Study on Microstructure and Wear Resistance of Al-Al₂O₃/YSZ Coatings on Magnesium Alloy Prepared by Supersonic Plasma Spraying

Al-Al₂O₃(AA) coatings with different Al₂O₃ contents and Al-Al₂O₃/5YSZ (AAZ) coatings with different Al₂O₃/5YSZ contents were prepared on the surface of AZ61 magnesium alloy by supersonic plasma spraying technology, and the effects of YSZ addition and ceramic content on the microstructure, porosity, microhardness and wear resistance of the coatings were studied. The results show that the cross-sectional structure of AAZ coatings is refined compared with that of AA coatings, the structure is more uniformly, the pores in Al₂O₃ phase are reduced, and YSZ is diffusely distributed with ribbon and microscopic spherical particles. The microhardness of the coating increases with the increase of Al₂O₃/5YSZ content, and the hardness of AAZ coatings has a higher hardness than that of AA coatings. In the sliding friction wear test, compared with the AA coatings, the degree of adhesive wear of the AAZ coatings is reduced by the increase of the hardness of the coatings. The wear resistance of the AAZ coating with ceramic content of 50% is lower than that of the AA coatings with ceramic content of 30% and 70%, a large number of pores at the phase interface in the original structure of the coating reduce the bonding strength between the metal phase and the ceramic particles, resulting in the shedding of the ceramic particles, increasing the friction coefficient and wear rate. The AAZ30 coating with ceramic content of 30% undergoes abrasive wear and adhesive wear. AAZ coating with ceramic content of 70% has the best wear resistance, and the abrasive dust scattered in the wear marks play a role in anti-friction and lubrication during wear.