The influence of yttrium ion implantation on the oxidation behaviour of powder metallurgically produced chromium

The beneficial effect of adding yttrium by ion implantation on the oxidation behaviour of powder metallurgically (PM) produced chromium at 900 degrees C has been investigated. Comparative studies were made in which yttrium was added as an oxide dispersoid. For further insight into the oxidation process, a two stage oxidation, using oxygen isotope tracers, was performed. The oxide scales formed were analysed by a wide range of analytical techniques, but mostly secondary neutral mass spectroscopy (SNMS). The addition of yttrium changes the oxide scale growth processes. Its presence in the oxide scale, possibly as a segregated phase on the oxide grain boundaries, reduces cation diffusion, causing the oxide growth to be dominated by anion transport. This segregation can cause many, if not all, of the reported beneficial reactive element effects. Ion implantation is shown to be a powerful tool in oxidation studies, and thus for advanced material development.