed promising failure resistance under plasma torch ablation.

Nb-SiC and Nb-SiC-Al system niobium carbide composite coatings were developed in-situ by plasma spraying NbSiC and Nb-SiC-Al system composite powders, respectively. As a comparison, NbC-Al2O3 system niobium carbide composite coating was developed ex-situ by plasma spraying NbC-Al2O3 composite powder. The ablation resistance of the three systems of niobium carbide composite coating was evaluated under plasma jet. The results showed that the Nb-SiC and Nb-SiC-Al system coatings developed in-situ have better ablation resistance than NbC-Al2O3 system coating. The microstructure of Nb-SiC and Nb-SiC-Al system coatings after different times of ablation was characterized by scanning electron microscopy to investigate the ablation mechanism. The results showed that the surface of the coating of both systems can form Nb2O5 film under ablation conditions to isolate the further penetration of oxygen and heat into the coating. The Al2O3 in the Nb-SiC-Al system coating reacted with Nb2O5 to form AlNbO4. The formation of AlNbO4 promoted the densification of Nb2O5 film, so that the Nb2O5 film formed on the surface of the Nb-SiC-Al system coating was uniform and dense, which improved the ability of the coating to resist plasma jet ablation.

目的 提高E690钢的耐磨损性能.方法 将E690钢基体经磨床打磨后进行超声清洗,利用PROCUDO® 200激光冲击系统,对其表面施加冲击强化处理.利用光学显微镜、扫描电子显微镜和X射线衍射仪分析激光冲击(LSP)对E690钢微观组织结构的影响.通过显微硬度测试、纳米压痕测试、干滑动摩擦磨损试验,评价未冲击处理和LSP处理E690钢试样的硬度、弹塑性性质和耐磨损性能.结果 LSP作用下,E690 钢基体表层晶粒尺寸细化,形成明显的梯度结构,试样的相组成仍然为α相和γ相,但α相最强衍射峰的半高宽由 0.218°增大到 0.266°.LSP处理后,E690 钢基体表层残余应力转变为较大的残余压应力,最大残余应力达到-268 MPa.LSP处理E690钢的影响层深度约为 700 μm,表面硬度为(302.5±12.2)HV100,与未冲击处理试样相比,提高了 8.7%.LSP处理E690 钢试样的弹性模量为(419.80±8.79)GPa,提高了21.4%,弹性恢复功略有提高.LSP处理使得E690 钢的摩擦系数由 0.59±0.03 减小为 0.55±0.03,同时使其磨损率降低了32%.未冲击处理和LSP处理E690 钢试样的磨损机制为黏着磨损、氧化磨损和磨粒磨损.结论 LSP处理可有效改善E690 钢基体表层的微观组织,形成明显的冲击影响层深度,有效提高E690 钢基体的硬度和弹性模量,降低其滑动摩擦系数.此外,LSP处理有效提高了E690 钢的耐干滑动磨损性能.

For this study, E690 steel claddings with different contents of TiC were prepared by laser cladding for revealing effects of TiC on microstructure, mechanical properties, and wear behavior of the cladded steel. The microstructure and mechanical properties of the cladded alloys were observed and measured. The wear resistance of the cladded alloys was tested using a ball-on-disc tribometer. The experimental results showed that TiC refined the grain of the cladded alloy obviously. However, excessive TiC could lead to the network-like distribution of submicro TiC particles in the claddings. The microhardness of the cladded alloy with 1% TiC increased to 418.5 +/- 10.7 HV500, and yield strength and ultimate tensile strength (UTS) increased by 11% and 7% compared with those of the cladded alloy without TiC. Excessive TiC decreased the tensile properties to an obvious degree. The addition of TiC improved the wear resistance of the cladded alloy significantly. When normal loads were 5 N and 10 N, the cladded alloy with 5% TiC exhibited high wear resistance, and the wear rates decreased by 59% and 78% compared with those of the cladded alloy without TiC. However, when normal load was 20 N, the cladded alloy with 1% TiC possessed superior wear resistance, and its wear rate decreased by 81% compared with that of the cladded alloy without TiC. The main wear mechanism of the cladded alloys was abrasion wear when normal load was low, but serious plastic deformation played a role in the wear process when normal load was high.

