Effect of heat treatment on the structure of high-nitrogen austenitic corrosion-resistant 04Kh22AG17N8M2F and 07Kh20AG9N8MF steels

The structures of high-strength austenitic 04Kh22AG17N8M2F and 07Kh20AG9N8MF steels are studied after various heat-treatment conditions, and the relation between these structures and the mechanical and chemical properties of these steels is analyzed. The phase compositions of the steels, the morphology of phases, the fine structure of austenite, and the mechanism of its decomposition upon heating are investigated by X-ray diffraction and transmission electron microscopy. The homogeneous decomposition of the supersaturated γ solid solution in the 04Kh22AG17N8M2F steel at 500 °C is shown to be accompanied by the formation of the CrN nitride, which is isomorphic to the matrix, and to increase the strength and elastic stresses in the austenite, decreasing the stress corrosion cracking (SCC) resistance of the steel. Heating at 800 °C facilitates stress relaxation and increases the SCC resistance of the steel.