SURFACE ANALYTICAL INVESTIGATIONS ON THE OXIDATION BEHAVIOR OF TIAL-BASE INTERMETALLICS

The oxidation behaviour of TiAl-base intermetallics has been investiga ted at 800-degrees-C in air. The main emphasis was placed on the mecha nism by which niobium additions decrease the oxidation rate of titaniu m aluminides. For this purpose specimens of Ti50Al and Ti45Al10Nb were oxidized in a two-stage oxidation technique using an O-18-tracer. The scale formed during this oxidation process was analyzed by SNMS. It w as found that niobium is mainly incorporated in the titanium dioxide a nd the nitride scale which forms beneath the initially formed alumina layer. The effect of this behaviour of the niobium on the oxide scale growth rates is discussed.