Cyclic oxidation resistance of Ni–Al alloy coatings deposited on steel by a cathodic arc plasma process

The cyclic oxidation resistance of nickel-aluminide coatings deposited on steel using a cathodic arc plasma (CAP) process has been investigated. Our results show that nickel-aluminide films can be successfully deposited on carbon steel and stainless steel substrates by this process; NiAl3 is the major phase in the deposited films. The thermal cycling behaviour suggests that such coatings can resist oxidation through physical blocking of oxygen, either by the coating itself or by the aluminium oxide scale subsequently formed in-service. Aluminium diffusion inwards to the substrate may also be beneficial to the thermal oxidation resistance. The coating protects stainless steel substrate materials at 500°C by transforming the NiAl3 phase into NiAl, producing aluminium oxide on the open substrate surface. At 800°C, oxide flaking is suppressed by the trace amounts of nickel or aluminium which have partially diffused into the substrate.