关节轴承喷涂MoS_2/石墨复合涂层摩擦学性能的研究

以Mo S2/石墨为固体润滑剂,无机磷酸盐为胶粘剂,利用喷涂方式在GE20ES型关节轴承表面制备不同配比的Mo S2/石墨复合涂层,考察了这些复合涂层在旋转摆动条件下的摩擦磨损性能。结果表明,不同配方的Mo S2/石墨复合涂层均显示了较好的减摩耐磨性能,其中当Mo S2与石墨的配比为3∶1时,Mo S2与石墨有较好的协同效果,复合涂层的摩擦学性能最好。     

Vacuum tribological behaviour of self‐lubricating quasicrystalline composite coatings

High‐temperature‐resistant self‐lubricating coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys as the hard phase for wear resistance can be deposited by a thermal spray technique. The coatings also contain lubricating materials (silver and BaF₂ CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating of this type, with a very good microstructural quality. The coating was deposited by high‐velocity oxygen fuel spraying and tested under vacuum using a pin‐on‐disc tribometer. Different loads, linear speeds, and pin materials were studied. The pin scars and disc wear tracks were characterised using a combination of scanning electron microscopy and energy dispersive spectrometry. A minimum mean steady friction coefficient of 0.32 was obtained when employing an X750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin.     

Calculation of tribological characteristics of composite materials

We present the formulas for calculating the friction coefficient when fibrous composite material is rubbed against the homogeneous rigid material. The wear of the composite is taken into consideration in the calculation.     

Study of tribological properties of detonation nanostructured WC-Co-based coatings

The study deals with tribological properties of the nanostructured WC-12%Co coatings deposited by the detonation method. It is found experimentally that their wear resistance depends on the concentration of monocarbide WC. The dependence of the WC concentration in the coating on deposition conditions is obtained. The microstructure of the coatings, their physical-mechanical properties, phase composition, porosity, hardness, and modulus of elasticity are studied. The advantage of the nanostructured coatings over the coatings deposited from micropowders is shown.     

Structure characterization of pulsed laser deposited MoS x –WSe y composite films of tribological interests

Pulsed laser deposition (PLD) was employed to grow MoS _x –WSe _y composite films, where x = 1.18, y = 0.78. Scanning electron micrographs show that the films have a dense granular morphology. Crystallization, d-spacing and hexagonal sheet curvature within the film were studied with X-ray diffraction, electron diffraction and transmission electron microscopy. A predominant hexagonal MoS _x phase was formed but contained W and Se, which were most likely present as substituents for Mo and S. There was no evidence for two separate crystalline phases. MoS _x –WSe _y composite films exhibited a larger expansion along the c-axis (d-spacing between basal planes) than PLD MoS₂ and WSe₂ films grown by laser ablation of pure targets. The lattice spacing along the a-axis was expanded in comparison to the MoS₂ film, and compressed in comparison to the WSe₂ film. X-ray photoelectron spectroscopy showed a significant sulfur deficiency, and verified both of S and Se bonding in the film. High-resolution electron microscope images exhibited significant curvatures of the (002) basal planes in the films. The bending behavior of basal planes was explained by S vacancies and Se substitution on the atomic site of S layers. The tribological properties of the composite films were measured in dry and wet conditions using a ball-on-disc tribometer. The reduced friction was correlated with the increased crystallinity and increased separation of basal planes in the composite films.     

Integration of wear-resistant titanium carbide coatings into MEMS fabrication processes

Microelectromechanical systems (MEMS) are a key technology for small-scale satellites, integrated sensors, and intelligent control systems. However, a major limitation for Si-based systems involving tribological components is their inability to withstand prolonged sliding surface contact that results in high wear and causes them to fail within minutes of operation. Our aim is to protect the Si surfaces with wear-resistant coatings. Due to practical limitations of coating fully released MEMS structures, we have addressed the integration of the coating into the MEMS processing sequence. This paper describes the direct integration of a pulsed-laser-deposited wear-resistant titanium carbide (TiC) coating into the Si MEMS fabrication process. The in situ deposited TiC layer also provides an ideal substrate to the various possible lubrication schemes proposed for moving MEMS. This revised version was published online in August 2006 with corrections to the Cover Date.     

