Application of a Grain-Size-Sensitive Model to Determine the Effect of Yttrium Additions on the Oxidation of Nickel

摘要

The beneficial effect of active-element additions in metals and alloys on the formation of protective oxide scales is well known. Such additives will generally result in better scale adhesion and slower oxidation rates. In order to understand the role of active-element additions to the scale, a grain-size-sensitive model is proposed to determine the effect of yttrium on the grain boundary diffusion rate of nickel in NiO using oxidation kinetics and oxide grain size data that are available in the literature. It was found that the addition of yttrium to nickel decreases grain boundary diffusion of nickel in NiO at T > 800 deg C. At 900 deg C and 0.3% yttrium in nickel, the grain boundary diffusion rate of nickel in NiO can be reduced by a factor of 15. At T < 700 deg C, the addition of yttrium to nickel has no effect on the oxide grain boundary diffusivity. Good agreement was found between oxide grain boundary diffusivities calculated from this analysis and those determined by tracer-sectioning experiments. (ERA citation 12:009359)