Titanium aluminides: For automotive and gas turbine applications

The present article focuses on the state of development of gamma-TiAl alloys for turbine blades in the last stage of low pressure turbines as well as for turbocharger wheels and exhaust valves in automotive engines. Within several materials technology projects extensive gamma-TiAl material characterization programs were carried out in order to prove the high potential of gamma-TiAl alloys for the applications stated above. Titanium aluminides exhibit a lower fracture toughness and a lower crack propagation resistance than titanium and nickel alloys. It has been demonstrated in previous studies, however, that gamma-TiAl based alloys with optimized microstructures exhibit tensile, fatigue and creep properties which fulfill the technical requirements for turbine blade and automotive valve applications. Despite the high potential of gamma-TiAl alloys for application in advanced engine systems, however, cost-effective production routes must be developed in order to make this new material economically competitive. First results on turbine blade testing concerning the influence of pre-damaging on fatigue properties as well as recent results of valve testing in automotive engines are presented.