基体偏压对反应共溅射TiN/Ni纳米复合膜力学性能的影响

贺春林, 陈宏志, 高建君, 王苓飞, 马国峰, 王建明

(沈阳大学 辽宁省先进材料制备技术重点实验室, 辽宁 沈阳 110044)

基体偏压对反应共溅射TiN/Ni纳米复合膜力学性能的影响

贺春林, 陈宏志, 高建君, 王苓飞, 马国峰, 王建明

(沈阳大学 辽宁省先进材料制备技术重点实验室, 辽宁 沈阳 110044)

以高纯Ti和Ni为靶材,在不同偏压下利用反应磁控共溅射法制备了TiN/Ni纳米复合膜,采用X射线衍射、纳米压痕和划痕试验研究了偏压对复合膜相结构和力学性能的影响.结果显示,反应共溅射TiN/Ni纳米复合膜由fcc-TiN和Ni组成,其择优取向与偏压有关.随负偏压增加,复合膜晶粒尺寸逐渐减小,硬度、弹性模量、H/E、H3/E2和膜基结合力则先增加后下降.在偏压为-80 V时所沉积的复合膜具有最好的力学性能,其硬度为(19.2±0.4) GPa、弹性模量为(311.0±5.0) GPa、H/E为0.062、H3/E2为0.073 GPa,膜基结合力为45 N.

TiN/Ni; 纳米复合膜; 反应磁控共溅射; 负偏压; 力学性能

尽管TiN、CrN等过渡金属氮化物薄膜在机械加工刀具、磨具防护涂层方面有大量应用,但因其较脆,因此应用受到限制.以往人们主要关心如何提高薄膜硬度.但近年来,人们逐渐意识到,在大多数工业应用中,薄膜仅具有高硬度还不够,还应具有高韧性.至少,韧性应与硬度同等重要[1],适度硬且韧性好的薄膜更有应用前景.10余年来,硬质薄膜增韧一直是薄膜科学研究热点和难点之一.添加韧性金属Ni或Cu是改善TiN或CrN基薄膜硬度和韧性的一种有效方法[2-3].Belov等[4-5]和Akbari等[6]报道,Ni和Cu可增加TiN或TiAlN的硬度、耐磨性和热稳定性.添加Ni可使CrN薄膜的韧性和耐磨性提高[7-9].由于Ni或Cu与N亲和力很低,因此,常采用反应共溅射方法制备TiN/Ni(或Cu)和CrN/Ni(或Cu)纳米复合薄膜.实验显示,基体偏压和沉积温度是影响磁控溅射薄膜形貌、晶粒尺寸、取向、致密度以及力学与腐蚀性能的重要参数[10].本文采用反应磁控共溅射技术在不同偏压下制备了TiN/Ni纳米复合薄膜,通过对微结构和性能的系统表征研究,探究了基体偏压对复合膜结构和力学性能的影响规律.

1 试验材料与方法

1.1 薄膜制备

基体选用304不锈钢和P-Si(100)基体.不锈钢表面先经砂纸逐级研磨后用1 μm金刚石研磨膏仔细抛光,然后与Si基体一样,用丙酮和酒精依次超声波清洗除油,冷风吹干后装入真空室待用.磁控溅射设备为中科院沈阳科学仪器有限公司生产的JGP 450三靶磁控溅射镀膜系统.靶材为直径60 mm、厚4 mm的高纯Ti靶(99.99%)和Ni靶(99.99%).开始溅射前,先将本底压强抽到0.6 mPa,然后通入高纯氩气(99.999%)和氮气(99.999%),采用反应磁控共溅射法沉积TiN/Ni纳米复合膜,具体沉积参数为:沉积室压力0.6 Pa,靶基距7 cm,N2与Ar气流量分别为16与40 mL·min-1, Ti直流靶电流0.2 A,Ni射频靶功率35 W,基体负偏压(Vb)为-40～-160 V,沉积温度300 ℃,沉积时间60 min.

