基底對類金剛石薄膜摩擦學性能的影響

張仁輝,趙 娟

(銅仁學院材料與化學工程學院,貴州銅仁 554300)

基底對類金剛石薄膜摩擦學性能的影響

張仁輝,趙 娟

(銅仁學院材料與化學工程學院,貴州銅仁 554300)

為了研究不同基底對類金剛石薄膜摩擦磨損性能的影響，采用等離子體增強化學氣相沉積方法在高速鋼、SiC和304不銹鋼基底上成功制備了類金剛石薄膜。采用SEM，TEM，Raman測試手段對膜層的微結構進行了表征：SEM表征結果顯示膜層總厚度約為6.5 μm，而且層與層之間有明顯的界面；TEM表征結果顯示沉積的膜層為無定型結構；Raman光譜分析顯示沉積的薄膜存在明顯的G峰和D峰，可以確定沉積的薄膜為類金剛石薄膜。摩擦測試結果顯示，基底對類金剛石薄膜摩擦磨損性能具有顯著影響，對于不同基底，鋼球對偶上均存在明顯的轉移膜，高速鋼基底的磨痕寬度最小，而且沉積在高速鋼基底上的類金剛石薄膜具有最低的磨損率，摩擦系數約為0.1。采用Raman光譜對不同基底磨痕表面微結構進行了分析，認為高速鋼基底具有最低磨損率可歸因于其磨痕的石墨化程度低。研究可為制備具有優異摩擦磨損性能的類金鋼石薄膜提供參考。

摩擦學；摩擦系數；類金剛石；Raman；SEM；TEM

眾所周知，類金剛石薄膜具有優異的摩擦磨損性能[1-3]，這主要歸因于其高硬度和高化學惰性。然而，類金剛石的高內應力限制了其在電子設備與汽車等領域中的應用[4]。研究發現，異質原子摻雜類金剛石薄膜能很好地降低其內應力[5-6]。異質原子摻雜不但能進一步提升類金剛石薄膜的沉積厚度，而且還可以進一步提升類金剛石薄膜的力學性能[7-10]。

近年來，黃金霞等[11-12]采用磁控濺射系統在聚合物基底(PEEK)上成功沉積了類金剛石薄膜，而且系統研究了其在NaCl體液中的摩擦磨損性能。一些研究人員[13-15]采用磁控濺射方法在織構化的不銹鋼基底上制備了織構化的類金剛石薄膜,其在水環境中顯示出優異的摩擦磨損性能。張仁輝等[5-6]采用化學氣相沉積方法制備了超厚類金剛石薄膜，制備的薄膜具有優異的力學和摩擦學性能。王永欣等[16]系統地研究了不同基底(Si3N4, SiC和WC)對類金剛石薄膜的摩擦磨損性能的影響。綜上所述，類金剛石薄膜的摩擦磨損性能不但與沉積方法有關，還與沉積的基底類型有關。基于此，本文采用等離子體增強化學氣相沉積系統在不銹鋼、碳化硅和高速鋼基底上成功制備了類金剛石薄膜，并系統地探討了不同基底對類金剛石薄膜的摩擦磨損性能的影響。

1 試驗部分

1.1 試驗材料及制備

拋光后的硅片，厚度相同(厚度均為4 mm)的304不銹鋼，SiC和高速鋼(鋼號：W6Mo5Cr4V2(M2))作為類金剛石薄膜的沉積基底，基底在無水乙醇和丙酮中分別超聲40 min，N2氣吹干后放入等離子體增強化學氣相沉積系統，將類金剛石薄膜沉積在硅片上，以便于觀察薄膜截面結構、高分辨形貌和拉曼光譜表征。腔體的初始氣壓抽至1.0 × 10-3Pa。基底在Ar等離子體中清洗30 min，氣壓為2.1 Pa。在設置的條件下，類金剛石薄膜采用交替沉積的方法沉積在特定的基底上。交替沉積方法的參數如下：a)SiH4(25 sccm)，CF4(22.5 sccm)，C2H2(150 sccm)和Ar(100 sccm)，氣壓為4.0 Pa；b)SiH4(25 sccm)，CF4(22.5 sccm)，C2H2(100 sccm)和Ar(100 sccm)，氣壓為2.8 Pa。沉積電壓統一設定為800 V，頻率為1.5 kHz，占空比為30%。為了增強膜基結合力，將厚度約200 nm的Si中間層沉積在基底上。

