Effect of Process Parameters on Microhardness and Erosion Resistance of Atmospheric Plasma Spraying Al₂O₃-13%TiO₂ Composite Coating

Al₂O₃-13%TiO₂ (mass fraction) composite coating was prepared by atmospheric plasma spraying. The effect of spraying distance (80, 100, 120 mm), current (530, 565, 600 A), argon flow rate (31, 36, 41 L·min⁻¹) and hydrogen flow rate (10, 12, 14 L · min⁻¹) on coating microhardness was studied by four factors and three levels orthogonal tests, and the optimal process parameters were obtained. The phase composition, microstructure, corrosion resistance and erosion resistance of the coating under optimal process parameters were analyzed comparetively. The results show that the degree of influence on microhardness was from large to small as spraying distance, current, argon flow rate and hydrogen flow rate. With the increase of spraying distance, the microhardness increased first and then decreased; with the increase of current, argon flow rate or hydrogen flow rate, the microhardness decreased first and then increased. The optimal process parameters were listed as follows: current of 530 A, spraying distance of 100 mm, argon flow rate of 41 L · min⁻¹, hydrogen flow rate of 10 L · min⁻¹. Under the optimal process, the prepared coating had the highest microhardness,less γ-Al₂O₃ metastable phase content, less surface pores and micro-cracks, small porosity, and good corrosion resistance and erosion resistance.