活塞环表面织构化镀层的摩擦性能研究

目的以缸套/活塞环为试验对象,研究激光织构化与固体润滑镀层的协同减摩作用。方法采用脉冲激光在活塞环表面进行微孔化处理,利用电脉冲沉积法在微孔内制备具有不同MoS_2微粒浓度的Ni-MoS_2复合镀层,通过往复式摩擦试验研究织构化表面沉积固体润滑剂对活塞环-缸套的影响机制。结果镀液中MoS_2微粒浓度对镀层的硬度和摩擦学性能影响较大,相同电流密度下,电镀液中MoS_2微粒的质量浓度为5g/L时的镀层硬度最高,该浓度下Ni-MoS_2复合镀层在干摩擦下具有最佳的摩擦系数和最低的磨损率。织构化复合镀层可以显著改善接触面间的摩擦性能,相比未织构化摩擦配副,摩擦系数降低约0.2,磨损率下降50%。结论干摩擦条件下,表面织构可以有效地储存摩擦副之间的固体润滑剂和磨粒,在接触表面形成连续润滑膜,减少磨粒磨损。     

Tribological coatings for lubrication over multiple thermal cycles

Nanocomposite materials demonstrating multiple temperature-adaptive mechanisms including diffusion, oxidation and/or catalysis mechanisms to yield low friction coefficients of < 0.2 from room temperature to 700 °C were combined with diffusion barrier layers in coatings with different architectures (e.g., layer thicknesses, number of layers, etc.) to examine adaptation of contact surface chemistry and morphology over multiple thermal cycles. Multilayered coatings consisting of ceramic-metal nanocomposite adaptive lubricant layers separated by diffusion barriers allowed adaptation to occur only upon exposure of the lubricant layer by wear, which resulted in prolonged wear life at static and cycled temperatures. It was also observed that a relationship between the number of adaptive lubricant layers and the number of thermal cycles existed, where one thermal cycle consumed two adaptive lubricant layers. The thickness of the adaptive coating layers was also important because diffusion- and oxidation-based adaptation in these particular coatings required a minimum volume of solid lubricant material. The surface roughness of the adaptive coating materials played a significant role in their performance within multilayered coatings, where rough coatings (> 100 nm R_a) failed after relatively few sliding cycles. The utility and application of adaptive coatings materials providing lubrication over multiple thermal cycles is discussed.     

固体润滑剂对无镀铜焊丝导电嘴磨损性能的影响

采用扫描电镜和体视显微镜研究了固体润滑剂对无镀铜焊丝导电嘴磨损性的影响. 结果表明,随着固体润滑剂成分的改变,导电嘴磨损形式发生变化,导电嘴质量损失率和导电嘴孔径磨损率随之改变;焊丝表面涂敷以石墨 + 纳米Fe₂O₃和石墨 + 纳米Fe₃O₄为主的固体润滑剂时,磨损形式以轻微磨粒磨损为主,导电嘴质量损失率和孔径磨损率显著降低,分别为0.27%和0.31%、16.2%和22.3%,导电嘴温度是影响固体润滑剂润滑性的重要因素,以石墨 + 纳米Fe₂O₃和石墨 + 纳米Fe₃O₄为主的固体润滑剂能实现从室温到较高温度范围内的连续润滑.     

聚酰胺酰亚胺涂层添加润滑剂对其摩擦性能的影响

目的研究固体润滑剂对聚酰胺酰亚胺(PAI)涂层摩擦磨损性能的影响。方法由偏苯三酸酐(TMA)和4,4-二苯甲烷二异氰酸酯(MDI)合成并添加二硫化钼、二硫化钨、石墨制备自润滑PAI涂层,并对其用HSR-2M型高速往复摩擦试验机进行磨损实验。结合ATR-FTIR、TA-TG热重、磨痕形貌等表征手段,对自润滑PAI涂层摩擦性能进行表征,探究了固体润滑剂的种类与含量对聚酰胺酰亚胺涂层摩擦性能的影响。结果载荷与PAI涂层的摩擦系数呈反比例关系,当Mo S2含量达到30%时,PAI涂层的摩擦系数降至0.1744。添加固体润滑剂后,PAI涂层的摩擦系数减小,磨痕宽度变窄,磨痕变浅,表面粗糙度相对较低。结论具备最佳摩擦性能的涂层添加了30%Mo S2,添加10%石墨的涂层次之,添加10%WS2的涂层较好。添加固体润滑剂可明显提高PAI涂层的摩擦磨损性能,增加其使用时长。     

