Effects of chemical composition and heat treatment on creep properties of Grade 91 steel base metal and welded joint

The effects of the chemical composition and heat treatment on the creep properties of Grade 91 steel base metal and welded joint were investigated by conducting creep tests on materials whose Al, Cr, and Ni contents were systematically varied or the normalising and tempering temperatures were varied. The effect of the chemical composition on the creep strength was similar for the base metal and the welded joint. That is, the creep strength decreased with increasing Al content, whereas the Ni content had little effect on the creep strength. Regarding the effect of heat treatment, the creep strength increased with increasing normalising temperature and decreasing tempering temperature for the base metal and the welded joint. The comparison of the test results of the welded joints with those of the base metals revealed a positive correlation between the creep strength of the base metals and that of the welded joints.