Modeling friction of tribological composite coatings

The paper reports the results of the indentation of Ni-P coatings on substrates made of various materials and the results of the calculation of their elastic modulus. The results of the tribological study of coatings of different thicknesses are presented. The obtained values of the elastic modulus and friction coefficient are used to determine the stress state of the Ni-P coatings during friction.     

Effect of current density,MoS2 content and bath agitation on tribological properties of electrodeposited nanostructured Ni-MoS2 composite coatings

ABSTRACT

Nanostructured nickel coatings with molybdenum disulphide particles were electrodeposited to form composite coatings. Three different current densities, i.e. 3, 5 and 7?A/dm² were investigated initially. The best results were obtained with 5 A/dm² for codeposition of nanostructured Ni-MoS₂ composite coatings. With the addition of 1–4?g/L molybdenum disulphide to the bath, the weight percentages of MoS₂ particles in the coatings were 23–38%. This increase of MoS₂ content was accompanied with decrease in friction coefficient of the coatings from 0.35 to 0.08. Wear resistance of the coatings was increased with increasing MoS₂ content and the weight loss was decreased from 1.4 to 0.7?mg. Hardness was decreased from 585 to 400 VHN with increasing the MoS₂ content. By increasing bath agitation speed up to 150?rpm, more MoS₂ particles were embedded in the matrix and the coatings showed better wear resistance. However, increase of agitation speed from 150 to 200?rpm caused a decrease of MoS₂ particles in the nickel matrix due to the turbulent motion of particles in the bath. Overall, it was shown that the lubricating effect of MoS₂ in the coating was more influential than the nanocrystallinity of the nickel matrix in improving tribological properties of these composite coatings.     

A comparative study of tribological behavior of microarc oxidation and hard-anodized coatings

Microarc oxidation (MAO), a novel coating technique capable of depositing dense, hard ceramic composite coatings on aluminium and its alloys, has the potential to replace conventional hazardous anodizing techniques. However, the emergence of such a scenario depends strongly on the properties and performance of MAO coatings in comparison to hard-anodized coatings. In order to facilitate such a comparative investigation, a 6061 T6 aluminium alloy was employed as the substrate and the coatings were deposited through microarc oxidation (MAO) and hard anodizing techniques. The tribological performance of the coatings was evaluated using dry-sand abrasive wheel tests at different normal loads and solid-particle erosion wear tests at different particle velocities and impact angles by employing silica as erodent. The hard-anodized coatings reduced the abrasive wear rate of 6061 Al alloy by a factor of 2, while the MAO coatings reduced the wear rate by a factor of 12-30. Under erosion conditions, the overall wear rate of MAO coatings is identical to that of bare alloy, whereas the hard-anodized coatings exhibit 10 times higher erosion rate.     

Multilayer composite ceramicmetal-DLC coatings for sliding wear applications

The design of anti-friction coatings able to perform well in different wear conditions without lubricants requires a combination of adequate hardness and toughness, good adhesion, a low friction coefficient and a low wear rate. Recently introduced metaldiamond like carbon (DLC) coatings produced by magnetron sputtering of metals from targets, which are to a controlled extent covered with carbon from the chamber atmosphere, can be a step towards the achievement of such a combination. These coatings consist of an amorphous a:CH matrix with the possible incorporation of metal (Ta, W, Nb, Ti), metal carbide and/or graphite grains. Previous studies of Ti_x%-DLC coatings showed their good protective properties against abrasive, impact and single scratch wear, as well as a requirement for supporting interlayers to successfully apply such coatings to low-cost steels. In the present work an example of the selection of metal-ceramic Ti-TiN-TiCN supporting interlayers is given based on studies of their morphology, structure and mechanical properties. This resulted in the development of Ti-TiN-TiCN-[TiC-(Ti_x%-DLC)] multilayer composite coatings. Several coatings were prepared with the same supporting interlayer and a variation in the preparation of the Ti_x%-DLC layer. Ball-on-disc experiments were carried out to investigate these coatings in conditions of sliding wear against steel and cemented tungsten carbide balls. CrN, TiN and TiCN coatings were also deposited and tested in the same conditions to provide a reference. Low friction coefficients (below 0.2 at an air humidity of 50% RH) in combination with low normalized wear rates were found for multilayer coatings with upper Ti_20%-DLC and Ti_35%-DLC layers.     

