Deformation Behavior And Finite Element Modeling Of Diamond Like Carbon Films Under Different Loading Modes

The deposition of a titanium-containing diamond like carbon (Ti-DLC) film was performed with the unbalanced magnetron sputtering process. Chromium molybdenum steel AISI 4118 in a quenched and tempered condition was used as substrate. The morphology and structure of Ti-DLC films were investigated by high resolution electron microscopy (HREM), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Raman spectroscopy. The mechanical properties were investigated by a MTS NANO Indenter XP system with a Berkovich indenter. The Ti-DLC film with a titanium content of 27at.% consisted mainly of amorphous phase. HREM images showed that the Ti-DLC film had a lamellar structure. The TiC phase with a size of 5 nm was located at the titanium-rich regions surrounded by amorphous carbon structures in the Ti-DLC film.The results of nanoindentation tests showed that elastic modulus and hardness of the Ti-DLC film were 249.8GPa and 26.4GPa, respectively. The nanoscratching data showed that the thickness of Ti-DLC film was about 700 nm. The load on the sample was 80mN and the friction force was 18mN when the film was lacerated.Three-dimensional finite element modeling (FEM) was introduced to calculate the stress distribution and deformation process during indenting. The stress distributed unevenly around the indent and mainly concentrated on the area near-by the tip of the indent. The stress distribution was discontinuous at the interface between the Ti-DLC film and the substrate. It's just the discontinuousness of stress distribution that protected substrate from breakage. The result of nanoscratching modeling showed that the load on the sample and friction force increased linearly at the initial stage. The load on the sample and the friction force increased suddenly when the film hardened.The results of finite element modeling are in good accord with the experimental data obtained from the nanoindentation and nanoscratching tests. It proved that FEM is an effective method to analyze the deformation behavior of Ti-DLC films.