Corrosion resistance of VC-reinforced Fe-based SMA coatings by laser cladding

Abstract

The corrosion resistance of 42CrMo steel is insufficient to meet the demands in the marine environment, despite its widespread application in bearings and other fields. Herein, Fe-Mn-Si-Cr-Ni-χ(VC) shape memory alloy (SMA) composite coatings were successfully fabricated on the surface of 42CrMo steel using laser cladding technology. The results present that the coatings are mainly composed of γ austenite (fcc) phase and ε martensite (hcp) phase. Based on research findings, the incorporation of VC has been found to promote the γ → ε martensite phase transition in shape memory alloys. Simultaneously, electrochemical tests were conducted on 42CrMo substrate and SMA coating in 3.5 wt% NaCl solution. It was found that the coatings doped with an appropriate amount of VC could effectively enhance its corrosion resistance. When the doping amount of VC reaches 1.5 wt%, the charge transfer resistance (Rct) is significantly higher than that of the 42CrMo substrate and the pure SMA coating, as well as that of the coating doped with 2.0 wt% VC, reaching 21, 2.6, and 3.3 times of them, respectively. The charge transfer resistance Rct of LS1.5 is much higher than that of 42CrMo, LS0, and LS2.0, reaching 21, 2.6, and 3.3 times, respectively. Additionally, the maximal polarization resistance (Rp) of coatings achieves 4.39 times that of 42CrMo. This study points out that VC can efficiently boost the corrosion resistance of SMA composite coatings and may have uncovered a novel approach for improving the surface corrosion resistance of medium carbon steel.