基體偏壓對(duì)反應(yīng)共濺射TiN/Ni納米復(fù)合膜力學(xué)性能的影響

賀春林, 陳宏志, 高建君, 王苓飛, 馬國(guó)峰, 王建明

(沈陽(yáng)大學(xué) 遼寧省先進(jìn)材料制備技術(shù)重點(diǎn)實(shí)驗(yàn)室, 遼寧 沈陽(yáng) 110044)

基體偏壓對(duì)反應(yīng)共濺射TiN/Ni納米復(fù)合膜力學(xué)性能的影響

賀春林, 陳宏志, 高建君, 王苓飛, 馬國(guó)峰, 王建明

(沈陽(yáng)大學(xué) 遼寧省先進(jìn)材料制備技術(shù)重點(diǎn)實(shí)驗(yàn)室, 遼寧 沈陽(yáng) 110044)

以高純Ti和Ni為靶材,在不同偏壓下利用反應(yīng)磁控共濺射法制備了TiN/Ni納米復(fù)合膜,采用X射線衍射、納米壓痕和劃痕試驗(yàn)研究了偏壓對(duì)復(fù)合膜相結(jié)構(gòu)和力學(xué)性能的影響.結(jié)果顯示,反應(yīng)共濺射TiN/Ni納米復(fù)合膜由fcc-TiN和Ni組成,其擇優(yōu)取向與偏壓有關(guān).隨負(fù)偏壓增加,復(fù)合膜晶粒尺寸逐漸減小,硬度、彈性模量、H/E、H3/E2和膜基結(jié)合力則先增加后下降.在偏壓為-80 V時(shí)所沉積的復(fù)合膜具有最好的力學(xué)性能,其硬度為(19.2±0.4) GPa、彈性模量為(311.0±5.0) GPa、H/E為0.062、H3/E2為0.073 GPa,膜基結(jié)合力為45 N.

TiN/Ni; 納米復(fù)合膜; 反應(yīng)磁控共濺射; 負(fù)偏壓; 力學(xué)性能

盡管TiN、CrN等過(guò)渡金屬氮化物薄膜在機(jī)械加工刀具、磨具防護(hù)涂層方面有大量應(yīng)用,但因其較脆,因此應(yīng)用受到限制.以往人們主要關(guān)心如何提高薄膜硬度.但近年來(lái),人們逐漸意識(shí)到,在大多數(shù)工業(yè)應(yīng)用中,薄膜僅具有高硬度還不夠,還應(yīng)具有高韌性.至少,韌性應(yīng)與硬度同等重要[1],適度硬且韌性好的薄膜更有應(yīng)用前景.10余年來(lái),硬質(zhì)薄膜增韌一直是薄膜科學(xué)研究熱點(diǎn)和難點(diǎn)之一.添加韌性金屬Ni或Cu是改善TiN或CrN基薄膜硬度和韌性的一種有效方法[2-3].Belov等[4-5]和Akbari等[6]報(bào)道,Ni和Cu可增加TiN或TiAlN的硬度、耐磨性和熱穩(wěn)定性.添加Ni可使CrN薄膜的韌性和耐磨性提高[7-9].由于Ni或Cu與N親和力很低,因此,常采用反應(yīng)共濺射方法制備TiN/Ni(或Cu)和CrN/Ni(或Cu)納米復(fù)合薄膜.實(shí)驗(yàn)顯示,基體偏壓和沉積溫度是影響磁控濺射薄膜形貌、晶粒尺寸、取向、致密度以及力學(xué)與腐蝕性能的重要參數(shù)[10].本文采用反應(yīng)磁控共濺射技術(shù)在不同偏壓下制備了TiN/Ni納米復(fù)合薄膜,通過(guò)對(duì)微結(jié)構(gòu)和性能的系統(tǒng)表征研究,探究了基體偏壓對(duì)復(fù)合膜結(jié)構(gòu)和力學(xué)性能的影響規(guī)律.

