Nitrocarburising 처리된 탄소강의 내식특성에 미치는 Post Oxidation 효과 = The Effect of Post Oxidation on Corrosion Characteristics of Gas Nitrocarburised Carbon Steels

다국어 초록 (Multilingual Abstract)

The effect of post oxidation, water-quenched after holding in air for 5∼420 seconds or cooling or furnace cooling, on corrosion resistance and phase formation characteristics of the surface layer of SM20C and SM45C carbon steels after gas nirtrocarbursing in the NH₃-5%CO₂-N₂gas atmosphere at 580℃ for 3hours is studied. The compound layers of two steels consist of ε-Fe_(2-3)N, γ'-Fe₄N and Fe₃O₄, phases, however, the quantity of γ'-Fe₄N phase increases for the furnace cooled specimen compared to that of air cooling specimen. With increasing NH₃content in the gas mixture and also increasing the keeping time in the air after gas nitrocarburising, the ε-Fe_(2-3)N phase of compound layer increases, while the decreased current density recognizing the improvement of corrosion resistance are shown. the passive current density of SM45C steel is lower than that of SM20C steel at the same nitrocarburising conditions.