Microstructural evolution and the effect on hardness and plasticity of S31042 heat-resistant steel during creep

The microstructural evolution and mechanical properties of S31042 heat-resistant steel after crept at 923 K were systematically investigated. Results show that secondary NbCrN and M23C6 are the predominant precipitates during creep. Long-term creep results in the precipitation of a small amount of σ phase and a few Cr3Ni2SiX. Secondary NbCrN is the most important strengthening precipitate of S31042 steel. At least 75% of the precipitation hardening results from secondary NbCrN. Furthermore, secondary NbCrN is the main factor to affect the variation of hardness of S31042 steel during creep. The dramatic degradation of plasticity is mainly caused by the precipitation of M23C6 at the grain boundaries. Chain-like M23C6, cuboids M23C6 and undissolved NbCrN are also harmful to the creep plasticity of S31042 steel.