Two-body abrasive wear of electroless nickel composite coatings

The two-body abrasive wear of electroless nickel (EN), EN-silicon carbide, and EN-alumina composite coatings have been investigated using a scratch test with a diamond indenter. The coatings were heat treated at temperatures of 100–500° C. The hardness of the coatings increased with heat treatment temperature from 500 HV100 for the as-deposited condition to 1008 HV100 when fully hardened. Scratch testing showed that the as-deposited coating had scratch tracks with a high degree of plasticity, signs of microploughing and tensile cracking and was characterised as a ductile failure. On the other hand, the heat-treated coatings showed chipping and cracking on the edge of the scratch tracks, failing in a brittle manner. The heat-treated EN-silicon carbide coatings, however, exhibited no cracking nor chipping, believed to be due to its higher fracture toughness than the other heat-treated coatings, attributable to its lower phosphorus content. The volume of material removed from the silicon carbide scratch track was 1/3 of the volume removed from the steel substrate at a 20 N load, and showed the best wear/ scratch resistance of any of the coatings tested.     

Deposition and tribological behavior of composite nickel coatings

Nickel-based composite coatings containing graphite nitrate as a dispersed phase are deposited by the electrochemical method. The process of electrodeposition of the coatings in the potentiodynamic and galvanostatic modes is studied. It is found that the sliding friction coefficient of the composite electrochemical coatings is half that of nickel coatings containing no dispersed phase. It is shown that the sliding friction coefficient of the coatings declines as the thickness of the electrolytic deposit grows.     

Electroless deposition and structure of Ni-MoSi2 composite coatings

Nickel-molybdenum silicide (Ni-MoSi₂) composite coatings were produced by a technique using an electroless nickel bath containing MoSi₂ in suspension. The operating conditions of the electroless deposition of Ni-MoSi₂ composite coatings and their structure were studied by X-ray fluorescence and X-ray diffraction. The mechanical properties of the composite coatings were determined. Some properties of the Ni-MoSi₂ composite coatings, such as oxidation resistance at high temperature, were investigated. These materials have potential for use in high-temperature applications involving oxidation resistance.     

A method for the tribological testing of thin,hard coatings

A new method has been developed for tribological testing of thin, hard antiwear coatings, using a ball‐on‐disc tribosystem, under conditions of dry sliding. In this, an Al₂O₃ ball is pressed against a coated steel disc. Wear debris is removed from the contact zone by a stream of dry argon in this novel method. This improves the stability of the tribological properties and the repeatability of the test results. All test conditions are precisely defined, in particular: the type of motion, air relative humidity, ambient temperature, sliding speed, load, tribosystem spatial configuration, substrate material, substrate hardness and roughness, and coating thickness. The method developed has been used to test various physical vapour deposition coatings (deposited by the vacuum arc method), i. e., single‐layer TiN, Ti(C,N), CrN, and Cr(C,N), and multilayer Cr(C,N)/CrN/Cr and Cr(C,N)/(CrN+Cr₂N)/CrN/Cr. It is shown that CrN coatings exhibit the best antiwear properties, and Ti(C,N) the worst. Friction coefficients for CrN and Cr(C,N) coatings are much lower than for the more commonly used TiN. Multilayer coatings have better antiwear properties than single‐layer ones.     

电泳-电镀沉积制备纳米Al_2O_3颗粒增强镍基复合镀层的耐磨性能

先采用电泳沉积工艺在铜基体上均匀沉积了粒径为20 nm的Al2O3涂层,然后采用电镀技术在Al2O3涂层中沉积金属镍,得到具有较高含量的纳米Al2O3增强镍基复合镀层;用扫描电镜及附带的能谱仪分析了镀层的表面形貌及成分,研究了镀层在干摩擦条件下的摩擦磨损性能,并对其磨损机理进行了探讨.结果表明:相比于纯镍镀层,纳米Al2O3颗粒增强镍基复合镀层的表面更加平整光滑,组织更加致密均匀;镀层中纳米Al2O3颗粒含量对镀层耐磨性能具有显著影响,当其体积分数约为30%时,镀层的耐磨性能最好.     

