The influence of a segregated MoN layer on the room temperature oxidation of a Fe()–3.5 wt.% Mo–N specimen

The room temperature oxidation of Fe(1 0 0), Fe(1 0 0)–3.5 wt.% Mo–N and a segregated MoN layer were compared with each other by using Auger electron spectroscopy. Linear temperature ramping was used to segregate the Mo and N from the Fe(1 0 0)–3.5 wt.% Mo–N specimen. There were striking differences in the oxidation behaviour of the segregated MoN layer compared to the other specimens. The oxidation of the Fe(1 0 0) and the Fe(1 0 0)–3.5 wt.% Mo–N reaction followed a logarithmic rate, while the segregated MoN layer has an inhibiting effect on the rate of the surface reaction. The hypothesis formulated suggested the dissociation of the MoN layer and the formation of volatile MoO ₃ and N _xO _y compounds. After the oxidation of the MoN layer there was no Mo or N enrichment detected underneath the oxide layer and the oxide formed on the surface was iron oxide.