Comparative study of corrosion behaviour of HVOF-coated boiler steel in actual boiler environment of a thermal power plant

The present study was focused on the performance and behaviour of high velocity oxy-fuel (HVOF) sprayed 75Cr 3 C 2 -25NiCr and 86WC-10CO-4Cr coatings on boiler steel alloys ASME SA213 T22 and ASME SA213 T91 in coal-fired boiler environment. Both coated and bare steel alloys were subjected to cyclic exposures, in the superheater zone of a coal-fired boiler for 10 cycles at 900 ° C to compare the effect of both the coatings in actual conditions. During the study, each cycle consisted of 100 h heating followed by 1 h cooling at ambient conditions and to establish the kinetics of corrosion thermogravimetric technique was used. Corrosion products were analysed by using X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) techniques. The hot corrosion resistance of both 75Cr 3 C 2 -25NiCr and 86WC-10CO-4Cr coating was found better on ASME SA213 T22 whereas 86WC-10CO-4Cr coating showed higher corrosion resistance on ASME SA213 T22 as compared to 75Cr 3 C 2 -25NiCr coating.