Effect of Water Adsorption on Microtribological Properties of Hydrogenated Diamond-Like Carbon Films

Microtribological properties of diamond-like carbon (DLC) films in the presence of water molecule have been studied. The amount of water adsorbed on DLC films was measured by the quartz crystal microbalance (QCM), while microtribological properties of the film were evaluated by an environment-controlled microtribometer. The hydrogenated-DLC showed an advancing water contact angle of 97°, indicating a relatively hydrophobic surface. No hysteresis in adsorption and desorption isotherms were observed. This suggests an absence of micropores at the DLC surface. The greatest adhesion and friction forces between a W-tip and DLC films deposited onto QCM were observed at a water coverage of 2-3 monolayers, which corresponds to a relative humidity of 70-80%. This abrupt increase in adhesion was explained by the generation of a meniscus from the condensed water between tip and DLC surface. The atomically flat DLC surface showed maximum adhesion and friction forces at lower humidity than those of DLC on OCM, implying the importance of surface texturing, which reduces the effect of water condensation.     

Effect of Diamond-Like Carbon Coatings on Ball Bearing Performance in Normal,Oil-Starved,and Debris-Damaged Conditions

In this study, a process was developed to deposit wear-resistant metal-doped diamond-like amorphous hydrocarbon and carbon coatings onto spherical rolling elements. Nanocomposite WC/a-C:H, TiC/a-C, and Ti/a-C:H coatings were applied in a closed-field unbalanced magnetron sputtering system and their mechanical, compositional, and microstructural properties were examined. The ability of the coated spherical rolling elements to affect bearing performance in normal, oil-starved, and debris-damaged conditions was evaluated in thrust bearing tests. WC/a-C:H-coated spherical rolling elements (balls) exhibit the ability to improve bearing performance in normal, oil-starved, and debris-damaged conditions.     

Effect of Sliding History on Super-Low Friction of Diamond-Like Carbon Coating in Water Lubrication

Water lubrication using diamond-like carbon (DLC) coatings is regarded as being a promising eco-friendly technology. However, it has been reported that delamination of DLC coatings occurs in water. The authors clarified that the application of friction in ambient air prior to self-mating DLC water lubrication, in addition to the suppression of DLC delamination, caused the friction coefficient to decrease more than when no processing is performed in the boundary lubrication region. When compared to the case when there was no pre-sliding, in terms of the wear scar, in this case, a much more hydrophilic and smoother surface was formed. Therefore, the friction-reducing process in water due to the presence of a sliding history (pre-sliding in ambient air) was clarified by an analysis of the DLC geometry, structure, chemical state and an in situ analysis that can measure the friction properties and the chemical state of DLC. We clarified that the process in which the oxidation and structural changes of the DLC proceed at the time of pre-sliding in ambient air using in situ Fourier transform infrared spectroscopy–attenuated total reflection. It was also revealed that the OH termination subsequently accelerated rapidly due to the friction in water after pre-sliding process. In addition, a time-of-flight secondary ion mass spectrometry analysis revealed that this OH group was derived from the lubricating water and unlike the case in which there was no pre-sliding in ambient air, the rate at which OH terminates increased considerably.     

Boundary Lubrication Properties of Nanoperiod Solid Lubricant Multilayer Films Composed of Diamond-Like Carbon and Gold Layers

To develop electroconductive and high-endurance solid lubricant nanoperiod multilayer (DLC/Au)_n films, diamond-like carbon (DLC) and gold layers were deposited while controlling the time the substrate was exposed graphite and gold targets. The electrical resistivity of the (DLC/Au)_n multilayer films was ~12.4 Ω cm. The hardness of the (DLC/Au)_n multilayer films was similar to that of DLC films and much higher than that of gold monolayer films. According to the results of oscillating sliding tests under water boundary lubrication and dry conditions, (DLC/Au)_n multilayer films exhibited the low friction coefficient, little damage, and high sliding durability than the monolayer films. (DLC/Au)_n films also have a lower friction coefficient and exhibit less damage than a Au monolayer under polyalphaolefin boundary lubrication.     

Effect of Carbon Diffusion on Friction and Wear Behaviors of Diamond-Like Carbon Coating Against Germanium in Boundary Base Oil Lubrication

Tribology Letters - The focus of the research was on investigating the influence of orientation of fibers in graphite fabric-reinforced polyetherimide composite on wear performance in selected wear...     

