Oxidation behavior of modified SUS316 (PNC316) stainless steel under low oxygen partial pressure

Abstract Oxidation behaviors of modified SUS316 (PNC316) and SUS316 stainless steels were investigated under the low oxygen partial pressure of 10 −31 −10 −22 atm at 600–800 °C. Oxygen uptake by these materials parabolically increased with time, and the kinetic rate constants depended on both oxygen partial pressure and temperature. Thus, semi-empirical equations of the parabolic rate constants were obtained to be 2.70×10 4 exp(−109/ RT ) P O 2 0.279 for PNC316 and 9.23×10 4 exp(−98/ RT ) P O 2 0.313 for SUS316. For the duplex layer formed under the low oxygen partial pressure, the inner layer consisted of such oxides as Cr 2 O 3 and FeCr 2 O 4 , while the outer layer consisted of non-oxidized α-Fe. Furthermore, oxidation along the grain boundaries was observed for samples oxidized for a long time. From the point of view of fuel cladding chemical interaction evaluation at high burn-up fuel for fast reactors, it is interesting that formation of non-oxidized α-Fe was observed under the low oxygen partial pressure.