東海大学紀要工学部 Vol.48, No.1, 2008, pp.137-142 ― 137 ― 真空加熱処理による Ti 添加 DLC 膜の密着力向上 神崎 昌郎 * Improvement of Adhesive Strength for Ti-doped DLC Films by Heat Treatment in Vacuum by Masao KOHZAKI * (Received on March 31, 2008 and accepted on July 9, 2008) Abstract Ti-doped DLC films have been prepared on silicon substrates by DC magnetron sputtering with C and Ti targets in Ar plasma. The amount of Ti in the film has been controlled with the input electric power to the Ti target from 0 to 200 W. The Ti concentration measured by X-ray photoelectron spectroscopy, increased up to 15 at.% at a Ti target power of 200 W. After the deposition, the DLC and the Ti-doped DLC films were heated at 500 ˚ C for 10 minutes in a vacuum of 1×10 -4 Pa. The frictional characteristics of the films were evaluated by using a ball on disk friction tester in an ambient atmosphere. Even after the heating, the DLC and the Ti-doped DLC films showed the good tribological performance with a low friction coefficient below 0.3 against a steel ball. The adhesive strength of the DLC film and the Ti-doped DLC films were measured by scratch tests with a loaded diamond stylus. The Ti-doped DLC films prepared at 250 ˚ C had almost constant values of the critical loads in the scratch tests irrespective of the Ti concentration. By the heat treatment in the vacuum, the adhesion of the Ti-doped DLC film with high Ti concentration was improved effectively and the critical loads of the films containing 15 at.% Ti increased from 180 mN to 400 mN. Furthermore, the critical loads of the Ti-doped DLC films increased with increasing the deposition temperature. The heat treated Ti-doped DLC films deposited at 350 ˚ C had the maximum critical load of 500 mN. The apparent increase in the critical loads will be caused by the chemical interaction between Ti and the substrate material. Keywords: DLC film, DC magnetron sputtering, Adhesion, Heat treatment 1.緒 言 現 在 ,機 械 シ ス テ ム に お い て 低 凝 着 性 ,低 摩 擦 特 性 ,高 耐 摩 耗 性 ,耐 熱 性 な ど を 材 料 に 付 与 す る こ と が出来る表面改質技術は必要不可欠なものとなっ ている.すでに TiN,TiC ,CrN,DLC ( Diamond Like Carbon )などのコーティング膜が摺動部や工具等に 幅広く使用されている 1) .特に DLC 膜は高硬度で 摩擦摩耗特性に優れ,表面が極めて平滑である等の 特徴を有しており,トライボロジー分野で大きな注 目を集めるとともに, DLC 膜を形成する技術が飛 躍的に発展している 2) .この DLC 膜を工具に適用 することで使用する潤滑油の量が少ない環境調和 型 切 削 が 可 能 と な り ,ま た ,摺 動 部 品 に 適 用 し た 場 合にはエネルギーロスを低減させることが可能に な る 等 ,近 年 関 心 が 集 ま っ て い る 低 燃 費 化 ,環 境 負 荷低減,省エネルギー等に大きく貢献している 3) . しかし, DLC 膜は一般的に密着力が低く,剥離し やすいことが課題となっている.そこで DLC 膜の 密着力を向上させることを目的として,膜と基板と の界面における中間層形成や DLC 膜中への W, Si , Ti 等の金属元素の添加という手法が試みられてい る 4) .特に Ti 元素の添加は DLC 膜の低摩擦特性を 保ったまま密着力を向上することが可能な手法で ある 5) .そこで,本研究では Ti 添加 DLC 膜の密着 力をさらに向上させるために, Ti 添加 DLC 膜に対 して真空加熱処理を行った.真空中で加熱すること により, Ti の酸化や C の気化を防ぎつつ,膜中の Ti と基板の結合強化や膜と基板界面における元素 拡散による中間層形成等の効果を発現させ,密着力 向上を目的とした. 2.実験方法 2.1 Ti 添加 DLC 膜の形成 DLC 膜および Ti 添加 DLC 膜の形成は DC 二元マ グネトロンスパッタリング法により行った. Fig.1 に DC 二元マグネトロンスパッタリング装置の外観 および使用したターゲットを, Fig.2 に Ti 添加 DLC 膜の形成の概略を示す.C ターゲット(三菱マテリ * 工学部機械工学科教授
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東海大学紀要工学部 Vol.48, No.1, 2008, pp.137-142
― 137 ―
真空加熱処理による Ti 添加 DLC 膜の密着力向上 神崎 昌郎*
Improvement of Adhesive Strength for Ti-doped DLC Films
by Heat Treatment in Vacuum
by
Masao KOHZAKI* (Received on March 31, 2008 and accepted on July 9, 2008)
Abstract
Ti-doped DLC films have been prepared on silicon substrates by DC magnetron sputtering with C and Ti targets in Ar plasma. The amount of Ti in the film has been controlled with the input electric power to the Ti target from 0 to 200 W. The Ti concentration measured by X-ray photoelectron spectroscopy, increased up to 15 at.% at a Ti target power of 200 W. After the deposition, the DLC and the Ti-doped DLC films were heated at 500 ˚C for 10 minutes in a vacuum of 1×10-4 Pa. The frictional characteristics of the films were evaluated by using a ball on disk friction tester in an ambient atmosphere. Even after the heating, the DLC and the Ti-doped DLC films showed the good tribological performance with a low friction coefficient below 0.3 against a steel ball. The adhesive strength of the DLC film and the Ti-doped DLC films were measured by scratch tests with a loaded diamond stylus. The Ti-doped DLC films prepared at 250 ˚C had almost constant values of the critical loads in the scratch tests irrespective of the Ti concentration. By the heat treatment in the vacuum, the adhesion of the Ti-doped DLC film with high Ti concentration was improved effectively and the critical loads of the films containing 15 at.% Ti increased from 180 mN to 400 mN. Furthermore, the critical loads of the Ti-doped DLC films increased with increasing the deposition temperature. The heat treated Ti-doped DLC films deposited at 350 ˚C had the maximum critical load of 500 mN. The apparent increase in the critical loads will be caused by the chemical interaction between Ti and the substrate material. Keywords: DLC film, DC magnetron sputtering, Adhesion, Heat treatment
1.緒 言
現在,機械システムにおいて低凝着性,低摩擦特
性,高耐摩耗性,耐熱性などを材料に付与すること
が出来る表面改質技術は必要不可欠なものとなっ
ている.すでに TiN,TiC,CrN,DLC(Diamond Like Carbon)などのコーティング膜が摺動部や工具等に