The mechanical behaviour of TiN and multi-layered coating of TiN/Ti on Ti6Al4V substrate during nano-indentation

摘要

Thin films of TiN mono-layer and TiN multi-layers that alternate with titanium (ductile) inter-layers were surface coated by filtered arc deposition system (FADS) onto Ti6Al4V substrates. The surface topography and chemical composition have been characterised by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively, and the fracture properties of coatings induced by nano-indentation with a sphere-cone tip have been investigated. Focused ion beam (FIB) and transmission electron microscopy (TEM) were used to identify the fracture modes. It was found that the multi-layer coating of TiN/Ti showed a higher pop-in force, which indicated good film ductility. Transmission electron microscope (TEM) observations showed that a small bending crack was the dominant crack in the TiN/Ti multi-layer coating but cracks along the inter-columnar and trans-granular cracks could be seen on the single TiN layer coating on Ti6Al4V. The Ti layer showed it could effectively suppress the propagation of cracks, which improved the ductility of the multi-layer coating of TiN/Ti. Finite element simulation (FEM) was used to simulate the indentation process and compare it with the experiment results.