The improvement of high temperature oxidation of Ti-50Al by sputtering Al film and subsequent interdiffusion treatment

The high temperature oxidation resistance of Ti-50Al can be improved by sputtering an Al film and subsequent interdiffusion treatment at 600 degreesC for 24 h in high vacuum. In these conditions, a TiAl(3) layer is formed on the surface, which exhibits good adhesion with Ti-50Al substrate and provides high oxidation resistance. Cyclic and isothermal oxidation tests show that the Ti-50Al with 3-5 mum Al film can dramatically reduce the oxidation at 900 degreesC in air, at which the parabolic oxidation rate constant K(p) of specimen with 5 mum At film is only about 1/15,000 of that of bare Ti-50Al. XRD and SEM results indicate that the TiAl(3) layer can promote the formation of a protective Al(2)O(3) scale on the surface as well as react with gamma-TiAl to form TiAl(2) during the oxidation. Simultaneously, layers of Al(2)O(3)/TiAl(2)/Al-enriched gamma-TiAl/Ti-50Al are also formed on specimens. The TiAl(2) layer thickness will decrease gradually with increasing the oxidation time. After oxidation at 900 degreesC for 300 h, there is a clearly discontinuous thin layer of Ti(37)Al(53)O(10) compound observed in between Al(2)O(3) and TiAl(2). (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.