The effect of plasma torch power on the microstructure and phase composition of alumina coatings

Alumina coatings were obtained by the atmospheric plasma spraying using Al 2 O 3 nanopowders. The powders were injected into the anode zone of the torch. The microstructures and phase compositions of the coatings were determined by the scanning electron microscopy and X-ray diffraction. The results indicated that the higher the plasma torch power, the lower the surface roughness is. The as-sprayed coatings are composed of γ-Al 2 O 3 and α-Al 2 O 3 , while the original powders were composed of δ-Al 2 O 3 and γ-Al 2 O 3 phases. The amount of γ-Al 2 O 3 in the coatings increases from 56.52% to 100% if the plasma torch power is increased from 3.2 kW to 4.5 k