1.2 試驗方法

采用TX-200V光學顯微鏡觀察磨斑形貌；采用場發射掃描電子顯微鏡(FESEM，JSM-6701F)表征膜層的截面形貌；采用高分辨透射電子顯微鏡(TecnaiTMG2F30, FEI, USA)表征膜層的微觀結構；采用拉曼光譜(LABRAM-HR800)對膜層的微觀結構進行表征，波長為532 nm，掃描范圍為800～2 000 cm-1；測試時間為60 s；膜層的硬度由納米壓痕儀測定(NanoTest600, Micromaterials Ltd., United Kingdom)；膜層的摩擦學性能由CSM球盤往復滑動摩擦磨損試驗機測定；大氣濕度為35%，鋼球半徑為6 mm，載荷為5 N，振幅為5 mm，頻率為5 Hz，滑動速度為7.45 cm/s。

2 結果與討論

圖1為制備的類金剛石薄膜的截面形貌。圖1顯示，膜層的截面微結構均勻致密，而且層與層之間具有明顯的界面，膜層的總厚度為6.5 μm。圖2為類金剛石薄膜的高分辨透射電鏡圖，顯示膜層的微結構為無定型結構。

圖3為類金剛石薄膜的拉曼光譜，類金剛石薄膜的拉曼光譜由高斯分峰法擬合為G峰(1 580 cm-1)和D峰(1 350 cm-1)[17-18]。2個明顯特征峰說明所制備的膜層為典型的類金剛石薄膜。峰位在860 cm-1附近為Si—O振動峰[19]，這歸因于硅基底的影響。

圖4為沉積在高速鋼、碳化硅和不銹鋼基底上的類金剛石薄膜的摩擦系數曲線圖。沉積在碳化硅基底上的類金剛石薄膜具有最高摩擦系數，約為0.22；沉積在不銹鋼基底上的類金剛石薄膜具有最低摩擦系數，約為0.1；沉積在高速鋼基底上的類金剛石薄膜的摩擦系數約為0.13。

圖5 a)—圖5 c)分別為沉積在高速鋼、碳化硅和不銹鋼基底上的類金剛石薄膜的磨損表面輪廓。沉積在高速鋼基底上的類金剛石薄膜的磨損體積為1.04×10-6mm3；沉積在碳化硅基底上的類金剛石薄膜的磨損體積為1.4×10-6mm3；沉積在不銹鋼基底上的類金剛石薄膜的磨損體積為2.44×10-6mm3。

圖1 類金剛石薄膜的截面形貌照片Fig.1 Cross-sectional image of DLC coating

圖2 類金剛石薄膜的高分辨透射電鏡圖Fig.2 HR TEM image of DLC coating

圖3 類金剛石薄膜的拉曼光譜Fig.3 Raman spectrum of DLC coating

圖4 沉積在高速鋼、碳化硅和不銹鋼基底上的 類金剛石薄膜的摩擦系數Fig.4 Friction coefficient of DLC coating deposition on the HSS, SiC and SS substrates

圖5 沉積在不同基底上的類金剛石薄膜的磨損表面輪廓Fig.5 Surface profiles across the wear track of the DLC coating deposition on different substrates

圖6 a)—圖6 c)分別為沉積在高速鋼、碳化硅和不銹鋼基底上的類金剛石薄膜與不銹鋼球配副摩擦測試后的磨斑光學形貌照片，顯示磨斑上存在明顯的轉移膜，而且周邊有大量磨屑。

圖6 類金剛石薄膜與不銹鋼球配副摩擦測試后的磨斑光學形貌照片Fig.6 Optical micrographs of the stainless steel ball surfaces after the sliding test against DLC coating

圖7 a)—7 c)分別為沉積在高速鋼、碳化硅和不銹鋼基底上的類金剛石薄膜的磨痕形貌圖，顯示磨痕周邊存在大量磨屑，而且在磨痕內存在不同深度的犁溝。說明膜層的磨損主要歸因于磨粒磨損。

