Formation of expanded martensite in plasma nitrided SUS420J2 stainless steel

Abstract

The martensitic stainless steel was expanded by plasma nitriding the AISl-420J2 steels in the similar manner to the phenomena of expansion in many austenitic steels by nitriding. In this work, high density RF-DC plasma system was utilized to make nitriding the AISl-420J2 specimens for various holding temperatures and RF-DC Powers. Optical emission spectroscopy and a Langmuir probe were used to characterize the generated plasmas and to investigate the effect of hydrogen gas on the formation of effective radicals in nitriding. Microstructural analysis was carried out by combination of XRD and Auger electron spectroscopy analysis. The expansion of martensitic phase must be responsible for solid-solubility hardening where the nitrogen solute occupies the preferred vacancy sites in the original martensitic stainless steels.