Effect of additions of TiC and Re on high temperature corrosion performance of cold sprayed Ni–20Cr coatings

Abstract

Thermal spray coatings have been widely used to combat corrosion and erosion–corrosion problems in power plant boilers. In the present work, commercially available Ni–20Cr powder, Ni–20Cr blended with TiC powder and Ni–20Cr blended with TiC and Re powder were successfully deposited on a boiler steel (SAE 213-T22) by the cold spraying technique. The uncoated and coated specimens were subjected to a molten salt environment of Na2SO4–60wt.%V2O5 at 900°C under cyclic conditions. Mass change was used to establish the kinetics of corrosion. X-ray diffraction, surface and cross-sectional FE-SEM/EDS techniques were used to analyze the corrosion products. All the cold spray coatings performed better than the uncoated steel; the better hot corrosion resistance of the coatings in comparison to the uncoated steel may be attributed to the formation of oxides and spinels of nickel and chromium. The hot corrosion resistance of cold sprayed Ni–20Cr–TiC–Re coating was found to be the best amongst all the studied coatings.