Improved corrosion properties of novel Fe-Cr-B based metamorphic alloy designed for thermal spray process by adding Nb and Mo

Abstract

ABSTRACT In this study, new metamorphic alloy powder (M+) with an optimised composition of Fe-Cr-B-Mo-Nb appropriate for thermal spray process was developed by adding Mo and Nb, and the novel metamorphic alloy coating was fabricated by atmospheric plasma spray (APS) process. Thereafter, the corrosion resistances of the coatings were investigated and compared with those of commercial Fe-Cr-B based metamorphic alloy (M). The high-temperature oxidation resistance of the developed M+ powder feedstock was 2.18 times better than that of the commercial M. The in-flight oxidation occurring during APS process in M+ alloy decreased by 39.5% compared to that in M alloy. The passivation behaviour of M+ alloy was more stable than that of M alloy in a 3.5 wt% NaCl solution. The effect of adding Nb and Mo on the corrosion resistance of M+ coatings was also discussed in connection with microstructural changes.