Fracture Characteristics and Damage Evolution of Coating Systems Under Four‐Point Bending

The fracture and damage behaviors of ceramic coating/alloy substrate systems under four-point bending were investigated using a scanning electron microscope to observe in situ tests. Both the thin and thick coatings fractured by tensile instability at the pure bending sections, and multiple transverse cracks that were vertical to the interface occurred in the coatings. The average crack spacing was greater for the thick coatings than for the thin ones. A catastrophic failure model was developed to explain the damage evolution behavior of the coatings. The damage was found to increase sharply near the failure point.