Microstructure and tempering response of Vanadis 6 steel after sub-zero treatment at -140 °C – POSTER
Microstructure and hardness of Cr-V ledeburitic cold work tool steel Vanadis 6 subjected to sub-zero treatment with soaking time of 24 h, at a temperature of -140 °C have been examined. Microstructures have been characterized using light microscopy and scanning electron microscopy. Hardness has been evaluated by Vickers method. Typical heat treated microstructure of Vanadis 6 ledeburitic steels consists, besides of the martensitic matrix with certain amount of retained austenite, of several types of carbides – eutectic carbides, secondary carbides, and small globular carbides. The amount of small globular carbides increases as a result of sub-zero treatment. Tempering of the material resulted in decrease in population density of small globular carbides with increasing the tempering temperature. The hardness of sub-zero treated material is higher than that of conventionally treated steel when tempered at low temperature. In contrast, the hardness of sub-zero treated samples decreases more rapidly compared to that of conventionally treated steel and, in addition, sub-zero treated material induces a loss the secondary hardening peak.