基体负偏压对CrAlN涂层组织和性能的影响

采用真空多弧离子镀技术,使用Cr30Al70(原子分数)复合靶,在不同的基体负偏压下,在不锈钢基体上制备了一系列CrAlN涂层;采用能谱仪、X射线衍射仪、扫描电子显微镜、粗糙度仪、显微硬度仪、摩擦磨损试验机和划痕仪等系统分析了涂层的成分、表面形貌、相结构、粗糙度、显微硬度、摩擦磨损性能和界面结合性能。结果表明:随着负偏压的增大,涂层中x(Cr)/x(Cr+Al)的比值先增大后减小,当负偏压为150V时,该值达到最大,并与靶材成分接近;基体负偏压为200V时,涂层的表面粗糙度最大,涂层结晶度、硬度最佳,晶体相为固溶铬的面心立方AlN;涂层的摩擦磨损性能不仅与涂层的表面粗糙度相关,还与涂层非晶相中铝元素的含量以及涂层的内应力大小密切相关;界面过渡层制备工艺相同时,基体偏压对涂层和基体之间的界面结合性能影响较小。     

Impact of Wire-EDM on Tribological Characteristics of ZrO<Subscript>2</Subscript>-based Composites in Dry Sliding Contact with WC–Co-Cemented Carbide

In the present investigation, experiments were conducted by unidirectional sliding of pins made of FCC metals (Pb, Al, and Cu) with significantly different hardness values against the steel plates of various surface textures and roughness using an inclined pin-on-plate sliding apparatus in ambient conditions under both the dry and lubricated conditions. For a given material pair, it was observed that transfer layer formation and the coefficient of friction along with its two components, namely adhesion and plowing, are controlled by the surface texture of the harder mating surfaces and are less dependent of surface roughness (R _a) of the harder mating surfaces. The effect of surface texture on the friction was attributed to the variation of the plowing component of friction for different surfaces. It was also observed that the variation of plowing friction as a function of hardness depends on surface textures. More specifically, the plowing friction varies with hardness of the soft materials for a given type of surface texture and it is independent of hardness of soft materials for other type of surface texture. These variations could be attributed to the extent of plane strain conditions taking place at the asperity level during sliding. It was also observed that among the surface roughness parameters, the mean slope of the profile, Δ _a, correlated best with the friction. Furthermore, dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing taking place at the asperity level.     

Investigation of antiwear coatings deposited by the pvd process

The tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr₂N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al₂O₃ ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics. It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN. A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.     

Architecture of Multilayer Cr/CrN Coatings for Wear Protection in Seawater: Cr/CrN Ratio and Total Thickness

Cr/CrN multilayer coatings with various Cr/CrN thickness ratios and total thicknesses were deposited on 316L stainless steel by multi-arc ion plating. The coatings were systematically characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and nanoindentation. Tribological behaviors were investigated using a ball-on-disk tribometer in artificial seawater. The results showed that the multilayer coating phases changed from Cr₂N + CrN to Cr + Cr₂N + CrN phases with an increase in Cr/CrN thickness ratio. The adhesion showed a slight difference for the coatings with different thickness ratios but significantly increased with total thickness. The hardness was also slightly improved by thickening the coatings. The friction coefficient and wear rate were lowest at a thickness ratio of about 0.3. However, there was no large difference in the friction coefficient between coatings with different thicknesses. The wear rate was lower for the thicker coatings under various loads. The load-bearing capacity was also improved by thickening the coatings.     

Thick rutile layer on titanium for tribological applications

In the present work, efforts have been made to oxidise the titanium surface, followed by very slow cooling to produce a thick and adherent oxide layer. The response of titanium to oxidation at various temperatures and timings has been investigated, in terms of layer thickness, phase evolution, surface morphology, oxide layer–substrate adhesion, hardness and tribological characteristics. A variety of experimental and analytical techniques, including X-ray diffraction, field-emission scanning electron microscopy, scanning electron microscopy, micro-hardness and tribological testing, have been used to characterise the resultant thermal oxidised surfaces. The results showed that a thick oxide layer with rutile TiO₂ and oxygen diffused Ti structure can be produced, which exhibited excellent adhesion with the titanium substrate, low friction and superior wear resistance during pin-on-disc sliding tests and thus good potential for tribological applications.     

