Ion-induced surface modification combining the halogen and the reactive element-effect for a Ni-base superalloy



The oxidation resistance of Ni-base superalloys with Al-contents of 2–5 wt% is commonly improved by the use of Al-rich coatings. An alternative way has been proposed by using the halogen effect. In this case, the Al activity on the alloy surface is increased by the transport of Al via gaseous Al-halides. Fluorine was chosen because of the good results obtained in the case of TiAl. The fluorine was applied by ion implantation. After oxidation at 1050 °C a dense protective alumina scale was formed on the surface of the alloy IN738. The fluorine effect was combined with the reactive element effect to improve the adherence of the alumina scale.