Investigation and optimization of marginal zone properties in electrochemical metalworking of iron aluminides to improve oxidation resistance

 

According to current forecasts by the International Air Transport Association (IATA), the annual passenger volume of civil aviation will increase to 7.8 billion by 2036, almost doubling compared to today's level. Increasing global demands for environmental protection and resource efficiency call for strong ecological and economic improvements in engines. According to the EU Commission's Flightpath 2050, for example, environmentally harmful nitrogen oxides are to be reduced by 90 % and carbon dioxide by 75 %. This poses major challenges for the aviation industry and the engine industry in particular. In order to meet these requirements, efficiency must be improved by increasing the combustion temperature. However, this is only possible through continuous further development of the materials to be used.

Iron aluminides are currently an increasingly attractive alternative to established materials in engine construction. They are characterized by low costs, low density, good wear resistance, simple forming and excellent corrosion resistance. In the past, iron aluminides could not arouse economic interest because they did not exhibit sufficient tensile strength at high temperatures, but this problem was solved by new alloy concepts. For example, the precipitation of finely divided borides at the grain boundaries instead of carbides improved ductility and prevented coarsening of the Fe-Al matrix at high temperatures.

Since iron aluminides, compared to titanium aluminides, have low-cost and non-strategic components and only require small amounts of additional alloying elements, the material is comparatively inexpensive. In order to predict the service life of iron aluminides, this project will therefore for the first time investigate the electrochemical machinability of iron aluminides as an important manufacturing process for engine blades for the production of various surface qualities. On the other hand, the oxidation behavior of the previously machined components will be investigated in the following in order to identify a relationship between the surface and the corrosion resistance. The analyses focus on the changes in the peripheral zone with regard to the microstructure and the surface roughness.