Ion implantation of TiN films with carbon or nitrogen for improved tribomechanical properties

In the field of engineering materials, the study of titanium nitride (TiN) films has attracted great interest because of its unique combination of properties. This paper is concerned with the implantation of nitrogen or carbon ions into TiN films to evaluate and obtain the optimum conditions for increased tribological resistance. A commercially available titanium nitride coating produced by ion plating, of approximately 3.5 μm thickness, was treated by implantation of nitrogen or carbon ions at energies of 100 and 75 keV, respectively. The dose range was between 5 × 10¹⁶ and 1 × 10¹⁸ ions cm^-2. It has been observed that a suitable implantation procedure can lead to a maximum hardness improvement of about 15%, as evaluated with a dynamic micro-indentation method at loads from 0.4 to 10 mN. Wear tests performed on an unlubricated reciprocating apparatus, using an alumina ball with a load of 9.8 N and at a speed of 150 cycles min^-1, showed that implantation of nitrogen and carbon can reduce wear by 22% and 42%, respectively. Small-area X-ray photoelectron spectroscopy (SAXPS) was used to evaluate the concentration of implanted elements as a function of depth. The analysis showed that in the high-dose C⁺-implanted sample a very high percentage of the carbon remained as pure carbon, whereas in the lower-dose C⁺-implanted sample the carbon stayed mainly in a carbidic form. In the case of nitrogen implantation, no large variations in the state or concentrations were recorded.