Duplex Surface Treatments of Plasma Nitrocarburizing and Plasma Oxidation of SKD 11 Steel

Abstract

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of SKD 11 steel. Plasma nitrocarburizing was conducted for 12h at 520C in the nitrogen, hydrogen and methane atmosphere to produce the -Fe2-3(N,C) phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of -phase, with a small proportion of - Fe4(N,C) phase. The thickness of the compound layer was about 5 m and the diffusion layer was about 150 m in thickness, respectively. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen / hydrogen ratio at constant temperature of 500C for 1 hour. The very thin magnetite (Fe3O4) layer 1-2 m in thickness on top of the compound layer was obtained by plasma post oxidation. It was confirmed that the corrosion characteristics of the nitrocarburized compound layer could be further improved by the application of the superficial magnetite layer.