Martensitic transformation of a high-speed tool steel during continuous heat treatment

This study focuses on the evolution of the amount of martensite, retained austenite and the volume fraction of primary carbides during the austenitisation process. The high-speed tool steel HS 6-5-2 is investigated. The continuous heat treatment is simulated in a quenching dilatometer with heating rates of 500 K/s and varying holding times. For each holding time, the martensite start temperature is identified, which gives some indication of the carbon content in solution. The volume fraction of retained austenite is analyzed by applying X-ray diffraction measurements and using Rietveld analyses. Atom probe tomography is used to characterize the matrix and the amount of primary carbides is investigated by scanning electron microscopy. The results are discussed in comparison to a conventionally heat treated material. (C) 2015 The Authors. Published by Elsevier Ltd.