TiN薄膜的残余应力调控及力学性能研究

残余应力是制约物理气相沉积（Physical vapor deposition,PVD）硬质薄膜厚度的关键因素。采用多弧离子镀技术在高速钢基体上制备了厚度从3.7 m到15.5 m的TiN薄膜,结合曲率法和有限元法研究残余应力及结合性能随膜厚的变化规律。结果表明,随着膜厚的增加,基片弯曲程度加剧,而薄膜平均残余应力降低;膜层内残余应力的整体水平决定了界面切应力大小,薄膜结合性能随界面切应力的增加而降低。增加基体偏压、降低工作气压均导致薄膜内部残余应力的升高。当残余压应力较高时,TiN薄膜具有细小、致密的柱状晶结构,并呈现（111）择优取向,薄膜硬度及断裂韧度较高,耐磨性能良好。研究结果提示我们,通过残余应力的调控可提高硬质薄膜的力学特性。     

Durability of plasma-sprayed Cr3C2-NiCr coatings under rolling contact conditions

The aim of this paper was to address the rolling contact fatigue (RCF) failure mechanisms of plasma-sprayed Cr3C2-NiCr coatings under different tribological conditions of contact stress. Weibull distribution plots of fatigue lives of the coated specimens at different contact stresses were obtained. The failure modes of coatings were identified on the basis of wore surface observations of the failed coatings. Results showed that the RCF failure modes can be classified into four main categories, i.e., surface abrasion, spalling, cohesive delamination, and interfacial delamination. The probabilities of the surface abrasion and spalling type failures were relatively high at low contact stress. When the coatings were subjected to abrasion and spalling type failures, the failure of the coating was depended on the microstrcture of the coating. The stress concentration near the micro-defects in the coating may be the may reason for the formation of spall. The coatings were prone to fail in delamination under higher contact stresses. However, the delamination of coating may be related to distribution of shear stress amplitude within coating. The location of maximum shear stress amplitude can be used as a key parameter to predict the initiation of subsurface cracks within coating in rolling contact.     

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。     

Effect of Surface Roughening of Substrate Steel on the Improvement of Delamination Strength and Tribological Behavior of Hydrogenated Amorphous Carbon Coating Under Lubricated Conditions

The adhesion strength of diamond-like carbon (DLC) coatings is an obstacle in efforts to improve the reliability of coated products. It is generally believed that the roughening of the substrate surface improves the adhesion between a substrate and coating. The effect of surface roughening of the substrate on the delamination strength of DLC coating and the tribological behavior under lubrication were studied. Five types of roughened substrates were prepared by a wet blast device with differing materials, shapes, and sizes of the shot particles. A hydrogenated DLC film was deposited using plasma-enhanced chemical vapor deposition on the roughened substrates. The tribological properties were investigated under air and lubrication with pure water or n-decane. It was found that the delamination strength of the DLC coating could be improved by roughening the substrate surface, especially by spherical particles. It was also found that slight polishing of either the DLC surface deposited on the rough substrate or the roughened substrate before deposition significantly reduced the wear of the counter surface. The remaining chemical element of alumina particles on the roughened surface affected the delamination strength of the DLC coating.     

基体表面粗糙度对磁控溅射TiN涂层界面结合力的影响

利用球与平面的赫兹接触应力分布的经验修正公式∧［1］,对磁控溅处理前的基体表面粗糙度对沉积层和基体的界面结合力进行了研究,并和其他涂层界面结合力的测量方法方法进行了比较。结果表明：基体表面粗糙度对界面结合力有很大影响,表面粗糙度的改善有利于TiN层/基体的界面结合力的提高,同时改善了TiN层的摩擦学性能。     

Investigation of the performance of carbide cutting tools with hard coatings in hard milling based on the response surface methodology

Machining of hard materials has become a great challenge for several decades. One of the problems in this machining process is early tool wear, and this affects the machinability of hard materials. In order to increase machinability, cutting tools are widely coated with nanostructured physical vapor deposition hard coatings. The main characteristics of such advanced hard coatings are high microhardness and toughness as well as good adhesion to the substrate. In this paper, the influence of hard coatings (nanolayer AlTiN/TiN, multilayer nanocomposite TiAlSiN/TiSiN/TiAlN, and commercially available TiN/TiAlN) and cutting parameters (cutting speed, feed rate, and depth of cut) on cutting forces and surface roughness were investigated during face milling of AISI O2 cold work tool steel (～61 HRC). The experiments were conducted based on 3¹³ factorial design by response surface methodology, and response surface equations of cutting forces and surface roughness were obtained. In addition, the cutting forces obtained with the coated and uncoated tools were compared. The results showed that the interaction of coating type and depth of cut affects surface roughness. The hard coating type has no significant effect on cutting forces, while the cutting force F _z is approximately two times higher in the case of uncoated tool.     

