Dong Yun

Classic contributions: cryogenic treatment Deep cryogenic treatment of high speed steel: microstructure and mechanism

AbstractIn this article, first published in 1998, it is demonstrated that martensite decomposition and precipitation of ultrafine carbides are important factors in improving the mechanical properties of high speed steels by deep cryogenic treatment (DCT) at 2 −196°C. Cryogenic processing has been found to double the service life of high speed steel tools. Microstructural examination shows that DCT not only transforms residual austenite into martensite, but also alters the morphology of the martensite that is already present, precipitating out ultrafine carbides. These additional changes brought about during DCT, after normal heat treatment by quenching and tempering, have fundamentally changed the conventional view of cold treatment. Application of DCT in several cycles, rather than as a single treatment for the same total period, was shown to be more effective. Similarly, DCT after quenching but before tempering produced a greater increase in bend strength and toughness than DCT after quenching and tempe...