Microstructure and Mechanical Properties of Ni5Al/Al₂O₃-3%TiO₂ Composite Structural Coating by Atmospheric Plasma Spraying

Ni5Al alloy adhesive coating was pre-prepared on the surface of 6061 aluminum alloy substrate, and then Al₂O₃-3%TiO₂ ceramic coating was prepared on the adhesive coating by atmospheric plasma spraying (APS) technique. The phase composition, micromorphology, microhardness, bonding strength, wear resistance and corrosion resistance of the coating were studied, and the tensile fracture mechanism was analyzed. The results show that the phases in the creamic coating mainly consisted of α-Al₂O₃, γ-Al₂O₃ and anatase TiO₂. Mechanical bonding was formed between adhesive coating and substrate, and between adhesive coating and ceramic coating, but the bonding interface between the adhesive coating and substrate was more dense. Compared with the substrate, the coating had higher microhardness, better corrosion resistance and better wear resistance. The bonding strength of the coating was lower than that of the adhesive coating. The tensile fracture mostly occured at interfaces between the adhesive coating and ceramic coating, and also in the ceramic coating. The tensile fracture mode at the interface was mixed fracture; the adhesive coating had a ductile fracture, and the ceramic coating had a brittle fracture.