聚苯硫醚/氟树脂梯度防腐蚀涂层的研究

在碳钢表面制备了具有梯度结构的PPS／FEP复合防腐蚀涂层,采用拉开法测定了各涂层体系的结合强度。结果表明：PPS／FEP梯度防腐蚀涂层明显改善了单纯氟树脂涂层对金属的不粘性,PPS／FEP五层梯度结构涂层与钢基体的结合强度可达11．8MPa;电子探针分析结果显示,五层体系中各组分沿横截面呈连续梯度分布,有效加强了层问结合。     

Estimation of rubber sliding friction from asperity interaction modeling

Interaction between a soft rubber asperity and its hard counterpart is traced with the help of a finite element computation. The analysis is aimed to estimate the influence of adhesion between rubber and rigid surfaces and the energy losses arising from the deformation of rubber bulk to the sliding resistance. At the contact zone, interfacial bonds are formed due to adhesion and their resistance to sliding is represented by the shear strength of the contact interface. In the rubber bulk, the hysteresis loss is calculated using an appropriate model of the viscoelastic mechanical behavior of rubber for large strains. Dependence of friction on sliding speeds and temperature is hence detected. Influence of surface roughness and contact pressure on friction is also examined.     

Study of tribological properties of coating/substrate system in micrometer and nanometer scales with a scanning probe microscope

We have used a scanning probe microscope equipped with a custom made diamond tip to study tribological properties of an inorganic–organic hybrid Si, O, H, and C coating produced by plasma enhanced chemical vapor deposition (PECVD) on siloxane/acrylic/polycarbonate multilayer substrates and on glass substrates. The micro indentation hardness and micro mar resistance were measured under different normal forces, and the critical loads for cracking, delamination, and chipping were evaluated. The effects of substrate, coating thickness, and interfacial adhesion on tribological properties of the coating/substrate systems are discussed. The results show that increasing coating thickness and strengthening interfacial adhesion can effectively inhibit cracking, delamination, and chipping of the coating/substrate systems under wear. Improving the physical properties of the PECVD coating and substrate, such as enhancing elastic recovery, reducing plasticity and brittleness, and matching the properties of coating and substrate better can improve the wear resistance of the systems further.     

The influence of surface defects on the mechanical and tribological properties of VN-based arc-evaporated coatings

The influence of surface defects, i.e., droplets and craters, on the mechanical and tribological properties of arc-evaporated V_xN coatings deposited on cemented carbide has been investigated in a scratching contact using a diamond stylus and a sliding contact using a stainless steel pin. Post-test characterisation using 3D optical surface profilometry and scanning electron microscopy was performed in order to investigate the mechanical and tribological response of the coatings. The results show that scratch induced coating cracking mainly is restricted to larger droplets showing a low interfacial bonding to the adjacent coating matrix. The influence of coating defects on the cohesive strength, i.e., the tendency to chipping of small coating fragments, was found to be relatively small. In contrast, the presence of defects may have a significant impact on the interfacial adhesive strength, increasing the tendency to spalling. In sliding contact, surface defects such as droplets and craters have a strong impact on the tribological behaviour of the coatings causing abrasive wear of the less hard counter material surface and material transfer to the coating, both mechanisms affecting the friction characteristics of sliding contact tribo systems.     

Tribological Behaviour of Nanostructured Al2O3-3 wt% TiO2 Coating Against Steel in Dry Sliding

Nanostructured and conventional Al₂O₃-3 wt% TiO₂ coatings were deposited by atmospheric plasma spraying. The wear and friction properties of both coatings against a steel ball under dry friction conditions were examined. It was found that the wear resistance of the nanostructured Al₂O₃-3 wt% TiO₂ coating was superior to that of the corresponding conventional counterpart. The improvement in wear resistance of the nanostructured coating was attributed to its higher toughness and cohesion strength between splats. As for the nanostructured coating, the wear mechanism was mainly adhesion with micro-abrasion at low loads (20 N). At high loads (80 N), the wear of the nanostructured coating was controlled by plastic deformation and associated delamination along the splat boundaries, which was similar to that of the conventional coating at low loads. However, the failure of the conventional coating was predominantly brittle fracture within the splats and delamination between splats at high loads.     

