from the conferences organized by TANGER Ltd.
The subject of this study is the temperature stability of a microstructure in X37CrMoV5-1 hot-work tool steel. Conventionally treated by quenching and high-tempering this steel is used for tools working at temperature up to 550 °C. In this study a non-conventional treatment consisting of austempering at 300 °C, which is slightly higher than martensite start temperature Ms = 293 °C, was used. As a result a microstructure of carbide-free nanocrystalline bainite with residual austenite was created. This microstructure ensures a very good compromise between high strength and plasticity at room temperature. The aim of this study was to determine temperature stability of the obtained microstructure in a range of temperatures 350 - 600 °C, which are higher than the temperature of the austempering treatment. For this purpose steel samples after austempering were subjected to dilatometric tests during continuous heating and isothermal annealing at various temperatures. Phase transformations were recorded during cooling of the samples after continuous and isothermal heating. These investigations allowed us to determine the highest temperature up to which any phase transformation was not observed to occur during dilatometric tests. The changes occurring in the carbide-free nanobainite with residual austenite after exceeding the critical temperature were characterised. The impact of the observed changes occurring in the microstructure above the critical temperature on the mechanical properties of steel was discussed.
Keywords: Dilatometric test; Phase transformations; Heat treatment; Carbide-free bainite; Thermal stability© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.