Abstract:
High-velocity oxy-fuel (HVOF) sprayed coatings have the potential to enhance the high-temperature
oxidation, corrosion, and erosion-corrosion resistance of boiler steels. In the current
work, 75 pct chromium carbide-25 pct (nickel-20 pct chromium) [Cr3C2-NiCr] coating was
deposited on ASTM SA213-T22 boiler steel using the HVOF thermal spray process. Hightemperature
oxidation, hot corrosion, and erosion-corrosion behavior of the coated and bare
steel was evaluated in the air, molten salt [Na2SO4-82 pct Fe2(SO4)3], and actual boiler environments
under cyclic conditions. Weight-change measurements were taken at the end of each
cycle. Efforts were made to formulate the kinetics of the oxidation, corrosion, and erosioncorrosion.
X-ray diffraction (XRD) and field-emission scanning electron microscopy
(FE-SEM)/energy dispersive spectroscopy (EDS) techniques were used to analyze the oxidation
products. The coating was found to be intact and spallation free in all the environments of the
study in general, whereas the bare steel suffered extensive spallation and a relatively higher rate
of degradation. The coating was found to be useful to enhance the high-temperature resistance
of the steel in all the three environments in this study.
