水合羟乙基纤维素润滑时钛合金的摩擦学特性

Tribological Properties of Titanium Alloy in Water-based Lubricating Process of Hydroxyethyl Cellulose

以羟乙基纤维素(HEC)作为水基润滑添加剂,研究点接触条件下Ti-6Al-4V的摩擦学特性。采用超景深显微镜测量钛合金表面粗糙度,激光共聚焦显微镜测试氮化硅球三维形貌,采用能谱分析和拉曼光谱分析磨痕的物质组成,在UMT-2摩擦磨损试验机上分析线速度和润滑液浓度对Ti-6Al-4V摩擦学特性的影响。结果表明,摩擦过程经不同的跑合阶段,达到稳定的超低摩擦状态(μ≈0.005);随线速度、浓度的增大,氮化硅球和Ti-6Al-4V的摩擦系数先减小后增大;低线速度以及低浓度时无法形成可靠润滑膜,线速度过高时,摩擦产热导致水分子蒸发,润滑液浓度过高时,黏度显著增大,都不能实现超低摩擦;实现超低摩擦需合适的线速度以及水合分子浓度,此时钛合金表面形成微凸体磨平区域,有利于水合分子层产生斥力,形成稳定的润滑膜。通过微观分析,提出了钛合金的水基润滑模型。

HEC solutions with varying concentrations were used as lubricants, which were introduced into the friction pairs of Ti-6 Al-4 V plates and Si3 N4 balls. Optical surface profiler and 3 D measuring laser microscope were used to measure the surface of plates and balls,respectively. EDS and Raman spectroscopy were used to analyze the chemical composition of the resulting wear scars. The friction tests for the effect of linear speed and solution concentration on the tribology properties of Ti-6 Al-4 V were carried out on a UMT-2 friction and wear tester. The results show that a super-low friction state(μ≈0.005) is achieved after a long running-in stage. The coefficient of friction(COF) decreases with the increasing linear speed(46.1~362.7 mm/s). The water will evaporate at high speed(>362.7 mm/s) owing to the heat generated by the friction. In addition, the COF decreases with the increasing concentration(0.25%~2.00%). However, the kinematic viscosity of the lubricant has a significantly negative effect on the COF when the concentration is larger than 2.00%. The surfaces of Ti-6 Al-4 V are worn with smoothed flats at appropriate speeds and concentrations, which is conducive for forming lubricating films. TiO2 is detected on the scar by Raman spectrum. On the basis of these experimental results, a lubrication model was proposed.