Plasma Sulfnitriding of SKD 61 Steel

Plasma Sulfnitriding of SKD 61 Steel

Plasma sulfnitriding technology was employed to harden the surface of SKD 61 steel. The plasma sulfnitriding is a process which adds a small amount of H2S gas to the mixed gas of N2 and H2 used at the glow discharge plasma nitriding method. This process was performed with 3 torr gas pressure at 580℃ for 20 hours. The plasma sulfnitriding resulted in the formation of very thin 2-3㎛ FeS iron sulfide layer on top of 15-20㎛ compound layer, which consisted of ε-Fe₂-₃N and a second phase of γ-Fe₄ In comparision with commercial plasma nitriding treatment, the plasma sulfnitriding treatment showed better surface roughness and corrosion resistance due to the presence of the thin FeS layer, which coated microvoids and microcracks on top of the nitrided layer. It was also found that plasma sulfnitrided sample revealed better wear resistance due to the presence of the thin FeS layer which acted as a solid lubricant.