Microstructure and Mechanical Property of Al₂O₃/YAG Wear-Resistant Composite Coating Deposited by Atmospheric Plasma Spraying

In this investigation, commercial Al₂O₃ and Y₂O₃ nanopowders were used to produce a composite powder feedstock that was plasma sprayed on graphite substrates. An Al₂O₃/Y₃Al₅O₁₂ (YAG) eutectic crystalline structure was expected in the coating due to the high enthalpy, large temperature gradient, and rapid solidification of the plasma spraying process, but microstructure and phase analysis of as-sprayed deposits revealed only a small amount of crystalline grains in an amorphous coating matrix. After heat treating, the expected structure was obtained and found to have excellent microstructure and microhardness stability at high temperatures.