Surface modification of Ti and low Al-content Ti alloys for enhanced environmental stability at elevated temperatures


Surface modification of Ti and low Al-content Ti alloys for enhanced environmental stability at elevated temperatures

Yankov, R. A.; Kolitsch, A.; von Borany, J.; Munnik, F.; Donchev, A.; Schütze, M.

It is now well-established that TiAl alloys containing Al between about 40 and 55 at.% may be modified by introducing a halogen element, notably F, into their near-surface region (the so-called halogen effect) to protect them against high-temperature environmental degradation. Upon subsequent high-temperature oxidation, the TiAl alloys modified in this way acquire а highly protective alumina scale, and are suitable for advanced automobile, aerospace and power generation applications. Low-Al content (typically < 10 at.%) Ti alloys, however, contain insufficient amounts of Al for the halogen effect to be activated necessitating enrichment with Al of their near-surface region. In this work, both α-Ti and low-Al content Ti alloys have been processed to render them oxidation-resistant in air at temperatures of 600 to 1050°C by promoting the formation of a protective scale. Surface processing has generally involved two steps, namely Al enrichment and introduction of F. The Al enrichment has in turn involved deposition of a thin Al film by magnetron sputtering followed by either Ar ion bombardment or rapid thermal annealing. The introduction of F has been achieved by plasma immersion ion implantation. Analytical techniques such as ERDA, RBS, XRD, SEM and EDX have been used for sample characterization. Under optimized processing conditions the metal samples so modified have shown high-temperature environmental stability comparable to that of standard TiAl (40 < Al < 55 at.%) alloys.

  • Poster
    Surface modification of Ti and low Al-content Ti alloys for enhanced environmental stability at elevated temperatures, 08.-12.06.2009, Strasbourg, France

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Publ.-Id: 13632