1.2 相结构

采用掠入射XRD法分析复合薄膜的相结构,X射线源为CuKα(λ=0.154 056 nm)射线,掠入射角为2°.

1.3 压痕试验

采用安捷伦G200型纳米压痕仪测量薄膜硬度和弹性模量,测量方法为连续刚度法,测量结果取10次测量的平均值.

1.4 划痕试验

利用中科院兰州化物所生产的MFT-4000型多功能材料表面性能试验仪测试薄膜的界面结合力,用金刚石压头,锥角120°,尖端半径0.2 mm.实验参数为:加载速度为50 N·min-1,终止载荷为100 N,划痕长度为5 mm.

2 实验结果与讨论

2.1 相结构

图1为Si(100)基体上在不同Vb下沉积的TiN/Ni纳米复合膜的XRD图谱.图中主要衍射峰分别对应于面心立方结构fcc-TiN(B1-NaCl型)的(111)、(200)和(220)面,(311)和(222)面谱峰不明显.由于N不易与Ni发生反应,因此图谱中Ni(111)衍射峰较弱,这说明Ni含量较少或Ni结晶度较差[11].Miina等[12]也发现Ti-Ni-N中的Ni为晶态.由于Ni与N亲和力低,二者间不易形成化合物,因此,Ni以金属形式存在,并偏聚在TiN颗粒的周围,阻碍TiN晶粒的生长,而所沉积膜的结构为TiN/Ni纳米复合结构[13].

图1 不同Vb条件在Si(100)上沉积TiN/Ni纳米复合膜的XRD图谱

由图1可见,TiN/Ni纳米复合膜的择优取向明显取决于Vb.薄膜的择优取向可用公式(1)中的织构系数Tc来表示[14]:

表1 偏压对TiN/Ni纳米复合膜的择优取向影响

TiN/Ni纳米复合膜的平均晶粒尺寸d可采用式(2)(Scherrer公式)来估算:

式中:d为晶粒尺寸;k为常数,值为0.91;λ为入射X射线波长;β为衍射峰半宽高;θ为布拉格角.图2给出了d随Vb的变化.当Vb从-40 V增至-120 V时,TiN相的d由16.2 nm快速降至10.7 nm,之后,继续增加Vb,d几乎不变.这是因为提高Vb,即是增加入射粒子能量,受高能粒子轰击后,已沉积膜中晶格缺陷增多,而晶格缺陷通常是晶核择优形核地点,结果会导致形核率增加和晶粒细化[15].但是,继续增加Vb,会导致入射粒子能量过高,膜表面吸附原子的迁移率随之增大,晶粒聚合长大几率增多,结果导致d变大[16].Kumar等[17]也发现,在Vb低于-80 V时,d随Vb增加而减小,但他们并没有研究更高Vb时薄膜d的变化.

图2 TiN/Ni纳米复合膜的d随Vb变化Fig.2 d vs Vb of the TiN/Ni nanocomposite films

2.2 H、E和H/E

图3为不同Vb下在304不锈钢基体上沉积的TiN/Ni纳米复合膜硬度H和弹性模量E变化

曲线.可见,随Vb增加,H和E的变化趋势相似,均是先增大后下降.在-80 V时,H和E均达到最大值,H为(19.2±0.4)GPa,E为(311.0±5.0)GPa.-120 V和-160 V偏压的薄膜H和E相差不大.通常,施加Vb可使薄膜表面吸附原子能量增加,表面扩散速率增大,膜致密度改善;同时还会使晶粒尺寸d减小,这些均有利于H和E增大[18].但是,Vb过大会使反溅射作用增强,膜中晶格缺陷和微孔增多,引起H和E下降.可见,适度Vb有利于获得高硬度的薄膜.

图3不同Vb下TiN/Ni纳米复合膜的硬度和弹性模量

Fig.3 Changes ofHandEof the TiN/Ni nannocomposite films withVb

薄膜抗弹性变形和塑性变形的能力可分别用H/E和H3/E2来表征,并以此来预测薄膜耐磨性.图4给出了H/E和H3/E2随Vb的变化.可见,H/E和H3/E2随Vb变化趋势与硬度变化相似(图3和图4),都是先增加后降低,并在-80 V达最大,分别为0.062和0.073 GPa.这表明,-80 V偏压的复合膜具有更高的抗机械破坏性能.

