Materials like titanium aluminide could present enough of an improvement in performance and economy over conventional alloys currently used for turbine blades that the European Space Agency is going to space to learn how to perfect them. The program is called IMPRESS — Intermetallic and Material Processing in Relation with Earth and Space Solidification — and is expected to become part of international space station activities, soon. Intermetallics are similar to alloys but differ in that they are actual chemical compounds — they are more than just a blend of metals. Titanium aluminide is one such intermetallic and it is substantially lighter than the alloys used to make modern turbine blades, which would translate to higher performance and economy. Unfortunately, when the material is produced while under the effects of gravity, its shortcomings are huge. The intermetallic is subject to oxidation and “embrittlement” at high temperatures, but that problem can be resolved simply by adding tantalum and niobium to the mix. The problem is that those are heavy atoms that, when added on earth, segregate and produce a heterogeneous material that does not adequately solve the problems of oxidation. But there may be a solution.
In outer space, or micro-gravity environments like parabolic flight or “drop towers,” the creation of these metals can be significantly improved and perhaps perfected. The IMPRESS program will examine intermetallics made in space and attempt to discern specifications for the materials that could then lead scientists to determine how they might be reproduced in less expensive environments here on earth.
