Enhancing gas nitriding efficiency of X12MФ steel through pre-nitriding surface roughness control

Abstract

This study focuses on improving the efficiency of the gas nitriding process for X12MФ cold-work die steel by adjusting the pre-nitriding surface roughness. Steel samples quenched and tempered to a hardness of 61.7 HRC surface-finished to different roughness levels (Ra=0.017-0.057 µm). The gas nitriding process was conducted at 510°C for eight hours. The experimental results indicate that surface roughness exerts a decisive influence on diffusion kinetics. Specifically, the sample with the highest roughness (Ra=0.057 µm) achieved a total nitrided layer thickness of 252.9 µm, over 65% greater than that of the polished sample (Ra=0.017 µm). Xray diffraction (XRD) analysis confirmed the formation of the hard phases Fe4N, Fe3N, and CrN. The findings demonstrate that maintaining an appropriate surface roughness is an effective technical solution for increasing the nitrided layer thickness without extending the nitriding time.