Mechanical behavior of 3Al2O3·2SiO2 films under nanoindentation

A complete and systematic nanoindentation study was conducted on a mullite (3Al2O3·2SiO2) coating ∼1 μm thick, deposited by means of chemical vapor deposition on a silicon carbide (SiC) substrate. The investigation included using different indenter tip geometries (Berkovich, spherical and cube-corner), complemented with atomic force microscopy and three-dimensional focused ion beam tomography to characterize the indentation response, deformation and damage micromechanisms. The intrinsic mechanical properties of the 3Al2O3·2SiO2 film and the interfacial toughness of the coated (3Al2O3·2SiO2/SiC) system were critically evaluated to assess the influence of substrate and film residual stresses. Through appropriate implementation of specific indenter tip geometry, different length-scale mechanical properties in the materials studied were successfully determined: yield strength and fracture toughness for the film, together with energy of adhesion per unit area and interface fracture toughness for the coated system.