Economic and efficient processing of Fe–Al turbine parts
Because of their excellent corrosion resistance, high wear resistance and comparable low density, Fe–Al-based alloys are an interesting alternative for replacing stainless steels and possibly even Ni-base superalloys. Recent progress in increasing strength at high temperatures has evoked interest by industries to evaluate possibilities to employ Fe–Al-based alloys for various applications. These activities have matured to a point that industrial processing of parts is now investigated in more detail by considering economic aspects.
Within the project “Pro FeAl” funded by the German Ministry of Economics (Bundesministerium für Wirtschaft, BMWi; Grant No. 0324317C) a consortium of seven industries and research centres is evaluating possibilities for the economic and efficient processing of various turbine parts from different Fe–Al-based alloys. Within the project, the production of parts by sand castings for application up to 300 °C and by forging and additive manufacturing for use at higher temperatures are investigated.
For the casting route, an alloy developed at MPIE has been selected. In a first large-scale casting trial, successful production of various parts has been demonstrated. Further optimisation of microstructure and subsequent characterisation of cast parts will be the task of MPIE in this part of the project.
For the forging route and for additive manufacturing, a new alloy has to be developed. Based on an existing alloy concept, MPIE will investigate a more cost effective alternative. Different alloy compositions are produced by vacuum induction melting. Microstructures are examined by light optical microscopy (LOM) and scanning electron microscopy (SEM). Phases and their compositions are established by X-ray diffraction (XRD) and electron probe microanalysis (EPMA), respectively. Specific microstructures are attained through annealing of the alloys. Basic mechanical properties such as microhardness, strength in compression and tension, brittle-to-ductile transition temperatures (BDTT), KIC by charpy tests and the creep behaviour are determined. Characterisation of fine-scaled microstructures by high-resolution methods is another task at MPIE.