Research On Microstructure And Properties Of TaN-based Composite Films And Multilayer Films

A series of TaN monolayer films deposited with deiffertent bias voltages, a seriesof TaVN composite films with different V content, a series of TaMoN films withdifferent Mo content, a series of TaN/VN multilayer films with different modulationperiods were prepared by magnetron sputtering technique. The surface topography,microstructures, mechanical properties, friction and wear properties at differenttemperatures of the films were measured by AFM, XRD, SEM and equipped EDS,nanoindentation, ball-on-disc tribometer and equipped3-D profilometer.The study on TaN deposited with different bias voltages showed that thestructure of TaN was composed of cubic TaN and orthorhombic Ta4N, while thepreferred orientation changed with the bias voltage. When the bias voltage was80V,the hardness and modulus of the films reached to peak value,30.103GPa and317.048GPa, respectively, and the interfacial adhesion was the best. At roomtemperature, the friction coefficients of the films ranged between0.64and0.68. Athigh temperatures, the friction coefficient of the films decreased as the temperatureincreased. This work discusses the wear mode and the reason of different frictioncoefficient at different temperatures based on the surface morphology and phases ofwear tracks formed at different temperatures.The study on TaVN composite films showed that the microstructure of TaVNfilms took the face-centred cubic structure. With increasing V content, the preferentialorientation changed from (111) to (200), and the hardness increased to the peak value(32.3GPa) and then decreased. At room temperature, the friction coefficient of TaVNfilms decreased as V content increased, which may be related to the formation ofV2O5. When temperatures ranged from room temperature to800℃, the frictioncoefficient increased and then decreased. Study on the friction properties of TaVNcomposited films and TaN film at high temperature based on the theory of crystalchemistry.The study on TaMoN composite films showed that the microstructure of TaMoNcomposite films changed to poly-phase structure with cubic, hexagonal andorthorhombic structure by adding Mo element to TaN film. The hardness of TaMoNcomposite film was higher than TaN monolayer film due to the solid solutionstrengthening. The friction coefficients of TaMoN films at room and high temperatures were lower than the friction coefficients of TaN film at room and hightemperatures, and the reasons are detailed analyzed based on the morphology andcontent of wear tracks formed at different temperatures.The study on TaN/VN multilayer films showed that with modulation period (Λ)increasing, the crystal structures of TaN/VN multilayers were similar to that of thesingle-layer TaN film and the hardness and average friction coefficient of mulitlayersdecreased. The maximum hardness of31.8GPa was obtained for the multilayer witha Λ of0.67nm. The average friction coefficient was low and the wear resistance wasimproved for the multilayers compared with TaN, VN monolayer films. The lowestfriction coefficient and wear rate were0.43and5.61×10-7mm3N-1m-1, respectively,when Λ was24nm, which is contributed to the formation of V2O5by a reactionbetween the coating surface and oxygen/moisture in the air.