图4 TiN/Ni纳米复合膜的H/E和H3/E2随Vb变化Fig.4 Effect of Vb on H/E and H3/E2 of the TiN/Ni nannocomposite films

2.3 界面结合力

图5示出了304不锈钢基体上沉积1 h的TiN/Ni纳米复合膜临界载荷随Vb的变化.薄膜的膜基结合力可根据划痕过程中硬质薄膜开裂的临界载荷来表征.可见,随Vb增加,膜基结合力先增加后下降;在-80 V偏压时,膜基结合力达最大值,约为45 N左右. 这说明,适当施加Vb可有效改善复合膜的界面结合力. 但是, 当Vb过高时, 溅射室内的Ar+离子能量提高, 对复合膜的表面撞击作用大大增强, 导致膜表面粗糙度增大、膜内部组织中缺陷增多[19]; 同时,Vb过高还会使界面残余应力增大, 这都会使膜基结合力下降.

图5 Vb对TiN/Ni纳米复合膜的临界载荷的影响

3 结 论

以高纯Ti和Ni为靶材,利用反应磁控共溅射方法在不同偏压下(-40～-160 V)制备了TiN/Ni纳米复合膜.TiN/Ni纳米复合膜由fcc型TiN和Ni组成,择优取向明显取决于偏压.随负偏压增加,复合膜晶粒尺寸逐渐减小,而H,E,H/E,H3/E2及膜基结合力则先增加后下降.在偏压为-80 V时,复合膜具有最好的力学性能,其硬度为(19.2±0.4) GPa、弹性模量为(311.0±5.0) GPa、H/E为0.062、H3/E2为0.073 GPa,膜基结合力为45 N.

[ 1 ] ZHANG S,WANG H L,ONG S E,et al. Hard yet tough nanocomposite coatings-present status and future trends[J]. Plasma Processes and Polymers, 2007,4(3):219-228.

[ 2 ] IRIE M,OHARA H,NAKAYAMA A,et al. Deposition of Ni-TiN nano-composite films by cathodic arc ion-plating[J]. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1997,121(1/2/3/4):133-136.

[ 4 ] BELOV D S,BLINKOV I V,VOLKHONSKII A O,et al. Thermal stability and chemical resistance of (Ti,Al)N-Cu and(Ti,Al)N-Ni metal-ceramic nanostructured coatings[J]. Applied Surface Science, 2016,388(Part A):2-12.

[ 5 ] BELOV D S,BLINKOV I V,VOLKHONSKII A O. The effect of Cu and Ni on the nanostructure and properties of arc-PVD coatings based on titanium nitride[J]. Surface and Coatings Technology, 2014,260:186-197.

[ 6 ] AKBARI A,RIVIERE J P,TEMPLIER C,et al. Structural and mechanical properties of IBAD deposited nanocomposite Ti-Ni-N coatings[J]. Surface and Coatings Technology, 2006,200(22/23):6298-6302.

[ 7 ] WO P C,MUNROE P R,JIANG Z T,et al. Enhancing toughness of CrN coatings by Ni addition for safety-critical applications[J]. Materials Science and Engineering: A, 2014,596:264-274.

[ 8 ] CHENG W L,ZHOU Z F,SHUM P W,et al. Effect of Ni addition on the structure and properties of Cr-Ni-N coatings deposited by closed-field unbalanced magnetron sputtering ion plating[J]. Surface and Coatings Technology, 2013,229(9):84-89.

[ 9 ] ZHANG Z G,RAPAUD O,ALLAIN N,et al. Influence of Ni content on the structure and properties of Cr-Ni-N coatings prepared by direct current magnetron sputtering[J]. Thin Solid Films, 2009,517(11):3304-3309.

