肖 娜，杜菲菲，楊 波(.東北大學(xué) 材料電磁過(guò)程研究教育部重點(diǎn)實(shí)驗(yàn)室，沈陽(yáng) 089；.東北大學(xué) 材料各向異性與織構(gòu)教育部重點(diǎn)實(shí)驗(yàn)室，沈陽(yáng) 089)

調(diào)制比對(duì)TiN/Ti多層膜結(jié)構(gòu)和力學(xué)性能的影響

肖 娜1，杜菲菲2，楊 波2
(1.東北大學(xué) 材料電磁過(guò)程研究教育部重點(diǎn)實(shí)驗(yàn)室，沈陽(yáng) 110819；2.東北大學(xué) 材料各向異性與織構(gòu)教育部重點(diǎn)實(shí)驗(yàn)室，沈陽(yáng) 110819)

采用反應(yīng)磁控濺射的方法在Ti6Al4V基板上沉積(TiN/Ti)n多層膜，交替沉積Ti層和TiN層，以通入/關(guān)閉氮?dú)鈱?shí)現(xiàn)對(duì)TiN含量的控制.共濺射10層，每層TiN膜和Ti膜的厚度之和即調(diào)制周期不變，二者之間的厚度比即調(diào)制比分別為1∶9、1∶5、1∶3和1∶2.利用XRD、SEM分別研究了薄膜的微觀結(jié)構(gòu)和表面形貌，利用顯微硬度儀和劃痕儀測(cè)量了薄膜的硬度和膜基結(jié)合力.研究結(jié)果表明：隨著調(diào)制比的增大，TiN(200)逐漸消失，出現(xiàn)Ti2N等新相；硬度、結(jié)合力有明顯增大的趨勢(shì)，與單層膜相比，多層膜的硬度和結(jié)合力最多分別增加250 HV 和22 N.

反應(yīng)磁控濺射；TiN/Ti；調(diào)制比；結(jié)合力

TiN具有高硬度、良好的耐磨性和耐腐蝕性能，已成為T(mén)i合金表面改性的主要材料，然而TiN薄膜在服役過(guò)程中極易從Ti合金表面脫落，使得Ti合金基體裸露最終導(dǎo)致合金器件失效.在TiN層和Ti合金基體之間沉積一層Ti作為過(guò)渡層，可以緩解界面壓力從而達(dá)到提高膜基結(jié)合力的目的[1].在對(duì)TiN薄膜性能的研究過(guò)程中，學(xué)者們發(fā)現(xiàn)TiN/Ti多層膜與TiN單層膜相比，抗腐蝕性能、力學(xué)性能等有著顯著提高[2～6].如，Zhang等人發(fā)現(xiàn)TiN/Ti多層膜的硬度和耐磨性在100 nm的調(diào)制周期下有著大幅度提高[7]，Mori等人發(fā)現(xiàn)隨著多層膜層數(shù)的增加TiN/Ti多層膜的硬度、屈服強(qiáng)度、結(jié)合強(qiáng)度等都隨之增大[4].在多層膜力學(xué)性能的研究工作中大量?jī)?nèi)容是圍繞調(diào)制周期對(duì)薄膜硬度影響展開(kāi)的[8～10]，趙陽(yáng)[11]和Li[12]分別指出了不僅僅調(diào)制周期對(duì)多層膜的力學(xué)性能有顯著影響，調(diào)制比的作用也不可忽視.但是關(guān)于調(diào)制比與TiN/Ti力學(xué)性能之間的關(guān)系還鮮有報(bào)道.本文通過(guò)制備一系列不同調(diào)制比的TiN/Ti多層膜，分析了薄膜的微觀組織、結(jié)構(gòu)與結(jié)合力、硬度等力學(xué)性能的關(guān)系.

1 實(shí)驗(yàn)材料和方法

本文利用JZCK-440S高真空鍍膜設(shè)備，采用直流反應(yīng)磁控濺射的方法制備薄膜，具體工藝參數(shù)見(jiàn)表1.通過(guò)周期性地通入/關(guān)閉氮?dú)猓赥i6Al4V基板上周期性地沉積Ti及TiN薄膜，從而實(shí)現(xiàn)TiN/Ti多層膜的制備.其中，調(diào)制周期指TiN層和Ti層厚度之和，調(diào)制比指Ti層和TiN層厚度之比.本文保持TiN/Ti納米多層膜的調(diào)制周期不變，為240 nm(即4 h沉積2400 nm，制備10層TiN/Ti納米多層膜)，圖1為一個(gè)周期內(nèi)沉積TiN/Ti的調(diào)制比.

