THE EFFECTS OF FE, CU AND AL IMPURITIES ON THE OXIDATION RESISTANCE OF TISI2 .1. FE

The effect of iron on the oxidation resistance of titanium disilicide (TiSi2) was investigated. The impurity was mixed with titanium disilic ide powder, compacted and then sintered. The compacts were oxidized at elevated temperatures for various times. The oxide coatings were exam ined by thin film diffractometry and also in a scanning electron micro scope equipped with energy dispersive spectroscopy. The oxidation prod ucts, parabolic rate constants and activation energies for TiSi2 conta ining up to 6 mass percent iron were similar to those of the pure disi licide. Diffusion of iron through the oxide layer was slow. A deficien cy in the amount of silicon in an iron-rich intergranular phase result ed in a local increase in the amount of titania produced on oxidation. The results suggest that the presence of iron does not change the bas ic mechanism of oxidation, but instead alters the nature of the oxide such that the diffusion rates increase with iron content.