Effect of Heating on the Structure, Phase Composition, and Micromechanical Properties of the Metastable Austenitic Steel Strengthened by Nanostructuring Frictional Treatment

Abstract

The influence of heat treatment in the 100–900°С temperature range on the phase composition, structure, and micromechanical characteristics of the surface layer of the 12Kh18N10T steel subjected to nanostructuring frictional treatment (FT) with a sliding indenter has been studied. This study considered opportunities for strengthening metastable austenitic steel using combined thermomechanical treatments. Annealing at 400–450°C allows for the retention of nanocrystalline martensitic–austenitic structures formed in the surface layer of the steel and a significant increase in the micromechanical characteristics owing to the strengthening of the strain-induced martensite. The annealing of the steel at 650°C leads to the formation in the surface layer of an austenitic predominantly submicrocrystalline and nanocrystalline structure with a hardness of 630 HV 0.025, which is almost 3 times higher than the hardness of steel in the initial quenched state. The transmission electron-microscopic studies of the surface layer of the austenitic steel deformed by FT made it possible to reveal the retention of highly dispersed austenitic regions in addition to the recrystallized regions upon heating to 800°C, as well as the absence of abnormal growth of recrystallized austenite grains upon heating to 900°C.