A concept for deep cryogenic treatment of tool steels

Abstract

A short review of experimental data about the effect of deep cryogenic treatment, DCT, on the abrasive 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. Moreover, the softness of the virgin isothermal martensite initiates the plastic deformation during martensitic deformation, which results in the partial removal of carbon atoms from the solid solution by the gliding dislocations. This effect eliminates the precipitation of the e(η)-carbide during subsequent tempering, shifts cementite precipitation towards higher temperatures and delays precipitation of special carbides at temperatures of secondary hardness. Thus, the precipitation potential of the γ solid solution is preserved and can be realized during the usage of tools increasing thereby the tools life. Based on the obtained results, a new concept of DCT is developed and the correction of its technology to the temperature range of the isothermal martensitic transformation is proposed.