There are many problems in the arc welding repair of aluminum alloy parts, such as excessive pores, coarse grains, and low hardness. Introducing external energy excitation is an effective solution. In this paper, 7075 aluminum alloy parts are repaired using the arc welding - laser shock forging technique. The effects of laser-wire spacing, laser pulse energy and frequency, welding current and speed, and V-groove depth on the surface morphology, section geometric characteristics, and porosity of the repaired layer are studied. Additionally, the hardness and microstructure of the repaired layer formed by arc welding - laser shock forging and arc welding are compared. The results show that a fine surface morphology of the repaired layer can be achieved by selecting reasonable laser-wire spacing, welding current, welding speed, and V-groove depth. It is also advised to select the maximum laser pulse energy and frequency possible, in order to increase the aspect ratio, reduce the residual coefficient, minimize porosity, and decrease the maximum pore diameter of the repaired layer. When compared to arc welding alone, arc welding - laser shock forging has the advantage of reducing grain size and improving the hardness of the repaired layer.

In this paper, nanostructured Al2O3-40%YSZ (AZ) and nano-MoS2/Al2O3–40%YSZ (AZM) powders and coatings are prepared and studied to reveal the effect of nano-MoS2 on the friction and wear behavior of the coating. The morphology, surface roughness and hardness are observed and measured by a scanning electron microscope, a laser scanning confocal microscope and a micro-hardness tester. The ability to resist fracture of the coatings is evaluated by scratch tests. The friction and wear tests of the coatings are conducted by a ball-on-disc tribometer. The experimental results show that AZ and AZM coatings have similar morphology and roughness. But nano-MoS2 decreases the hardness and improves the ability to resist fracture of the coating. Besides, nano-MoS2 decreases the coefficients of friction of the coating when the normal loads are high. The wear rates of AZM coating decrease by 38.7%, 29.7%, 23.6% and 11% compared with those of AZ coating under normal loads of 5N, 10N, 15N and 20N. The addition of nano-MoS2 endows the coating self-lubricating function. The main wear mechanism of the coatings is micro-fracture accompanied by splat delamination and slight abrasion wear.

The effect of Cr2O3 on the friction and wear behaviour and wear mechanism of Al2O3-Cr2O3 composite coating sliding against ceramic ball with high hardness is still unknown. Atmospheric plasma spraying is used to deposit Al2O3-Cr2O3 composite coatings with different contents of Cr2O3 to reveal its influential mechanism. The experimental results show that Cr2O3 decreases the voids in the coating obviously. The relative alpha-Al2O3 gamma-Al2O3 content ratios in the composite coatings are larger than 37%. The micro-hardness of Al2O3-40%Cr2O3 composite coating increases by 48% compared with Al2O3 coating, the fracture toughness of which is twice as large as that of Al2O3 coating. Al2O3-40%Cr2O3 composite coating has lower friction factor and wear rates when the wear loads are 5 N, 10 N and 15 N than Al2O3 coating, their wear rates decrease by 60%, 85% and 79% compared with those of Al2O3 coating. But when the wear load is 20 N, Al2O3-20%Cr2O3 composite coating has lower friction factor than Al2O3 coating, its wear rate decreases by 50% compared with that of Al2O3 coating. The main wear mechanism of the coatings is micro-fracture. The wear resistance of the composite coating is determined by the content of Cr2O3 and wear condition. Microstructure, hardness, fracture toughness and coefficient of thermal conductivity are important factors affecting the wear resistance of Al2O3-Cr2O3 composite coating. The research results can provide guidance for the design and application of Al2O3-based coating with high wear resistance.

The accumulation of debris between the inter-electrode gap caused by inefficient flushing during the micro-electrical discharge machining (micro-EDM) process leads to severe tool electrode wear and decreases the machining accuracy of micro-holes. In this study, a novel method using tool electrode spiral motion feed mode combined with fixed reference axial compensation (FRAC) is proposed to promote the debris evacuation and improve the machining accuracy of micro-holes. Different depths of micro-holes in titanium alloy were drilled using the tool electrode linear motion feed mode and spiral motion feed mode combined with FRAC and without compensation. The process parameters were optimized and determined by means of response-surface experiments to improve machining accuracy and machining efficiency. The results showed that the tool electrode spiral motion feed mode can improve the debris evacuation more effectively than the tool electrode linear motion feed mode. The micro-holes without cone at the bottom could be fabricated using the tool electrode spiral motion feed mode. The introduction of FRAC could improve the depth error of micro-holes furtherly. A high accuracy micro-hole with a depth error of only 0.21% could be fabricated efficiently under the condition of the optimal process parameters. The tool electrode spiral motion feed mode combined with FRAC has an obvious advantage in the fabrication of high accuracy micro-holes during the micro-EDM process.

