Oxygen-18 and deuterium profiling in thick films on Fe-9% Cr alloys by 3 MeV nuclear microprobe

The oxidation of Fe-9% Cr alloys with different Si contents has been studied in dry and wet CO2. C18O2 and D2O were used as tracers and detected by the 18O(p,α)15/N and 2D(3He,p)4He reactions at 0.84 and 0.75 MeV respectively using a scanning ion microbeam. With 0.04 wt.% Si most of the 18O was taken up at the outer oxide-gas interface. Higher silicon levels lowered the oxidation rate and the outward diffusion of iron. No difference was found between 18O profiles from material oxidized in wet or dry CO2. Deuterium was found only in the inner Fe-Cr spinel layer of material oxidizes in CO2-D2O mixtures. (author)