等离子喷涂纳米氧化锆涂层摩擦性能研究

利用大气等离子喷涂技术,在不锈钢基体上用不同颗粒尺寸的纳米粉末制备了两种纳米氧化锆涂层S1(平均粒度较小颗粒的喷雾造粒粉末所得)和B1(平均粒度较大颗粒的喷雾造粒粉末所得).运用XRD、SEM、TEM、拉曼光谱和金相技术等分析手段对喷涂用的粉末原料和涂层的显微结构、物相组成进行了观察与确定;利用环-块摩擦试验在干摩擦条件下对涂层的摩擦磨损性能进行了测试.结果表明,两种氧化锆涂层的摩擦系数均随载荷增大而减小.在较低载荷(100 N)条件下,S1涂层与不锈钢的摩擦系数低于B1涂层与不锈钢的摩擦系数;而在较高(400 N)载荷下,两种氧化锆涂层的摩擦系数开始趋于一致.其原因在于:较低的载荷下两种涂层与不锈钢摩擦副的摩擦磨损机制不同,S1涂层的磨损属于粘着磨损,B1涂层的磨损属于磨粒磨损;而在较高载荷下,两种涂层的磨损机制趋于一致,均为粘着磨损.     

等离子喷涂法制备铁基硬质涂层的力学性能

为了在碳钢表面制备耐磨涂层,使涂层与基体的膨胀系数相近,减少涂层应力,将80％ Fe,13％P,7％C(质量分数,％)机械混合粉末进行等离子喷涂,制备铁基耐磨涂层.采用粘结剂对偶试样拉伸试验法测定涂层结合强度,采用表面显微硬度法分析涂层硬度,采用MMW-2型(高温)摩擦磨损试验机以40Cr硬质合金为对磨材料对涂层进行耐磨性试验.结果表明,涂层的结合强度平均值为29.16 MPa,显微硬度的平均值为7.889 MPa,高于陶瓷涂层硬度值,涂层的耐磨性能较好,磨损200 min后,涂层的磨损量在36 mg左右,磨损量约为对磨件的1/13,涂层磨损主要为磨粒磨损机制.     

Tribological properties of molybdenum coatings sprayed by electro-thermal explosion directional spraying

The microstructure and the mechanical properties of the electro-thermal explosion directionally sprayed molybdenum coatings were determined by means of SEM, XRD and microhardness tester, respectively. Experiments on the tribological property of the coatings were performed using a ring-on-block type wear tester. Results showed that the molybdenum coatings were characterized by compact microstructure, high bonding strength and high wear resistance. The applied loads and the counterpart's hardness have an obvious influence on the tribological properties of the coatings. Several wear failure modes, such as micro-plowing and pits, were identified in the post-testing analysis.     

Mechanical, tribological and erosion behaviour of super-elastic hard Ti-Si-C coatings prepared by PECVD

Titaniun carbide (TiC) based coatings prepared by low temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) are investigated as attractive candidates for wear resistance, and particularly for protection against solid particle erosion. In the present work, we incorporated silicon (Si) as an alloying element to TiC, to obtain ternary nanostructured Ti-Si-C films. The incorporation of Si in TiC resulted in significant microstructural, mechanical and tribological modifications. By controlling the Si content in the films, we observed a transition between films consisting of fine nano-sized TiC crystallites (nc-TiC) embedded in an amorphous C:H matrix (a-C:H) to a microstructure formed by nc-TiC encapsulated in a-SiC/a-C:H matrix. This allowed one to selectively control the main mechanical characteristics, namely the hardness (H), the Young's modulus (E), and the friction coefficient (μ), in the range of 14-32 GPa, 140-240 GPa, and 0.16-0.6, respectively. For films prepared under optimized conditions, high elastic strain to failure and high resistance to plastic deformation of the Ti-Si-C films, expressed by H/E and H³/E² ratios, resulted in an 8 fold increase of the erosion resistance at an impact angle of 90° compared to a bare steel substrate. Erosion resistance at 30° increased by a factor of 22 compared to bare substrate due to a simultaneous combination of high H and low μ. Taking into consideration the severe erosion test conditions and the Ti-Si-C film thickness of less than 5 μm in this work, further improvement is expected for thicker films.     

