Laser based manufacturing of titanium aluminides

Abstract

Lightweight titanium aluminides (TiAl, ρ = 3.9 – 4.1 g/cm3) gain in importance as high temperature structural material. The known properties like high strength and creep resistance combined with high corrosion and wear are of continuous interest for turbomachinery applications like low pressure turbine blades. Additive manufacturing (AM) provides the possibility for near-net-shape production of functional complex parts and can contribute to reduce consumption and costs of material, tooling and finishing. The typical high brittleness and oxygen affinity of TiAl cause special requirements for processing this material with AM. In this work, recent progress in Additive Manufacturing of the TiAl alloys of the nominal compositions Ti-43.5Al-4Nb-1Mo-0.1B (at.-percent, TNM™-B1), Ti-48Al-2Cr-2Nb (at.-percent, GE4822) and Ti-45Al-2Nb-2Mn-0.8B (at.-percent, 4522XDTM) is presented. Microstructures resulting from both Laser Powder Bed Fusion (LPBF) and Direct Laser Deposition (DED) are compared with respect to the characteristics of the manufacturing processes. Hardness measurements according to Vickers are performed, and pressure strength tests are performed on selected samples. The crack-free additive manufacturing of complex geometries made of TiAl is demonstrated as well as an approach for manufacturing hybrid parts combining DED and LPBF.