Surface Study of Ti3Al and Ti3Al-11Nb, TiAl and TiAl-2Cr by X-Ray Photoelectron Spectroscopy

Abstract

Oxide films formed on intermetallics Ti 3 Al , Ti 3 Al -11at.%Nb, TiAl and TiAl-2at.%Cr were studied by X-Ray Photoelectron Spectroscopy (XPS). An addition of 11at%Nb to Ti 3 Al increases the Ti:Al atomic ratio on the surface from 2.8:1 to 20:1. This may explain the better electrochemical corrosion resistance of Ti 3 Al -11Nb than Ti 3 Al . Meanwhile, an addition of 2at.%Cr to TiAl decreases the Ti atomic percentage from 11.8 to 9.5. The Ti:Al atomic ratio changes from 1:0.2 to 1:1.8. The Cr addition enhances the formation of an Al-enriched passive film, which may be the reason for the improved TiAl high temperature oxidation resistance. TiO 2 is the main component of the top oxide layers formed on the intermetallics of Ti 3 Al , Ti 3 Al -11Nb and TiAl. In contrast the top layer of TiAl-2Cr is mainly Al 2 O 3. XPS results show that the compositions are quite different between the bulk materials and the top oxide layer on these intermetallics.