DEEP CRYOGENIC TREATMENT OF STEELS

Abstract

A short review of experimental data about the effect of deep cryogenic treatment, DCT, on the wear of tool steels is presented along with available hypotheses. Using Mossbauer spectroscopy, X-ray diffraction, mechanical spectroscopy and transmission electron microscopy, it is shown that the isothermal martensitic transformation proceeds in the course of DCT. At that, because of softness of the low temperature martensite, plastic deformation occurs during martensitic transformation and the gliding dislocations remove a part of carbon atoms from the solid solution. As the enthalpy of binding between carbon atoms and dislocations exceeds that of s-carbide and cementite formation, the precipitation of carbides is delayed during tempering. For this reason, the alpha solid solution contains clusters of carbon and alloying elements, which reserves potential for precipitation during the practical usage of tools increasing thereby the tools life. A new concept of DCT is developed and the correction of its technology is proposed accounting for the temperature range of the isothermal martensitic transformation.