Performance of NiCrAlY, Ni–Cr, Stellite-6 and Ni 3Al coatings in Na 2SO 4–60% V 2O 5 environment at 900 °C under cyclic conditions

Abstract

Ni–22Cr–10Al–1Y (NiCrAlY), Ni–20Cr, Ni 3Al and Stellite-6 (St-6) coatings were formulated by a plasma spray process on boiler tube steels. The NiCrAlY has also been sprayed as a bond coat of approximately 150 μm thickness in each case before the final coating. After characterization, the cyclic hot corrosion behaviour of these coatings was studied in molten salt (Na 2SO 4–60% V 2O 5) at 900 °C. The internal oxidation and cracking of scale was observed during the testing. The coatings have been found to be beneficial in increasing the hot corrosion resistance of boiler tube steels. The maximum protection was observed in case of St-6 coating and was a minimum in case of Ni 3Al coating.