Microstructure,Mechanical And Tribological Properties Of Tungsten Disulphide-based Coatings In Air

The WS?C?films,WSN films and WSCN films were prepared on singal crystal Si?100?wafers by using magnetron sputtering system in order to improve the tribological performance of MEMS devices.The micrstructures,compoents and chemical bonding structures of coatings were analyzed by X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?,and the surface and cross-sectional morphologies were observed by scanning electron microscopy?SEM?.The hardness and adhesion strength of coatings were measured by nano-indentation tester and acoustic emission scratch tester,respectively.The tribological properties of coatings against Si₃N₄ balls in air were tested by ball-on-disk tribometer,and the wear tracks on coatings and balls were analyzed by optical microscope,non-contact three dimensional profilometer and SEM equipped with Energy Dispersive Spectroscopy?EDS?.The results showed that:1)The WS?C?thin films with different compositions were prepared by changing the sputtering power of WS₂ target?from 100 to 300W?,Which using the magnetron sputtering technique.The films were named WSC-X,where X represented the sputtering power of WS₂ target).The hardness of WSC films with different compositions were from 1.99GPa to 4.43GPa.The lowest friction coefficient was0.4 for WSC-250 film whose S/W atomic ratio was 0.63.The preparation parameters of the WSC-250film were selected to prepare WSC films with different bias voltages by changing the negative bias of the substrates.The films were all amorphous.The WSC film prepared at-210V exhibited good mechanical properties,and the lowest friction coefficient and wear rate were obtained,which were0.35 and 4.69×10^-5mm³/?N·m?,respectively.2)The WSN thin films with different compositions were prepared by changing the flow rate of N₂?from 5 to 25sccm?,Which using magnetron sputtering equipment.The films were named WSN-Y,where Y represented the flow rate of N₂.The doped N elements were mainly performed as amorphous WN phases.The lowest friction coefficient and wear rate of films obtained for the WSN-25 film with N content of 10.35at.%were 0.55 and 2.7×10^-4mm³/?N·m?,respectively,which due to its highest hardness and adhesion.The preparation parameters of the WSN-25 film were selected to prepare WSN films with different bias voltages by changing the bias voltage of substrates.The crystallinity of the films decreased with the increase of bias voltage,while the friction coefficient and wear rate decreased first and then increased.The friction coefficient and wear rate of WSN films prepared at-160V were both lowest,which were 0.09 and 5.18×10^-5mm³/?N·m?,respectively.3)The WSCN films with different compositions were prepared by changing the N₂ flow rate?from 15 to 35sccm?under the N₂ and C₂H₂ atmosphere.The films were numbered WSCN-Z,where Z represented the flow rate of N₂.The doped C elements were showed as the amorphous WC phases and the sp²C-C phases,while the doped N elements mainly performed as the WN phases.with the increase of N₂ flow rate,the hardness of the films first decreased and then increased.WSCN-30 film with N content of 11.1at.%with the strongest adhesion force to substrate was behaved the lowest wear rate of 1.28×10^-5mm³/?N·m?.The preparation parameters of WSCN-30 thin films were choosed to prepare the different biased WSCN films by changing the substrate bias voltage.with the increase of bias voltage,the binding force between the films and the substrate first decreased and then increased.The good mechanical and tribological properties were performed for the WSCN film prepared at-260V.