希土類元素による焼結耐熱合金の高温耐酸化性改善について

概要

論文の詳細を見る
The effect of various rare earth elements added in various forms, i.e. metallic addition, dispersion of oxide and superficial application of oxide particles, on the high temperature oxidation resistance of Ni-Cr and Fe-Cr alloys was investigated. Rare earth elements exhibited two excellent improving effects in reducing the oxidation rate and in suppressing the spalling of the scale. The effects of rare earth elements were much stronger than those of the other reactive elements in all additional forms. In order to understand the mechanism by which the rare earth elements improved the oxidation resistance of the alloys, the oxygen pressure dependence of the electrical conductivity of the Cr2O3 doped with NiO and rare earths was measured. It was found that the simultaneous doping of NiO and rare earth elements changed the defect structure of Cr2O3 from p-type to n-type semiconductor at very low oxygen pressure, Po2≅10-9Pa. This result suggested that the formation of an n-type region in the scale adjacent to the alloy might act to improve the oxidation resistance by reducing the diffusion rate of cations in the scale.
社団法人粉体粉末冶金協会の論文