The investigation of microstructure and tribological properties of PTFE/PI-PAI composite coating added with VN

Abstract

Four PTFE/PI-PAI coatings filled with different contents of VN were designed to improve the tribological properties of engine bearing bush. These composite coatings were prepared on copper alloy substrates by liquid spraying. The tribological properties of these coatings at different temperatures and different lubrication ways were studied. Results show that the wear mechanisms of these coatings under dry sliding wear are transformed from adhesive wear at room temperature to abrasive wear at high temperatures under 8 wt% and 12 wt% VN. The coating under 4 wt% VN has the best wear resistance. As the content of VN exceeds 8 wt%, the hardness and tribological properties of these polymer coatings are decreased due to the agglomerated materials. The CoFs (coefficients of friction) of these composite coatings under 0 wt% VN and 4 wt% VN at 150 °C are lower than those at room temperature. On the contrary, as the VN exceeds 8 wt%, these CoFs under high temperature are higher than those at room temperature. The wear rate of the composite coating under 4 wt% VN increases with the temperature under oil lubrication. However, the wear rates of these coatings under dry sliding wear show a trend of first decrease and then increase with temperature. The non-uniformly softened polymers and VN, agglomeration of large particle materials, and the characteristics of oil viscosity under rising temperature and different frictional contact are the main reasons.