Fretting Wear Behavior of Microarc Oxidation Film on A356 Aluminum Alloy

The micro-arc oxidation (MAO) ceramic film with wear resistance was prepared on the surface of A356 aluminum alloy by MAO technology. The investigation of MAO effect on the fretting wear mechanism of A356 aluminum alloy was explored on an SRV-V fretting friction and wear testing machine by sphere-plane point contact under different normal loads and displacements. The results show that the MAO film consists of a porous outer layer and a dense inner layer with good homogeneity, denseness and bonding strength. The friction coefficient and wear rate of MAO film are lower than those of A356 aluminum alloy when the normal load and displacement increase. It indicates that the MAO film has good friction reduction and wear resistance. The frictional dissipation energy coefficient of MAO film is lower than that of A356 aluminum alloy when the displacement increases, which can enhance the wear stability of fretting wear process of A356 aluminum alloy. The wear mechanism of A356 aluminum alloy changes from abrasive wear to adhesive wear when the normal load increases, accompanied by ploughing and fatigue peeling. The wear mechanism of MAO film changes from abrasive wear to adhesive wear and fatigue peeling when the normal load increases. The wear mechanism of A356 aluminum alloy changes from adhesive wear and fatigue peeling to adhesive wear and abrasive wear when displacement increases. The wear mechanism of MAO film changes from adhesive wear and fatigue peeling to adhesive wear and abrasive wear when displacement increases. The accumulated Fe and O elements are gathered within the A356 aluminum alloy wear scars, which indicates that there is material transfer and oxidation wear during the fretting wear process of GCr15/A356 aluminum frictional counterparts. The Fe atoms are gathered within the MAO film wear scars, which indicates that there is material transfer of GCr15/MAO film frictional counterparts.