Oxidation protection of Ni‐base superalloys by halogen treatment

A new concept of oxidation protection is proposed for Ni‐base alloys with Al‐amounts of 2–5 wt%. Following Wagner ' s theory of oxidation the formation of a dense protective alumina scale is possible if the Al‐activity is sufficiently high. This condition can be fulfilled by using the halogen effect. Thermodynamical calculations reveal the existence of regions for a positive effect of F and Cl for the alloys IN738 and IN939. In the case of fluorine these results are transformed into F concentrations in a screening by using ion implantation. By the F‐effect the oxidation mechanism at 1050 °C/air was changed from internal oxidation of Al to an external formation of an Al 2 O 3 – scale. Optimal implantation parameters were defined. The formation and stability of the protective alumina scale was proved within 1000 h/1050 °C.