118 / 2021-12-01 10:56:11

The investigation on tribological property and service life of PI coatings on engine bearing

composite coating，wear，wide range temperature, life

In order to improve the tribological performance of aluminum alloy engine bearing under conditions of oil lubrication and even dry friction. Four kinds of PI/EP-PTFE composites filled with different contents of ZrO₂ were designed. The coating was prepared on the surface of A370 aluminum alloy by liquid spraying process. The tribological properties of the coating at different temperatures and different lubrication modes were studied by friction and wear test, nano indentation test, morphological characteristics and element distribution test. With the increase of ZrO₂ content, the agglomeration phenomenon becomes worse. The hardness of the coating increases firstly, and then decreases with the increase of ZrO₂ content. The wear rate decreases firstly, and then increases with the increase of ZrO₂ content under dry friction conditions at room temperature. When ZrO₂ content exceeds 8wt.%, the time of entering the dynamic equilibrium stage becomes longer. The addition of 4wt.% ZrO₂ is the best, and the dry friction coefficient and wear rate at room temperature are 0.09 and 1.01×10^-6mm³/Nm, respectively. With the increase of temperature, the friction coefficient increases firstly, and then decreases. However, the wear rate increases gradually. As ZrO₂ content is less than 4wt.%, the coating is mainly adhesive wear at room temperature. When ZrO₂ 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 friction coefficient and wear amount decrease further. After 8h 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 ZrO₂, 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. The wear life of the coating is predicted by ABAQUS based on the calculation of wear depth, and the maximum error of wear life prediction is 5.71%.