Surface Hardening of High-Nitrogen Austenitic Steel by Severe Deformation-Heat Treatment

N. A. Narkevich, M. N. Volochaev, I. A. Shulepov & Yu. F. Gomorova // Physics Of Metals And Metallography//

The structure and mechanical properties of austenitic high-nitrogen steel (16.5 Cr, 18.8 Mn, 0.07 C, 0.53 N, 0.52 wt % Si, Fe for balance) have been investigated after severe deformation–heat treatment, which has involved shock surface forging at the ultrasonic frequency (USF) and electron-beam heat treatment (EBT). A subgrain structure hardened by CrN nanoparticles has been shown to form in the surface layer as a result of deformation–heat treatment. No discontinuous decomposition of austenite with the formation of Cr2N nitrides takes place. This structure modification in the surface layer enhances the strength properties of the steel, namely, σ0.2 increases to 712 MPa and σu to 923 MPa at a plasticity of 25%. The yield strength increases by 50% compared to the state after quenching.