圖7類金剛石薄膜摩擦測試后磨痕形貌照片Fig.7 Optical micrographs of wear tracks of DLC coating

圖8為原類金剛石表面和不同類金剛石薄膜磨痕內的拉曼光譜圖。隨著滑動摩擦測試的不斷往復，D峰峰形逐漸變得突出，G峰峰位不斷向高頻方向移動，這表明磨痕內的類金剛石薄膜表面已經發生了明顯的石墨化[20-21]，而且石墨化程度越高摩擦系數越小，因此，沉積在不銹鋼基底上的類金剛石薄膜具有最小的摩擦系數，而膜層的石墨化導致了膜層具有較大的磨損體積。另外，高速鋼(W6Mo5Cr4V2(M2))的硬度為8.6 GPa[22]，碳化硅的硬度為31.2～38.3 GPa[23]，304不銹鋼的硬度為4.6 GPa[24]。圖9為測試得到的不同基底的類金剛

圖8 原類金剛石薄膜、沉積在高速鋼、碳化硅和不銹鋼基底上類金剛石薄膜磨痕內的拉曼光譜Fig.8 Raman spectra of original DLC coating and wear track of and DLC coating deposition on HSS, SiC and SS substrates

圖9 沉積在高速鋼、碳化硅和不銹鋼基底上的 類金剛石薄膜的納米壓痕曲線Fig.9 Nanoindentation load-displacement curve of DLC coatings deposition on HSS, SiC and SS substrates

石薄膜的硬度曲線圖。沉積在高速鋼、碳化硅和不銹鋼基底上的類金剛石薄膜的硬度分別為9.05，11.4和8.97 GPa。高速鋼具有較小的磨損體積，這與類金剛石薄膜的硬度和高速鋼的硬度接近有關。

3 結 語

采用等離子體增強化學氣相沉積的方法在高速鋼、碳化硅和不銹鋼基底上制備了類金剛石薄膜[25]，研究了不同基底對類金剛石薄膜的摩擦磨損性能。結果顯示，基底對膜層的摩擦磨損性能具有顯著影響，摩擦系數在0.05～0.25變化，磨損體積在1.04×10-6～2.4×10-6mm3變化。沉積在高速鋼上的類金剛石薄膜具有最低的磨損體積，摩擦系數約為0.1。本文只討論了大氣氣氛下不同基底對類金剛石薄膜的摩擦磨損性能的影響，未來將重點研究不同基底在水環境和氮氣環境下基底對類金剛石薄膜摩擦磨損性能的影響。

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Effect of substrates on tribological properties of diamond-like carbon coating

ZHANG Renhui, ZHAO Juan

(School of Material and Chemical Engineering, Tongren University, Tongren, Guizhou 554300, China)

In order to well investigate the effect of different substrates on the friction and wear of diamond-like carbon (DLC) coating, the DLC coatings are deposited on substrates like the high-speed steel (HSS), SiC and 304 stainless steel by using plasma enhanced chemical vapor deposition method. The diamond-like carbon is prepared. The microstructure of the coatings is characterized using SEM, TEM and Raman. The SEM results exhibit that the total thickness of the coatings is about 6.5 μm, and there's apparent interfaces between layers. The TEM results imply that the coatings have an amorphous structure. Raman spectrum exhibits that G and D peaks are observed, which implies that the deposition coatings are diamond-like carbon coating. The results of tribological tests show that the substrates have a significant effect on the friction and wear of the coating. For different substrates, the transfer film is found on the steel counterpart surface, the wear track of the HSS has a lowest width, and the DLC coating that deposited on HSS exhibits the lowest wear and low friction coefficient (about 0.1).The microstructure of different substrates wear track surfaces is analyzed by using Raman spectrum, and the lowest wear of the HSS is attributed to the lower degree of the graphitization. The research provides reference for preparing the DLC coating with excellent tribological properties.

tribology; friction coefficient; diamond-like carbon; Raman; SEM; TEM

1008-1542(2017)03-0244-05

10.7535/hbkd.2017yx03005

2017-03-09；

2017-03-24；責任編輯：馮 民

國家自然科學基金(51605336)；貴州省自然科學基金(KY[2016]009)

張仁輝(1985—)，男，湖南辰溪人，副教授，博士，主要從事材料物理與化學方面的研究。

E-mail：zrh_111@126.com

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A

張仁輝,趙 娟.基底對類金剛石薄膜摩擦學性能的影響[J].河北科技大學學報,2017,38(3):244-248. ZHANG Renhui, ZHAO Juan.Effect of substrates on tribological properties of diamond-like carbon coating[J].Journal of Hebei University of Science and Technology,2017,38(3):244-248.