Microstructural characterization and properties of ZrO2/Al2O3 thermal barrier coatings by gas tunnel-type plasma spraying

Spraying condition plays an important role in the plasma-sprayed coating process and affects the final properties of the coatings. Zirconia, alumina and zirconia/alumina composite coatings were prepared on a stainless-steel substrate (SUS304) by the gas tunnel-type plasma spraying. Effects of different alumina mixing ratios on the coating properties were investigated. The results indicated that the mixing ratio of powders and the traverse number of substrate had an influence on the hardness, porosity and wear weight loss of composite coatings. The hardness increased while the porosity decreased with the increase in alumina mixing ratio. The porosity that was less than 10% and a hardness about Hv=1400 was obtained for the alumina coating. The adhesive strength and wear weight loss of the composite coatings were also clarified at different alumina mixing ratios.