Corrosion Behavior of a Ni–Cr–Mo Alloy Coating Fabricated by Laser Cladding in a Simulated Sulfuric Acid Dew Point Corrosion Environment

Abstract

For this study, aimed at proposing a potential direction to prevent sulfuric acid dew point corrosion, a Ni–Cr–Mo alloy Hastelloy C22 coating was fabricated by coaxial laser cladding technology. The phase composition, microstructure, and corrosion behavior in a simulated sulfuric acid dew point corrosion environment were investigated and compared with a Hastelloy C22 alloy, a titanium alloy TC4, and 09CrCuSb steel (ND). The results showed that the phase composition of the C22 coating is essentially similar to that of the C22 alloy, consisting of a γ-Ni solid solution and Ni6Mo6C1.06. The finer microstructure of the C22 coating mainly contains eutectic and dentrite, presenting a typical solidification feature of laser cladding. The corrosion resistance of the C22 coating is very close to that of the C22 alloy, and outclasses that of TC4 and ND. The corrosion behavior of the C22 coating is intergranular corrosion resulting from the segregation of molybdenum, chromium containing corrosion products, and smaller anode micro-batteries.