MIM components are to go into series production for the EJ200 engine used in the Eurofighter aircraft following successful testing in rigs and engines. MIM is said to have the potential for substantial cost reductions in aero engine applications. Modern aero-engines have to fulfil extreme requirements concerning reliability, minimum weight, high performance, economy and long life. Over the 40 years since the first generation of commercial turbo-jets were introduced, reliability has improved by a factor of 10.
This success was possible thanks to progress in materials, manufacturing and surface technologies, and aero engine producers such as MTU Aero Engines in Munich, Germany, see a maturing of the design and materials in this sector but with competitiveness coming mainly from the ability to cut costs in parallel with continuing to improve engine performance.
Today’s relevant aero engine materials are said to be titanium alloys, Ni-base superalloys and high strength steels. In a report published by MTU, Dr Klaus Steffens and Dr Hans Wilhem state that for many years engine disk alloys with higher temperature properties could only be made by powder metallurgy, e.g Udimet 700, Rene 95 and IN 100. Now it is possible to produce similar alloys by casting plus forging.
Blades and vanes in the turbine are today cast but MTU has been studying MIM to achieve near-net shape HPC blades, vanes, levers and fasteners with tight tolerances and good surface quality (Rt = 1µm).
By optimising MIM processing parameters, nearly full density can be achieved with gt;95% of the strength of forged materials being reported. The remaining lack of properties can be compensated by material selection, states MTU. For example if the strength of forged IN 718 superalloy is need then there is the option to produce the part from MIM using Udimet 720LI.