Sliding wear characteristics of solid lubricant coating on titanium alloy surface modified by laser texturing and ternary hard coatings

Titanium alloys are poor in wear resistance and it is not suitable under sliding conditions even with lubrication because of its severe adhesive wear tendency. The surface modifications through texturing and surface coating were used to enhance the surface properties of the titanium alloy substrate. Hard and wear resistant coatings such as TiAlN and AlCrN were applied over textured titanium alloy surfaces with chromium as interlayer. To improve the friction and wear resisting performance of hard coatings further, solid lubricant, molybdenum disulphide (MoS2), was deposited on dimples made over hard coatings. Unidirectional sliding wear tests were performed with pin on disc contact geometry, to evaluate the tribological performance of coated substrates. The tests were performed under three different normal loads for a period of 40 min at sliding velocity of 2 m/s. The tribological behaviours of multi-layer coatings such as coating structure, friction coefficient and specific wear rate were investigated and analyzed. The lower friction coefficient of approximately 0.1 was found at the early sliding stage, which reduces the material transfer and increases the wear life. Although, the friction coefficient increased to high values after MoS₂ coating was partially removed, substrate was still protected against wear by underlying hard composite layer.     

Feasibility Study of Using DLC Coating in Conjunction with Laser Ablation process to Improve the Tribological Performance of an Engineering Surface

Increasing demands such as low friction,low wear rate,and long life-time have reached the limits of single DLC coatings.In order to meet the requirements,we propose to use an integrated approach to improve the wear property of an engineering surface.Firstly,dimples are introduced perpendicular to an engineering surface by a Nd:YAG laser emitting at 1064 nm.Subsequently,solid lubricant DLC is prepared on the patterned surface by magnetron sputtering technique.The effect of dimple densities from 7%to 45 %on tribological properties of the coating surface was revealed.The wear performance of the textured DLC surfaces was studied by a pin-on-disk reciprocating sliding wear tester under boundary lubrication and dry conditions.The results showed that the DLC coatings with appropriate dimple densities have an obvious improvement on wear performance in term of friction coefficient,wear rate and wear life,as compared to un-textured DLC coatings.In boundary lubrication conditions,the improved wear performance can be explained by the promotion of reservoirs to enhance lubricant retention during sliding.In dry condition,the dimples trap wear particles and leave a free interface between pin and sliding contact surface,and avoid the surface worn by abrasive manner,thereby improving the wear performance of the DLC coating.     

Graphite-like and Diamond-like Carbon Coatings with Exceptional Tribological Properties

THE PHYSICAL DEMANDS on engineeringcomponents are continually increasing whilstenvironmental controls on the use of lubricants becomemore and more restrictive.This has led to increasingdemand for high load bearing,solid lubricant coatingsthat enable engineered surfaces to rub against oneanother with reduced friction and wear.One of themost promising candidate coatings is diamond-likecarbon,DLC.However,the term DLC is used to describe a broadrange of carbon-based coatings that includes…     

Relationships between the fretting wear behavior and the ball cratering resistance of solid lubricant coatings

Employing solid lubricant coatings to reduce friction is one of the most effective methods to mitigate fretting damage. However, facing numerous available coatings, users often feel confounded, and the selection of the optimum coating for a specific application is still a tough task. Some simple methods are expected to help the selection. Ball cratering as a promising technique is becoming popular in the developing process of new coatings to assess their abrasion resistance. The objective of this paper is to identify the relationships between the fretting behavior and the ball cratering resistance of coatings, and attempt to use ball cratering to pre-select coatings for fretting conditions in order to cut down the number of candidate coatings and shorten the fretting tests. In this study, several bonded solid lubricant coatings, principally based on PTFE or MoS₂, were investigated by ball cratering and fretting tests. The results showed that the coatings in ball cratering presented similar tribological performance as in fretting tests in terms of endurance and wear resistance, i.e., the coatings with good ball cratering resistance also exhibited long lifetime in fretting tests, so ball cratering can be considered as a simple test to pre-select solid lubricant coatings for fretting applications.     