Characterization and wear properties of nanoscaled TiN/TaN multilayer coatings

The structural, morphological, mechanical and tribological characterization of nanoscaled multilayer TiN/TaN coatings deposited by magnetron sputtering technology were investigated by low angle X-ray diffractometry, high angle X-ray diffractometry, atomic force microscopy, microhardness, pin-on-disc testing and 3-D surface profiler. The results show that the TiN/TaN coatings exhibit good modulation period and sharp interface between TiN and TaN layers. In mutilayered TiN/TaN coatings, TiN layers have cubic structure, but hexagonal structure emerged among TaN layers besides cubic structure as modulation period is beyond 8.5 nm. The mierohardness is affected by modulation period and the maximum hardness value of 31.5 GPa appears at a modulation period of 8.5 rim. The coefficient of friction is high and the wear resistance is improved for TiN/TaN coatings compared with those of TiN coating; the wear mechanism exhibits predominantly ploughing, material transfer and localized spallation.     

Tribological properties of Cr- and Ti-doped MoS2 composite coatings under different humidity atmosphere

Solid-lubricant MoS₂ coatings have been successfully applied in high vacuum and aerospace environments. However, these coatings are very sensitive to water vapor and not suitable for applications in moist environments. In this work, Cr- and T-doped MoS₂ composite coatings were developed. The results demonstrated that these composite coatings are promising for applications in high humidity environments.MoS₂-Cr and MoS₂-Ti composite coatings with different Cr or Ti content were deposited on high speed steel substrate by unbalanced magnetron sputtering. The composition, microstructure, and mechanical properties of the as-deposited MoS₂-metal composite coatings were analyzed by energy dispersive analysis of X-ray (EDX), X-ray diffraction (XRD), and nanoindentation experiments. The tribological properties of the coatings were evaluated against an alumina ball under different relative humidity atmosphere using a ball-on-disc tribometer. The MoS₂-Cr and MoS₂-Ti coatings showed a maximum hardness of 7.5 GPa and 8.4 GPa at a dopant content of 16.6 at.% Cr or 20.2 at.% Ti, respectively. The tribological test results showed that, with a small amount of Cr and/or Ti doping, the tribological properties of MoS₂ coatings under humid atmosphere could be significantly improved. The optimum doping level was found to be around 10 at.% for both MoS₂-Cr coatings and MoS₂-Ti coatings to show the best tribological properties, with both the lowest friction coefficient and wear rate. The excellent tribological properties of the MoS₂-Cr and MoS₂-Ti coatings with an appropriate metal doping level in moist atmosphere are found due to their ability to form stable transfer layer on the surface of the counterbody, which supplies lubrication for the contact surface.     

Recycled hard metal-base wear-resistant composite coatings

The abrasion-erosion wear resistance of composite coatings from self-fluxing Ni-base alloy and WC-Co hard metal powders is evaluated. The resistance of thermal sprayed and melted NiCrSiB-(WC-Co) coatings was found to be markedly higher than that of NiCrSiB and slightly higher than that of comparative welded coatings. Microstructural and surface analyses were used to describe the coatings and the wear damage. Based on the principles of creating wear-resistant coatings and on experimental studies of wear resistance, high wear-resistant, composite NiCrSiB-(WC-Co) coatings were fabricated. These coatings exhibited 300% higher wear resistance than 0.45% C steel.     

