Influence ultrafine-grained structure of martensitic steel on diffusion process at low temperature ion nitriding

A ultrafine-grained structure was fabricated on a martensitic steel 13H11N2V2MF by means of high pressure torsion (HPT). The effect of the ultrafine-grained structure on the ion nitriding at a lower temperature was investigated by using structural analysis and microhardness tests. The ultrafine-grained structure enhances nitriding kinetics and promotes the formation of an ultrafine nitride layer. The results of the investigation showed that process of diffusion of ion nitriding at low temperature can effectively increase the hardness in comparsion with conventional nitriding. Surface microhardness of nitrided ultrafine-grained steel 13H11N2V2MF was 1200 HV, indicating a high concentration of nitrides in the surface layer, while at the fault coarse-grained steel surface microhardness was 525 HV.