Microstructural stability of ODS steel after very long-term creep test

Microstructure of 9Cr oxide dispersion strengthened (ODS) tempered martensitic steel (TMS) cladding and 12Cr-ODS ferritic steel cladding after very long-term internal pressurized creep tests was observed. The creep test conditions were 700 degrees C for 46,504 h and 750 degrees C for 45,550 h for 9Cr-ODS TMS and 700 degrees C for 30,116 h for 12Cr-ODS ferritic steel. The stability of martensite and ferrite matrix structure, including carbide distribution, dislocation density, and lath boundary, and that of nano-particle distribution were investigated. It was confirmed that the nano-particles were stably present during the high-temperature and very long-term stress loading environment, contributing to the prevention of matrix structure degradation. The results of observation are consistent with the fact that the 9Cr-ODS TMS and 12Cr-ODS ferritic steel exhibit excellent creep strength and show no reduction in the slope of the stress versus time to rupture curve over a significantly extended period of time in the creep test. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The microstructure of 9Cr oxide dispersion strengthened tempered martensitic steel (TMS) cladding and 12Cr-ODS ferritic steel cladding after very long-term internal pressurized creep tests was observed. The stability of martensite and ferrite matrix structure, including carbide distribution and nano-particle distribution, were investigated. Results confirmed that nano-particles were stably present during high-temperature and very long-term stress loading, contributing to preventing matrix structure degradation and excellent creep strength of the materials.