The influence of yttrium implantation on the oxidation of impure iron containing C and Mn at 700°C

A study of impurity-yttrium interactions has been performed during iron oxidation [p(O-2) = 0.04 Pa, T = 700 degrees C]. Yttrium-implanted specimens always exhibit better oxidation behavior compared with blank specimens. On pure iron or the Fe 0.054 wt.%C alloy the beneficial effect is attributed to Fe2YO4 formation. With the manganese-containing allays (Fe 0.2 wt.%Mn), the protective effect of yttrium is attributed to YMnO3 formation. The best oxidation behavior is obtained with implanted Fe0.18 wt.%Mn-0.041 wt.%C alloys due to the formation of an YMnO3 oxide subscale at the scale-alloy interface. Yttrium implantation also hinders carbon segregation at the oxide-alloy interface. This effect ensures better scale adherence. With the most-impure alloy, yttrium implantation also changes the growth process from external cation diffusion to predominant inward-oxygen diffusion.