A study to enhance the mechanical durability of the MAO coating fabricated on the 7075 Al alloy for wear-related high temperature applications

This work has been initiated with the aim of increasing the success of micro-arc oxidation coatings fabricated on aluminium alloys against degradation under sliding contact conditions at high temperatures. For this purpose, the 7075 Al alloy has been micro-arc oxidised in an aluminate-based electrolyte with or without the adding monoclinic ZrO2 particles. Microstructural analyses revealed that the coating synthesised in a ZrO2-added electrolyte consisted of a ZrO2 particles participated Al2O3-based outer layer and a monolithic Al2O3-based inner layer, which exhibited similar features with that of the synthesised in the ZrO2-free aluminate-based electrolyte. Moreover, the coating fabricated in the ZrO2-added electrolyte exhibited enhanced wear resistance during the dry sliding wear tests conducted at room temperature and had higher durability during the tests done at 300 degrees C. Since the examined coatings were worn by fatigue wear mechanism, their durability during high temperature wear tests was analysed by using the conventional stress-based fatigue approach. From the derived equations, the maximum contact pressures at which coatings can endure 106 contact cycles at 300 degrees C were estimated as 851 and 331 MPa for the coatings fabricated in the ZrO2-added and ZrO2-free aluminate-based electrolytes, respectively.