Study on the oxidation resistance mechanism of self-healable NiAl coating deposited by atmospheric plasma spraying

A dense NiAl coating with low oxide content was deposited on the GH4202 superalloy substrate by atmospheric plasma spraying (APS) using carbon-containing Ni/Al composite powders. Compared with traditional APS NiAl coatings with high oxide content, this coating exhibits better long-term oxidation resistance at 900 & DEG;C in air. For the NiAl coating with low oxide content, it was found that the improved inter-splat bonding, due to limited oxide inclusions, promotes the formation of a continuous protective Al2O3 layer on the coating surface during oxidation. During long-term oxidation, the dispersion of oxide scales within the coating and element diffusion across splats result in the in-situ healing of unbonded inter-splat interfaces.