Interlayer thickness influence on the tribological response of bi-layer coatings

The present work deals with the influence of coating thickness on the tribological response of bi-layer model coatings consisting of CrN with Cr interlayer with varying Cr/CrN thickness ratios on high-speed steel. Ball-on-disc experiments were carried out in ambient air at room temperature and alumina balls as counterbodies. The mechanical stresses in both layers generated during the tests were calculated with the software package Elastica. Wear tracks on the samples were characterised using both scanning electron microscopy and optical profilometry. The results show that the interlayer thickness plays a determinant role in the tribological response of the coatings provided that the CrN layer thickness exceeds a critical value to withstand mechanical wear.     

The tribological behaviour of electroless Ni-P-Gr-SiC composite

The tribological behaviour and wear mechanism of Ni-P-Gr (graphite)-SiC (manufactured by electroless plating) is surveyed in this paper. The worn surface, wear debris and the compositional changes that take place during wear were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX). By comparison with Ni-P-Gr and Ni-P-SiC, the results indicate that hybrid Ni-P-Gr-SiC composite presented well anti-friction and wear resistance which is resulted from a graphite-rich mechanical mixed layer (GRMML) formed on the contact surface. Hard SiC particles mixed with GRMML played a load-bearing role at high load when relative motion occurs. After heat treatment at 400 °C for 1 h, the wear rate of the hybrid composite decreased with an increase in microhardness. During sliding, the temperature of the hybrid composite occured less change than Ni-P-SiC coating and further guaranteed the stable state of the whole wear process.     

A study of mirror-like grinding of fine ceramics with in-process electrolytic dressing

Fine ceramics have the properties of high hardness, chemical inertness, high thermal resistance and low electrical conductivity, but, because of high hardness and brittleness, they are very difficult to machine. Therefore, a superabrasive diamond wheel is used for mirror-like grinding of this material. In this study, an in-process electrolytic dressing system for carrying out mirror-like surface grinding was constructed. Using this system the grinding force for fine ceramics was reduced. This work shows that the application of electrolytic dressing is beneficial in obtaining a mirror-like surface when grinding fine ceramics.     

Structural and tribological characterization of tungsten nitride coatings at elevated temperature

Transition metal nitrides exhibit excellent mechanical properties (hardness and Young's modulus), high melting point, good chemical stability and high electrical conductivity. However, tungsten nitrides still stand aside of the main attention. In our previous study, tungsten nitride coatings with different nitrogen content showed excellent wear resistance at room temperature. Nevertheless, many engineering applications require good tribological properties at elevated temperature. Thus, the present study is focused on the tribological behaviour (friction coefficient and wear rate) of tungsten nitride coatings at temperature up to 600 °C.

The structure, hardness, friction and wear of tungsten nitride coatings with nitrogen content in the range 30–58 at.% prepared by dc reactive magnetron sputtering were investigated. The tribological tests were performed on a pin-on-disc tribometer in terrestrial atmosphere with Al₂O₃ balls as sliding partner. The coating wear rate was negligible up to 200 °C exhibiting a decreasing tendency; however, the wear dramatically increased at higher temperatures. The coating peeled off after the test at 600 °C, which is connected with the oxidation of the coating.     

Investigation of mechanical and tribological properties of amorphous diamond-like carbon coatings

We investigated the mechanical and tribological properties of amorphous diamond-like carbon (DLC) coatings deposited on Si(100) by a pulsed bias deposition technique. Tribological studies were performed using a pin-on-disc (POD) apparatus under a normal load of 6.25 N and at 10% relative humidity, with a ruby pin as a slider. Hardness measurements were performed using a nanoindenter and apparent fracture toughness using indentation techniques. We studied the influence of residual stresses on apparent fracture toughness. The data revealed that the thickness, hardness and compressive stress of the coating play different roles in the apparent fracture toughness. Crack initiation is influenced by the thickness and hardness of the coating, whereas crack propagation is influenced by the compressive stress in the film. The apparent fracture toughness of DLC coatings increased with coating hardness.