The effect of composition and microstructure on the creep behaviour of 14 Cr ODS steels consolidated by SPS

There is a general need for alternative structural materials to improve power plants' efficiency and reduce CO2 emissions. Within this framework, two new compositions of temperature-resistant sintered ODS ferritic steels (14Cr-5Al-3W), strengthened by a fine dispersion of precipitates (5·1022 ox. /m3), have been developed. This work focuses on creep properties and microstructure evolution. The creep resistance (at 650°C) could be improved by prior microstructural optimisation, thanks to the consolidation by spark plasma sintering and the tailoring of precipitates' nature when a single compound introduces the oxide-forming elements (Y-Ti-Zr-O) synthesised for this purpose. To this end, the initial pre-alloyed ferritic powder was mechanically alloyed with the synthesised compound and sintered by spark plasma sintering (SPS). Afterwards, EBSD and TEM characterisation were employed to study the microstructures. Small punch creep tests (SPCT) were performed on the steels to analyse their creep performance. These showed an exceptional enhancement of the creep resistance in the steels containing the Y-Ti-Zr-O additions.