The oxidation of chromium- and nickel-implanted nickel at high temperatures

Abstract

The isothermal oxidation behaviour in oxygen of nickel, implanted with nickel and chromium ions, has been studied in the range 950–1150°C using kinetic and electronoptical techniques. Implantation with nickel ions has a significant and lasting effect on the oxidation kinetics and on the morphology and grain configuration of the NiO scale. The oxide grains are generally smaller, more facetted and more mismatched for the implanted surfaces and there is more extensive stress generation during oxide growth. After an initially slower rate, the oxide on the implanted surfaces develops at a faster rate than that on the unimplanted surfaces, particularly at the higher temperatures. Implantation with chromium ions inhibits the initial development of the NiO scale. However, subsequently, the oxidation rate is more rapid for the implanted surfaces and increases progressively with increasing chromium ion dose. The results can be accounted for in terms of doping of the NiO and the much decreased grain size of the oxide. It is concluded that short-circuit grain boundary diffusion processes, as well as bulk lattice diffusion of Ni 2+ ions, are important in the oxidation of nickel at high temperatures.