Microstructure and tribological behaviour of nitrocarburizing-quenching duplex treated steel

This paper explores salt bath nitrocarburizing and nitrocarburizing-quenching duplex treatment technologies. For comparison, a quenching-tempering treatment was also conducted. By means of metallographic examination, microhardness tests and X-ray diffraction analysis, the microstructures, phase structures, surface hardnesses and hardness profiles of 1045 steel treated by several techniques were investigated. The ball-on-block and ring-on-block apparatuses were employed to investigate the friction coefficient and wear-resistance respectively. The surface roughness was also measured by a profilometer. The experimental results indicate that a higher sub-surface hardness and a superior hardness profile are obtained by nitrocarburizing-quenching duplex process. This in turn improves the wear-resistance and fatigue strength, although the surface hardness is somewhat lower compared with that obtained by nitrocarburizing. It also demonstrates that the -phase formed on the steel surface has significant effects on reducing friction and improving wear-resistance. X-ray diffraction analysis shows that the phases at the nitrocarburized specimen surface are mainly -compound [Fe₃(N,C)] and small amounts of Fe₄N(γ′) and Fe_2–3(N,C). While the phases at the nitrocarburized-quenched specimen surface are very different from those at the nitrocarburized specimen. In this case, the -compound has decomposed almost completely and the nitrogen and carbon diffuse to the γ-Fe at the temperature of quenching to form the supersaturated solid solution which will become martensite containing nitrogen and carbon along with retained austenite after subsequent water cooling.     

甘油润滑下CrCN涂层的超低摩擦特性

为开发与CrCN涂层具有良好配伍润滑性能的绿色润滑剂,使用磁控溅射技术在304不锈钢表面沉积CrCN涂层,利用场发射扫描电子显微镜、原子力显微镜、纳米压痕仪、维氏硬度计、X射线衍射仪、X射线光电子能谱仪分别对其表面形貌、涂层厚度、力学性能、物相组成以及元素化学价态进行分析,并借助多功能摩擦磨损试验机评价在甘油润滑下CrCN涂层的摩擦学性能,并与PAO6润滑下结果进行比较。利用磁控溅射技术在不锈钢表面构筑的CrCN涂层表面光滑致密,粗糙度仅为1.01 nm,硬度可达14.39 GPa。对比钢-钢和钢-CrCN体系的摩擦学性能发现,钢-CrCN体系在甘油润滑下展现出优异的润滑性能;当负载为0.5 N时,钢-CrCN体系在甘油润滑下的摩擦因数可低至0.01,大大低于PAO6润滑下的摩擦因数。对磨痕的XPS分析表明,在摩擦过程中,甘油发生摩擦化学反应,在CrCN涂层的接触表面生成一层FeOOH层,甘油分子及其降解产物可能进一步吸附在FeOOH层,形成流体润滑层,有效降低了摩擦和磨损。     

High-temperature low-friction properties of vanadium-alloyed AlCrN coatings

V-alloyed AlCrN hard coatings were deposited by reactive arc-evaporation in a commercial Balzers RCS coating system. The Al/(Al + Cr + V) atomic ratio in the target was kept constant at 0.7, while the Cr was stepwise substituted by V. Alloying V into the AlCrN coatings led to the partial transformation to a hexagonal phase of the otherwise metastable cubic lattice, whereas the hexagonal phase fraction was observed to increase with the V concentration in the coating. This results in a reduction of hardness (from 28 to 19 GPa) and biaxial coating stress (from − 1700 to − 900 MPa). The performed tribological tests at high temperature revealed a significantly lower coefficient of friction down to a value of 0.2 for Al_0.67Cr_0.05V_0.28N at 700 °C. This behaviour is due to the formation and melting of the Magnéli phase oxide V₂O₅ forming a low-friction layer on the surface as indicated by Raman spectroscopy and scanning electron microscopy.     

