Abstract: LPPS (Low Pressure Plasma Spray) alumina coatings with deposition efficiency higher than 50% and porosity lower than 2% were elaborated using fine alumina powder as feedstock. Characteristics of alumina coatings prepared with different LPPS parameters, including deposition efficiency, phase composition and microstructure, were investigated. The effects of plasma power and chamber pressure on the LPPS alumina coatings were also studied. The results demonstrate that LPPS alumina coating consists of α-Al₂O₃ and γ-Al₂O phase. The porosity is evidently decreased with the increase of power and chamber pressure, but plasma power has insignificant influence on the porosity when the chamber pressure is as high as 23.7kPa. The particle temperature and velocity in plasma plume are obtained on the basis of empirical formula, which reveals that particles with high velocity in plasma plume are completely molten when the pressure is 23.7kPa.

Key words: low pressure plasma spray, alumina coating, characteristics