Fabrication of Titanium Aluminide Matrix Composites by Laser Engineered Net Shaping

TiAl-based titanium aluminide alloys and their composites reinforced with ceramic particles are considered to be important candidate materials for high temperature structural applications. Laser Engineered Net Shaping (LENS) is a layered manufacturing process, which involves laser processing fine powders into three-dimensional components directly from a CAD design. In this work, the LENS process has been employed to fabricate carbide particle reinforced titanium aluminide matrix composites using TiC and gas-atomized Ti-48Al-2Cr-2Nb powders as the feedstock materials. The composites deposited by the LENS process exhibited a susceptibility to solid-state cracking due to the generated high thermal stresses. The microstructures of the laser-deposited monolithic and composite titanium aluminide materials were characterized using light optical microscopy and XRD techniques. Effects of the LENS processing parameters on the cracking susceptibility and microstructure were studied. Crack-free deposits can be fabricated by preheating the substrate to 450~500°C during LENS processing. The fabricated composite deposits exhibit a hardness of more than twice the value of the Ti-6Al-4V alloy.