THE INFLUENCE OF YTTRIUM ION-IMPLANTATION ON THE OXIDATION BEHAVIOR OF POWDER METALLURGICALLY PRODUCED CHROMIUM

The beneficial effect of adding yttrium by ion implantation on the oxi dation behaviour of powder metallurgically (PM) produced chromium at 9 00 degrees C has been investigated. Comparative studies were made in w hich yttrium was added as an oxide dispersoid. For further insight int o the oxidation process, a two stage oxidation, using oxygen isotope t racers, was performed. The oxide scales formed were analysed by a wide range of analytical techniques, but mostly secondary neutral mass spe ctroscopy (SNMS). The addition of yttrium changes the oxide scale grow th processes. Its presence in the oxide scale, possibly as a segregate d phase on the oxide grain boundaries, reduces cation diffusion, causi ng the oxide growth to be dominated by anion transport. This segregati on can cause many, if not all, of the reported beneficial reactive ele ment effects. Ion implantation is shown to be a powerful tool in oxida tion studies, and thus for advanced material development.