Fe - 36% Ni 인바합금의 표면석출과 산화막 형성에 대한 연구

The effect of heat treatment on the surface precipitation of trace impurities and on the subsequent oxidation of an Invar alloy was investigated. An Fe-36% Ni Invar alloy with Mn, Cr, Si, S and C as impurities was heat-treated at 1100˚C in vacuum as well as in 60% N₂＋ 40% H₂gas. Surface analysis with AES, SEM and EPMA has revealed that BN compound and nonmetallic elements such as S, C and O precipitated on the surface of the Invar alloy after a heat treatment in vacuum, while metallic impurities like Mn, Al and Si precipitated as oxide particles especially along grain boundaries after a heat treatment in 60% N₂＋ 40% H₂gas. And it was found that the oxidation occured preferentially near the precipitated nonmetallic and metallic oxide particles. The oxide layers formed on vacuum heat-treated alloys showed the best adherence, while the oxide layers formed without any prior heat treatment spalled on the outer-inner oxide interface.