调制周期对AlCrSiN/AlCrMoSiN多层膜微结构和性能的影响

Effect of Modulation Period on Microstructure and Properties of AlCrSiN/AlCrMoSiN Multilayered Coatings

目的通过优化AlCrSiN/AlCrMoSiN多层复合涂层的调制周期,提升涂层的力学性能和摩擦学性能。方法采用高功率脉冲磁控溅射与脉冲直流磁控溅射复合技术,固定调制比为5∶1,制备具有不同调制周期的AlCrSiN/AlCrMoSiN多层复合涂层。利用XRD和SEM分析涂层物相组成,观察其微观形貌;借助纳米压痕仪、划痕仪、高温摩擦试验机及轮廓仪测试涂层的硬度、弹性模量、临界载荷,以及摩擦磨损性能。结果掺杂Mo元素后,AlCrMoSiN层生成了大量的非晶相,并观察到沿AlN(111)晶面共格外延生长。AlCrSiN/AlCrMoSiN多层复合涂层表面颗粒随着调制周期的增大逐渐变小,整体呈“花椰菜”状,且致密、无缺陷。随着调制周期的增大,硬度、H/E和H^(3)/E^(*2)呈先升高后降低的趋势;涂层的平均摩擦因数呈先降低后升高的趋势。当调制周期为145 nm(AlCrSiN层厚度约为120 nm,AlCrMoSiN层厚度约为25 nm)时,多层涂层中层间界面清晰,涂层的硬度最高,约为24.9GPa,摩擦因数和磨损率均最低,分别为0.57、1.46×10^(-6)mm^(3)/(N·m),临界载荷为75.8N。结论多层复合涂层的调制周期对其结构和性能具有重要影响,当调制周期为145nm时,AlCrSiN/AlCrMoSiN多层复合涂层具有最佳的综合性能。

AlCrSiN coatings with exceptional oxidation resistance and remarkable mechanical properties are often used as promising protective layers on cutting tool surfaces.Due to their inferior frictional properties at elevated temperatures,AlCrSiN coatings are unable to meet the machining requirements at higher cutting speed.The addition of Mo element is an effective method to reduce friction because MoO_(3) lubricating phases could be generated during the friction contact.In this work,the AlCrMoSiN layer was implanted periodically into the AlCrSiN coatings to be used as solid lubricant.A series of AlCrSiN/AlCrMoSiN multilayers with different modulation periods were prepared by high power impulse magnetron sputtering and pulsed DC magnetron sputtering hybrid techniques.The modulation ratio in all the multilayered coatings was 5∶1,namely the layer thickness ratio of AlCrSiN and AlCrMoSiN in each cycle was 5∶1.Through regulating the heterogeneous interfaces of the multilayers,the mechanical and tribological properties of the AlCrSiN/AlCrMoSiN multilayers were improved,and the service life and machining efficiency of coated carbide tools were also increased.The polished cemented carbide sheets with a shape of 25 mm×25 mm×3 mm were used as the substrates.They were washed and dried with anhydrous ethanol and were fixed on the holder into the vacuum chamber.The hybrid magnetron sputtering equipment made in Dalian V-TECH was used to fabricate the AlCrSiN/AlCrMoSiN multilayered coatings.During the deposition process,the deposition temperature was set to 400℃,the working pressure was 0.6 Pa,and the N_(2) flow rate was 200 cm^(3)/min The sputtering power of target AlCrSi(atomic ratio 6∶3∶1)and CrMo(atomic ratio 55∶45)were set to 1.2 kW and 0.4 kW,respectively.The surface morphology,chemical composition,hardness,elastic modulus,friction coefficient,and wear rate of the AlCrSiN/AlCrMoSiN multilayered coatings were tested by SEM,XRD,TEM,nano-indenter,and tribometer,respectively.After the friction tests,XPS was employed to analyze the chemical valence states of Mo element on the worn surface.The results showed that the AlCrMoSiN layer contained a large amount of amorphous phases due to doping Mo,and the coherent epitaxial growth along the AlN(111)crystal plane was observed.With the increase of the modulation period,the amount and size of macroparticles on the AlCrSiN/AlCrMoSiN multilayered coating surface became less and less.The coating surface was dense and defect free,and the top of the micro area was shaped like a"cauliflower".By TEM observation,the AlCrSiN/AlCrMoSiN multilayered coating possessed a typical nano-composite structure.The numerous multilayered interfaces impeded the grain growth,dislocation motion,and crack propagation,which resulted in the grain refinement,toughening,and strengthening.When the modulation period was 145 nm(the thickness of the AlCrSiN layer and the AlCrMoSiN layer was 120 nm and 25 nm,respectively),the AlCrSiN/AlCrMoSiN multilayered coating showed the clear interfaces.In this case,the coating hardness reached the highest,which was about 24.9 GPa.Both the friction coefficient and the wear rate were the lowest,which were 0.57 and 1.46×10^(-6) mm^(3)/(N·m).The critical load arrived about 75.8 N.In conclusion,the modulation period of the multilayered coatings has an important influence on its microstructure and various properties.As the modulation period is 145 nm,the AlCrSiN/AlCrMoSiN multilayered coating presents the best comprehensive performance.