Micromechanical testing of a thermally grown oxide on a MCrAlY coating

The stiffness and fracture toughness of a thermally grown oxide (TGO) on a MCrAlY coating were measured by the microcantilever bending technique. TGO cantilevers were prepared by a focused ion beam and bent in-situ by a nanoindenter in a scanning electron microscope. The Young’s modulus and fracture toughness of the TGO were determined to be 352 GPa and 4.4 MPa·m1/2, respectively. The measurement results were compared with mechanical properties of the TGOs and bulk α-Al2O3 ceramics reported in the literature to develop a mechanistic understanding of the microstructural features governing the stiffness and fracture toughness of the TGO.