Precipitation and Properties at Elevated Temperature in Austenitic Heat-Resistant Steels-A Review

The austenitic heat-resistant steels are significant materials used in boilers and nuclear reactors, owing to the excellent creep, fatigue, corrosion resistance, and mechanical properties. The precipitation and properties degenerate with the increasing temperature. It is necessary to clarify the main precipitation and properties under the service situation. Herein, the characteristic of main precipitation and the potential degraded mechanism of creep, fatigue, oxidation resistance, and corrosion resistance at high temperature are briefly reviewed. The main secondary phases under prolonged service environment include MX phase, M23C6 carbide, Z phase, Laves phase, and sigma phase. Precipitation scattered uniformly is conductive to strength properties of steel and vice versa. Coarsening precipitation and the decrease of dislocation density are critical reason for the deteriorated mechanical properties at high temperature. The protective oxide films destroyed after exposure to boiler gas lead to failure of materials.