自潤性氮化釩鈦硬質薄膜之陰極電弧沉積製程設計與磨潤機制研究

Self-lubrication and Tribological Mechanisms of TiVN Hard Coatings Synthesized by Cathodic Arc Evaporation

邱文通(Wen-Tung Chiu)

指導教授 ： 張銀祐

國立虎尾科技大學/工程學院/機械與電腦輔助工程系碩士班/碩士(2017年)

摘要

PVD物理氣相沉積目前常用來改善切削工具、成形工具及機械零件等的磨潤性能，本研究利用電漿光譜分析儀(OES)來辨別各種不同電漿種類及原子價數與薄膜特性之間的關聯，且含氮化釩(VN)的薄膜不僅表現出高硬度及韌性，亦會生成自潤性Magnéli相，因此磨耗試驗表現出低摩擦係數特性，故此類薄膜常用於需要滑動接觸的磨潤系統中。
TiVN薄膜使用陰極電弧沉積系統鍍製，靶材為純Ti靶和TiV合金靶，透過改變不同偏壓來觀察薄膜的電漿特性、微結構及機械性質。本研究藉由電漿光譜分析儀(OES)觀察電漿特性，薄膜微結構則透過場發射式電子顯微鏡(FE-SEM)搭配能量散射光譜分析儀(EDS)觀察薄膜表面形貌、橫截面結構及定性半定量元素分析，再透過X光繞射分析儀(XRD)進行薄膜晶相分析，接著藉由場發射穿透式電子顯微鏡(FE-TEM)對高溫氧化500˚C後的TiVN-200V薄膜進行顯微結構觀察、EDS元素分析及晶體結構鑑定，X射線光電子能譜儀(XPS)則用來判定磨耗軌跡表面各元素鍵結情形。薄膜機械性質部分，首先藉由洛氏壓痕及動態衝擊疲勞試驗機對薄膜附著力與衝擊疲勞試驗進行分析，薄膜硬度使用微小維克氏壓痕試驗機測試，薄膜磨耗性質則由球對盤磨耗試驗機(ball-on-disk)針對常溫及高溫退火後試片進行檢測，最後透過銑削加工SUS 304不鏽鋼探討刀具薄膜磨耗情形及工件表面粗糙度。
由實驗結果得知TiVN薄膜為B1-NaCl結構，且觀察其表面形貌在偏壓為-200V時微粒分布百分比相對較少，機械性質方面，所有偏壓下薄膜附著力皆良好(class 0)，最佳薄膜硬度落於-200V的TiVN薄膜(25GPa)亦擁有良好抗衝擊性能(四十萬次以上)，薄膜殘餘應力則有隨偏壓增加而上升的趨勢，此外磨耗實驗整體而言以偏壓-200V的表現較佳，因在此偏壓下表現出較低摩擦係數(0.38)及較少磨耗率(7.5×10-7mm3/Nm)，接著藉由實際銑削加工觀察不同偏壓下端銑刀之刀腹磨耗及工件表面粗糙度，由結果得知當偏壓為-200V時有較少刀腹磨耗(40.7µm)，且工件表面粗糙度(Ra：0.5µm)也較低，綜觀以上實驗結果得知薄膜產生自潤性及低摩擦係數特性是由於釩元素在磨耗時因高溫生成的氧化物所導致。

關鍵字

TiVN ； 機械性質 ； 銑削加工 ； 自潤性 ； 氧化物

並列摘要

PVD coatings are today frequently used in order to improve the tribological performance of cutting tools, forming tools and machine components. In this study, optical emission spectroscopy (OES) was employed to identify the species present in the plasma and to correlate them with the properties of the deposited thin films. VN-based coatings are known to show a combination of high hardness and toughness and the possibility to form a low friction Magnéli phase, promoting low friction coefficient in sliding contact, and consequently these coatings are of interest for sliding contact tribosystems.
In this study, TiVN coatings were synthesized by cathodic arc evaporation (CAE). Pure Ti and TiV alloy cathodes were used for the deposition of TiVN coatings. By controlling the different bias voltage, the deposited monolayered TiVN coatings possessed different mechanical properties and plasma characteristics of TiVN hard coatings. Plasma characteristics were observed by optical emission spectroscopy (OES). The microstructure of the deposited coatings was investigated by a field emission scanning electron microscope (FE-SEM), equipped with an X-ray energy dispersive spectrometer (EDS). Glancing angle X-ray diffraction was used to characterize the microstructure and phase identification of the films. A field emission transmission electron microscope (FE-TEM) to characterize the microstructure and phase identification of TiVN-200V coating after oxidation at 500˚C. The information of surface element distribution and chemical bonding of wear tracks is measured by X-ray photoelectron spectrometer (XPS). Mechanical properties, such as the hardness, were measured by means of Vickers indentation. The adhesion strength and impact fatigue performance of the coatings were evaluated by Rockwell indentation and dynamic impact fatigue device. Ball-on-disk wear test at room temperature and high temperature was conducted to evaluate the tribological properties of the deposited coatings. Finally, a field end milling test of SUS 304 stainless steel was conducted to investigate the tool performance by employing the TiVN coatings. Flank wear of the coated end mills and the surface roughness of the machined workpieces were measured.
The experimental result showed that monolayered TiVN-200V coating possessed the B1-NaCl structure and the fewest microparticles. It possessed the highest hardness (25.8GPa) and the best adhesion (class 0). Besides, the TiVN-200V coating showed good impact resistance (higher than 4×105 impacts). The residual stress of TiVN coatings increased as bias voltage increased. The best tribological performance of TiVN coatings is TiVN-200V. It possessed low friction coefficient (0.38) and low wear rate (7.5×10-7mm3/Nm). A field end milling test also showed TiVN-200V coating possessed the lowest flank wear (40.7µm) and the best surface roughness (Ra：0.5µm) of the machined workpieces. Finally, it can be concluded that vanadium incorporation provided self-lubricous abilities achieving low friction coefficient due to oxide formation at elevated temperatures.

並列關鍵字

TiVN ； Mechanical Properties ； End Milling Test ； Self-lubricous ； Oxide

參考文獻

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