Microstructure and Wear Resistance of Fe-Cr-C Hardfacing Alloy Reinforced by Titanium Carbonitride

In order to improve the wear resistance of Fe-Cr-C hardfacing alloy, titanium carbonitride was introduced in situ and a TiC-Ti_x(C,N)_y coating was deposited on the surface of ASTM G3101 steel by a gas metal arc welding process. The microstructure and wear resistance of the hardfacing layer were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), macroscopic hardness meter, spectrometry, and transmission electron microscopy (TEM). The results show that the hardfacing layers mainly consist of (Cr,Fe)₇C₃, TiC carbides, Ti_x(C,N)_y carbonitrides, and α-Fe (C_0.14Fe_1.86 and C_0.12Fe_1.88 martensite) (BCT) in addition to a low content of retained CFe_15.1 austenite (FCC). The titanium carbonitride–reinforced coating has high hardness and excellent wear resistance under dry sliding wear test conditions.     

铁素体不锈钢激光熔覆层组织和性能研究

采用无碳合金粉末和低碳合金粉末对铁素体不锈钢进行激光表面熔覆处理,借助光学显微镜(Optical microscope,OM)、扫描电子显微镜(Scanning electron microscopy,SEM)、能谱分析仪(Energy dispersive spectrometry,EDS)、X射线衍射仪(X-ray diffractometry,XRD)、显微硬度仪、摩擦磨损试验仪、电化学工作站对熔覆层显微组织、化学成分、硬度、耐磨性和耐蚀性进行评价。结果表明,两种激光熔覆层均无裂纹、气孔等宏观缺陷,显微组织主要由等轴晶、包状晶、树枝晶和枝间共晶组成。无碳熔覆层与低碳熔覆层均含有α-Fe、Fe-Cr合金相、Cr单质相以及Cr_(9.1)Si_(0.9)、Fe_(9.7)Mo_(0.3)、Fe_(10.8)Ni、Fe_(19)Mn等金属间化合物。此外,低碳熔覆层还产生了间隙化合物Cr_7C_3以及马氏体相C_(0.055)Fe_(1.945)。低碳熔覆层硬度为750 HV0.5,显著高于母材硬度250 HV0.5;无碳熔覆层硬度为650 HV0.5,其热影响区发生软化。激光熔覆层相对于母材具有更为稳定的摩擦特性以及优异的耐磨性和耐蚀性,其中低碳熔覆层耐磨性和耐蚀性均优于无碳熔覆层。     

Performance and surface alloying characteristics of Cu–Cr and Cu–Mo powder metal tool electrodes in electrical discharge machining

The main objective of this study is to investigate the effect of Cu–Cr and Cu–Mo powder metal (PM) tool electrodes on electrical discharge machining (EDM) performance outputs. The EDM performance measures used in the study are material removal rate (MRR), tool electrode wear rate (EWR), average workpiece surface roughness (R_a), machined workpiece surface hardness, abrasive wear resistance, corrosion resistance, and workpiece alloyed layer depth and composition. The EDM performance of Cu–Cr and Cu–Mo PM electrodes produced at three different mixing ratios (15, 25, and 35 wt% Cr or Mo), compacting pressures (P_c = 600, 700, and 800 MPa), and sintering temperatures (T_s = 800, 850, and 900 °C) are compared with those machined with electrolytic Cu and Cu PM electrodes when machining SAE 1040 steel workpiece. Analyses revealed that tool materials were deposited as a layer over the work surface yielding high surface hardness, strong abrasion, and corrosion resistance. Moreover, the mixing ratio, P_c, and T_s affect the MRR, EWR, and R_a values.     

Tribological properties of plasma nitrided stainless steel against SAE52100 steel under ionic liquid lubrication condition

1Cr18Ni9Ti stainless steel was modified by plasma nitriding. The phase composition of the plasma nitrided layer was examined by means of X-ray diffraction. The friction and wear properties of the modified and unmodified 1Cr18Ni9Ti stainless steel specimens sliding against SAE52100 steel under the lubrication of ionic liquid of 1-ethyl-3-hexylimidazolium hexafluorophosphate (L-P308) and poly α-olefin (PAO) were investigated on an Optimol SRV oscillating friction and wear tester, with the interactions among the modified surface layer and the ionic liquids and PAO to be focused on. The morphologies of the worn surfaces were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces of the modified steel surfaces were examined by means of X-ray photoelectron spectroscopy. Results showed that the modified sample had better anti-wear abilities than the unmodified one, but the modified sample had a slightly higher friction coefficient than the untreated one. This was partly attributed to the change in the hardness and phase composition of the stainless steel surfaces after plasma nitriding and tribochemical reactions between the steel and the lubricant. The resultant surface protective films composed of various tribochemical products together with the adsorbed boundary lubricating film contributed to reduce the friction and wear.     

