A comparative study of tribological behavior of microarc oxidation and hard-anodized coatings

Microarc oxidation (MAO), a novel coating technique capable of depositing dense, hard ceramic composite coatings on aluminium and its alloys, has the potential to replace conventional hazardous anodizing techniques. However, the emergence of such a scenario depends strongly on the properties and performance of MAO coatings in comparison to hard-anodized coatings. In order to facilitate such a comparative investigation, a 6061 T6 aluminium alloy was employed as the substrate and the coatings were deposited through microarc oxidation (MAO) and hard anodizing techniques. The tribological performance of the coatings was evaluated using dry-sand abrasive wheel tests at different normal loads and solid-particle erosion wear tests at different particle velocities and impact angles by employing silica as erodent. The hard-anodized coatings reduced the abrasive wear rate of 6061 Al alloy by a factor of 2, while the MAO coatings reduced the wear rate by a factor of 12–30. Under erosion conditions, the overall wear rate of MAO coatings is identical to that of bare alloy, whereas the hard-anodized coatings exhibit 10 times higher erosion rate.