本文利用SmartlabX射線衍射儀分析薄膜的晶體結(jié)構(gòu)、WS-2005涂層附著力自動(dòng)劃痕儀測(cè)量膜基結(jié)合力、401MVDTM顯微硬度儀測(cè)量薄膜的硬度.

表1 改變調(diào)制比沉積TiN/Ti納米多層膜工藝參數(shù)Table 1 Deposition parameters of TiN/Ti multilayer films with different modulation ratio

圖1 一個(gè)周期內(nèi)沉積TiN/Ti的調(diào)制比Fig.1 Modulation ratio of TiN/Ti multilayer films in one period

2 結(jié)果與討論

2.1 調(diào)制比對(duì)TiN/Ti多層膜晶體結(jié)構(gòu)的影響

圖2為不同調(diào)制比下所制備樣品的X射線衍射譜圖，由圖(a)可知，譜圖中幾乎都出現(xiàn)了TiN(111)、(200)、(220)、(311)和(222)特征峰.由圖(b)可知，調(diào)制比為1∶9時(shí)，薄膜中同時(shí)存在TiN(111)和(200)晶面.調(diào)制比為1∶5時(shí)，譜圖中主要存在TiN(111)和Ti2N(111)晶面，其中TiN(111) 峰強(qiáng)遠(yuǎn)高于其他樣品，可以看出明顯的TiN(111)擇優(yōu)取向.調(diào)制比為1∶3和1∶2時(shí)，譜圖中出現(xiàn)TiN0.26(002)和Ti2N晶面.這是由于隨著調(diào)制比變大，每層薄膜中Ti含量增多，N原子在Ti與TiN層界面擴(kuò)散，形成穩(wěn)定的Ti2N和TiN0.26相.

2.2 調(diào)制比對(duì)TiN/Ti多層膜微觀組織的影響

圖3為不同調(diào)制比下TiN薄膜的表面形貌，可以看出當(dāng)調(diào)制比為1∶9時(shí)，薄膜表面的均勻度較差；當(dāng)調(diào)制比為1∶5時(shí)，薄膜表面光滑，晶粒尺寸約200 nm左右，膜層平整致密；當(dāng)調(diào)制比為1∶3 時(shí)，薄膜表面平整致密，晶粒均勻；當(dāng)調(diào)制比為1∶2 時(shí)，由于Ti含量很高，并根據(jù)XRD衍射圖譜，TiN衍射峰的峰強(qiáng)非常弱判斷薄膜結(jié)晶性差，故薄膜表面形貌變?yōu)榍蛐?

2.3調(diào)制比對(duì)TiN/Ti多層膜力學(xué)性能的影響

圖4為不同調(diào)制比下TiN薄膜的硬度，沉積4 h單層TiN薄膜的硬度為1360.3 HV，當(dāng)調(diào)制比為1∶2時(shí)，TiN薄膜的硬度為1230.5 HV，說(shuō)明當(dāng)調(diào)制比為1∶2時(shí)，不僅不能提高薄膜的硬度，反而降低了TiN薄膜的硬度，是因?yàn)楫?dāng)調(diào)制比為1∶2時(shí)每個(gè)周期的鈦層厚度幾乎為80 nm而TiN厚度也只有160 nm，鈦層厚度太厚起到了應(yīng)力釋放作用，但是沒(méi)有起到阻止位錯(cuò)遷移的作用.

當(dāng)調(diào)制比在1∶3～1∶9時(shí)，薄膜的硬度比調(diào)制比為1∶2時(shí)的硬度大，與單層TiN薄膜相比，硬度升高了接近300 HV.這種硬度的變化可能有兩方面原因：一是隨著調(diào)制比的減小，薄膜層間Ti層和TiN層逐漸擴(kuò)散形成了硬度較高的Ti2N，所以薄膜的硬度會(huì)提高.二是多層薄膜存在一定的層厚，當(dāng)層厚達(dá)到一定值時(shí)，位錯(cuò)不能在層內(nèi)生成，位錯(cuò)的滑移受到了阻礙，也會(huì)使硬度升高.

圖2 不同調(diào)制比下TiN/Ti多層膜的XRD圖譜Fig.2 XRD patterns of TiN/Ti multilayer films with different modulation ratio(a)—全譜圖;(b)—局部譜圖

圖3 不同調(diào)制比下TiN薄膜的表面形貌Fig.3 Morphology of TiN/Ti multilayer films with different modulation ratio(a)—1∶9; (b)—1∶5; (c)—1∶3; (d)—1∶2

圖4 不同調(diào)制比下TiN薄膜的硬度Fig.4 Hardness of TiN/Ti multilayer films with different modulation ratio

圖5 不同調(diào)制比下TiN薄膜的劃痕形貌Fig.5 Scratch morphology of TiN/Ti multilayer films with different modulation ratio(a)—1∶2; (b)—1∶3; (c)—1∶5; (d)—1∶9

圖5是不同調(diào)制比下劃痕形貌：

圖5(a)是調(diào)制比為1∶2的薄膜，觀察劃痕形貌，薄膜開(kāi)始出現(xiàn)剝落時(shí)臨界載荷值為62 N左右，所以調(diào)制比為1∶2時(shí)所對(duì)應(yīng)的結(jié)合力為62 N.

