Structural and Phase Transformations in Internally Nitrided Corrosion‐Resistant Steel during Severe Plastic Deformation and Subsequent Annealings

Abstract

The effect of severe plastic deformation (SPD) by high‐pressure torsion (HPT) and subsequent annealings on structural and phase transformations in 0.08C–18Cr–0.5Ti steel, which is preliminarily hardened by high‐temperature internal nitriding (the microhardness is 3.2 GPa), has been studied. The HPT results in the formation of nanostructure with an average structural‐element size of 55 nm and the refining and in part dissolution of Cr2N particles. After HPT, the microhardness of steel increases by 2.7 times (to 8.6 GPa at the midradius of samples), which is substantially higher than the microhardness of non‐nitrided steel after HPT. The hardening of the material remains during heating to a temperature of no less than 450 °С at the expense of precipitation of disperse Cr2N particles and despite of coarsening structural elements. HPT of nitrided steel leads to a shift of phase transformations, namely the temperature of chromium nitride precipitation decreases.