Oxidation rate of advanced heat-resistant steels for ultra-supercritical boilers in pressurized superheated steam

Oxidation kinetics of recently developed ferritic heat-resistant steels, HC M12A, NF616, and HCM2S, were investigated in a superheated steam to evaluat e the effects of chemical composition of the steels, testing temperature (5 60-700 degreesC), steam pressure (1-10 MPa), and degrees of microstructural evolution by aging on oxidation. The contribution of alloyed Cr to oxidati on resistance was pronounced above 600 degreesC, while no material dependen cy was found at 600 degreesC or lower. The apparent activation energy of th e oxidation rate clearly changed at around 600 degreesC for NF616 and HCM12 A. In contrast, HCM2S showed single activation energy over the range of tem peratures. Although temperature and chemical composition were the major fac tors, steam pressure also showed a clear negative effect on the oxidation r ate in the lower temperature range, 570-600 degreesC.