Investigation of Tribo-Chemistry by Means of Stable Isotopic Tracers,Part 2: Lubrication Mechanism of Friction Modifiers on Diamond-Like Carbon

A solution of glycerol monooleate (GMO) in polyalphaolefin (PAO) considerably reduced the friction between the steel and the diamond-like carbon (DLC) under boundary conditions. The combination of the material-oil-additive is of importance. Model additives composed of a stable isotope ( ² H or ¹³ C) were employed to trace the additive molecule by time-of-flight secondary ion mass spectroscopy (TOF-SIMS). It was found that the additive interacted with DLC surfaces in the form of an ester. Inclusion of PAO in the boundary film on DLC was found by TOF-SIMS analysis.The utility of the isotopic tracer technique in tribo-chemistry was demonstrated in this study.     

类金刚石膜的性质及应用

介绍了类金刚石膜（Diamond—like Carbon films，DLC films）的结构、制备方法和发展现状。综述了DLC膜的机械、电子、光学和医学等性能以及在这些领域中的应用状况。     

Tribological Behaviors of Different Diamond-Like Carbon Coatings on Nitrided Mild Steel Lubricated With Benzotriazole-Containing Borate Esters

Three synthesized benzotriazole-containing borate esters were separately added into poly-alpha-olefin (PAO) as additives, using molybdenum dithiocarbamate (MoDTC) as the comparison. The friction and wear behavior of Ti-DLC and Ti/Al-DLC coating on nitrided AISI-1045 steel sliding against AISI 52100 steel under the lubrication of PAO containing various additives was evaluated using a reciprocating ball-on-disk friction and wear tester. The morphology and chemical feature of the worn surfaces of the DLC coatings were observed and analyzed using a three dimensional (3D) surface profiler, a scanning electron microscope (SEM), and an X-ray photoelectron spectroscope (XPS). Results show that the three kinds of benzotriazole-containing borate esters as additives in PAO had much better tribological properties than MoDTC; the wear resistance of Ti/Al-DLC coating was better than Ti-DLC coating.     

Tribological Performance of Boronized,Nitrided, and Normalized AISI 4140 Steel against Hydrogenated Diamond-Like Carbon-Coated AISI D2 Steel

In the current work, AISI 4140 steel was pack-boronized at 950°C for 3 h and gas-nitrided at 550°C for 72 h. All specimens used in this work were prepared from the same steel bar. A 3-µm-thick diamond-like carbon (DLC) coating (a-C:H) was deposited on the AISI D2 high-carbon, high-chromium, cold-worked tool steel by a plasma-assisted chemical vapor deposition technique. Normalized, boronized, and nitrided steel pins were tested against DLC-coated AISI D2 steel at various normal loads (15, 30, 60, and 80 N) for 1,000 and 3,000 m sliding distance in ambient air. Specific wear rate of all pins decreased with increasing load, and a similar trend was observed for the coefficient of friction (COF). Microscopic and energy-dispersive spectroscopic (EDS) analysis confirmed the role of the transfer layer for a low COF with increasing load. At all loads, the specific wear rate of boronized pins was lower than that of the nitrided and normalized pin specimens. Boronized pins showed a specific wear rate in the range of 0.27 × 10^?8 to 0.44 × 10^?8 mm³/Nm and the COF was about 0.1.     

类金刚石表面改性C/C复合材料的摩擦磨损性能

采用等离子体增强化学气相沉积法在C/C复合材料基底表面制备了不同厚度的类金刚石（DLC）表面改性膜;用球-盘对磨的方式测试了C/C复合材料基底和DLC膜在干态下的摩擦磨损性能。结果表明:制备的表面改性膜具有典型的DLC结构特征,均匀致密;随着沉积时间的延长,DLC膜厚度逐渐增大,膜基结合强度依次减小;C/C复合材料基底的平均摩擦因数为0.285 8,磨损率约为1.6×10^-4mm³·N^-1·m^-1,表面改性膜的摩擦因数较基底有较大程度的降低,在0.08～0.27之间,磨损率也降低了1～2个数量级,且沉积时间越长其摩擦因数越小、磨损率越低。     

Evaluation of the Wear Energy Consumption of Nitrogenated Diamond-Like Carbon Against Alumina

The wear energy consumption of nitrogenated diamond-like carbon (NDLC) in the tribo-test against alumina was evaluated. The energy input induced by the power source of the tribometer is applied to the contact area of two sliding bodies. The energy is dissipated into the two bodies with various transforming energies, such as (1) wear energy, (2) friction heat, (3) strain energy, (4) plastic deformation energy, and (5) chemical reaction energy used to form the tribo-layer. Determining the breakdown of the energy consumption into each mode is notably important for the investigation of the tribological mechanism. The surface fracture energy of NDLCs was evaluated by the micro-indentation method. The newly created surface area was estimated using the wear particles size distribution measured by image processing. The consumed wear energy was obtained by the surface fracture energy multiplied by the new created surface area corresponding to the generation of the wear particles in the tribo-test. The index numbers of the wear consumption energy/energy input ratio of the NDLCs were almost the same as those of their wear coefficients.     