圖5(b)是調(diào)制比為1∶3的薄膜劃痕形貌，可以看出在劃痕內(nèi)部幾乎沒(méi)有剝落，為典型的屈曲剝落現(xiàn)象，隨著載荷的施加并未發(fā)生界面裂紋擴(kuò)展.直到載荷加載到70 N左右薄膜開(kāi)始剝落，由此可認(rèn)為調(diào)制比為1∶3時(shí)所對(duì)應(yīng)結(jié)合力為70 N.

圖5(c)是調(diào)制比為1∶5的薄膜劃痕形貌，加載載荷施加到60 N以上，薄膜才出現(xiàn)大面積連續(xù)剝落，所以60 N左右才是調(diào)制比為1∶5時(shí)薄膜的結(jié)合力.

圖5(d)是調(diào)制比為1∶9時(shí)薄膜的劃痕形貌，可以看出薄膜在基體“暴露”前劃痕周邊并沒(méi)有薄膜崩落，直到加載載荷施加到44 N左右，薄膜開(kāi)始出現(xiàn)剝落，所以調(diào)制比為1∶9時(shí)薄膜的結(jié)合力為44 N.

圖6為不同調(diào)制比下TiN薄膜的結(jié)合力變化趨勢(shì)，隨TiN/Ti調(diào)制比減少，結(jié)合力出現(xiàn)先增大后減小的趨勢(shì).是因?yàn)殡S著TiN/Ti調(diào)制比減少，TiN含量增加而Ti含量減少.起初Ti含量較多時(shí)，加載載荷較小時(shí)壓頭就能很容易壓入薄膜內(nèi)部，而當(dāng)Ti含量較少時(shí)，Ti層又不能起到吸收應(yīng)力的作用.所以存在最佳TiN/Ti層厚度比，使薄膜的結(jié)合力達(dá)到最佳值.

圖6 不同調(diào)制比下TiN薄膜的結(jié)合力Fig.6 Critical load of TiN/Ti multilayer films with different modulation ratio

3 結(jié) 論

與單層膜相比，多層膜的力學(xué)性能有著顯著提高.隨著調(diào)制比從1∶9增加到1∶2時(shí)，TiN/Ti多層薄膜硬度存在峰值，由于硬度的峰值與調(diào)制比不同層的寬度有關(guān)；TiN/Ti多層膜結(jié)合力先增加后減小.當(dāng)調(diào)制比為1∶5時(shí)，本文得到的最優(yōu)厚度層為純Ti層40 nm/TiN層200 nm，硬度達(dá)到了1610.5 HV，結(jié)合力為60 N左右.與單層膜相比硬度提高了250 HV左右，結(jié)合力增大了一倍.

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EffectofmodulationratioonstructureandmechanicalpropertiesofTiN/Timultilayerfilms

Xiao Na1，Du Feifei2，Yang Bo2

(1. Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China；2. Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819, China.)

(TiN/Ti)n multilayer films were deposited on Ti6Al4V substrate through reactive magnetron sputtering method, by using Ar-N2mixture gas. TiN content was controlled by N2 flow. With the same modulation period for all samples, the modulation ratios were changed from 1∶9, 1∶5, 1∶3 to 1∶2. Crystal structures, surface morphology and cross-sectional microstructure were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Microhardness of TiN film was measured by microhardness tester. Adhesive strength between films and substrate was determined by scratch test apparatus. The main results are as follows: with the modulation ratio increment, TiN(200) disappears gradually and Ti2N phase appears. Hardness and adhesion of the TiN/Ti multilayer films increase with the modulation ratio changed from 1∶9 to 1∶2. Compared with TiN monolayer films, hardness of TiN/Ti multilayer films increases by about 250 HV and adhesion increases by 22 N. Mechanical properties of TiN/Ti multilayer films are better than monolayer films.

reactive magnetron sputtering；TiN/Ti；modulation ratio ；adhesion

2014-01-05.

中央高校基本科研業(yè)務(wù)費(fèi)(N120309001)；教育部科學(xué)技術(shù)研究重大項(xiàng)目(313014).

肖娜(1981—)，女，東北大學(xué)實(shí)驗(yàn)師，E-mail:xiaona@epm.neu.edu.cn.

O484.2

A

1671-6620(2014)04-0276-04