介層對鑽石膜刀具機械性質改善之研究

Abstract

本實驗利用微波電漿化學氣相沈積法，以甲烷和氫氣做為反應氣體， 使用燒結碳化鎢WC-Co(3~5% Co)刀具為底材，加入不同材質的中間介層， 採用兩階段沉積法蒸鍍鑽石膜，探討中間層對鑽石膜的成長、殘留應力及 附著性的影響。使用SEM、XRD、Raman、EDS及AES分析及鑑定鑽石膜的特 性；殘留應力以Raman 偏移法及X-Ray的LIBAD法量測；並採用Rockwell壓 痕實驗來評估附著性。 實驗結果顯示，以Ni、Ni-Si為介層時對鑽石的孕核造成阻礙，原因應該 是Ni對碳的合金效應溶解大量的碳，及Ni使鑽石轉變為石墨的催化作用； 以非晶質Si為介層時，Si不易附著於WC-Co底材上，經過950℃熱處理後， 則有助於改善與底材的附著性，並間接提高鑽石成核密度。 採用Ti- Si中間層處理可大大地增進鑽石的孕核，Si可增加鑽石的孕核密度，Ti則 可以產生很好的鍵結力量。實驗中改變Ti的厚度量測對殘留應力的影響， 由Rmana偏移法求得Ti-Si介層處理過的鑽石膜之應力，在Ti厚度為1000 ~35000( 範圍內約為 -2.660~-3.070 GPa，比只經過去鈷處理但無中間層 處理的鑽石膜殘留髭N□-4.487 GPa減小了許多，充分發揮了應力緩衝層 的作用。附著性方面，無中間層處理之鑽石膜的dP/dx值為78.3 Kgf/mm， 有Ti-Si中間層處理的鑽石膜則提昇至 119.4 ~ 262.3 Kgf/mm，實驗結果 並顯示Ti厚度在某一範圍內，有最大的dP/dx值，顯示具有最佳的附著性 。 利用Ti-Si介層配合二次鑽石沉積的"鑽石顆粒型複合鍍層"，第一 次沉積的鑽石顆粒作為晶種及強化材之用，Ti金屬層填充顆粒間及底材與 顆粒間的空隙，緊緊抓住鑽石顆粒，扮演金屬黏結劑(Metal Binder)的角 色，附著性dP/dx值明顯地提高至268.2 ~ 1073.1 Kgf/mm。 本實驗 並對鍍膜前的中間層施加熱處理，使介層間及介層與底材彼此產生鍵結， 明顯地改善了附著性。這與使用EDS、AES分析破裂介面時，發現Ti原子和 碳及碳化鎢底材相互作用形成TiC的結果是一致的，這種強鍵結因而強化 了鑽石膜的附著性。 Diamond films were deposited on the sintered WC-Co (3~5%Co) substrates by means of microwave plasma chemical vapor deposition (MPCVD) method, using a mixture of CH4/H2 as the reactant gases. The WC-Co subtrates were precoated with various interlayer materials before diamond deposition. Effects of interlayers on growth, residual stress and adhesion of diamond films were investigated. The films and interlayers were characterized by SEM, XRD, RAMAN, EDS and AES. The residual stress was estimated by Raman shifand X-ray diffraction (LIBAD) methods. The Rockwell indentation tests were used to evaluate the adhesion property of diamond films. For Ni and Ni-Si interlayers , the results indicate that they are detrimental to diamond nucleation due to alloying effect of Ni with C and catalytic effect of Ni on graphite formation. For armorphous Si interlayers, it is revealed that the bonding between Si and WC-Co substrate is poor. But after heat treatment at 950℃ before diamond deposition, the bonding of Si and the nucleation density of diamond crystals are increased. In terms of diamond nucleation and growth, the Ti-Si interlayers show a great increase in nucleation density and diamond quality. The Si interlayer acts to increase the diamond nucleation and the Ti interlayer acts to form strong bonding. Also there are no significant differences in films morphologies for Ti thickness between 1000~35000 (. By comparing the effect of interlayer on residual stress of the films, it is compressive in nature, and from -4.49 to -4.14 GPa for the substrates without interlayer, anfrom -3.07 to -2.66 GPa for the substrates with Ti-Si interlayer. The results also show that there exists a range of Ti thickness for a minimum stress. As for adhesion of the films, the values of the adhesion index, dP/dx are ranging from 119.4 to 262.3 Kgf/mm for the substrates with Ti-Si interlayers, and are about 78.3 Kgf/mm for the substrates without interlayer. The results also reveal that there exists a range of Ti thickness for a best adhesion of the films. As for the deposition process, the dual diamond deposition processes matching with Ti-Si interlayer application are found to have a tremendous improvement in adhesion of the films. The values of dP/dx are ranging from 268.2 to 1073.1 Kgf/mm. At a Ti thickness of 28000( and area coverage of diamond crystals after the first diamond deposition process of 50~60%, it has the greatest adhesion. The results indicate that an improvement in adhesion in this case may be due to the facts that Ti metal is a good bindefor diamond, and also result in a great decrease in voids at the interface. Effects of heat treatments of the interlayers before diamond deposition on ad Adhesion of diamond films were also investigated. The results show a significiant improvement in bonding. This is in agreement with the results of interface analysis that Ti atoms react with C in both WC and diamond to form a strong bonding of TiC.