Research On Microstructure,mechanical And Tribological Properties Of TiN、Ti-W-N And Ti-W-V-N Films

In this paper,TiN films with different ratio of nitrogen and argon,Ti-W-N composite films with different W content and Ti-W-V-N composite films with different V content were prepared by multi target reactive RF magnetron sputtering technique.The phase structure,chemical composition,mechanical properties and tribology properties of the films were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersive spectrometer（EDS）,transmission electron microscopy（TEM）,nano-indentater,high-temperature ball-on-disc tribo-meter and surface profilometer.The formation energies of TiN phase and the possible existence form of W atom in TiN lattice were calculated by First-principle.The main results are as follows:The study of TiN films with different ratio of nitrogen and argon showed that the TiN films exhibited a face-centered cubic（fcc）structure.The First-principle calculation showed that the phase formation energy of perfect TiN lattice was the lowest and its phase structure was the stablest,with the increase of the nitrogen flow,the formation energies of the phases increased gradually,meanwhile the stability decreased gradually.The hardness of TiN films with different ratio of nitrogen and argon fluctuated between 17 and 18 GPa.The average friction coefficient of TiN films with different ratio of nitrogen and argon fluctuated between0.6 and 0.8.With the increase of the test temperature,the average friction coefficient of TiN films first increased and then decreased while the wear rate of TiN films increased gradually.W was introduced into binary TiN films to improve the mechanical and tribology properties of the films.The study of the Ti-W-N composite films with different W content showed that all the Ti-W-N films exhibited a fcc structure.The results of First-principle calculation showed that the defect formation energy of Ti replaced by W atoms forming the fcc-（Ti,W）N solid solution was the lowest,while the defect formation energy of W existed with interstitial atoms in TiN lattice was the highest.The hardness of the Ti-W-N films increased first and then decreased with the increase of W content.The elastic modulus of the Ti-W-N films increased gradually with the increase of W content.The critical load of the Ti-W-N films reached the maximum value at 11.1 at.%W.The average friction coefficient and wear rate of the Ti-W-N films decreased first and then increased with the increase of W content.Both the average friction coefficient and wear rate of the films reached the minimum values at 26.2 at.%W.Magnéli element V was introduced to the ternary Ti-W-N composite films in order to make the films have good friction and wear performance at high temperature.The study of Ti-W-V-N films with different V content showed that all the Ti-W-V-N films exhibited a fcc structure.When the content of V was below 21.5 at.%,the films were composed of fcc-（Ti,W,V）N solid solution,when the V content was≥21.5 at.%,fcc-（Ti,W,V）N and fcc-VN were co-existed in the films.With the increase of V content,the hardness and elastic modulus of the films increased first and then decreased.The indentation depth decreased first and then increases with the increase of V content.For the Ti-W-V-N films with 21.5 at.%V,the average friction coefficient increased first and then decreased with the increase of the test temperature.The average friction coefficient of the reached the minimum value at the test temperature of700℃.The wear rate of the films increased with the increase of the test temperature.The lubrications V₂O₅ and WO₃ generated at high temperature was the main reason for the reduction of the average friction coefficient of the films.