ZrO_(2)填充PI/EP–PTFE固体润滑涂层的制备及其摩擦学性能

Preparation and Tribological Properties of PI/EP-PTFE Solid Lubrication Coating Filled with ZrO2

目的提高发动机铝合金轴瓦在温升的油润滑甚至干摩擦工况下的摩擦磨损性能。方法设计4种不同添加量的ZrO_(2)填充PI/EP–PTFE涂层材料,采用液体喷涂工艺在A370铝合金基体表面制备涂层。通过摩擦磨损试验、纳米压痕试验、形貌特征及元素分布等测试试验,研究涂层在不同温度及不同润滑方式下的摩擦磨损性能。结果涂层的硬度随ZrO_(2)添加量的增加呈先增后减的趋势。在室温干摩擦工况下,涂层磨损率随ZrO_(2)添加量的增加呈先减后增的趋势。当ZrO_(2)添加量超过8%时,涂层进入动态平衡阶段的时间变长。4%ZrO_(2)添加量的涂层性能最佳,室温干摩擦因数和磨损率分别为0.09和1.01×10^(‒6) mm^(3)/(N·m)。随着温度增加,摩擦因数呈先增后减的趋势,磨损率呈逐渐上升趋势。当ZrO_(2)质量分数小于4%时,室温工况下涂层以黏着磨损为主;当添加量高于8%时,磨损机制以磨粒磨损为主。随着温度增加,涂层犁沟和磨损坑道更加明显。在油润滑工况下,摩擦因数和磨损量进一步减小。8 h油润滑和30 min干摩擦试验后,涂层出现磨痕深度高度相近,宽度不同现象。结论在温升和不同摩擦接触状态下,涂层中高分子材料和ZrO_(2)软化程度不均匀、大颗粒材料团聚、润滑油黏温特性是导致上述摩擦磨损变化的主要原因。

Self-lubricating polymer composite coating has excellent frictional and mechanical properties,which improves the surface properties of engine bearing without changing the original properties of the substrate.Due to heavy environment pollution from the electroplate,the plating technology for engine bearing is taking place by polymer coating.The functional filler added into the single polymer coating would improve the mechanical properties such as low friction,wear resistance,high temperature resistance and so on.The tribological properties of PI/EP-PTFE composite coating filled by ZrO_(2) on the surface of A370 aluminum alloy are studied in this paper.The A370 aluminum alloys were cut into 20 mm×20 mm×3 mm cubes,and they were used as the base material for sand blasting,cleaning and preheating.Firstly,polyimide(PI),epoxy resin(E44),acetone and dimethylformamide were put into a ball milling.Then,different proportions of ZrO_(2)(mass fractions of 0%,4%,8%and 12%)were added and mixed.The uniformly mixed materials were sprayed on the surface of the preheated A370 aluminum alloy surface.The pressure of spray was 0.3 MPa,the distance of spray was(230±20)mm,and the angle of spray was(80±5)°.The sample was obtained after high temperature curing.Scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS)were used to characterize the cross-sectional morphology and element distribution of the coating.Then,the two-dimensional morphology and wear volume of the coating wear mark section were analyzed by a three-dimensional optical profiled analyzer(UP-Lambda).The wear trace morphology of the coating was observed and analyzed by optical microscope(SU500).The hardness and elastic modulus of the coating were tested with a nano indentation instrument(Hysitron Ti premier).The frictional tests were carried out on CSM-01 high frequency friction and wear tester.The wear rate of the sample was calculated,and the wear morphology after friction test was observed.With the increase of ZrO_(2) content,the agglomeration phenomenon becomes worse.The hardness of the coating increases firstly,and then decreases with the increase of ZrO_(2) content.The wear rate decreases firstly,and then increases with the increase of ZrO_(2) content under dry frictional conditions at room temperature.When ZrO_(2) content exceeds 8wt.%,the time of entering the dynamic equilibrium stage becomes longer.The addition of 4wt.%ZrO_(2) is the best,and the dry frictional coefficient and wear rate at room temperature are 0.09 and 1.01×10^(‒6) mm3/(N·m),respectively.With the increase of temperature,the frictional coefficient increases firstly,and then decreases.However,the wear rate increases gradually.As ZrO_(2) content is less than 4wt.%,the coating is mainly adhesive wear at room temperature.When ZrO_(2) content is more than 8wt.%,the coating is mainly abrasive wear.As temperature increases,furrows and worn tunnels become more pronounced.Under the condition of oil lubrication,the frictional coefficient and wear amount decrease further.After 8 h oil lubrication and 30 min dry friction test,the wear depth of the coating is approximately similar,and the width is different.The non-uniformly softened of polymer materials and ZrO_(2),agglomeration of large particle materials,viscosity characteristics of lubricating oil under temperature rise,and different friction and contact states are the main reasons,that leads to the above variations of friction and wear.