THE EFFECT OF ION-IMPLANTATION ON THE OXIDATION BEHAVIOR OF TIAL-BASED INTERMETALLIC ALLOYS AT 900-DEGREES-C

The effect of various elements added by ion implantation on the isothe rmal (up to 150 h) and cyclic (up to 1500 h) oxidation behaviour of tw o Nb-containing gamma-TiAl-based intermetallic alloys, i.e. Ti-48Al-2C r-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 expo sure times a similar oxidation behaviour was found as for the non-impl anted material, indicating that the effect of ion implantation is negl igible after longer exposure times. Also for cyclic oxidation experime nts, after longer exposure times no differences were found between the non-implanted and the material implanted with various elements. A ste ady state condition is reached with a net linear mass loss rate, due o xidation, 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 spalla tion. (C) 1998 Elsevier Science S.A.