Abstract:The effects of main gas flow rate, spraying power and powder feeding rate on the bonding strength and microhardness of Al₂O₃ ceramic coating were studied by orthogonal experiment. The structure of powder and coating was studied by X-ray diffraction and scanning electron microscopy. The bonding strength and cross- section hardness of coating were measured by WDW-50 microcomputer controlled electronic universal testing machine and HV-1000 Vickers hardness tester. The experimental results were analyzed by range analysis and variance analysis combined with the coating structure, and the optimized process parameters were obtained. The results showed that the coating was composed of melted and unmelted regions, and the cross-section morphology was concave-convex occlusion, mainly mechanical bonding. The order of process parameters of sound atmospheric plasma spraying Al₂O₃ coating was spraying power, main gas flow rate and powder feeding rate. With the increase of power and main gas flow rate, the bonding strength and hardness of the coating increased first and then decreased. The optimum technological parameters of atmospheric plasma spraying Al₂O₃ were spraying power 44KW, main gas flow rate 40L/min, powder feeding rate 40g/min, bonding strength 52MPa, microhardness 1219.4HV0.3 and porosity 4.00%.