2009 Volume 50 Issue 5 Pages 1169-1173
Low carbon steel S15CK was nitrided by active screen plasma nitriding (ASPN) using various stainless steel cages to investigate the effect of the cage on the nitriding properties. Three types of austenitic stainless steel cages, such as pipe, foil, and wire mesh, were used. The sample was treated for 18 ks at 773 K under 630 Pa in 50% N2 + 50% H2 gases. The nitrided samples were characterized by surface roughness tests, optical microscopy, scanning electron microscopy, X-ray diffraction, and microhardness testing. In all samples nitrided by the ASPN process, the ‘edging effect’ was completely eliminated whereas hardness and thickness of the surface layer were comparable with those obtained from the DC plasma nitriding. Moreover, a comparison of the screens used in the ASPN process revealed that the screen hole size had a slight influence on surface properties such as microstructure and hardness.