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 s teel using a cathodic are plasma (CAP) process has been investigated. Our r esults show that nickel-aluminide films can be successfully deposited on ca rbon steel and stainless steel substrates by this process; NiAl3 is the maj or phase in the deposited films. The thermal cycling behaviour suggests tha t such coatings can resist oxidation through physical blocking of oxygen, e ither by the coating itself or by the aluminium oxide scale subsequently fo rmed in-service. Aluminium diffusion inwards to the substrate may also be b eneficial to the thermal oxidation resistance. The coating protects stainle ss steel substrate materials at 500 degreesC by transforming the NiAl3 phas e into NiAl, producing aluminium oxide on the open substrate surface. At 80 0 degreesC, oxide flaking is suppressed by the trace amounts of nickel or a luminium which have partially diffused into the substrate. (C) 2001 Elsevie r Science B.V. All rights reserved.