Abstract
High-temperature lightweight alloys based on TiAl intermetallic are promising for manufacturing low-pressure turbine blades. Various methods of additive manufacturing (AM) from such alloys are being developed. The AM is attractive because of its flexibility and possible reducing the number of assembly and machining operations. However, the issues of defect and microstructure formation at AM of TiAl alloys have not been sufficiently studied to ensure an industrial application. In the present work, a Cr- and Nb-doped TiAl alloy is obtained by self-propagating high-temperature synthesis under an overload necessary for better separation of slag impurities. Samples of the alloy are processed with a laser beam in the conditions typical for AM by selective laser melting (SLM) in the ranges of the scanning speed from 5 to 4000 mm/s, the laser power from 10 to 165 W, and the preheating temperature 25 and 800 oC. It is shown that cracking can be avoided in laser processing with preheating up to 800 oC in the range of the scanning speed from 10 to 200 mm/s. The formed material microstructure is studied by SEM and related to the cracking ability. A strategy for theoretical assistance in the SLM parameter optimization is proposed based on a model of heat transfer in the laser-interaction zone. This strategy is validated by the experimental data: it is shown that several experiments are sufficient to predict the integrity of optimal combinations of the following process parameters: the laser power, the scanning speed, and the preheating temperature.
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