Microstructure and phase formation of atmospheric plasma sprayed YAG coatings

Abstract

In this study, a YAG coating was prepared on a titanium alloy (Ti60) utilizing the Atmospheric Plasma Spraying (APS) technique. SEM, XRD, and TEM were employed to analyze the microscopic morphology and phase composition of the coating. The results show that the APS YAG coating is complete, compact and well-bonded. The coating is primarily amorphous and composed of YAG, YAP, YAM and other Y-rich composition. The formation of Y-rich components is caused by the loss of Al2O3.However, due to continuous heating of the plasma plume, the surface of the coating exhibits higher crystallinity. The main crystalline phases in the coating are YAG, YAP and YAM. Besides the plasma plume, recrystallization of melted YAG particles and un-melted portion of YAG particles contribute to other crystalline phases in the coating. Furthermore, the formation of Y-rich stringer structure in the coating is also associated with droplet splashing.