Resource-Efficient Manufacturing Technology for Titanium Aluminide Aerospace Components

Abstract

Titanium aluminide (TiAl) has been identified as a key material for achieving significant emission reductions in aircraft jet engines due to its high-temperature properties combined with its very low weight compared with conventional nickel-based alloys. Well-known engine manufacturers, therefore, introduced TiAl low-pressure turbine blades in their engines. To enter the market, all manufacturers initially relied on enormous machining allowances for safety reasons, thus accepting a poor buy-to-fly ratio: MTU Aero Engines AG used the casting/forging route with the alloy TNM [Ti–43.5Al–4Nb–1Mo–0.1B (at.-%)] for the highly stressed GTF (geared turbofan), Safran used machining of the alloy GE48-2-2 (Ti–33Al–2.6Cr–4.8Nb (wt.-%)) from the solid, and GE (General Electric) used ‘massive-overstock’ investment casting and 3D printing of GE48-2-2. More cost-effective and material-efficient processes are needed for titanium aluminide to establish itself sustainably in new aerospace applications in the long term. Access has, therefore, developed an economical TiAl investment casting process to industrial maturity, realizing a minimum machining allowance of 0.7 mm in a process-safe manner. In a study, it was evaluated that carbide cutters with AlTiN coating are excellently suited for machining TiAl. Extensive studies of the economic viability of TiAl investment casting have shown that it is competitive.