HOT CORROSION BEHAVIOUR OF Cr3C2-NiCr COATED Gr A-1 AND T-22 BOILER STEEL BY HVOF PROCESS, IN Na2SO4-60%V2O5SALT

Abstract

High-temperature corrosion-resistant coatings is required so that the service lifetime of components used at higher temperatures in corrosive environments can be prolonged Boiler steels which are subjected to high temperature services can undergo hot corrosion. To prevent hot corrosion, coatings are applied on boiler steels. The present study concerned with the performance evolution of boiler steel by High Velocity Oxy Fuel sprayed Cr3C2-NiCr coatings on ASTM SA-210 (Gr A-1) and ASTM-213(T-22)steel and the coated and un coated samples were studied for high temp oxidation in air and molten (Na2So4-60% V205) salt at 900°C under cyclic conditions. The thermo-gravimetric technique was used to establish the kinetics of corrosion. X-ray diffraction and scanning electron microscopy/energy-dispersive analysis techniques were used to characterize the as sprayed coatings and corrosion products. All these coated samples showed better resistance to hot corrosion as compared to that of uncoated steel. It is concluded that in air oxidation coated T-22 and in salt oxidation coated Gr A-] showed better corrosion resistance. The formation of Cr203 may contribute to the development of hot corrosion resistance in the coating. The un coated steel suffered corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of un protective Fe203 oxide scale.