[10] 贺春林,朱跃长,张金林,等. 磁控溅射沉积TiN薄膜工艺优化[J]. 沈阳大学学报(自然科学版), 2014,26(4):272-276.

HE C L,ZHU Y C,ZHANG J L,et al. Process optimization of TiN thin films prepared by magnetron sputtering[J]. Journal of Shenyang University (Natural Science), 2014,26(4):272-276.

[11] LI W,LIU P,ZHAO S,et al. Microstructural evolution, mechanical properties and strengthening mechanism ofTiN/Ni nanocomposite film[J]. Journal of Alloys and Compounds, 2017,691:159-164.

[12] MIŜINA M, MUSIL J, KADLEC S. CompositeTiN-Ni thin films deposited by reactive magnetron sputter ion-plating[J]. Surface and Coatings Technology, 1998,110(3):168-172.

[13] 宋贵宏,杜昊,贺春林. 硬质与超硬涂层:结构、性能、制备与表征[M]. 北京:化学工业出版社, 2007:197-199.

SONG G H,DU H,HE C L. Hard and superhard coatings: microstructure, properties, preparation and characterization[M]. Beijing: Chemical Industry Press, 2007:197-199.

[14] LEE D N. A model for development of orientation of vapor deposits[J]. Journal of Materials Science, 1989,24(12):4375-4378.

[15] WANG H,ZHANG S,LI Y,et al. Bias effect on microstructure and mechanical properties of magnetron sputtered nanocrystalline titanium carbide thin films[J]. Thin Solid Films, 2008,516(16):5419-5423.

[16] TAY B K,SHI X,YANG H S,et al. The effect of deposition conditions on the properties of TiN thin films prepared by filtered cathodic vacuum-arc technique[J]. Surface and Coatings Technology, 1999, 111(2/3):229-233.

[17] KUMAR M,MITRA R. Effect of substrate temperature and annealing on structure, stress and properties of reactively co-sputtered Ni-TiN nanocomposite thin films[J]. Thin Solid Films, 2017,624:70-82.

[18] DEVIA D M,RESTREPO-PARRA E,ARANGO P J,et al. TiAlN coatings deposited by triode magnetron sputtering varying the bias voltage[J]. Applied Surface Science, 2011,57(14):6181-6185.

[19] SUNDGREN J E,JOHANSSON B O,HENZELL H T,et al. Mechanisms of reactive sputtering of titanium nitride and titanium carbide Ⅲ: Influence of substrate bias on composition and structure[J]. Thin Solid Films, 1983,105(4):385-393.

【责任编辑:胡天慧】

EffectofBiasVoltageonMechanicalPropertiesofReactiveMagnetronCo-SputteredTiN/NiNanocompositeFilms

HeChunlin,ChenHongzhi,GaoJianjun,WangLingfei,MaGuofeng,WangJianming

(Liaoning Provincial Key Laboratory of Advanced Materials, Shenyang University, Shenyang 110044, China)

TiN/Ni nanocomposite films have been deposited under different bias voltage by reactive magnetron co-sputtering of Ti and Ni targets in N2gas atmosphere, and the influence of substrate bias voltage on the phase structure and mechanical properties was investigated by X-ray diffraction, nanoindenter and scratch tests. The TiN/Ni films are composed of fcc TiN and Ni, and their preferential orientations strongly depend on bias voltage. When the bias voltage increases, the grain sizes are reduced whereasH,E,H/E,H3/E2and adhesion strength are first improved and then decreased. The highest values ofH,E,H/E,H3/E2and adhesion strength are all presented at -80 V, which are (19.2±0.4) GPa,(311.0±5.0) GPa,0.062,0.073 GPa and 45 N, respectively.

TiN/Ni; nanocomposite film; reactive magnetron co-sputtering; negative bias voltage; mechanical property

TB 79; TB 34

A

2017-09-27

国家自然科学基金资助项目(51171118)；辽宁省高等学校优秀人才支持计划(LR2013054)．

贺春林(1964——)，男，辽宁葫芦岛人，沈阳大学教授，博士生导师．

2095-5456(2017)06-0431-04