This paper describes the cracking behavior of cast gamma titanium aluminide welds produced by gas tungsten arc welding (GTAW). Two different cracking mechanisms were observed in GTAW of γ-TiAl: solidification cracking and solid state cracking. However, a higher frequency of solidification cracks was observed. Traditional hot cracking was not the operative mechanism as corroborated by microstructural analysis of the cracks. No evidence of grain boundary liquation or fracture features associated with the occurrence of subsolid liquid microconstituents was observed. Regardless of the cracking mechanism, it was found that the cracking susceptibility increases with a decrease in the welding current, which corresponds to higher cooling rates. This suggests that the cooling rate plays a key role in the weldability of gamma titanium aluminides. The cooling rate at the weld centerline was measured and it was found that a cooling rate of 560 K/s or less is necessary to avoid cracking.
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