Optimum Me-DLC coatings and hard coatings for tribological performance

In this study, hard coatings (TiN, TiCN, CrN, and CrCN) and Me-DLC coatings (Ti _x%-C:H and Cr _x%-C:H) were deposited on tungsten carbide (WC) substrate by multiarc physical vapor deposition (MAPVD) and unbalanced magnetron (UBM) sputtering, respectively. Counterbodies of the AISI 1045 steel cylinder and the AA7075T651 aluminum cylinder were used in the cylinder-on-disk, line-contact wear mode under dry condition; a counterbody of the AISI 52100 steel ball was used in the ball-on-disk, point-contact wear mode, under both dry and lubricated conditions. All wear tests were conducted with a reciprocating machine. After the tests, the most suitable coating for various counterbodies and test environments was selected. For the coating/1045 steel cylinder, the Ti_10%-C:H coating possesses excellent tribological characteristics. For the coating/7075T651 aluminum cylinder, hard coatings display excellent wear resistance. For the coating/steel ball, CrCN and CrN coatings display very little wear under both dry and lubricated conditions. On TiN and TiCN coatings, special wear mechanisms of material transfer, adhesion wear, and fatigue fracture occurred during initial tests under kerosene lubrication.     

Tribological properties of TiAlN-coated cermets

Ti(C,N)-based cermets were coated with TiAlN using multi-arc ion plating technology. Sliding wear tests were performed on the coated cermets. The microstructure and morphologies of the coated cermets before and after friction and wear tests were characterized. The results show that the TiAlN coating surface was smooth and its root mean square roughness was 16.6 nm. The hardness (HK) of TiAlN coating layers reached approximately 3200 and the critical load (L _c) under which the coating failure occurred was 59 N. The sliding wear test results show that the friction coefficients of the TiAlN-coated cermets were lower than that of the cermets without any coating. Under the same load, the adhesion phenomenon of the counterpart materials on the specimens was improved and the mean friction coefficient increased with increasing sliding velocity. When the sliding velocity was 0.26 m·s⁻¹, the mass of the coated cermets reduced. At the same sliding velocity, the average friction coefficient of the TiAlN-coated cermets was lower under a higher load. The wear mechanisms of the TiAlN-coated cermets were mainly adhesive and abrasive wear.     

Tribological properties of TiA1N-coated cermets

Ti(C,N)-based cermets were coated with TiAlN using multi-arc ion plating technology. Sliding wear tests were performed on the coated cermets. The microstructure and morphologies oftbe coated cermets before and after friction and wear tests were characterized. The results show that the TiAlN coating surface was smooth and its root mean square roughness was 16.6 nm. The hardness (HK) of TiAlN coating lay-ers reached approximately 3200 and the critical load (Lc) under which the coating failure occurred was 59 N. The sliding wear test results show that the friction coefficients of the TiAlN-coated cermets were lower than that of the cermets without any coating. Under the same load, the adhesion phenomenon of the counterpart materials on the specimens was improved and the mean friction coefficient increased with in-average friction coefficient of the TiAlN-coated cermets was lower under a higher load. The wear mechanisms of the TiAIN-coated cermets were mainly adhesive and abrasive wear.     

Thermally sprayed wear resistant coatings with nanostructured hard phases

The aim of this investigation was the development of a new quality of thermally sprayed coatings with high resistance against wear and corrosion and to evaluate the application potential of nano-sized hard phases in thermally sprayed layers. The newly developed material consists of a highly corrosion-resistant matrix of stainless steel (even without nickel) combined with nano-structured hard phases of vanadium nitrides (VN). On the other hand, matrices consisting of cobalt-chromium (CoCr) with submicron hard phases of tungstencarbides (WC) were investigated with respect to microstructure and wear resistance compared with conventional ones.     

