Formation of Reversed Austenite in High Temperature Tempering Process and its Effect on Mechanical Properties of Cr15 Super Martensitic Stainless Steel Alloyed with Copper

Abstract

AbstractFormation mechanism of the reversed austenite of Cr15 super martensitic stainless steel (SMSS) alloyed with copper after high temperature tempering was investigated by means of thermo‐calc software, transmission electron microscope (TEM), and X‐ray diffraction (XRD). The mechanical properties of the SMSS were also tested. The experimental results show that the reversed austenite with low dislocation density is formed at high temperature tempering processing. The transformation of the martensite to reversed austenite is a diffused phase transformation, and the growth of the reversed austenite is closely related to the diffusion process of Ni. The bulk reversed austenite with large amount of stacking faults is formed with the increase of the tempering temperature. The volume fraction of reversed austenite increases at first and then decreases with increasing tempering temperature, and the maximum amount of the reversed austenite is obtained at 650°C. The reversed austenite is unstable at the tempering temperature above 650°C and the martensitic phase transformation will occur at the following cooling process. The mechanical properties of Cr15 super martensitic stainless steel are significantly influenced by the volume fraction of reversed austenite.