2020 Volume 1 Issue 1 Pages 13-20
Stainless steel specimens were plasma nitrided at 753 K and 623 K to describe the difference in inner nitriding behavior. The high temperature nitriding was characterized by precipitation of chromium nitrides in the surface layer. No microstructure change was seen below the nitriding front end. The low temperature nitriding was characterized by localization in the nitrogen supersaturation. This behavior was analyzed and described by observation and measurement of microstructure below the nitriding front end. This localized nitrogen supersaturation was driven by the grain boundary diffusion of nitrogen atoms. The effect of this localization on the microstructural change at the depth of 435 um from the surface was further discussed to describe the essential mechanism of nitrogen supersaturation. This difference in these two inner nitriding processes was also theoretically discussed by the diffusion model.
