Cryogenic Processing of HSS M2: Mechanical Properties and XRD Analysis

Abstract

The purpose of this study was to reveal the changes in properties of deep cryogenic treatment (DCT) processed high speed steel, in comparison to conventional heat treatment for secondary hardness. Tool properties were assessed in terms of hardness, and tensile strength. Statistically significant enhancement in the mechanical properties was observed. Cryogenic processing of HSS tool steel eliminated the retained austenite, and hence increased the hardness of the material. This treatment initiated nucleation sites for precipitation of large numbers of very fine carbide particles.Tensile values for cryogenically treated HSS samples can be attributed to the fact that the tool becomes more brittle after the treatment. XRD analysis illustrated the contraction in lattice of martensite and austenite. Deep cryogenic treatment practically removed all traces of austenite in the sample. The superior performance of cryogenically treated HSS can be attributed to the transformation of almost all retained austenite into martensite, a harder structure and precipitation of fine and hard carbides.