Modification of initial oxidation kinetics of TiAl, NbAl3 and 25-25-50 Nb-Ti-Al by oxygen ion implantation

One approach to the development of high temperature oxidation resistance in alloys of the system Nb-Ti-Al is based on the formation of continuous alumina layers by selective oxidation of aluminum. This approach has met with limited success, due to the formation of non-protective Nb or Ti based (''transient'') oxides from the onset of exposure. The authors have bypassed the selective oxidation route by implantation of 18O just below the surface to form a thin oxide layer. Implantation doses suitable for studying the initial stages of oxidation have been used. The implanted specimens were subsequently exposed to oxygen at 1,000 C. The use of 18O provides a built-in tracer for SIMS analysis both to determine the actual implanted profile and to study the high temperature oxidation kinetics. Near-surface oxidation states have been studied using XPS. Materials investigated include the intermetallic compounds NbAl3, TiAl, and a ternary alloy, 25-25-50 Nb-Ti-Al