Microstructural degeneration of simulated heat-affected zone in 2.25Cr–1Mo steel during high-temperature exposure

The microstructural of simulated heat-affected zone (HAZ) in 2.25Cr–1Mo steels has been investigated. The experiments with different heat inputs were carried out in a high speed dilatometer; the thermal cycles used corresponded to the actual thermal cycles that occurred in the coarse-grained region of the real HAZ. It was found that with a heat input of 20 kJ cm−1, the simulated HAZ microstructure gave larger amounts of lower bainite with significant amounts of martensite. The 20 kJ cm−1 heat input specimens were tempered at 700 °C for different time intervals ranging from 1 to 50 h. A sequence for corresponding microstructural degradation has been proposed.