Eutectic ceramic for novel optimised yield turbine blade – CiNATRA

The project aims at designing new gas turbine blades for ultra-high temperature uses and at developing an industrial process for their manufacture.
In a general context of energy saving, an improvement in gas turbine efficiency (aeronautical or terrestrial) will need a significant increase in the gas temperature. Consequently, materials stable above 1500°C will be necessary. Turbine blades, which are facing the highest temperatures in gas turbines, are presently fabricated in single crystal nickel based superalloys that already reached their limit (1050°C-1100°C). Oxide ceramics are a possible alternative with advantages of a lower mass and a higher temperature use. However they are brittle, compared to metals and alloys, and their mechanical properties decrease sharply beyond 1300°C, essentially due to grain boundary sliding. Therefore use of single crystal ceramics would open new possibilities and directionally solidified refractory oxide eutectics appear as the best candidates. Our recent studies show that, for given compositions, it is possible to get very specific microstructures, known as “interconnected”, without grain boundaries and with exceptional mechanical properties up to 1700°C (creep and fracture strengths). Their use as high temperature components would be a real innovation and a huge technical improvement in terms of motor efficiency and weight decrease.
Objectives of the project are addressing simultaneously the material and its elaboration, by a technique never used before for this kind of material:
- Development of a crystal growth process, with reproducibility of mechanical properties of the industrially grown ceramics and with a crystal shape which decreases the subsequent complex machining steps,
- Optimization of the composition and microstructure in relation with the conditions of use as turbine blades.
The growth process is already mastered by the partner RSA, for the production of sapphire single crystals, but will need to be adapted to the growth of these “in situ” composites. This improvement will be based on the recent studies of the project partners, using other growth techniques, and on specific works performed during this CiNATRA project, aiming at improving the growth conditions and obtaining large ceramic pieces.
Several binary and ternary eutectic compositions have already been studied and grown by the partners by other methods. Studies will be performed in order to either optimize these compositions or propose new oxide systems, allowing getting properties in agreement with use as turbine blades. High temperature mechanical properties of the material will be characterized (toughness, creep and fracture strengths, thermal shock) and the phenomena involved during thermo mechanical loading will be studied. Corrosion resistance to the turbine gas environment will be studied, as well as possible material degradation, in which case protective solutions will be proposed.