1 試驗(yàn)材料與方法

1.1 薄膜制備

基體選用304不銹鋼和P-Si(100)基體.不銹鋼表面先經(jīng)砂紙逐級(jí)研磨后用1 μm金剛石研磨膏仔細(xì)拋光,然后與Si基體一樣,用丙酮和酒精依次超聲波清洗除油,冷風(fēng)吹干后裝入真空室待用.磁控濺射設(shè)備為中科院沈陽(yáng)科學(xué)儀器有限公司生產(chǎn)的JGP 450三靶磁控濺射鍍膜系統(tǒng).靶材為直徑60 mm、厚4 mm的高純Ti靶(99.99%)和Ni靶(99.99%).開始濺射前,先將本底壓強(qiáng)抽到0.6 mPa,然后通入高純氬氣(99.999%)和氮?dú)?99.999%),采用反應(yīng)磁控共濺射法沉積TiN/Ni納米復(fù)合膜,具體沉積參數(shù)為:沉積室壓力0.6 Pa,靶基距7 cm,N2與Ar氣流量分別為16與40 mL·min-1, Ti直流靶電流0.2 A,Ni射頻靶功率35 W,基體負(fù)偏壓(Vb)為-40～-160 V,沉積溫度300 ℃,沉積時(shí)間60 min.

1.2 相結(jié)構(gòu)

采用掠入射XRD法分析復(fù)合薄膜的相結(jié)構(gòu),X射線源為CuKα(λ=0.154 056 nm)射線,掠入射角為2°.

1.3 壓痕試驗(yàn)

采用安捷倫G200型納米壓痕儀測(cè)量薄膜硬度和彈性模量,測(cè)量方法為連續(xù)剛度法,測(cè)量結(jié)果取10次測(cè)量的平均值.

1.4 劃痕試驗(yàn)

利用中科院蘭州化物所生產(chǎn)的MFT-4000型多功能材料表面性能試驗(yàn)儀測(cè)試薄膜的界面結(jié)合力,用金剛石壓頭,錐角120°,尖端半徑0.2 mm.實(shí)驗(yàn)參數(shù)為:加載速度為50 N·min-1,終止載荷為100 N,劃痕長(zhǎng)度為5 mm.

2 實(shí)驗(yàn)結(jié)果與討論

2.1 相結(jié)構(gòu)

圖1為Si(100)基體上在不同Vb下沉積的TiN/Ni納米復(fù)合膜的XRD圖譜.圖中主要衍射峰分別對(duì)應(yīng)于面心立方結(jié)構(gòu)fcc-TiN(B1-NaCl型)的(111)、(200)和(220)面,(311)和(222)面譜峰不明顯.由于N不易與Ni發(fā)生反應(yīng),因此圖譜中Ni(111)衍射峰較弱,這說(shuō)明Ni含量較少或Ni結(jié)晶度較差[11].Miina等[12]也發(fā)現(xiàn)Ti-Ni-N中的Ni為晶態(tài).由于Ni與N親和力低,二者間不易形成化合物,因此,Ni以金屬形式存在,并偏聚在TiN顆粒的周圍,阻礙TiN晶粒的生長(zhǎng),而所沉積膜的結(jié)構(gòu)為TiN/Ni納米復(fù)合結(jié)構(gòu)[13].

圖1 不同Vb條件在Si(100)上沉積TiN/Ni納米復(fù)合膜的XRD圖譜

由圖1可見,TiN/Ni納米復(fù)合膜的擇優(yōu)取向明顯取決于Vb.薄膜的擇優(yōu)取向可用公式(1)中的織構(gòu)系數(shù)Tc來(lái)表示[14]:

表1 偏壓對(duì)TiN/Ni納米復(fù)合膜的擇優(yōu)取向影響

TiN/Ni納米復(fù)合膜的平均晶粒尺寸d可采用式(2)(Scherrer公式)來(lái)估算:

式中:d為晶粒尺寸;k為常數(shù),值為0.91;λ為入射X射線波長(zhǎng);β為衍射峰半寬高;θ為布拉格角.圖2給出了d隨Vb的變化.當(dāng)Vb從-40 V增至-120 V時(shí),TiN相的d由16.2 nm快速降至10.7 nm,之后,繼續(xù)增加Vb,d幾乎不變.這是因?yàn)樘岣遃b,即是增加入射粒子能量,受高能粒子轟擊后,已沉積膜中晶格缺陷增多,而晶格缺陷通常是晶核擇優(yōu)形核地點(diǎn),結(jié)果會(huì)導(dǎo)致形核率增加和晶粒細(xì)化[15].但是,繼續(xù)增加Vb,會(huì)導(dǎo)致入射粒子能量過(guò)高,膜表面吸附原子的遷移率隨之增大,晶粒聚合長(zhǎng)大幾率增多,結(jié)果導(dǎo)致d變大[16].Kumar等[17]也發(fā)現(xiàn),在Vb低于-80 V時(shí),d隨Vb增加而減小,但他們并沒(méi)有研究更高Vb時(shí)薄膜d的變化.

