Role of Thermo-Mechanical Treatment on Creep Deformation Behaviour of Reduced Activation Ferritic Martensitic Steel

To enhance the microstructural and mechanical properties of Reduced Activation and Ferritic-Martensitic (RAFM) steel thermo mechanical treatment (TMT) was performed on as received Normalised and Tempered steel (N+T). The RAFM with 9Cr-1W-0.06Ta major alloying elements steel was used in the study in N+T and TMT conditions. The refinement in microstructure and precipitates was observed in TMT steel in comparison to N+T steel. There is a drastic improvement in mechanical properties such as hardness, tensile properties are observed without losing the ductility. The creep deformation behaviour of thermo-mechanical treated steel and N+T steel were studied at different stress levels at 823 K. The comparative creep rupture and strain properties were studied, and various creep deformation regimes were also analysed for both the conditions of steel. The rate of exhaustion of primary creep (r), minimum creep rate and time spent in primary and tertiary creep regime, rate of acceleration of tertiary creep and time to reach the onset of tertiary creep. Microstructural studies on Optical and Scanning electron microscopy and transmission electron microscopy results were correlated with the mechanical properties of steels. On a whole, a comparative investigation was performed on various reasons for drastic improvement in tensile and creep rupture properties of TMT steel than the steel in N+T steel and necessary microstructural investigation support is considered.