High-Temperature Sulfate Corrosion Resistance and Wear Performance of NiCr-Cr3C2 Coatings for the Water Wall of Power Plant Boilers

Water walls in power plant boilers are prone to failure under extreme conditions involving high temperature, corrosion, and wear, which severely threaten unit reliability and operational economy. In this work, a NiCr-Cr3C2 protective coating was deposited on SA213-T12 steel substrates using high-velocity oxy-fuel (HVOF) spraying, with arc-sprayed PS45 coating as a reference. The NiCr-Cr3C2 coating exhibited a dense, low-porosity structure with homogeneous dispersion of Cr3C2 hard phases in the NiCr matrix, forming a typical cauliflower-like composite morphology. During high-temperature sulfate corrosion tests at 750 °C, the NiCr-Cr3C2 coating demonstrated superior corrosion resistance, with a weight gain of only 2.7 mg/cm2, significantly lower than that of the PS45 coating and the SA213-T12 substrate. The higher microhardness and lower friction coefficient also indicate excellent high-temperature wear resistance. The enhanced performance of the NiCr-Cr3C2 coating is attributed to the high Cr content, which promotes the formation of a continuous and protective scale composed of Cr2O3 and NiCr2O4, effectively inhibiting corrosive diffusion and penetration. This work demonstrates the application prospects of NiCr-Cr3C2 coatings on water walls of power plant boilers and guides the development of advanced HVOF coatings.