溅射技术对TiN涂层结构和力学性能的影响

Effect of Sputtering Technology on Microstructure and Mechanical Properties of TiN Coatings

目的沉积条件对TiN涂层的组织结构和力学性能有着至关重要的影响,而溅射技术又决定了涂层的沉积条件,探究不同溅射技术对TiN涂层的微观组织结构和性能的影响,提高TiN涂层的力学性能和高温摩擦磨损性能。方法采用不同的溅射技术(dcMS、HiPMS、Hybrid)在M2高速钢表面沉积TiN涂层,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、sin2ψ法、纳米压痕仪、洛氏压痕法、划痕法和CSM球盘式摩擦试验机分别测试了TiN涂层的组织结构特征、沉积速率、残余应力、纳米硬度、膜基结合力和高温摩擦磨损性能。结果不同溅射技术制备的TiN涂层均为柱状晶结构和TiN(111)择优取向。HiPIMS-TiN涂层具有最高的纳米硬度(29.7 GPa)和最低的膜基结合力(HF2),而Hybrid-TiN涂层呈现出最小的残余应力、高沉积速率和高膜基结合力,其膜基结合力达到HF1级,临界载荷(Lc2)达到82.5 N。不同溅射技术制备的TiN涂层的摩擦因数均随着温度的升高而降低,在500℃时,TiN涂层的摩擦因数约为0.53。TiN涂层的磨损率随着温度的升高而升高,在不同温度下,Hybrid-TiN涂层均呈现出最低的磨损率。结论溅射技术对TiN涂层的组织结构和力学性能有着重要影响,Hybrid-TiN涂层呈现出最优的综合力学性能和高温摩擦磨损性能。

The microstructure properties of TiN coating are mainly affected by the deposition conditions,which in turn are affected by the sputtering technology.The proper use of the sputtering technology allows to control the state of ion bombardment during coating growth and tailors the crystal structure,thereby improving the properties of TiN coating.Therefore,TiN coatings were deposited on the M2 high-speed steel by different sputtering technologies(dcMS,HiPMS,and Hybrid)in this work.The effects of different sputtering technologies on the microstructure,mechanical properties,and high temperature wear properties of TiN coatings were investigated.Before coating preparation,theϕ40 mm×5 mm M2 high speed steel substrate was mechanically polished.The polished substrate was ultrasonically cleaned in ethanol,acetone,and isopropanol sequentially to remove residues on the surface.To improve the adhesion strength between coating and substrate,the M2 high speed steel substrate was etched by applying an intermediate frequency pulse bias(−650 V)with a frequency of 250 kHz,and a 200 nm Ti buffer layer was prepared by dcMS technology.Then,TiN coatings were prepared by different sputtering technologies such as dcMS,HiPIMS,and Hybrid,respectively,in which the average power of Ti targets was always 4.5 kW.During coating deposition,a negative DC bias of−100 V was applied to the substrate.The workpiece holder always maintained the mode of revolution and rotation.The cross-sectional morphology and thickness of the coatings were measured by scanning electron microscopy(SEM,Zeiss Supra 55).The composition of the coatings was analyzed by energy dispersive spectroscopy(EDS).The phase and crystalline structure of the coatings were characterized by X-ray diffraction(XRD,D/Max 2500).The residual stress of the coatings was analyzed by the sin2ψmethod.The nanohardness of the coatings was measured by a nanoindenter(Nano-Indentor G200,Agilent).The adhesion of the coatings was evaluated through Rockwell C indentation test and scratch test.The high temperature wear properties of the coatings were tested on a ball-on-disk friction tester(CSM-Instruments,Peseux),and the test temperature was set at 25℃,300℃,and 500℃,respectively.After the high temperature wear test,the cross-sectional profile of the wear tracks was analyzed by a surface profilometer(Infinite Focus Alicona,Austria),and the wear rates of the coatings were calculated.The TiN coatings prepared by different sputtering technologies all exhibit columnar crystal structures and a preferred orientation at TiN(111).The HiPIMS-TiN coatings have high density,residual stress,and nanohardness.The highest hardness of HiPIMS-TiN coatings reaches 29.7 GPa.The dcMS-TiN coatings show high adhesion with a critical load Lc3 of 100 N.The Hybrid-TiN coatings exhibit the lowest residual stress,high deposition rate,and high adhesion.The adhesion of the Hybrid-TiN coating reaches HF1 level,and the critical load Lc2 is about 82.5 N.The friction coefficient of TiN coatings prepared by different sputtering technologies decreases with increasing temperature.At 500℃,the friction coefficient of TiN coatings is about 0.53.However,the wear rate increases with increasing temperature.At different temperatures,the Hybrid-TiN coatings show the lowest wear rate.Sputtering technology plays a more significant role in improving the microstructure and mechanical properties of TiN coatings.Hybrid-TiN coatings exhibit the optimum comprehensive mechanical properties and high temperature wear properties.