Research on the high temperature oxidation mechanism of Cr3C2–NiCrCoMo coating for surface remanufacturing

To improve the high-temperature oxidation performance of remanufactured coatings, a novel Cr3C2–NiCrCoMo (NCC) coating with modified multielement alloy adhesive phase was developed. The objective of this work is to explore the synergistic effect of multiple alloying phases on the oxidation resistance of coating based on theoretical calculation and reveal the oxidation mechanism of coating at high temperature. First, the NCC composite powder was deposited by high-velocity oxygen fuel spray and the high temperature cycle oxidation experiments at 700 °C, 800 °C and 900 °C were conducted for coated specimens. Then the oxidation reactions and the integrity of oxidation film were analyzed and calculated based on Gibbs free energy calculation and Pilling-Bedworth ratio (PBR). Additionally, the microstructure and phase composition of the oxide scale were characterized by SEM and XRD. The results indicate that, compared with the original Cr3C2–NiCr (NC) coating, the novel NCC coatings exhibit lower oxidation rate, remarkable oxidation resistance and preferable interface matching between the oxide scale and the coating. The enhanced oxidation resistance is attributed by the multicomponent composite oxide scales formed within NCC coatings which improves the density and stability of the oxide scale and reduces the diffusion of metal ions and oxygen.