Enhanced mechanical properties induced by refined heat treatment for 9Cr–0.5Mo–1.8W martensitic heat resistant steel

Highlights: ► The evolution of microstructure of T92 steel during heating process has been revealed. ► Heat treatment technologies of T92 steel have been optimized by orthogonal experiment method. ► The mechanical properties of T92 steel can be greatly improved under the optimized heat treatment technology. ► The strengthening mechanism for T92 steel was clarified by TEM observation. - Abstract: In this work, the phase transformation in 9Cr–1.8W–0.5Mo steel was investigated to provide the theoretical basis for the design of the temperature of heat treatment process. Refined heat treatment technologies including normalizing and tempering processes were designed by using orthogonal experiment method. By evaluating the room temperature and high temperature mechanical properties, optimum heat treatment parameters were determined. It is shown that under the optimum heat treatment condition, the room temperature elongation can reach 25% or above, while the tensile strength and yield strength at 650 °C were increased by 48.3% and 50%, respectively, compared with those of supplied steel. The strengthening mechanism of this steel was also investigated by microstructure observation. This work is hopeful to benefit the service safety and the life time extension of power plants