DLC coatings for hydraulic applications

Replacement of lubricating oils with water or low-viscosity fluids is highly desirable in many industrial fields, on account of the environmental and economical advantages. Low lubricity of water might be insufficient for proper operation of hydraulic components, and diamond-like carbon(DLC) coatings are very attractive as solid lubricant films. A remote-plasma PACVD process was utilized to deposit hydrogenated DLC coatings (a-C:H) on different substrates. Microindentation measurements show that the coating hardness is around 35 GPa. Tribological behavior was evaluated by block-on-ring tests performed in water and water with alumina. The wear rate was calculated after measuring the wear volume by a laser profilemeter. Morphological and compositional analysis of the wear tracks reveal that coating failure may occur by abrasive wear or delamination, depending on the substrate properties. Hard and smooth substrates give the best results and dispersed alumina particles increase the wear rate.     

Nanostructured Al-Based Metal Matrix Composite Coating Production by Pulsed Gas Dynamic Spraying Process

The advantage of combining cryomilling and pulsed gas dynamic spraying (PGDS) processes in order to produce a nanostructured, dense and wear resistant coating was demonstrated. Cryomilling was successfully employed to synthesize particulate B₄C reinforced Al matrix nanocomposite feedstock powders, while the PGDS process shows the ability of preserving the microstructure of the starting material. In this study, nanocrystalline and conventional Al5356?+?20%B₄C composite as well as the unreinforced Al5356 alloy feedstock powders were used. The influence of the nature of the feedstock material on the microstructure and mechanical properties of the coatings was studied. The PGDS process provides an opportunity to preserve the phase of the starting material, to produce hard and dense coatings with good cohesion between deformed particles and good adhesion to the substrate. High dry sliding wear resistance was observed when cryomilled composite material was used.     

Friction reduction by texturing of DLC coatings sliding against steel under oil lubrication

It has been demonstrated that tetrahedral amorphous carbon (ta-C) films provide excellent wear and friction properties in dry sliding. Recently the applications of ta-C coatings in lubricated conditions have become more important. The use of carbon coatings aims at reducing the wear and coefficient of friction under minimum lubrication and without hazardous lubricant additives. For optimum tribological performance, a modification of the ta-C coated surfaces is required. The present paper describes an innovative method of coated surface texturing, by which nanometer and micrometer size pores are processed by various methods. Particle masking was used for processing micrometer size pores and for controlling the coating growth conditions in order to produce nanometer size pores in the ta-C surface. The masking by particles yielded a pore geometry which varied from complex shaped channels to small individual pores. The texturing was performed by distributing metallic powder particles on the surface or by direct chemical deposition of metal particles on the substrate in prior to pulsed vacuum arc deposition. The tribological characterization was carried out by applying reciprocating friction tests with controlled lubricant replenishment, in order to simulate metal forming processes. The friction reducing effect, which was observed in the tribological tests, indicated a microlubrication effect of the textured coating surfaces.     

Sliding wear evaluation of hot isostatically pressed thermal spray ceramet coatings

The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed) thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of these microstructural changes on the physical properties and wear resistance are discussed.     

NiCrAlYSi/h-BN高温可磨耗封严涂层摩擦磨损性能研究

目的加入h-BN和团聚聚苯酯分别作为固体润滑剂和造孔剂,以提高NiCrAlYSi基封严涂层的高温摩擦磨损性能。方法采用真空熔炼雾化造粒和料浆喷雾造粒技术制备NiCrAlYSi/h-BN聚苯酯复合粉体,再利用大气等离子喷涂技术制备高温可磨耗封严涂层,通过扫描电子显微镜(SEM)、能谱仪(EDS)、CSM摩擦磨损试验机和三维轮廓仪等手段,研究NiCrAlYSi/h-BN封严涂层显微结构、元素组成以及室温和800℃下的摩擦磨损性能,探究涂层在室温和800℃下的磨损机理。结果等离子喷涂NiCrAlYSi/h-BN封严涂层组织比较均匀,涂层结合强度可达15MPa,孔隙率约为32%。室温下封严涂层与DD6镍基单晶高温合金球间的平均摩擦因数为0.897,涂层磨损体积为2.09×10~8μm~3;800℃高温下平均摩擦因数为0.425,涂层磨损体积为3.22×10~8μm~3;封严涂层800℃下有良好的可磨耗性,相应对偶件的磨损较轻;高温下,封严涂层金属基相软化、h-BN的润滑作用和部分金属基相高温下生成自润滑性氧化物,是摩擦因数降低和对偶件磨损较轻的主要原因。NiCrAlYSi/h-BN封严涂层室温的主要磨损机理为涂抹、磨粒磨损和轻微氧化,高温下的主要磨损机理为切削、塑性变形、氧化和粘着磨损。结论等离子喷涂NiCrAlYSi/h-BN高温封严涂层在高温下的可磨耗性能较好。     

