In this study, the process optimization of sprayed powders and deposition performance for amorphous Al2O3–Y3Al5O12 (YAG) coatings was investigated. The solid-state reaction mechanism of the nano-sized Al2O3 and Y2O3 powders with eutectic molar ratio was studied by multiple step-by-step heating cycle calcination processes. The calcination process could be adjusted according the dominant control factors like chemical reaction rate or ion diffusion rate. Finally, the actual deposition performance of the calcined powders (Al2O3/YAG) was examined by atmospheric plasma spraying (APS). XRD, SEM and DTA were used to characterize the powders and the as-sprayed coatings. The results showed that the reaction of Al2O3–Y2O3 system is a high temperature solid reaction dominated by Al3+ diffusion, the initial reaction process was usually belong to chemical kinetic range, then the reaction will be transformed from chemical kinetic range to diffusion dynamic range with the temperature increasing. The process optimization of powders was very effective, and the deposition effect of coating was effective.

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