Surface Plasma Spraying and High Temperature Oxidation Performance of Automotive Internal Combustion Engine

CoNiCrAlY coating and MoSi₂-CoNiCrAlY composite coating were prepared on the surface of GH4169 alloy for automotive internal combustion engine by plasma spraying. The phase composition, microstructure and high temperature oxidation resistance of single coating and composite coating were comparatively analyzed, and the mechanism of high temperature oxidation of coatings was explored. The results show that the CoNiCrAlY coating was mainly composed of γ'-Ni₃Al, ɑ-Al₂O₃ and γ-Co, MoSi₂ and Mo₅Si₃ phases also appeared in MoSi₂-CoNiCrAlY composite coatings; the phases of CoNiCrAlY coating at 1 025 ℃ with different oxidation times were Cr₂O₃, ɑ-Al₂O₃, NiCr₂O₄ and (Co,Ni) Cr₂O₄, while SiO₂ phase was also formed in the oxide film of MoSi₂-CoNiCrAlY composite coating; the hardness of the MoSi₂-CoNiCrAlY composite coating was higher than that of CoNiCrAlY coating, the antioxidant capacity was significantly better than that of CoNiCrAlY coating. Influence factors in “rapid oxidation stage” and “stable oxidation stage” of CoNiCrAlY coating were NiO, NiCr₂O₄ and (Co, Ni) Cr₂O₄ spinel phase growth rate and the growth rates of Al₂O₃ compact oxide film, and the key factors affecting MoSi₂-CoNiCrAlY composite coating for high temperature oxidation were diffusion and flow capacity of SiO₂.