REPOSITORY > RESULTS

Abstract

Deep cryogenic treatment (DCT) is a type of cryogenic treatment, during which a material is subjected to temperatures below −160 °C. When a metallic material is modified with DCT, changes occur down to the nanoscopic level. DCT induces microstructural changes such as grain size refinement, formation of new grains, movement of dislocations, change of solubility of alloying atoms, alteration of crystal structure and new phase formation. Changes in the material can have positive or negative effects or can conjointly render negligible changes on the final properties of steels, which was evaluated and proven within this work. The steel’s performance and later performance of manufactured components and tools from this specific material strongly depend on the selection of proper material, proper design, accuracy with which the tool is made from untreated material and application of proper heat treatment, including DCT. Furthermore, DCT treatment has shown to reduce density of defects in crystal structure, increase wear resistance of steel, increase hardness, improve toughness, tensile strength as well as corrosion resistance. However, the performance of DCT strongly depends on steel type as well as manufacturing type (wrought or powder metallurgy steel), chemical composition of steel (the ratio of alloying elements, such as chromium, tungsten etc.). Additionally, heat treatment parameters (austenitizing and tempering temperature) and presence of microstructure-related phenomena within the steel (such as transformation-induced plasticity (TRIP)) also influence DCT effectiveness. This study provides a systematic approach and research of DCT and its effectiveness on steels. The study also aims at unravelling the underlying mechanisms in selected ferrous alloys (high-speed steels, tool steels, stainless steel and bearing steel) to provide in-depth fundamental understanding of DCT on ferrous alloys.