NANOSTRUCTURING COMBINED FRICTIONAL-THERMAL TREATMENT OF 12KH18N10T AUSTENIC STEEL
Corrosion-resistant austenitic chromium-nickel steels have low strength properties that cannot be improved using thermal treatment. The application of frictional treatment as the finishing operation allows providing the increased wear resistance, effective strain hardening and high quality of work surface of 2Kh18N10T steel. During operation and processing, the austenic steel parts could be subjected to heating. In this paper, the authors used the methods of transmission electronic microscopy, X-ray diffraction analysis, and microhardness testing to study the influence of heating in the temperature range of 100-750 °С on the structural-phase state and microhardness of 2Kh18N10T steel subjected to frictional treatment and to consider the possibilities of hardening of metastable austenic steel using combined frictional thermal treatment. It is determined, that during frictional treatment, 65 vol. % of strain-induced α'-martensite appears in the steel surface layer and the microhardness increases up to HV 0,025=690. Two-hour annealing at 450 °С ensures the retention of 65 vol. % of α'-phase in the structure and the additional increase of surface hardness up to HV 0,025=900 due to nanoscale Cr<sub>23</sub>C<sub>6</sub> carbides precipitation, and their application for hardening of nano- and sub-microcrystalline martensite-austenic structures formed in surface layer after the frictional treatment. In the result of heating up to 650 °С, the austenic submicro- and nanocrystalline structure with HV 0,025=630 hardness exceeding the initial hardness of austenic steel in hardened condition by about three times appears on the steel surface. Based on the results obtained, the authors proposed two regimes of nanostructuring combined strain-heat treatment, which involve frictional treatment and further annealings at the temperatures of 450 and 650 °С.