EFFECTS OF SUBZERO TREATMENTS ON CACBIDE ORGANIZATION TRANSFER OF SKD11 STEEL AFTER QUENCHING METHOD

Abstract

The carbide organization determines the hardness and wear resistance of SKD11 steel. However, depending on the heat treatment method, this organization may change to improve the hardness of SKD11 steel. This paper presents the results of studying the carbide transformation process and properties of SKD11 steel when quenched at 1050^oC with a holding time of 30 minutes and then cold-treated at temperatures (-20^oC; -80^oC) with two different time modes 2h and 24h. The results show that: In case SKD11 steel is tempered and kept heat, inside the steel appears carbide organization mainly in the form of M₇C₃ and the hardness is about 57HRC. In the case of cold-treated SKD11 steel, the residual martensite and austenitic solid solution in the steel has secreted a fine M₃C₂ carbide phase with size 0.1÷ 0.5μm; the amount of carbide tends to change depending on the temperature cold treatment -20^oC (~16% carbide); -80^oC (~20% carbide). Extended sub-zero treatment times tend to increase the carbide content in steel slightly but not significantly. After cryogenic treatment at different temperatures, steel samples have high hardness and stability above 63HRC.