Influence of MoSi2 Addition in Co Based Alloy Cladding Coating on Microstructure Evolution and Pitting Corrosion Behaviour

Abstract

In the present paper the influence of the addition of MoSi2particles on the microstructure and pitting corrosion behaviour of laser cladding Co based alloy coatings deposited on 304 stainless steel substrate has been reported. The coating microstructure was investigated by SEM, OM, XRD and EPMA etc.. And the pitting corrosion resistance of coating was evaluated in the 3.5% NaCl solution. The results showed that: (1) The microstructure is fined by increasing MoSi2percentage. And the coating microstructure evolved from dendrites and interdendritic eutectics to various faceted dendrites with the bamboo leaf, flower, or butterfly morphology, when the MoSi2content is from 0~20% to 30~40%; (2) the (Epit-Eprot) of Co based alloy/MoSi2composite coating was lower than that of Co based alloy, and which presented higher self-repairing capability. The pitting potential Epitof Co +(0~20wt.%) MoSi2cladding coatings is higher than that of stainless steel, the pitting corrosion resistance is enhanced; When more MoSi2(30wt.%) was added, the pitting corrosion resistance decreases due to microstructure inhomogeneity and exiting of inclusion.