Evaluation of Local Mechanical Properties in Depth in MoDTC/ZDDP and ZDDP Tribochemical Reacted Films Using Nanoindentation

Local mechanical properties in depth and near the surface of MoDTC/ZDDP and ZDDP tribofilms, which exhibited obviously different friction coefficients in a pin-on-disc test, were determined by using a nanoindentation technique combined with in-situ atomic force microscopy (AFM) observation. Tapping-mode AFM observation revealed that the MoDTC/ZDDP film was much rougher than the ZDDP film. Nanoindentation measurement revealed that the MoDTC/ZDDP and ZDDP tribofilms possessed different elasto-plasticities around a depth of several nanometers from the surface, although both films showed the same hardness and modulus depth distributions except in the surface area. The same mechanical depth distributions indicated that both kinds of tribofilm were functionally graded materials; that is, they consisted of a layer near the surface with lower hardness and modulus and providing lubrication and a base layer with higher hardness and modulus and serving to modify property differences at the interface. Most importantly, the different elasto-plasticities near the tribofilm surfaces revealed that the MoDTC/ZDDP tribofilm possessed lower shearing yield stress than the ZDDP tribofilm. The results of this study suggest that the presence of some solid lubricants such as MoS₂ just below the MoDTC/ZDDP film surface reduced the boundary friction coefficient.     

Influence of surface texture and roughness parameters on friction and transfer layer formation during sliding of aluminium pin on steel plate

Surface texture of harder mating surfaces plays an important role during sliding against softer materials and hence the importance of characterizing the surfaces in terms of roughness parameters. In the present investigation, basic studies were conducted using inclined pin-on-plate sliding tester to understand the surface texture effect of hard surfaces on coefficient of friction and transfer layer formation. A tribological couple made of a super purity aluminium pin against steel plate was used in the tests. Two surface parameters of steel plates, namely roughness and texture, were varied in the tests. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely, the adhesion and plowing, are controlled by the surface texture and are independent of surface roughness (R_a). Among the various surface roughness parameters, the average or the mean slope of the profile was found to explain the variations best. Under lubricated conditions, stick–slip phenomena was observed, the amplitude of which depends on the plowing component of friction. The presence of stick–slip motion under lubricated conditions could be attributed to the molecular deformation of the lubricant component confined between asperities.     

Optimizing the PVD TiN thin film coating’s parameters on aerospace AL7075-T6 alloy for higher coating hardness and adhesion with better tribological properties of the coating surface

An optimization study on the parameters of titanium nitride coating on aerospace Al7075-T6 alloy, using magnetron sputtering technique is presented. The effects of the temperature, DC bias voltage, rate of nitrogen, and DC power on the surface hardness, adhesion, surface roughness, and microstructure of the coated samples are investigated. Taguchi optimization method is used with the orthogonal array of L₁₆ (4⁴). However, to obtain the most optimum parameters for the best surface hardness, adhesion, and surface roughness, the signal to noise (S/N) response analysis method is implemented. Finally, the confirmation tests were carried out to show the improvement using the best parameters combination obtained from the optimization process. The improvement of 14?% in surface hardness, 4.15?% in adhesion, and 9.43?% in surface roughness are achieved.     

