Intermetallics: Why is it so difficult to introduce them in gas turbine engines?

The intermetallic systems are considered as potential substitutes to metallic alloys for aerospace applications. An enormous research activity was spend during the last 30 years to develop applications of NiAl and TiAl. Although successful technical results were obtained, no applications are yet visible in aero engines. This paper explains the main reasons of this situation. The first reasons are due to the materials’ intrinsic properties (brittleness, small range of operating temperature, unfavourable property balance, scattered properties). The other reasons are manufacturing related (difficult processing, high cost). This is illustrated by NiAl and TiAl applications; some criteria for successful applications are given.