油润滑下水含量对DLC薄膜摩擦学性能的影响

Effect of Water Content on the Tribological Performance of DLC Films under Oil Lubrication

类金刚石(DLC)薄膜已被广泛应用于发动机核心部件的摩擦学防护。为了研究在发动机运行工况下水含量对DLC薄膜摩擦学性能的影响,本研究以水-PAO6混合乳液为润滑剂,考察了发动机中广泛使用的2种DLC薄膜(a-C薄膜和a-C:H薄膜)在不同温度下的摩擦磨损性能。结果表明:在水-PAO6混合乳液的润滑条件下,摩擦系数受含水量的影响较小,总体上存在小幅增加。a-C薄膜部分失效,而a-C:H薄膜尚未出现基底暴露现象,2种薄膜的磨损率随着含水量的增加而降低。表面分析表明,水含量的增加抑制了二硫代氨基甲酸钼(MoDTC)的降解过程,从而减少了润滑添加剂MoS_(2)的形成。此外,水含量的升高还促进了碳向对偶球表面的转移。碳质转移膜、MoS_(2)和铁氧化物的共同作用影响了DLC薄膜的摩擦学行为。

Diamond-like carbon(DLC) films have been extensively applied in tribological protection of core components in engines. In order to investigate the effect of water content on the tribological properties of DLC films under engine operating conditions, a water-PAO6 emulsion was used as the lubricant to examine the friction and wear behavior of two types of DLC films commonly applied in engines(a-C and a-C:H films) at different temperatures. Results showed that under the lubrication conditions of the water-PAO6 emulsion, the friction coefficient was slightly influenced by the water content, showing a minor overall increase. Partial failure occurred in the a-C films, whereas no substrate exposure was observed in the a-C:H films. The wear rates of both films decreased with the increase in water content. Surface analysis revealed that the increase in water content inhibited the degradation of molybdenum dithiocarbamate(MoDTC), thereby reducing the formation of the lubricant additive MoS_(2). Moreover, the rise in water content promoted the transfer of carbon to the counter-ball surface. The combined effects of the carbon transfer film, MoS_(2) and iron oxides influenced the tribological behavior of the DLC films.