TiC颗粒增强镍基合金复合涂层的摩擦学性能(英文)

运用等离子喷涂技术制备了TiC颗粒增强镍基合金复合涂层,分析了TiC颗粒增强镍基合金复合涂层的微观结构,研究了其摩擦磨损行为与机理。结果表明:TiC颗粒增强镍基合金复合涂层主要由γ-Ni,CrB,Cr7C3和TiC构成;复合涂层与基底材料间形成了厚度为9.4μm的过渡层,达到了冶金结合。当TiC颗粒含量为30%(体积分数)时,复合涂层的摩擦系数和磨损率均最低,即其摩擦系数为0.33,较纯镍基合金涂层降低了30%;其磨损率为0.3×10-3mm3/m,是纯镍基合金涂层的1/3。当载荷在6～10N的范围内时,复合涂层呈轻微磨损,其磨损机理主要为粘着磨损;当载荷达到12N时,复合涂层产生严重磨损,其磨损机制转变为硬质相的脱落和转移层的层脱剥落。     

Tribological properties of titanium aluminides coatings produced on pure Ti by laser surface alloying

Titanium aluminides coatings were in-situ synthesized on a pure Ti substrate with a preplaced Al powder layer by laser surface alloying. The friction and wear properties of the titanium aluminides coatings at different normal loads and sliding speeds were investigated. It was found that the hardness of the titanium aluminides coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating. Friction and wear tests revealed that, at a given sliding speed of 0.10 m/s, the wear volume of pure Ti and the titanium aluminum coatings all increased with increasing normal load. At a given normal load of 2 N, for pure Ti, its wear volume increased with increasing sliding speed; for the titanium aluminides coatings, the wear volume of Ti₃Al coating and TiAl coating first increased and then decreased, while the wear volume of TiAl₃ coating first decreased and then increased with increasing sliding speed. In addition, the friction coefficients of pure Ti and the titanium aluminides coating decreased drastically with increasing sliding speed. Under the same dry sliding test conditions, the wear resistance of the titanium aluminium coatings was in the following order: Ti₃Al coating > TiAl coating > TiAl₃ coating.     

含Ag硬质涂层的结构及其摩擦腐蚀与抗菌特性的研究进展

从含Ag元素的硬质涂层入手,综述了二元含Ag的Ag-DLC涂层到三元含Ag的CrN/Ag、TiN/Ag、ZrN/Ag涂层,再到多元含Ag的CrSiN/Ag、TiCN/Ag、ZrCN/Ag等涂层的研究进展,分析了不同制备技术和参数、不同元素添加等手段对涂层结构、摩擦腐蚀及抗菌特性的影响.在含Ag硬质涂层从二元到多元的研究过程中,发现元素的含量和制备参数会对涂层的微观组织结构产生重要的影响,并且Ag元素的含量极大地影响着硬质涂层的摩擦学特性、耐腐蚀性能和抗菌性.已有研究表明:低剪切强度的软质Ag相的添加往往能提高涂层的耐磨特性,故将具有高热化学稳定性的Ag固体润滑剂与高耐磨性的硬质涂层相结合,可以改善硬质涂层的摩擦学特性;少量的Ag元素添加可以保持或略微改善涂层的耐腐蚀性能,但是掺杂较高含量的Ag会使硬质涂层的耐腐蚀性能降低;同时,Ag元素对能够引起金属腐蚀的细菌有很好的抗菌效果,且是对环境和人体安全性好的金属元素.若能在金属部件表面沉积含Ag的纳米复合涂层,可以满足水润滑部件耐磨和防污的使用要求.研究在水环境中具有耐磨、抗生物腐蚀的含Ag纳米复合涂层,有利于对机械工程设备中关键零部件的保护,对于海洋开发和社会发展具有重大意义.     

Manufacture and properties of composite coatings: An introduction

Composite layers are capable of varying surface properties of parts over wide ranges. The galvanic route and thermal spraying are predestined to create composite layers. Wear resistance can be realized by a metallic matrix and nonmetallic reinforcing component that serves as a disperse phase. The goal of this article is to report on experimental results gained from samples produced galvanically. Improved wear resistance and hardness of the composite layers are main topics. The thermal spray process requires more sophisticated processing techniques if the desired components cannot be supplied by individual injectors or mechanically premixed. In cases where pneumatic material feed (e.g., carbon short fibers) is not possible, the material supply must be achieved by agglomerated powders containing the second phase as a constituent. Suitable agglomerated powders allow a control of thermal decomposition of the sprayed materials by using additives as admixture to the agglomerate. Practical examples are outlined in the article.     

