Long-term creep properties of low C-2.25Cr-1.6W-V-Nb steel (T23/P23) for fossil fired and heat recovery boilers

Long-term creep-rupture strength of low C-2.25Cr-1.6W-V-Nb steel (HCM2S; KA-STBA/PA24J1, T23/P23, ASME CC2199) has been studied and reassessed using the oxidation correction method after Nakashiro et al. Their long-term creep strengths are found to be very stable at temperatures between 500 and 600 °C. A severe oxidation of the creep-rupture specimens has been identified at high temperatures above 600 °C and the longer term rupture time tends to decline below the extrapolated curve. An oxidation correction has been found to be effective to evaluate the long-term creep-strength stability of the steel and worked well in the case of 2.25Cr-1Mo steel (ASME T22/P22). It is thus concluded that in low C-2.25Cr-1.6W-V-Nb steel no creep-strength degradation apart from that due to oxidation at high temperatures is expected, in contrast to results on advanced high Cr steels.