A method for in situ measurement of the elastic behavior of a columnar thermal barrier coating

The mechanical behavior of a ceramic coating and the evolution of this behavior in-service play crucial roles in governing the performance and lifetime of these materials. A protocol is presented that allows for characterization of the in-plane elastic modulus and strain to failure of fragile ceramic coatings. The protocol employs digital image correlation (DIC) to measure time-resolved, full-field strain maps of bilayer microbeams, and material properties are extracted through direct comparison with finite element simulations of microbending experiments. The efficacy of the method is demonstrated by the measurement of the in-plane Young’s modulus (ETBC = 15–30 GPa) and the strain to fracture (3.5–5 × 10−3) of electron beam physical vapor deposited 7% yttria-stabilized zirconia thermal barrier coatings (TBCs). The results from this study also indicate that the in-plane TBC modulus has no strain dependence when measured in tension.

Research highlights
► Novel experimental method providing mechanical properties for TBCs as input for lifetime models.
► 3-point bending beams are cut by micro EDM from cross sections and loaded by custom setup.
► Free digital image correlation Matlab functions are used in concert with FE simulations.
► 7YSZ EB-PVD on NiCoCrAlY bond coat has in-plane modulus of 15-30GPa, no strain dependence.
► TBC underwent brittle fracture at strains of 3.5-5·10−3.