Structure and indentation behavior of nanocomposite Ti-B-N films

Titanium-boron-nitrogen (Ti-B-N) films were deposited by DC reactive magnetron sputtering using single titanium diboride (TiB2) target in argon, argon-nitrogen mixtures and pure nitrogen gas. The effects of nitrogen incorporation on the microstructure and mechanical properties of the deposited films were investigated. The films were characterized by X-ray diffraction, atomic force microscope, scanning electron microscope, and X-ray-photoelectron spectroscopy. Under pure argon the films showed the formation of TiB2. The films deposited in Ar-N2 mixture showed a transition from a hexagonal P6/mmm structure of TiB2 to the cubic (Fm3m) one of TiN and then again to hexagonal P6/mmm structure of TiB2 with decreasing nitrogen partial pressure. TiN was the major crystalline phase for the films deposited in pure nitrogen gas. Mechanical properties of the films were evaluated by nanoindentation. The hardness varied from 45 GPa for pure TiB2 films to 11.15 GPa for Ti-B-N films. The energy of indentation analysis from the load-depth curves, % elastic recovery (%Er) and plots of H3/E2, where H is hardness and E is elastic modulus, at different indentation depths has been used to study the Ti-B-N film deformation process.