以電漿輔助化學氣相沈積法在超硬碳化鎢基材上鍍著類鑽碳膜與機械性質研究

Abstract

摘要 本研究利用化學輔助氣相沈積法(PECVD)在玻璃模造產業所使用的超硬碳化鎢模具上製備類鑽碳膜以探討薄膜鍍著於模具上之機械與磨潤性質的最佳化研究，並將實驗分為兩大部份。 第一部份是應用「L9(34)田口實驗」(L代表田口直交表，9代表實驗次數，4代表控制因子數，3代表水準數)在四個控制因子(Factor)，反應氣體源、反應溫度、基材偏壓、沈積時間，各選定三個水準(Level)進行實驗，其中反應氣體源有苯(Benzene, C6H6)、六甲基二矽氧烷(Hexamethyldisiloxane, HMDSO)、六甲基二矽氮烷(Hexamethyldisilazane, HMDSN)三種，利用田口實驗找出何者最適合沈積於超硬碳化鎢模具上當做中間層，並對表層的類鑽碳膜(Diamond-Like Carbon film, DLC film)進行機械與磨潤性質最佳化。由實驗結果顯示，苯(Benzene, C6H6)所沈積的薄膜之拉曼光譜最接近類鑽碳膜曲線，而且硬度值較高、摩擦係數最小，適合當類鑽碳膜的表層；而HMDSO所沈積的薄膜附著力為三者之中最佳，最適合當此種模具之中間層，並以硬度值望大、摩擦係數望小進行田口S/N比(signal to noise ratio)分析，獲得最佳化因子水準為：反應溫度250℃、基材偏壓-2000 V、沈積時間150 min，其中影響最大者為基材偏壓，由S/N比顯示朝著偏壓小的方向還可以再次進行優化得到DLC的最佳機械與磨潤性質。 故第二部份即以「HMDSO薄膜」當中間層，苯(Benzene，C6H6)沈積之類鑽碳膜當表層鍍著於超硬碳化鎢模具，並由上述L9(34)田口實驗的最佳化因子水準往偏壓小的方向對表層類鑽碳膜進行參數再優化，稱之為「類鑽碳膜偏壓優化實驗」。結果為基材偏壓於 -500 V時附著力最大為27±2 N，硬度值最高26.35±0.6 GPa，光學能隙值最高1.25 eV，表面粗糙度最小0.83 nm，摩擦係數(μ)為0.065，綜合判定具有最佳的機械與磨潤性質表現。 最後利用此最佳化參數分別在超硬碳化鎢與傳統碳化鎢模具上先鍍上中間層「HMDSO薄膜」，再鍍著DLC層，探討模具之機械性質對其實際成形壽命的影響，結果超硬碳化鎢模具之機械性質優於傳統碳化鎢，成形壽命最佳為330次優於傳統碳化鎢的252次。

Abstract In this study, Diamond-like carbon films prepared by plasma enhanced chemical vapor deposition(PECVD) on superhard tungsten carbides and we divided it into two parts to optimize DLC films of mechanical and tribological properties. First, we used L9 Taguchi Method then chose four control factors：precursor、reactive temperature、substrate bias、deposition time and three levels to carry out the experiment. And there were three kinds of precursors：benzene, hexamethyldisiloxane and hexamethyldisilazane in this part of experiment. According to the results, we have discovered that only the deposition films of benzene’s Raman spectra curve belongs to diamond-like carbon, and it has higher hardness values and lower friction coefficient, it’s suitable for diamond-like carbon layer. The other precursor that the deposition of hexamethyldisiloxane has the highest adhesion, it’s suitable for intermediate layer. In addition, we analyzed the signal to noise(S/N) ratio of hardness in larger the better (LTB) and friction coefficient in smaller the better (STB) then obtained the optimum parameter：reactive temperature at 250℃, substrate bias at -2000 V, deposition time at 150 minutes. Otherwise, the signal to noise ratio also indicated that we could try to toward the lower substrate bias and obtained better mechanical and tribological properties. Second, we deposited DLC films by benzene, intermediate layer by HMDSO precursors on superhard tungsten carbides and according to the L9 Taguchi Method we could try to toward the lower substrate bias to optimize parameters. We named it as「DLC experiment of bias optimization」. The results showed the best mechanical and tribological performance was at -500 V bias and had the largest adhesion 27±2 N, the maximum hardness 26.35±0.6 GPa, the maximum optical band gap 1.25 eV, the minimum roughness 0.83 nm and friction coefficient 0.065. Finally, we deposited intermediate layer by HMDSO precursors and DLC layer by benzene on superhard tungsten carbides and traditional tungsten carbides. To discusse the life time on superhard and traditional tungsten carbides. The results are superhard tungsten carbides’ mechanical properties is better than traditional tungsten carbides and its life time is 330 times higher than traditional tungsten carbides life time 252 times.