Optimization of the Fluorine Effect for Improving the Oxidation Resistance of Tial-Alloys

TLDR: In this paper, the surface of the TiAl-alloys was treated with small amounts of fluorine to suppress the formation of a fast growing mixed oxide scale on untreated alloys, and a thin protective alumina scale was formed on samples after fluorine treatment.

Abstract: The oxidation resistance of TiAl-alloys can be improved drastically by treating the surface of the components with small amounts of fluorine. The oxidation mechanism is changed. Hence, the formation of a fast growing mixed oxide scale on untreated alloys is suppressed. Instead a thin protective alumina scale is formed on samples after fluorine treatment. The different methods only influence the surface region of the components so that the bulk properties are not affected. Recent results achieved with F-containing inorganic compounds showed that the fluorine effect can be improved even further. TiAl-specimens were treated only with fluorine and with F-containing compounds in several ways and their performance during high temperature oxidation tests in air was investigated. Results of isothermal and thermocyclic oxidation tests are presented. The results are discussed in terms of a later use of the fluorine effect for technical applications.