Assessment of the toughness of thin coatings using nanoindentation under displacement control

Various indentation models have been developed to measure the toughness of bulk materials and coatings. Most of them are based on the formation of well-developed cracks. However, in order to eliminate the influence of elastic–plastic deformation in the substrate, it is preferable to perform small indentations in thin coatings and thus the cracks may not be well-developed compared to the indentation size. Relatively little work has been done to investigate this kind of small cracks. The ultra small cracks (< 500 nm in length) in thin coatings (∼ 500 nm in thickness) confined to indentation zone are investigated here. A new method to assess the toughness of the main components of solar control coatings such as SnO 2, TiO x N y and ITO deposited on soda–lime glass is proposed here. This method is able to separate the energy contributions from other deformation mechanisms from that dissipated in the fracture event. The energy release rate of these ceramics coating are in the range 15–45 J/m 2 by this method.