Sliding Wear Response of a Bronze Bushing: Influence of Applied Load and Test Environment

This investigation pertains to the examination of the sliding wear behavior of a leaded-tin bronze bushing under the conditions of varying applied loads and test environments against a steel shaft. The test environment was changed by adding 5% of solid lubricants like talc and lead to an oil lubricant separately as well as in combination; the fraction of the two (solid) lubricants within the solid lubricant mixture was varied in the range of 25-75% in the latter case. The wear performance of the bushing was characterized in terms of the wear rate, frictional heating, and friction coefficient. The increasing load led to deterioration in the wear response, while the addition of the solid lubricant particles produced a reverse effect. Further, an appreciable difference in the wear behavior was not observed when the tests were conducted in the oil plus talc and oil plus lead lubricant mixtures. However, the oil containing lead and talc together brought about a significant improvement in the wear response; best results were obtained in the case of the lubricant mixture consisting of lead and talc together in the ratio of 3:1 in the oil. The observed wear behavior of the samples has been discussed in terms of specific characteristics of various microconstituents. The features of the wear surfaces and subsurface regions further substantiated the wear response and enabled us to understand the operating material removal mechanisms.     

Ni-P-多壁碳纳米管复合镀层的制备及摩擦磨损性能(英文)

采用湿式球磨对多壁碳纳米管(MWNTs)预处理,通过化学镀制备Ni-P-MWNTs复合镀层;对45钢、传统Ni-P镀层和Ni-P-MWNTs复合镀层在干摩擦条件下的摩擦磨损性能进行考察和比较。结果表明,球磨后MWNTs长径比降低,长度均匀,且多数端部处于敞开状态。与45钢和Ni-P镀层相比,Ni-P-MWNTs复合镀层的减摩耐磨能力显著强化。当复合镀层中MWNTs的质量分数为0.74%~1.97%时,其摩擦因数和磨损率随MWNTs含量的增加而减少;对于MWNTs质量分数为1.97%的复合镀层,其摩擦因数和磨损率仅为0.08和6.22×10?15m3/(N·m)。复合镀层优良的摩擦磨损性能归因于MWNTs优异的力学性能和自润滑特性。     

Fabrication and tribological properties of titanium nitride coatings incorporating solid lubricant microreservoirs

The concept of incorporating microscopic reservoirs within a hard coating for the purpose of solid lubricant storage and supply during wear of interacting surfaces has been investigated in this study. A novel method was devised using ceramic beads (1.5-10 μm diameter) as placeholders during the deposition of a TiN coating by reactive sputter deposition. A pin-on-disk wear test was used to test these coatings using graphite and sputter-deposited carbon as the solid lubricant, and an alumina counterface. When tested without any lubricant, the presence of the microreservoirs in the TiN coating appeared to degrade the mechanical integrity of the coating leading to rapid failure. With the graphite lubricant present, the frictional behavior ranged from levels similar to the TiN coating alone, to that of graphite alone. Tests of the TiN coating made using 10 μm beads running against an aluminum counterface showed substantial improvement when the microreservoirs were present. Optical microscopy examination of the wear tracks showed the microreservoirs were generally successful at trapping the graphite lubricant during wear. With a sufficient density and appropriate distribution of the microreservoirs significant improvements in tribological performance can be realized.     

