Techniques for evaluating mechanical properties of hard coatings

This paper describes specialized methods for measuring coating adhesion, microhardness, and microfracture toughness of hard coatings. Coating adhesion is an interfacial property which may be characterized by scratch or indentation techniques which yield a decohesion critical load or an interfacial fracture toughness parameter. Microhardness measurements are shown to be satisfactory if light indenter loads are applied to polished coating surfaces; microhardness profiles may be measured at room and elevated temperatures on a taper section of the coating. The Palmqvist microfracture toughness of hard coatings may additionally be determined from the same microhardness indentations.