圖2 TiN/Ni納米復(fù)合膜的d隨Vb變化Fig.2 d vs Vb of the TiN/Ni nanocomposite films

2.2 H、E和H/E

圖3為不同Vb下在304不銹鋼基體上沉積的TiN/Ni納米復(fù)合膜硬度H和彈性模量E變化

曲線.可見,隨Vb增加,H和E的變化趨勢(shì)相似,均是先增大后下降.在-80 V時(shí),H和E均達(dá)到最大值,H為(19.2±0.4)GPa,E為(311.0±5.0)GPa.-120 V和-160 V偏壓的薄膜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,表面擴(kuò)散速率增大,膜致密度改善;同時(shí)還會(huì)使晶粒尺寸d減小,這些均有利于H和E增大[18].但是,Vb過(guò)大會(huì)使反濺射作用增強(qiáng),膜中晶格缺陷和微孔增多,引起H和E下降.可見,適度Vb有利于獲得高硬度的薄膜.

圖3不同Vb下TiN/Ni納米復(fù)合膜的硬度和彈性模量

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

薄膜抗彈性變形和塑性變形的能力可分別用H/E和H3/E2來(lái)表征,并以此來(lái)預(yù)測(cè)薄膜耐磨性.圖4給出了H/E和H3/E2隨Vb的變化.可見,H/E和H3/E2隨Vb變化趨勢(shì)與硬度變化相似(圖3和圖4),都是先增加后降低,并在-80 V達(dá)最大,分別為0.062和0.073 GPa.這表明,-80 V偏壓的復(fù)合膜具有更高的抗機(jī)械破壞性能.

圖4 TiN/Ni納米復(fù)合膜的H/E和H3/E2隨Vb變化Fig.4 Effect of Vb on H/E and H3/E2 of the TiN/Ni nannocomposite films

2.3 界面結(jié)合力

圖5示出了304不銹鋼基體上沉積1 h的TiN/Ni納米復(fù)合膜臨界載荷隨Vb的變化.薄膜的膜基結(jié)合力可根據(jù)劃痕過(guò)程中硬質(zhì)薄膜開裂的臨界載荷來(lái)表征.可見,隨Vb增加,膜基結(jié)合力先增加后下降;在-80 V偏壓時(shí),膜基結(jié)合力達(dá)最大值,約為45 N左右. 這說(shuō)明,適當(dāng)施加Vb可有效改善復(fù)合膜的界面結(jié)合力. 但是, 當(dāng)Vb過(guò)高時(shí), 濺射室內(nèi)的Ar+離子能量提高, 對(duì)復(fù)合膜的表面撞擊作用大大增強(qiáng), 導(dǎo)致膜表面粗糙度增大、膜內(nèi)部組織中缺陷增多[19]; 同時(shí),Vb過(guò)高還會(huì)使界面殘余應(yīng)力增大, 這都會(huì)使膜基結(jié)合力下降.

圖5 Vb對(duì)TiN/Ni納米復(fù)合膜的臨界載荷的影響

3 結(jié) 論

以高純Ti和Ni為靶材,利用反應(yīng)磁控共濺射方法在不同偏壓下(-40～-160 V)制備了TiN/Ni納米復(fù)合膜.TiN/Ni納米復(fù)合膜由fcc型TiN和Ni組成,擇優(yōu)取向明顯取決于偏壓.隨負(fù)偏壓增加,復(fù)合膜晶粒尺寸逐漸減小,而H,E,H/E,H3/E2及膜基結(jié)合力則先增加后下降.在偏壓為-80 V時(shí),復(fù)合膜具有最好的力學(xué)性能,其硬度為(19.2±0.4) GPa、彈性模量為(311.0±5.0) GPa、H/E為0.062、H3/E2為0.073 GPa,膜基結(jié)合力為45 N.

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【責(zé)任編輯: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

國(guó)家自然科學(xué)基金資助項(xiàng)目(51171118)；遼寧省高等學(xué)校優(yōu)秀人才支持計(jì)劃(LR2013054)．

賀春林(1964——)，男，遼寧葫蘆島人，沈陽(yáng)大學(xué)教授，博士生導(dǎo)師．

2095-5456(2017)06-0431-04