Effects of tungsten alloying and fluorination on the oxidation behavior of intermetallic titanium aluminides for aerospace applications

Current limitations to a wider use of intermetallic TiAl alloys in aircraft and automotive engines arise from an insufficient oxidation resistance at temperatures above approximately 800 °C. In this paper, the high temperature behavior three engineering ?-TiAl-based 900 °C air is reported. The performance TNM alloy (Ti-43.5Al–4Nb–1Mo-0.1B), 4822 (Ti–48Al–2Cr–2Nb), Nb-free IRIS (Ti–48Al–2W-0.08B) compared (all chemical compositions are given at.%). During testing non-protective mixed oxide scales developed on all untreated samples, but with different thicknesses. These layers characterized their formation mechanisms discussed. presence W leads better 4822. This was changed direction protective alumina layer via so-called “fluorine effect”. above-mentioned were treated fluorine liquid phase process by evenly spraying containing polymer faces specimens. samples significantly improved Due fluorination test coupons exhibited slow kinetics. results isothermal as well thermocyclic exposure tests presented discussed view composition processing conditioned microstructure investigated alloys.