Remarkable Improvement of Creep Strength by Vanadium Addition in 2.25Cr Heat-Resistant Steel

Abstract

This paper reports the effect of vanadium (V) addition on elimination of easily coarsening M23C6 carbide and on remarkable creep strength improvement in T/P23 heat-resistant steel (2.25Cr-1.5W-VNbTi). Increase in V content eliminates coarse M23C6 and allows only precipitation of MX carbo-nitrides in T/P23 heat-resistant steel. Fine MX effectively stabilizes sub-boundaries of bainite microstructure, so coalescence of neighboring sub-boundaries and subsequent creep strength loss are suppressed. This steel even surpasses the creep life of conventional 9 wt.% Cr steels due to powerful sub-boundary hardening.