Fracture toughness characterization of advanced coatings

We present an experimental technique for the measurement of the fracture toughness of advanced surface coatings in situ in a scanning electron microscope. The technique is demonstrated on titanium-titanium nitride multi-layer thin films. Titanium-titanium nitride multi-layers are part of a new class of advanced erosion-resistant coatings with optimized toughness and hardness for performance and life respectively, and the fracture properties of these surface coatings determine their effectiveness. Thin film specimens were prepared using a lift-out technique in focused ion beam-scanning electron microscope. The fracture toughness of a 300 nm thick specimen perpendicular to the multi-layer thickness was measured to be 2.90 0.3 MPa m^+1/2. The fracture characterization technique can be applied for a wide variety of surface coatings, and thin films in general.