Chemical Modification of Titanium Nitride Films via Ion Implantation

Titanium nitride, TiN is a typical ceramic coating film for cutting tools and dies; it often suffers from low oxidation temperature and high friction coefficient and wear volume. Its wearing and oxidation resistance is drastically improved by chemical modification via ion implantation. Carbon-, aluminum- and chlorine-ion implantation is introduced to describe the difference in the modified microstructure at the vicinity of surface. Ion-plated TiN films on a high-speed tool steel substrate are employed as a common specimen to be implanted. Each modified titanium nitride has its intrinsic, as-implanted nanostructure to the selected species. In the carbon implantation, the near-surface structure of TiN film is modified to have the layered bonding state with Ti-C/C-C/Ti-C. The Al-implantation modifies TiN to have non-equilibrium solid solution phase of (Ti, Al) N and metallic aluminum cluster. No change is seen in the chlorine implanted TiN except for increase of dislocations or point defects. The wear resistance is improved by the above as-implanted nano-structuring in the case of carbon implantation. Al- and Cl-implantation significantly improves the original oxidation and wearing resistance of TiN by the post-implantation nano-structuring. The stable, dense aluminum oxide layer is in-situ formed as a tight protective shield during the oxidation test by surface reaction between penetrating oxygen and diffusing aluminum. The lubricious titanium oxide film is also in-situ formed in the wear track at the presence of chlorine to sustain low friction and wear rate even in dry, severe wearing conditions.