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 of Hydroxyethyl Cellulose

摘要:

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上分析转速和润滑液浓度对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)；随转速、浓度的增大,氮化硅球和Ti-6Al-4V摩擦副的摩擦系数先减小后增大；低转速以及低浓度时无法形成可靠润滑膜,转速过高时,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转速以及水合分子浓度,此时钛合金表面形成的微凸体磨平区域,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。

Abstract:

HEC solutions of varying concentration were used as lubricant, which were introduced into friction pairs of Ti-6Al-4V plates and Si₃N₄ balls. Optical Surface Profiler and 3D Measuring Laser Microscope were used to measure the surface of plates and balls, respectively. The EDS and Raman spectroscopy were used to analysis the chemical composition on the resulting wear scars. The friction tests for the effect of speed and concentration of solution on tribology properties of Ti-6Al-4V were carried out on UMT-2. The results showed that a super-low friction state (μ≈0.005) was ahiceved after a long running-in stage. The COF decreases with the increasing rotational speed (80~630 r/min). The water will evaporate under high speed (> 630 r/min), which is owing to the heat by friction. In addition, the COF decreases with the increasing concentration (0.25%-2.00%). However, the kinematic viscosity of lubricant takes significant negative effect on COF when the concentration is larger than 2.00%. The surfaces of Ti-6Al-4V were worn down with smoothed flats under appropriate speeds and solutions, which was conducive for forming lubrication films. TiO₂ was detected on the scar by Raman spectrum. On the basis of these experimental results, a lubrication model was proposed.