AISI 420 martensitic stainless steel low-temperature plasma assisted carburizing kinetics

► Modified surface is mainly composed of carbides and expanded martensite. ► Activation energy for the outer and diffusion layer growth is 29 and 85 kJ mol− 1, respectively. ► The process is diffusion controlled for long period treatments. ► Diffusion layer was identified by microhardness profile only. ► Excessive treatment time can lead to a surface hardness reduction.