COMPARISON OF HOT CORROSION PERFORMANCE OF BARE AND NiCoCrAlY-COATED AUSTENITIC STAINLESS STEEL AISI 347 IN AGGRESSIVE WASTE HEAT INCINERATOR ENVIRONMENT AT 650∘C

Abstract

The hot corrosion behavior of bare and NiCoCrAlY-coated AISI 347 steel is investigated in Na2SO4-40%K2SO4-10%NaCl-10%KCl salt atmosphere at [Formula: see text]C for 10 cycles. Each cycle contains 5[Formula: see text]h heating and 30[Formula: see text]min cooling to ambient temperature. The NiCoCrAlY coating is employed on the austenitic stainless steel AISI 347 using high-velocity oxy-fuel (HVOF) coating method. Corrosion kinetics of the hot corroded steels are determined by thermo-gravimetric technique. The surface microstructures and compositions of the coating and corrosion products of the steels are characterized using a scanning electron microscope and energy dispersive spectroscopy. The phases of the coating are analyzed using X-ray diffraction method. Higher weight gain is observed on the uncoated specimen, and more oxide scale spallation is observed due to Fe2O3 oxide layer formation. In the coated specimen, there is no spallation of any oxide scales. The coating provides the resistance to the spallation of oxide scales. The EDS point analysis and elemental mapping analysis are performed on the cross-section to analyze the distribution of corrosion products with respect to depth.