Development of India-specific RAFM steel through optimization of tungsten and tantalum contents for better combination of impact, tensile, low cycle fatigue and creep properties

Abstract

Effects of tungsten and tantalum contents on impact, tensile, low cycle fatigue and creep properties of Reduced Activation Ferritic–Martensitic (RAFM) steel were studied to develop India-specific RAFM steel. Four heats of the steel have been melted with tungsten and tantalum contents in the ranges 1–2wt.% and 0.06–0.14wt.% respectively. Increase in tungsten content increased the ductile-to-brittle transition temperature (DBTT), low cycle fatigue and creep strength of the steel, whereas the tensile strength was not changed significantly. Increase in tantalum content increased the DBTT and low cycle fatigue strength of the steel whereas the tensile and creep strength decreased. Detailed TEM investigations revealed enhanced microstructural stability of the steel against creep exposure on tungsten addition. The RAFM steel having 1.4wt.% tungsten with 0.06wt.% tantalum was found to possess optimum combination of impact, tensile, low cycle fatigue and creep properties and is considered for Indian-specific RAFM steel.