Fabrication of nanocomposite Ti-Al-Si-N films deposited by reactive unbalanced magnetron sputtering and their properties-modification by high-energy carbon ion implantation
非平衡磁控濺射沉積製造 Ti-Al-Si-N 納米結構薄膜並通過高能碳離子注入改進其性能
Student thesis: Master's Thesis
Ti-Al-Si-N is an excellent candidate for use as hard wear-resistant coatings in high speed machines with the combination of high hardness, excellent thermal stability and oxidation resistance. In this research work, Ti-Al-Si-N films were deposited onto Si and steel substrates by using reactive close-field unbalanced magnetron sputtering at 500 ◦C in an Ar–N2 mixture. By changing the current of different targets, Ti-Al-Si-N films with different compositions were fabricated. The effects of Si content, Al content, bias voltage and vacuum annealing temperature to the micro-structural and mechanical properties of the Ti-Al-Si-N films were then investigated respectively and systematically. The optimized deposition condition was established, obtaining Ti-Al-Si-N films with 1.5 at.% Si and 9.0 at.% Al reaching a hardness of 35 GPa. Under such atomic contents, the Ti-Al-Si-N films exhibited a nanocomposite structure and good thermal stability, enduring vacuum annealing at the temperature up to 900 ◦C for 3 hours. It was found that the deposited Ti-Al-Si-N films with high hardness and good thermal stability usually had a relatively high friction coefficient (~0.6). It was believed that further modification on the tribological performances would enhance their application potential in the engineering sectors. To do this, high-energy carbon ion implantation was applied to the Ti-Al-Si-N films, altering the near-surface structure and tribological properties without the loss of bulk coating properties. Carbon ion implantation was carried out by metal vapour vacuum arc ion source (MEVVA) with solid cathode at 50 keV energy and the doses of 5×1016, 1×1017, 5×1017, and 1×1018 atoms cm-2. The effects of carbon ion implantation on the structural, mechanical and tribological properties of the Ti-Al-Si-N films were investigated systematically by means of Raman spectroscopy, Glancing-angle X-ray diffraction (GA-XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental energy spectroscopy (EDS), X-ray photo-electron spectroscopy (XPS), surface profilometer (PGI), nanoindentation measurement and ball-on-disk test. Tribological performances of the Ti-Al-Si-N films were improved with the reduction of friction coefficient and wear rate by up to 80 %. The formation of new phases and the change of the micro-structure caused such improvement and no hardness reduction happened at suitable carbon ion doses, proving the good effects of the carbon ion implantation.
- Industrial applications, Carbon, Ion implantation, Thin films, Nanostructured materials, Sputtering (Physics)