Corrosion Resistance Mechanism of Stellite-6 Coating on 42CrMo Substrate by Overlap Remelting

Abstract

To delay the corrosion rate of 42CrMo steel in oil and gas drilling industry, Co-based coatings were prepared on 42CrMo steel through laser cladding at different overlap rate (20%, 50% and 60%). The relationships between microstructure and corrosion behaviour of Stellite-6 coating in Cl ion corrosion medium were analysed by means of SEM, polarization curve and EIS. The results showed that the microstructures of Stellite-6 coating were mainly equiaxial crystal, and the corrosion form of cladding Stellite-6 alloy was pitting corrosion. The best corrosion resistance of Stellite-6 coating was the coating prepared at the overlap rate 50%. The formation of passivation films (Cr2O3 and Cr(OH)3) on the coating could obviously improve the corrosion resistance in Cl ion corrosion medium.