Surface nanocrystallization on stainless steel with high hardness induced by electron beam direct irradiation

There remains a challenge to realize the 4Cr13 stainless steel with high hardness for surface strengthening. Herein, a novel method for surface nanocrystallization of 4Cr13 stainless steel by direct electron beam irradiation was proposed. Results revealed that nano-sized grains are homogeneously distributed in the modified layer, which the average grain size was approximately 30 nm. Surface microhardness remarkably enhanced from 230 HV to 720 HV, as tripled the substrate. The high hardness was attributed to the fine-grain and dispersion strengthening that benefited from surface nanocrystallization. This study can provide a worthy insight for the surface strengthening of next generation ultrastrong stainless steel. •A new method of surface nanocrystallization on stainless steel was developed.•Stainless steel with high hardness was fabricated by SEB irradiation.•Nanograins formation and the strengthening mechanism were revealed.•SEB irradiation advances the hardness to 3.1 times higher than that of matrix.