| With the rapid development of modern machining field,the number of refractory materials is increasing gradually.Among them,titanium alloy materials are widely used in aerospace and other militarized fields because of their high strength,good corrosion resistance,and high heat resistance.However,due to its low thermal conductivity,high cutting temperature and other processing difficulties,higher heat resistance requirements are put forward for coated tools.Among many coating systems,Zr-B-N coating has attracted much attention because of its good toughness,wear resistance,and high temperature thermal stability,but the coating hardness is low.Therefore,the coating performance can be optimized from two aspects of reducing the impurity oxygen element doped in the vacuum chamber and enhancing the solid solution doped with Ti element in the coating,which is expected to develop a more promising nanocomposite coating.To this end,Zr-Ti-B-N nanocomposite coatings were deposited by high-power pulsed and pulsed DC magnetron sputtering in a reducing atmosphere.The effects of reducing gas atmosphere,reaction gas flow rate and Ti B2 target power on phase composition,hardness and wear rate of the coatings were systematically studied,the specific research content was as follows:Introducing a small amount of reducing gas into the vacuum chamber to neutralize the remaining oxygen impurities can inhibit the generation of Ti-O bonds and B-O bonds at the interface between nanocrystals and amorphous,and reduce the damage of oxygen impurities to the nanoscale interface of the coating.With the addition of the reducing gas H2,the coating grain size was significantly reduced,the microstructure became denser,and the columnar crystal structure was more remarkable;the hardness increased from 14.3 GPa to 17.6 GPa,and the wear resistance of the coating was greatly improved,the wear rate decreased from 4.67×10-14m3/(N·m)to 2.05×10-14m3/(N·m).The change of reactant gas flow will affect the phase ratio of the hard phase and the amorphous phase in the coating,and then affect the internal structure and mechanical properties of the coating.The Zr-Ti-B-N coatings prepared by the hybrid magnetron sputtering technology all have a Zr B2 phase diffraction peak that was preferentially grown along the(001)crystal plane,and the diffraction peak was the strongest when the reaction gas flow rate was 10 sccm.With the increase of reaction gas flow rate,the disorder of grain growth and cluster phenomenon on the surface of the coating are intensified,and the number of nanocrystals in the coating increases.When the reaction gas flow rate was 10 sccm,the friction coefficient and wear rate of the coating were the lowest,0.83 and 1.63×10-14m3/(N·m),respectively,and the wear resistance was the best.After adding Ti element to the Zr-B-N coating,due to the lower Ti-B ion bond energy,it is easy to be preferentially opened by N ions to form amorphous BN,making the remaining Ti ions dissolve in the crystal lattice and cause lattice distortion,which can strengthen the mechanical properties of the coating.The results show that the structure density of the coating increased obviously after adding Ti element into the coating.With the increase of Ti B2 target power,the crystal strength of(001)crystal plane Zr B2 phase diffraction peak increases rapidly.When Ti B2target power was 0.8 k W,the coating hardness reaches a maximum of 25.2 GPa.In terms of friction performance:when Ti B2 target power was 1.0 k W,the friction coefficient and wear rate of the coating were the lowest,which were 0.64 and 1.16×10-14m3/(N·m),respectively.At this time,the H/E value and H3/E*2 value of the coating reached the maximum,showing the best tribological performance. |
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