Correlation between adhesion and wear behaviour of commercial carbon based coating

Adhesion and wear behaviour of hard coatings are two important properties that concern researchers. We need to use different tests to obtain these two values and the correlation between adhesion and wear is not always obvious. The purpose of this paper is to find the relationship between the wear rate and the critical load for commercial hard coatings.Commercial carbon based coatings were deposited on M42 high speed steel by magnetron sputtering. Different lengths of pre-sputtering time were used to change the properties of the coatings. Single pass scratch tests and multi-pass bidirectional wear tests were used to obtain the critical load and wear rate values, respectively. Results showed that there was a correlation between wear and adhesion. It was found that adhesion increases, and wear rate decreases when the pre-sputtering time increases. It was also observed that adhesion strength varies with pre-sputtering time in a step function manner. To a large extent, the adhesion behaviour is related to the wear behaviour as far as the commercial carbon based coating is concerned. However, as different coatings have different microstructure and properties, further work should be done to decide whether a similar relationship can be applied in other cases.     

Mechanical Modeling of Scratch Behavior of Polymeric Coatings on Hard and Soft Substrates

An ASTM standard scratch test is utilized to study the scratch behavior of polymeric coatings on soft and hard substrates. Depending on the different combination of polymeric coatings and substrates utilized, various damage modes can take place, which include coating delamination, transverse cracking, and buckling failure. A soft coating on a hard substrate will give rise to an entirely different scratch damage pattern from those of a hard coating on a soft substrate. The stress and strain responses of scratch on polymeric coating are analyzed using three-dimensional finite element (FE) simulation. The analysis provides mechanistic insights for the observed polymer coating deformation mechanisms and failure modes. Usefulness of the ASTM scratch method and FE modeling to evaluate polymer coating scratch behavior is discussed.     

An overview of the potential of quantitative coating adhesion measurement by scratch testing

The scratch test has been used to assess the adhesion of thin hard coatings for some time now and is a useful tool for coating development or quality assurance. However, the test is influenced by a number of intrinsic and extrinsic factors which are not adhesion-related and the results of the test are usually regarded as only semi-quantitative. The stress state around a moving indenter scratching a coating/substrate system is very complex and it is difficult to determine the stresses which lead to detachment. Furthermore, the interfacial defect state responsible for failure is unknown. However, by a careful analysis of the observed failure modes in the scratch test (not all of which are related to adhesion) it is possible to identify adhesive failures and in some cases these occur in regions where the stress state is relatively simple and quantification can be attempted.Ideally engineers would like a material parameter (such as work of adhesion or interfacial toughness) which can be used in an appropriate model of the coating-substrate system stress state to determine if detachment will occur under the loading conditions experienced in service. This data is not usually available and the development of such models must be seen as a long-term goal. In modern indentation and scratch systems the work of friction (or indentation) can be directly measured and the relationship between this parameter and adhesive failure can be demonstrated in some cases. This paper reviews the main adhesion-related failure modes and the stresses responsible for them and indicates where quantification is possible illustrating this with results from hard coatings on steel, thermally grown oxide scales and optical coatings on glass. The use of empirical calibration studies, directly measured work of friction and quantification by finite element methods is discussed.     

Sliding wear resistance of metallic coated surfaces

The role of metallic coatings in sliding wear is examined experimentally. The results indicate that the tribological behavior of soft coatings is consistent with the delamination theory of wear, especially the critical nature of the plating thickness. It is shown that a reduction in wear rate of three orders of magnitude is possible when the coating material is softer than the substrate and thinner than a critical thickness. The optimum plate thickness is found to be of the order of 0.1 μm for cadmium, silver, gold or nickel plated on various types of steel. Cadmium, silver and nickel reduce wear only in non-oxidizing environments, whereas gold reduces wear both in air and in inert atmospheres.The roughness of the substrate surface prior to plating and the nature of the coating/substrate bond have significant effects on the life of these coatings. The life of the coatings is increased by polishing the substrate to 0.1 μm (c.l.a.) prior to plating, and also by diffusion of the plated material into the substrate, which increases the coating/substrate bond strength.     

高能离子源清洗对AlCrN刀具涂层结构及性能的影响

采用自主研发的离子源增强多弧离子镀设备,研究涂层沉积前不同清洗工艺对基材表面粗糙度以及所制备的AlCrN涂层的表面形貌、硬度、膜基结合力、摩擦磨损和切削性能的影响。研究结果表明,高能Ar⁺清洗可以更有效清洁基材表面。与传统弧源清洗技术相比,经高能离子源清洗后的基体表面粗糙度降低,沉积态涂层的表面粗糙度更低。相比于传统弧源清洗工艺,高能Ar⁺清洗可以显著提高膜基结合强度,达到48.7 N,摩擦因数和磨损率均降低,涂层刀具寿命提高了3倍。     

Achieving High Tribological Performance of Graphite-like Carbon Coatings on Ti6Al4V in Aqueous Environments by Gradient Interface Design

