Comparative analysis of microstructure and corrosion resistance in laser-clad austenitic and martensitic stainless-steel coatings

Abstract

Post-casting austenite often possesses better corrosion resistance than martensite. In order to compare the difference of corrosion resistance between austenitic stainless steel coating (ASSC) and martensitic stainless steel coating (MSSC) in the powder metallurgical state, two stainless steel Fe-based alloy coatings of the same process parameter were prepared on the surface of 40Cr steel by using laser cladding technology. Through SEM, EBSD, XRD and electrochemical tests, the microstructure, phase and cross-section metallurgical bonding condition of the coating were studied, and the difference in corrosion resistance between the two was comprehensively analyzed. The results showed that the main phase structure of ASSC was the FCC phase, and the main phase structure of MSSC was the BCC phase. The average self-corrosion current (9.92 × 10−8 A/cm2) and average self-corrosion rate (1.04 × 10−3 g/m2·h) of MSSC were 4.77 % and 5.62 % of ASSC, respectively. In addition, the polarization resistance, impedance value, and passivation film density of MSSC are higher than ASSC, MSSC has less damage from corrosion. The combination of factors, such as fabric refinement and passivation film density, makes the corrosion resistance of MSSC better than ASSC.