Enhancing the High Temperature Capability of Ti-Alloys

A. Donchev, M. Schütze, A. Kolitsch, R. Yankov

Titanium is a widely used structural material for applications below approximately 500°C but right now it cannot be used at higher temperatures. Titanium forms a fast growing rutile layer under these conditions. Furthermore enhanced oxygen uptake into the metal subsurface zone leads to embrittlement which deteriorates the mechanical properties. To overcome this problem a combined Al- plus F-treatment was developed. The combination of Al-enrichment in the surface zone so that intermetallic TixAly-layers are produced which form a protective alumina layer during high temperature exposure plus stabilization of the Al2O3-scale by the fluorine effect led to significantly improved resistance against increased oxidation and embrittlement in high temperature exposure tests of several Ti-alloys. In this paper, the experimental procedures and achieved improvements are described. The results will be discussed for the use of Ti-alloys at elevated temperatures.

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