Deep Subzero Processing of Metals and Alloys: Evolution of Microstructure of AISI T42 Tool Steel

The improvement in the life of tool and alloy steels, when treated at 88K for 24 hours has been conclusively established. It is however not clear as to what factors of the Deep Subzero process (DSZ) actually contribute towards improved performance of tools. It is also not clear, whether treatment for 24 hours is applicable to all steels or not. In the present investigation, an attempt to study the evolution of microstructure in AISI T42 high speed steel during DSZ treatment is performed. The results indicate clear evidence of changes beginning within the first 8 hours of DSZ. Changes in the morphology of carbides with the phenomenon of dissolution, precipitation, and merging are observed. Scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) were used during the investigation.