The present paper is addressing the issue of the Fatigue Crack Growth (FCG) behaviour of aluminides with a special emphasis placed on the role of environment. The behaviour of two alloys, a cast quaternary TiAl alloy and a Fe-40Al alloy prepared by mechanical alloying, were investigated under various atmospheres with different levels of moisture and at different temperatures. Although the fatigue crack growth resistance of both compounds was altered in moist environments, particularly in air, major differences have been noticed. Hence, while hydrogen is believed to be responsible for the degraded FCG resistance of the TiAl alloy, FCG in the FeAl alloy is shown to be mainly governed by adsorption of water vapour. Besides, competitive adsorption of oxygen has been shown to be efficient to prevent moisture-induced loss of FCG resistance enhancement in FeAl, but not in TiAl, even at elevated temperature.
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