Fracture behaviours of TiN and TiN/Ti multilayer coatings on Ti substrate during nanoindentation
TiN monolayer and TiN/Ti multilayer thin films were deposited on commercially pure Ti substrates using a filtered arc deposition system (FADS). Surface topography and chemical composition have been characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. Fracture properties of coatings induced by nanoindentation have been investigated. Focused ion beam (FIB) and transmission electron microscopy (TEM) were used to identify the fracture modes. It was found that the TiN/Ti multilayer coating exhibited a higher pop-in force, which indicated good film ductility. Transmission electron microscope (TEM) observation showed that the small bending crack was the dominant crack in the TiN/Ti multilayer coating. The Ti layer shows that it could efficiently suppress the crack propagation, which was responsible for the improved ductility of the TiN/Ti multilayer coating.