不同PVD技术沉积TiN涂层的形貌和力学性能研究

本文采用阴极弧沉积、中频磁控溅射及二者的复合技术在GCr15基底上制备了TiN涂层。通过扫描电镜、XRD谱、微米划痕测试、硬度测试以及摩擦磨损测试对涂层的组织结构和力学性能进行了表征及对比。结构表明,采用复合磁控阴极弧技术制备的TiN涂层具有较好的综合性能,如较光滑的表面、较高的结合力和硬度,故磨损率较低。     

Tribological Performance of Coated Surfaces

The fundamentals of coating tribology is presented in a generalised holistic approach to friction and wear mechanisms of coated surfaces in dry sliding contacts. It is based on a classification of the tribological contact process into macromechanical, micromechanical, tribochemical contact mechanisms and material transfer. The tribological contact process is dominated by the macromechanical mechanisms, which have been systematically analysed by using four main parameters: the coating-to-substrate hardness relationship, the film thickness, the surface roughness and the debris in the contact. In this paper special attention is given to the microlevel mechanisms, and in particular new techniques for modelling the elastic, plastic and brittle behaviour of the surface by finite element (FEM) computer simulations. The contact condition with a sphere sliding over a plate coated with a very thin hard coating is analysed. A three dimensional FEM model has been developed for calculating the first principal stress distribution in the scratch tester contact of a diamond spherical tip moving with increased load on a 2μm thick titanium nitride (TIN) coated steel surface. The model is comprehensive in that sense that it considers elastic, plastic and fracture behaviour of the contact surfaces. By identifying from a scratch experiment the location of the first crack and using this as input data can the fracture toughness of the coating be determined.     

Structure, mechanical properties and oxidation behaviour of arc-evaporated NbAlN hard coatings

Nb_1 − xAl_xN hard coatings were synthesised by cathodic arc-evaporation in order to study the influence of the Al concentration on crystal structure, mechanical properties and oxidation resistance. Structural investigations by X-ray diffraction revealed a transition from the face-centered cubic structure of δ-NbN to the wurtzite structure of AlN at x = 0.45… 0.56 depending on the deposition parameters. The maximum values of the mechanical properties like hardness and residual stress obtained by nanoindentation and biaxial stress temperature measurements, respectively, were found for the coatings with cubic structure and generally decrease with increasing Al content. On the other hand, higher Al concentrations are beneficial in terms of oxidation resistance as shown by annealing experiments in ambient air. The onset temperature for oxidation rises from 600 to 700 °C for Nb_0.73Al_0.27N to above 800 °C for Nb_0.29Al_0.71N regardless of changes in the crystal structure.     

海水环境下均质和梯度CrCN薄膜摩擦学性能研究

利用多弧离子镀技术在316L不锈钢和单晶硅上制备了均质和梯度Cr CN薄膜,通过X射线衍射仪(XRD)、扫描电镜(SEM)、X射线光电子能谱仪(XPS)、纳米压痕仪、273A电化学工作站、Revetest划痕测试系统和多功能摩擦磨损试验机等对薄膜的微观结构、力学性能、耐腐蚀性能和摩擦学性能进行表征。结果表明:较之于均质CrCN薄膜,梯度CrCN薄膜平均晶粒较小,Cr_7C_3(421)晶面的结晶度高,力学性能较好;在海水环境下,梯度CrCN薄膜在摩擦过程中对裂纹的萌生及扩展有较强的抑制作用,能有效抵制海水渗透,表现出良好的耐腐蚀性能;与WC摩擦配副对磨时平均摩擦系数与磨损率均较低,磨痕形貌光洁,表现出良好的摩擦学性能。