Low-temperature ion nitriding of structure highly alloyed austenitic and martensitic steels with ultrafine-grained structure

Abstract

In this work, the effect of ionic nitriding at various temperatures on the mechanical properties of austenitic and martensitic steel grades with ultra-fine-grained (UFG) structure is investigated. It was established that the average grain size for austenitic steel was about 150 nm, and for martensite steel, the ferritic phase was about 120 nm and the carbide phase was 150 nm. It is shown that after ion nitriding at a temperature of 450°C, the maximum degree of surface hardening is observed for steels with a UFG structure of both classes. Surface microhardness for austenitic steel was 700 kgf/mm2, and the thickness of the hardened layer was about 70 ?m. For steel of martensitic class, the surface microhardness was 900 kgf/mm2, and the thickness of the hardened layer was 90-95 ?m.