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Hot Salt Corrosion of titanium aluminides
Author(s) -
Nicholls J. R.,
Leggett J.,
Andrews P.
Publication year - 1997
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.19970480110
Subject(s) - corrosion , titanium , metallurgy , materials science , salt (chemistry) , chemistry
There is considerable interest in the use of γ‐TiAl within advanced gas turbines where they offer greater high temperature capability over conventional titanium at reduced weight. These factors would enable engines with greater thrust to weight ratio to be developed. Thus γ‐TiAl offers the potential of replacing nickel based alloys within the high pressure compressor and potentially the fourth stage turbine. Service in both of these locations would require that the γ‐TiAl be resistant, not only to oxidation, but hot salt corrosion. This paper presents a study of the hot salt corrosion resistance of γ‐TiAl over the temperature range 500–700°C. At 700°C, laboratory tests have shown that corrosion rates in a salt ladened environment are some 20X that of equivalent oxidation for exposures out to 100 h. The morphology of attack is consistent with a corrosion mechanism involving the vapour phase transport of aluminium from within the alloy and formation of a non protective oxide scale. A model for the corrosion mechanisms is presented, involving intermediate chloride phases. The mechanism is believed to be self sustaining, requires little chloride present, and leads to the observed accelerated oxidation rates.