It is widely accepted that the evolution of Gas Turbines can be mapped in terms of the turbine entry temperature (TET) and as such, any new developments require TETs to increase even further than the present state-of-the-art levels. This continuous need has been addressed by turbine materials (superalloys) developments, new cooling concepts, novel combustor designs and by the gradual introduction of TBCs in the engine hot sections. The latter option, undertaken in the last couple of decades has shown to be the most beneficial one not only for the present but also for the near future. However, to reach the targets demanded by the new class of clean, lean, safe and affordable GTs, new TBCs are ultimately required with much better properties and with a capacity to function in a ”prime reliant” mode.
This project was directed towards the implementation of efficient and environmental friendly technologies for gas turbines (aero-engines and land-based gas turbines). The goal was to increase the efficiency and to reduce the harmful emissions. This was intended by the development of advanced thermal barrier coatings (TBC), which should allow to increase the entry working temperature by at least 50°C.
- Development and investigation of the various TBC candidates with regard to their main physical properties and microstructure produced under laboratory conditions as basis for the subsequent down-selection of the most suitable coatings.
- Production of the down-selected TBCs under industrial conditions with subsequent investigation of the material properties and intensive testing with regard to their structural, mechanical, fatigue, corrosion and erosion properties.
- The characterisation of the microstructure and the determination of the physical properties revealed advantages of the new coating LaMg-Hexaaluminate compared to the zirconia coatings.
- The fatigue properties of the zirconia coatings 8YPSZ and 14YSZ were comparable, while the LaMg–Hexaaluminate revealed worse results; but an improvement was achieved by applying a stabilisation heat treatment or even better a different APS powder of better quality from DCF.
Component tests on all down selected coating systems in a burner rig facility were started and showed first promising results, but they couldn’t be completed until the project end and were still on-going. It is planned that after passing all required tests and approvals selected coating systems produced by EB-PVD (YPSZ plus full stabilised zirconia) and APS (YPSZ plus metal oxide doped hexaaluminate) will be subjected to a component test in the aircraft industry as well as in the gas turbine industry.