Laser-based Additive Manufacturing of Titanium Aluminides

Fabrication of titanium parts by laser-based processes has recently attracted considerable attention. In addition to powder-bed based processes, free form fabrication (FFF) using powder- and wire-feed processes has been established to generate large-volume parts as well as high-precision parts. A major advantage of this manufacturing technology is seen in its near net shape capabilities that avoids substantial time-consuming machining of expensive aerospace materials.  Today, FFF parts can be build-up with considerable deposition rates of the order of several kilograms per hour, thus enabling rapid and cost efficient manufacture of large structural parts. For this purpose lasers in the kW-range are used. Due to the high heat input during manufacturing considerable distortion is typically found that can be minimized by sophisticated building strategies. At the other end of the spectrum, high precision additive manufacturing results in weld bead sizes of around 30 µm; here brilliant laser sources in the power range of a few hundred Watts are neccessary. Due to their brittleness intermetallic titanium aluminides are particularly challenging to be fabricated by conventional manufacturing such as casting and forging as well as by additive manufacturing. In the present paper, recent advances in free-form fabrication of titanium aluminides will be reviewed. Obviously, tight control of the processing parameters is key for good material quality. Differences in processing results will be compared with conventional titanium alloys to highlight challenges associated with the intermetallic alloys.