分析了激光切割连杆裂解槽的温度场特性及对工件材料的热影响,建立了脉冲激光热源加工裂解槽温度场模型,分析了数值模拟中材料的初始条件、网格划分和热物理特性.通过数值模拟不同激光加工参数(脉冲功率、脉冲频率、脉冲宽度和切割速度)的温度场分布,得出激光参数对46MnVS5连杆裂解槽几何尺寸(槽深、槽宽和张角)的影响规律,为激光加工参数对连杆裂解槽质量参数影响的实验研究提供理论参考依据.

为了实现在复杂内植体表面抗菌改性,采用银作为抗菌物质,通过电火花沉积技术将银添加在内植体表面.使用电火花沉积电源,将工件链接负级,工具电极链接正极,将工具电极的材料转移到工件上.使用X射线衍射观测加工后样品的表面物相组成;采用激光共聚焦与扫描电镜观测加工后的表面形貌;通过抗菌试验测定加工后样品的抗菌性能.结果表明,采用电火花沉积加工的方法能够在复杂的结构表面构含银的微结构.加工后样品对液体具有良好的接触性能.样品表面银的尺寸越小,抗菌性能越良好,抗菌率最高达到100％.抗菌的机理为银的微结构水解成银离子作为抗菌剂.该方法具有操作简单、良好的表面适应性和制备样品稳定等优点.

In this paper, the effects of temperature and pH value of the conversion solution on the morphology and corrosion resistance of the titanium-containing conversion coating prepared on AZ91 magnesium alloy were studied. The morphology and composition of the coatings were studied by a scanning electron microscope, an energy dispersive spectrometer and an X-ray photoelectron spectroscopy. The potentiodynamic polarization tests and electrochemical impedance spectroscopy tests were performed by an electrochemical workstation. The results showed that both of the temperature and pH value of solution had an obvious effect on the micro-cracks and thickness of the coatings. With the increase of solution temperature, the micro-cracks became wide and deep. And the corrosion resistance of the coatings increased firstly and then decreased with the increase of temperature. The coating thickness and number of the micro-cracks decreased with the increase of pH value. Increasing the pH value of solution was favorable to the corrosion resistance improvement. The coating prepared in the solution at 40°C with the pH value in the range from 3.5 to 4.5 possessed good corrosion resistance.

利用电火花线切割的方法制备具有双尺度结构的超疏水多孔钛表面,用于实现油水混合物的分离.以多孔钛为基材,通过电火花线切割的方法在表面加工出阵列微沟槽结构,该表面经过全氟癸基三乙氧基硅烷的低表面能修饰后,制得超疏水多孔钛表面.利用接触角测试仪和电子显微镜等手段对超疏水多孔钛表面进行润湿性测量和形貌特征的分析,利用油水分离器测试超疏水多孔钛的油水分离能力.制备的超疏水多孔钛表面的接触角为162.6°,滚动角为0.5°,表现出低的粘附性.在油水分离试验中,超疏水多孔钛对于不同的油水混合物的分离率超过98％,耐压性测试发现该表面具有较好的耐压性能.化学稳定性测试和耐腐蚀性测试表明,超疏水多孔钛比基材具有更好的化学稳定性和耐腐蚀性.

This paper studied the wear resistance of Fe-Cr-C-B hardfacing alloy modified with nano-CeO2 and revealed its mechanisms of modification. The microstructure, coefficient of friction, wear rate, wear track and wear debris of the hardfacing specimens were studied. The results showed that the hardfacing specimens with 0.288 wt% and 0.432 wt% nano-CeO2 had better wear resistance. Nano-CeO2 promoted the heterogeneous nucleation of primary carbide by forming compound containing Ce, O and S, improving the wear resistance and bending strength of the hardfacing specimen. The addition of nano-CeO2 decreased the amount of MnS and improved the distribution and shape of inclusions by forming new rare earth compound inclusions. Excessive nano-CeO2 had no obvious effect on the refinement of primary carbide, even though new rare earth compound inclusions formed which was favorable to the bending strength improvement but unhelpful for the wear-resistance improvement.