Development and trends in HVOF spraying technology

Three actual trends in development of HVOF spraying technology are described and discussed. The trends concern application fields as well as gun and feedstock characteristics. At the example of demountable draw bars it is shown that HVOF sprayed cermet coatings are capable to protect light weight material components subject to dynamical load against wear without detraction of fatigue strength. Personnel and production time savings can be exploited. High deposition efficiency at considerable powder feed rate, high density and negligible oxygen content in corrosion protective iron or nickel based coatings is achieved for spraying with newly developed HVOF guns operating at increased combustion chamber pressures. Also spraying of highly reactive materials like titanium under atmospheric conditions becomes feasible. A major obstacle for industrial use of respective coatings is the lack of adapted characterisation methods that permit to ascertain corrosion protective function. Ultrafine powder feedstock is used in order to reduce overall costs of wear protective cermet coatings due to the possibility to finish coatings by comparatively cheap belt grinding. However, it is shown that the replacement of coatings produced with conventional powder size fractions requires careful consideration of the particular tribological system. While cermet coatings produced with ultrafine powders outperform conventional coatings for sliding wear conditions, their capability to withstand dry abrasive wear stress is poor. The benefits concerning coating production costs may be outweighed by significantly decreased component life time.     

Influence of solid contaminants in oil on wear characteristics of nano-Al2O3／Ni composite coating

Solid conlaminants in Iubrication system will cause severe wear of sliding components. In order 1o improve the wear resistance of the material in oil containing solid contaminants, the brush plated nano-Al2O3/Ni composite coating was prepared and the influence of the sand content and sand size on the tribological property of the coating in oil containing solid contaminants was tested with ball-on-disc tester. The results show that the wear volume increases with increasing the sand content and sand size, and the wear resistance of the composite coating is 20% higher than that of the high-speed plain nickel coating. The main wear mechanisms of the coatings are abrasive wear and adhesive wear. And due to the nano-particle strengthening effect, the wear resistance of the composite coating is improved.     

铟锡锌软金属修复润滑剂对钢的自修复及其摩擦学特性

针对目前润滑自修复技术生成的修复层厚度较薄,难以修复较严重磨损表面的不足,研制了含铟、锡和锌三种软金属添加剂的新型磨损自修复润滑剂。在摩擦磨损试验机上,考察了使用该润滑剂的钢?钢面接触摩擦副的磨损自修复行为及其摩擦学性能。用X射线能谱(EDS)和扫描电镜(SEM)分析了修复表面的主要化学元素和自修复涂层的厚度。用淬冷试验测试了涂层与基体的结合强度。结果表明,研制的铟锡锌润滑脂能在钢表面摩擦形成约30μm厚度的自修复涂层,涂层与基体结合性能良好,修复后的钢表面有良好的减摩抗磨性能。     

Effect of hydrogen content in a-C:H coatings on their tribological behaviour at room temperature up to 150 °C

Hydrogenated amorphous carbon (a-C:H) coatings deposited onto steel substrates by plasma assisted CVD, using different precursor gases (1 < H/C ratio < 4) were tested for their tribological behaviour. The H content in these coatings ranged from 25 to 29 at.%. Fretting mode I tests were performed on different couples consisting of coated and/or uncoated first bodies. Some tests were performed after a heat treatment of the coatings. As-deposited a-C:H/corundum couples tested at 23 °C and 50% RH showed lowering of the coefficient of friction at increasing normal load. Graphitisation is taking place in sliding contacts at high normal loads. For a-C:H/corundum couples a clear minimum in the coefficient of friction was noticed at 100 °C for coatings containing 27 at.% H. The coefficient of friction recorded on such couples is high compared to the one recorded on as-deposited a-C:H/a-C:H couples. However for the a-C:H/a-C:H couple, a lowering of the coefficient of friction with increasing fretting test temperature was noticed. The decreasing coefficient of friction was accompanied by an increasing wear. Graphitisation is causing severe degradation of a-C:H coatings at high test temperatures. An energetic analysis of the wear is finally reported. It appeared that the wear volume recorded at RT on as-deposited a-C:H coatings varies linearly with the cumulative dissipated energy. The wear rate coefficient decreases with increasing H-content. A stabilization of the sp³ bonds with increasing H-content might explain this behaviour. Confirmation was found by performing high temperature fretting tests. Interesting is the finding that fretting tests at RT performed after a thermal treatment of a-C:H coatings at either 100 or 150 °C, show a friction and wear behaviour identical to the ones recorded on as-deposited coatings tested at RT.