Effects of increase extent of voltage on wear and corrosion resistance of micro-arc oxidation coatings on AZ91D alloy

The effects of increase extent of voltage on the wear resistance and corrosion resistance of micro-arc oxidation (MAO) coatings on AZ91D magnesium alloy were investigated in silicate electrolyte. The results show that with increasing extent of voltage, both of the thickness and bonding force of MAO coatings first increase, and then decrease. These parameters are all up to their maximum values when the increase extent of voltage is 20 V. The roughness of the coatings always increases. The coating has the best corrosion resistance when the increase extent of voltage is not below 25 V, and the coating has the best wear resistance when the increase extent of voltage is 10 V. The wear mechanisms for the micro-arc oxidation are abrasive wear and micromachining wear. These are related to their microstructures.