ReactiYe Plasma Spraying of AlN/Al_2O_3 Feedstock Powder upon Fabrication of AlN coating

摘要

Plasma spraying is a versatile technique for producing abradable and protective ceramic coatings. However, it was difficult to fabricate aluminium nitride (AlN) coating by conventional plasma spray processes. It is due to the thermal decomposition of the feedstock AlN powder during spraying without a stable melting phase. Reactive plasma spraying (RPS) has been considered as a promising technology for in-situ formation of AlN thermally sprayed coatings. Recently, thick Al_2O_3/AlN composite coatings were fabricated through reactive plasma spraying of alumina (Al_2O_3) powder in N_2/H_2 plasma. The fabricated coating consists of c-AlN, Al_5O_6N, γ-Al_2O_3 with high content of α-Al_2O_3 feedstock. This study investigates the feasibility of improving the nitriding conversion and the nitride content through spraying of fine Al_2O_3/AlN feedstock mixture. Furthermore, the effect of nitriding species (N_2, H_2) on the fabrication process, the coating microstructure and properties was investigated.