Effect Of Particle Morphology On The Tribological Behavior Of Cold Sprayed Al MMC Coatings

Cold sprayed pure aluminum or Al-Al₂O₃ coatings are used for repair and corrosion protection for magnesium aerospace gearbox components. Al-Al₂O₃ coatings are sprayed from an admixed feedstock of Al and Al₂O₃ powders, and during deposition some Al₂O₃ particles are recovered into the final coating. In this study, the effect of Al₂O₃ particle morphology on the tribological performance was examined, where the more common angular particle morphology was compared to spherical particles. Cold sprayed Al-Al₂O₃ coatings were deposited using angular and spherical Al₂O₃ powders and subjected to both dry sliding wear tests and high pressure torsion. The effect of Al₂O₃ morphology was explored in terms of Al₂O₃ recovery in the coating, microstructure, and the subsequent tribological behavior in dry sliding. Microstructures from high pressure torsion experiments revealed different deformation mechanisms near Al₂O₃ particles of different morphology. Comparisons to near surface microstructures from dry sliding wear led to correlations between the two testing methods that helps to explain the differences in wear performance due to particle morphology.