Reducing Friction Force of Si Material by Means of Atomic Layer-Deposited ZnO Films

With excellent lubricating property, zinc oxide (ZnO) films are promising candidates to act as protective coatings in Si-based microelectromechanical system devices for the purpose of decreasing friction forces of silicon (Si) material. In this paper, the nanotribological behavior of ZnO films prepared by atomic layer deposition on a Si (100) substrate is investigated by an atomic force microscope. The ZnO films have various thicknesses ranging from 10.0 to 182.1 nm. With the increase of film thickness, the root-mean-square roughness of the films increases, while the ratio of hardness to Young’s modulus (H/E) decreases. Due to their large surface roughness, the thick ZnO films are low in adhesion force. The friction force of the ZnO films is smaller than that of the Si (100) substrate and is greatly influenced by their adhesion force and mechanical property. In a low-load condition, the friction force is dominated by the adhesion force, and thus, the friction force of the ZnO films decreases as film thickness increases. While in a high-load condition, the friction force is dominated by plowing. Films with higher H/E possess smaller friction force, and thus, the friction force increases with the decreasing film thickness.     

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.     

Tribological behaviour and microstructure of TiCxN(1−x) coatings deposited by filtered arc

A series of macroparticle-free TiN, TiC_xN_(1−x) and TiC coatings were deposited on 316 austenitic stainless steel using a titanium target in a filtered arc deposition system (FADS) and reactive mixtures of N₂ and/or CH₄ gases. The surface topography, chemical composition and microstructure of these coatings were characterised by optical microscopy (OM), atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The microhardness has been measured and the adhesion of the coatings has been evaluated. Further, the wear and friction behaviour of the coatings were assessed under controlled test conditions in a pin-on-disc tribometer.The results show a significant increase in surface roughness, microhardness and wear resistance as the CH₄:N₂ gas flow rate ratio is increased. The composition of the coatings was strongly dependent on reactive gas flow rate during deposition. Surface particles were observed on high carbon content coatings and subsequently determined to be carbonaceous particles by using OM, AFM and EDS. At lowest load (10 N), all coatings exhibited low friction and wear. At loads of 15 and 25 N, the higher carbon content TiCN and TiC coatings showed a much lower friction and wear compared to TiN and low carbon TiCN.     

Tribological Dependence of the High-Performance Ferrous-Based Coating on Different Coating Counterparts in Engine Oil

A ferrous-based coating with significant chromium was fabricated on aluminum alloy substrate using a plasma spray technique. The tribological performance of the as-fabricated ferrous-based coating sliding against different coatings including Cr, CrN, TiN, and diamond-like carbon (DLC) in an engine oil environment were comparatively studied. Results showed that the high hardness of the sprayed ferrous-based coating was achieved due to the dispersion strengthening effect of Cr₇C₃ phase embedded in the austenite matrix. The ferrous-based coating exhibited low friction coefficients when coupled with these four coating counterparts, which could be attributed to the boundary lubricating effect of engine oil. However, both friction and wear of the ferrous-based coating were different when sliding against these different coating counterparts, which might be closely related to the surface roughness, self-lubricating effect, and mechanical properties of the coupled coatings. Ferrous-based coating sliding against CrN and DLC coatings exhibited good tribological performance in engine oil. The best coating counterpart for the ferrous-based coating in an engine was DLC coating.     

Tribological and mechanical investigation of SiO2 and Si3N4 coatings on fused silica and borosilicate glass

Amorphous SiO₂ and Si₃N₄ plasma‐enhanced chemical vapour deposited (PECVD) coatings were deposited on two different substrate materials (fused silica and borosilicate glass), with three coating thicknesses (0.1, 0.5, and 1.0 μm). The mechanical properties (hardness and elastic modulus) were determined by depth‐sensing indentation, with loads from 700 mN down to 0.1 mN. Tribological behaviour was studied in instrumented oscillating sliding tests at room temperature with a ball‐on‐flat arrangement, in which the coated disc was tested against an alumina ball, at a load of 1 N. Interpretation of the measurement of hardness and modulus of the coatings has to take into consideration the influence of layer thickness and the effect of the substrate. Tensile film stress and crack generation were only observed for Si₃N₄ on fused silica above a threshold thickness. Friction and wear measurements show that the coating has an effect on friction, while wear is affected by the thin coatings only for a short running‐in phase. The morphology of the wear scars indicates that the coatings have good adhesion. Despite crack generation, delamination effects were not observed. Indentation patterns similarly showed excellent lateral homogeneity of the mechanical properties over the entire film surface, and indicated that load‐displacement curves may be used to characterise the system.