The increasingly severe and complex mechanical and thermal loading conditions which gas turbine blades are being subjected to often lead to fatigue cracks initiating in regions where cyclic plasticity highly localizes, due to mechanical and thermal cyclic stressing. Moreover, creep damage is observed due to high temperatures dwell times, which also generate oxidation damaging processes. The complexity of such processes is further underlined by the interaction between cyclic plasticity damage and creep damage. Current and future engine developments rely on thermal barrier coatings (TBC) applied on some strategic places of components to raise turbine inlet temperatures and hence increase thermodynamic efficiency. Substrate damage, oxidation and TBC degradation can however significantly reduce component life time.
The aim of this basis research proposal is to develop tools for life assessment of single crystal superalloys components. Two distinct aspects will be considered for damage analysis:
fatigue damage of uncoated single crystal;
degradation of the thermal barrier coating (TBC) itself.
The two aspects will be studied in parallel, as they involve completely different damage mechanisms. The study will provide the physical basis to model the damage by taking into account the role of the various interactions with the microstructure. Micromechanical and macroscopical models will be developed.
The specific objectives of the work programme are to develop: a basic understanding of the dominant high temperature degradation and damage mechanisms in coated and uncoated monocrystalline Ni base superalloy components used in gas turbine applications,
the development of mechanical models at both the mesoscopic and macroscopic levels, together with computational tools for life assessments,
the validation of the life assessment method on the basis of structure analyses.
Funding SchemeCSC - Cost-sharing contracts
ST17 4LN Stafford
45466 Mülheim An Der Ruhr
461 81 Trollhättan