Oxidation and corrosion behaviour of CoNiCrAlY bond coats

CoNiCrAlY coating for protection against oxidation at elevated temperature was prepared on the surface of the 316L by high velocity oxygen fuel (HVOF) and cold gas dynamic spray (CGDS) techniques. The phase composition, microstructure and oxidation resistance of the coating were investigated at 900 degrees C in air. According to the results, the CGDS coating shows low oxide growth rate as a result of low porosity, oxide content and high hardness. CGDS coating provided excellent oxidation protective ability at 900 degrees C in air, whereas HVOF coating showed high levels of visible defects, oxide content, spinel type oxide and high oxide growth rate. Electrochemical study shows that the HVOF process provided better corrosion resistance as compared to CGDS process.