Formation of Microstructure during Sub-Zero Treatments of Chromium and Chromium-Vanadium Ledeburitic Steels

Abstract

Despite the fact that the sub-zero treatment has widely been employed in various industrial branches more than 100 years, metallurgical principles of microstructural alterations was discovered only over past several years. Many experimental works have been done in order to describe what happens in the microstructures of various steels when they are subjected to the treatment within a temperature range 4 - 273 K and for different durations of this treatment. The obtained results infer that the changes in microstructure and thus in mechanical properties depend not only on the treatment regime used, but they are closely related to the steel chemistry. The current paper summarizes the findings obtained by sub-zero treatments of two different ledeburitic tool steels (AISI D2 and Vanadis 6). The changes in retained austenite characteristics, alterations in martensitic structures, variations in carbide characteristics and modifications in precipitation behaviour are demonstrated and discussed.