The effect of ion implantation on the oxidation behaviour of TiAl-based intermetallic alloys at 900°C

The effect of various elements added by ion implantation on the isothermal (up to 150 h) and cyclic (up to 1500 h) oxidation behaviour of two Nb-containing gamma-TiAl-based intermetallic alloys, i.e. Ti-48Al-2Cr-2Nb and Ti-48Al-2Cr-2Nb at 900 degrees C in air is discussed. During the initial stage of exposure some differences were found between the different implanted elements, i.e. Si: Nb, Ta and W. Upon longer exposure times a similar oxidation behaviour was found as for the non-implanted material, indicating that the effect of ion implantation is negligible after longer exposure times. Also for cyclic oxidation experiments, after longer exposure times no differences were found between the non-implanted and the material implanted with various elements. A steady state condition is reached with a net linear mass loss rate, due oxidation, spallation, and re-growth of the oxide scale. The net linear mass loss rate for Ti-48Al-2Mn-2Nb was higher than found for Ti-48Al-2Cr-2Nb, indicative of a higher susceptibility for cracking and spallation. (C) 1998 Elsevier Science S.A.