Tribological Properties of Diamond-Like Carbon Films in Low and High Moist Air

Diamond-like carbon (DLC) film was deposited on Si wafer by a plasma CVD deposition system using benzene. Tribological properties of the DLC film were evaluated using a ball-on-disk tribo-meter in low (RH 1720 %) and high humidity (RH 9095 %) conditions in air. The effect of sliding speed (4.2 mm/s to 25 mm/s) and load (1.06 N to 3.08 N) on friction and wear was investigated. The friction behavior of the DLC film was obviously different in low and high humidity. When tested under low humidity conditions, the friction coefficient decreased significantly with increasing speed, and increased with load. However, under high humidity conditions, the friction coefficient increased with the speed and decreased with increasing load. The wear of the DLC film was little influenced by the sliding speed, normal load and humidity; a level of 10^-8 mm³/Nm could be obtained in all tests. The formation of a uniform transfer layer would be the main factor which controlled the friction coefficient of the DLC films. Unlike the friction, the wear resistance of the DLC film is not so easy to discuss and may be affected mainly by the tribo-chemical reaction in all the test conditions.     

巴基管的润滑性能研究

本文实验研究了镍－磷－巴基管复合镀层的润滑性能,结果表明：巴基管复合镀层具有优良的减摩,耐磨特性,说明巴基管是一种性能优异的固体润滑材料。     

石墨含量对石墨固体润滑涂层摩擦学性能的影响

利用简便的刷涂法在钢基体表面制备了石墨固体润滑涂层。利用MM-200型摩擦磨损试验机对不同石墨含量的固体润滑涂层进行了详细的摩擦学性能对比试验。结果发现．石墨固体润滑涂层的摩擦学性能与石墨含量之间呈“马鞍形”变化规律，当石墨的质量分数为28％时，固体润滑涂层的减摩、耐磨性能最佳。     

润滑油膜电磁损伤故障的机理及防治方法

以PWM变频凋速高速电主轴为研究背景，建立了诱发润滑油膜电磁损伤故障的共模电压的物理模型，分析了润滑油膜在共模电压作用下发生放电导致油膜劣化的物理化学机理，系统地提出了抑制润滑油膜电磁损伤故障的方法和途径。     

精轧机组油气润滑系统的故障分析及改进

针对韶钢高线厂精轧机组油气润滑系统使用中存在的导卫轴承寿命短、油耗量大、部分轴承供油不足等问题,对精轧机组油气润滑系统进行改造:采用电磁给油器对精轧机组油气系统的原双线递进式分配器进行改造,通过PLC智能控制各润滑点给油量和给油周期,改善各润滑部件的润滑状况;通过在压缩空气管道上增加一组气动三联件,以除去压缩空气中的水和杂质,减少对润滑油的污染;通过对待换设备的预润滑,提高了其使用寿命。     

温度的非牛顿效应及其润滑失效机理分析

本文通过分析温度对粘度的影响建立了润滑剂因温度而产生的非牛顿流体模型。通过对简化问题分析表明：由于温度效应的普遍存在，一般润滑条件下也会表现出十分明显的流体非牛顿化现象。并根据给出的剪应力极值曲线指出了温度引起的非牛顿性可以导致重载条件下的润滑失效发生。     

齿轮润滑中PV曲线新特性及计算模型

大量资料表明,预测齿轮胶合常用的PV曲线在较宽的速度范围内具有抛物线型特征,过去还没有一种理论能对此作出合理的解释,本文根据齿轮润滑中不同的节线速度范围提出了反应膜的机械磨损和化学分解两种失效机理,进而对这两种机理作出了定量描述。在此基础上建立了一个综合计算模型,即胶合载荷与节线速度间是近似的二次函数关系,该综合模型与有关文献的试验结果相一致。本文为PV典线的高—低—高变化规律提供了合理的解释。     

重型汽车变速器润滑失效模式分析及控制

应用现代设计DFEMA分析技术,对重型汽车变速器润滑失效模式进行了分析研究,提出了针对组合式、多档位、大转矩重型汽车变速器润滑系统所采用的一种全新的强制润滑加辅助喷淋润滑设计技术,有效地提升了润滑系统的使用性能,延长了变速器的使用寿命。