Microstructure And Tribological Properties In Different Environments Of WS_x/a-C Nanomultilayer Films With Various Modulation Periods

Magnetron sputtering coating is the most common method used in laboratory.As a solid lubricant,tungsten disulfide is applied in the field of vacuum equipment and space technology because of its low friction coefficient,high working temperature and excellent wear resistance.However,how to improve the wear resistance of WS₂ in humid atmosphere has become one of the study directions of many scholars from home and abroad.Concerning this tissue,WS_x/a-C nanomultilayer films with various modulation periods,pure WS_x film and pure a-C film were prepared by magnetron sputtering.The microstructure and tribological properties of the films in different environments were analyzed to provide theory basis for the preparation of WS₂ film used in complicated environment.Five nanomultilayer films,pure WS_x film and pure a-C film were prepared in selected parameter.The microstructure of the films and the chemical valence state of the elements were analyzed by scanning electron microscopy?SEM?,energy disperse spectroscopy?EDS?,X-ray diffraction?XRD?,Raman spectrometer?Raman?and X-ray photoelectron spectroscopy?XPS?.The hardness,adhesion to the substrate and tribological behavior of the films were investigated by nano-indenter test,scratch test,and ball-on-disk tribometer.The wear mechanism was also expounded.The results show that a loose microstructure was found in pure WS_x film with sputtering coating feature.Nanomultilayer films have compact microstructure and smooth surface which is similar to featureless morphology.The S/W mole ratio of the nanomultilayer films decreases with the increase of modulation period.The bigger the modulation period is,the more obviously the layer structure shows.The pure WSx diffraction peak was found obviously,but nanomultilayer films and a-C film are amorphous structure,the addition of a-C layer to the films leads to the crystallinity change of WS_x phase.WC phase doesn't form in nanomultilayer films,excessive W was oxidated to form amorphous WO₃ and S was adsorbed to the interface.The hardness of nanomultilayer films increases slightly and is bigger than that of any single films with the increase of modulation period.This indicates that boundary strengthening occurred in the films.However,the adhesion shows opposite regular and the nanomultilayer film with modulation period of 4nm has the highest adhesion of 46.3N.In humid air,the friction coefficient of the nanomultilayer films is higher than those of single films and decrease with the increase of modulation period.The wear resistance decreases with an increasing modulation period and the film with modulation period of 4 nm shows the best wear resistance,and the wear rate is 3.43×10^-14m³N^-1m^-1.In vacuum,the friction coefficient of the nanomultilayer films decreases greatly and is prone to be stable between 0.06 and 0.08.The friction coefficient of nanomultilayer films is lower two thirds than that in humid air,and the nanomultilayer film with modulation period of4nm has the lowest wear resistance of 0.99×10^-14m³N^-1m^-1.In water,the friction coefficient of nanomultilayer films are higher than that in humid air,but the wear resistance increases and is bigger than that of any single films.The nanomultilayer film with modulation period of 4nm also has the lowest wear resistance of8.18×10^-14m³N^-1m^-1.The major wear mechanism of films is adhesive wear under humid air and under vacuum but abrasire wear in water.The wear resistance becomes lower with the modulation period getting smaller.