表面微织构涂层-基体系统重载弹流润滑性能分析

Heavy Load Elastohydrodynamic Lubrication Performance of Surface Micro-textured Coating-substrate System

目的研究表面涂层与织构化协同作用时摩擦副的重载弹流润滑性能,为重载传动的摩擦学设计提供参考。方法基于广义Reynolds方程、线弹性方程以及载荷平衡方程,建立表面微织构涂层-基体系统的弹流润滑模型,并无量纲化,然后运用Full-system有限元法编程求解,探讨涂层的弹性模量以及三角形织构深度、宽度、密度对系统弹流响应的影响。结果载荷一定时,薄膜涂层(2μm)的弹性模量变化(50~500 GPa)对油膜压力整体分布影响较小,但二次压力峰在硬质涂层上更为显著。在涂层与基体存在弹性模量差时,其上由微织构引起的集中应力是无涂层的2~3倍。最小油膜厚度随着涂层弹性模量的增大而增大。随着织构深度的增大(0~5μm),油膜压力和厚度波动更加明显,最小油膜厚度随之减小,系统最大等效应力也显著增大。当织构宽度增大(10~20μm)时,油膜压力和厚度波动减弱,最小油膜厚度先减小后增大。如果织构密度增大(0.5~2),油膜压力波动更为剧烈,油膜厚度波动变化不大,但其波动周期变化明显,最小油膜厚度先减小后增大。膜基界面最大剪应力出现在二次压力峰附近,织构化表面油膜压力波动越大,膜基界面剪应力波动也越大。结论存在一个最优的织构深度、宽度和密度,使得镀膜齿轮的承载能力最佳。合理的涂层选配和微织构设计,可以有效地提高齿轮的摩擦学性能,提前预防膜基系统失效。

The paper aims to study the heavy load elastohydrodynamic lubrication(EHL)performance of friction pairs under the synergistic effect of surface coating and texturing,and to provide reference for the tribological design of heavy duty transmission.Based on equations such as generalized Reynolds,linear elastic,and load balance,the dimensionless EHL model of micro-textured coating-substrate system was established and non-dimensionalized.Then,the influences of the coating elastic modulus as well as depth,width,and density of triangular texture on the EHL response of the system were individually investigated by the Full-system finite element method.It was found that when the load was constant,the change of elastic modulus(50~500 GPa)of film coating(2μm)had little effect on the overall distribution of oil film pressure,but the second pressure peak on the stiffer coating was more significant.When the elastic modulus difference existed between the coating and substrate,the concentrated stress caused by micro-texture was 2~3 times as much as that uncoated solid.The minimum oil film thickness increased with the increase of the coating elastic modulus.With the increase of texture depth(0~5μm),the fluctuations of oil film pressure and thickness were more obvious.The minimum oil film thickness decreased accordingly.The maximum equivalent stress of the system also increased significantly.When the texture width increased(10~20μm),the undulations of oil film pressure and thickness decreased,and the minimum oil film thickness decreased first and then increased.If the texture density increased(0.5~2),the fluctuation of oil film pressure became more intense.The undulation of oil film thickness did not change much,but the fluctuation period changed obviously,and the minimum oil film thickness reduced firstly and increased afterward.The maximum interfacial shear stress appeared near the secondary pressure peak.The greater the fluctuation of oil film pressure on textured surface,the greater the undulation of interfacial shear stress.Thus,there is an optimal combination of depth,width,and density of texture for the coated gear to reach the largest load carrying capacity.Rational coating selection and micro-texture design can effectively improve the tribological performance of gears and prevent the failure of coating-substrate system in advance.