Thermal Barrier Coatings for greener heat-to-power applications: understanding limits of operation under hydrogen combustion and sustainable outlook – TBC4H2

The goal of the project is to gain new knowledge on the high temperature behaviour of Thermal Barrier Coatings (TBC) deposited using Suspension Plasma Spraying (SPS) and Electron Beam Physical Vapor Deposition (EB-PVD) methods on a single crystal Ni-base superalloy with diffusion and overlay bond coatings (BC) for aircraft engine turbines operating at temperatures beyond the capabilities of currently used superalloys – 1200 °C and under hydrogen combustion conditions. Increasing the operational temperature and therefore efficiency of aircraft engine turbines will reduce fuel consumption by new generation of airplanes and directly contribute to the reduction of CO2 emitted to the environment, thus fulfilling global needs in terms of building climate neutrality. In this way, the project is in line with the objectives of the Green Deal policy related to sustainable transport, assuming a significant reduction of CO2 emissions by the transport sector by 90% by 2050. Moreover, the project envisages the determination of the effect of elevated water vapor content in the atmosphere, characteristic of hydrogen combustion, on the durability of advanced TBCs on Ni-based superalloys. Use of green hydrogen in gas turbines envisages complete avoidance of CO2 emissions.

The project involves the application of diffusion as well as overlay bond coatings for operation at 1200 °C. These will include diffusion Pt-?/?' as an alternative to Pt-aluminide as well as overlay BCs by atmospheric plasma spraying (APS) methods. The ceramic top coatings (TC) will include the standard 7 wt. % yttria stabilized zirconia (7YSZ) and new gadolinium zirconate (Gd2Zr2O7 – GZ) deposited using SPS and EB-PVD methods. The project is aiming to pursue an optimization route that will enable a faster and materials saving approach for the assessment of TBC adhesion and high temperature damaging behaviour involving a novel laser shock-driven methodology - the laser adhesion test (LASAT). Moreover, LASAT will be utilized to evaluate the effect of high temperature exposures in atmospheres rich in water vapor on the fracture toughness (bulk or interfacial toughness) of the TBCs (Fig. 1). The scientific goals of the project include the elucidation of isothermal and cyclic oxidation behaviour of various bond coatings and TBCs at 1200 °C as well as systematic microstructural STEM investigations on the nanometric scale of the BC/TGO and TGO/TC interfaces with or without effect of water vapor.

The combination of deposit optimization, complex aging within hydrogen combustion atmosphere, microstructure in-depth analysis and global adhesion testing by LASAT makes a complementarity to build fundamental understanding to optimal material design. Modelling strategy of laser shock, will finally be achieved so as to gain understanding in the role of morphology of TC and interfaces in adhesion. The results, if correlated to experiment, will consist in abaqus that could be further used as guidelines for processing optimisation. The project will start with TRL 1 and finish with TRL 5 (TRL values differ by partner and the technology being employed) by demonstrating the developed technology on a set of aircraft turbine blades.