A duplex treatment involving nitrogen ion pre-implantation and gradient interfacial transition was performed to obtain a high-performance graphite-like carbon (GLC) coating on a Ti6Al4V alloy. Characteristics of the as-deposited coating systems were systemically investigated by Raman spectrometry, scanning electron microscopy, atomic force microscopy, nano-indentation, and scratch tests. The friction and wear behaviors in distilled water and sea water environments were evaluated by a ball-on-disk tribometer. The results showed that the GLC multilayer coating on nitrogen ion-implanted Ti6Al4V possessed a greater hardness and adhesion strength than to that on un-implanted Ti6Al4V. The tribological performances of these duplex process systems showed a great improvement in both the distilled water and sea water environments. In particular, the Cr/CrN/GLC coatings on nitrogen ion-implanted substrates demonstrated the best friction and wear behaviors. These striking improvements were attributed to the greatly enhanced interface strength between substrate and coating by the nitrogen ion implantation process and improved adhesion strength between gradient layers by the appropriate gradient interlayers with a similar thermal expansion coefficient.     

Cavitation resistance of Cr–N coatings deposited on austenitic stainless steel at various temperatures

Cr–N coatings were deposited on austenitic stainless steel, X6CrNiTi18-10, by means of the cathodic arc evaporation method at three substrate temperatures: 200 °C, 350 °C and 500 °C. All coatings were found to have a composition of Cr(N), CrN and Cr₂N. The substrate temperature was found to have an influence on the hardness and Young's modulus of the Cr–N coatings. The investigation of nanocrystalline Cr–N coatings resistance to cavitation was performed in a cavitation tunnel with a slot cavitator and tap water as the medium. The estimated cavitation resistance parameters of the coatings were the incubation period of damage and total mass loss. It was found that the optimal coating cavitation resistance was deposited at 500 °C. The incubation period for the 500 °C deposition coating was the same as that of the uncoated X6CrNiTi18-10 steel, but the total mass loss was significantly lower than on the uncoated specimen. The scanning electron microscope analysis indicated that the damage process of the Cr–N coating mainly originates from the plastic deformation of the steel substrate–hard coating system, which appears by “micro-folding” of the surface. An increase of tensile stresses at the top of micro-folds initiates micro-cracks and delamination of Cr–N coating. The results of the investigation and the analysis indicate that the factors mainly responsible for cavitation resistance of the steel substrate/hard coating system are resistant to plastic deformation of the total system and coating adhesion.     

Sliding wear behavior of Fe-Al and Fe-Al/WC coatings prepared by high velocity arc spraying

A comparative study was carried out to investigate the microstructure and tribological behavior of Fe-Al and Fe-Al/WC iron aluminide based coatings against Si₃N₄ under dry sliding at room temperature using a pin-on-disc tribotester. The coatings were prepared by high velocity arc spraying (HVAS) and cored wires. The effect of normal load on friction coefficient and wear rate of the coatings was studied. The microstructure and the worn surfaces of the coatings were analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersion spectroscope (EDS). The results showed that, the main phases in both coatings were iron aluminide (Fe₃Al and FeAl) and α. WC/W₂C particles were embedded in the matrix of the composite coating. With adding WC hard particles, the Fe-Al/WC composite coating exhibited higher wear-resistance than Fe-Al coating. But the friction coefficient of both coatings showed little difference. As the load increased, the friction coefficient decreases slightly due to a rise of friction contact temperature and larger areas of oxide film formation on the worn surface, which act as a solid lubricant. Increasing load causes the maximum shear stress occurring at the deeper position below the surface, thereby aggravating the wear. The coating surface is subjected to alternately tensile stress and compression stress during sliding, and the predominant wear mechanism of the coatings appears to be delamination.     

Microtribological Performance of Au–MoS2 and Ti–MoS2 Coatings with Varying Contact Pressure

Solid lubricant coatings with co-sputtered metal and MoS₂ have shown favorable macrotribological properties at a wide range of contact stresses and humidity levels. These materials are also candidates for use in microcontacts and micro-electromechanical systems (MEMS), but their performance at this scale is poorly understood. For this study, microtribological properties of Au–MoS₂ and Ti–MoS₂ coatings, with varying metal additives of less than 15 at%, were examined using a nanoindentation instrument. Titanium and gold were chosen for this study as metal additives due to their different influence on the mechanical properties of the coating. The hardness and reduced modulus of the coatings increased with the addition of metal, when compared to pure MoS₂. Reciprocating microscratch tests were performed with two spherical diamond tips (50 and 10 μm radii) in dry air. A range of normal loads were used between 0.2 and 5.0 mN. Friction and wear measurements were analyzed with respect to the variation in the contact pressure and compared to literature studies performed at the macroscale. Correlations were found between the coating mechanical properties, tip-coating adhesion, interfacial shear strength, and the formation of transfer films and tribofilms.