Microstructure, adhesion, microhardness, abrasive wear resistance and electrical resistivity of the plasma sprayed alumina and alumina-titania coatings

Al2O3 and its mixtures with TiO2 powders were prepared by a fused and crushed method. Prepared powders were sprayed at 10, 12 and 16 kW power in atmospheric plasma spraying. Microstructure of the coatings was analysed by SEM. Alumina coatings showed better quality than composite coatings. Different types of pores were observed in alumina-titania (AT4016) coating. Pore forming mechanisms are reported. Adhesion strength, microhardness and abrasive wear resistance of alumina and alumina-titania coatings were measured and results are explained. The influence of the power to the plasma torch, powder particle size and its distribution and feed rate of the powder on the abovesaid properties of the coatings are explained. Electrical resistivity was measured in composite coatings. The electrical conductivity increases with increased titania content in the coating. (C) 1998 Elsevier Science S,A.