本研究使用自行發明的封閉式表面放電被覆裝置與自製的工具電極以及CNC放電加工機，在SKD 11工具鋼的工件表面上被覆WC/Co/Fe的硬質層。工具電極是由銅棒與半燒結之壓粉體電極組合而成。壓粉體棒材的製作程序是將WC/Co粉末與Fe粉末以8：1，4：1，2：1及1：1等四種重量比例分別均勻混合之後，在不同的擠壓壓力(50 ~ 200 MPa)以及燒結溫度(300 ~ 900 ℃)製作成為直徑8 mm、長度約18 mm之圓柱體。放電加工的條件是放電電流1 ~ 12 A，脈衝放電時間25 ~ 500μs，衝擊係數50 %。以壓粉體棒材為陰極，工件為陽極，在煤油中進行放電被覆實驗。主要的實驗結果如下。
壓粉體電極的最佳製作條件以WC/Co粉末與Fe粉末的混合比例1：1、擠壓壓力200MPa及燒結溫度900℃的條件所製作的壓粉體電極之電阻率最小。使用最佳製作條件下之壓粉體電極，在最佳的放電加工條件，亦即脈衝放電時間 τon = 50 μs、脈衝休止時間τoff = 50 μs、放電電流8A以及放電加工時間1.5分鐘的條件下，面積覆蓋率即達100 ％。
工件表面被覆層之硬度隨放電加工時間的增加而增加。尤其是被覆層之硬度於放電加工時間1.5分鐘以上時更加顯著增至Hv1500。其硬度相當於一般WC/Co粉體本身的硬度，因此有最佳的耐磨耗性。在表面下約48 μm以內的硬度遠高於工件的SKD 11工具鋼基材。尤其是在表面下約30 μm以內的硬度可達Hv1200。表面被覆層的厚度隨放電時間的增加而呈線性增加。但被覆層的厚度的極限值為30 μm，其所需的放電時間約5分鐘以內。

This paper aims to create a hard modification layer of WC/Co/Fe on the surface of SKD11 work steel by using a new closed-type method of surface electrical discharge coating with the self-made tool electrode and CNC electrical discharge machine. The tool electrode is the composition of a semi-sintered powder compacted electrode and a cooper rod. The sintered powder compacted electrode making process is first to mix the WC/Co and Fe powders uniformly at 8:1, 4:1, 2:1 and 1:1 in weight ratio. Continually, it will form the cylinder of 8mm in diameter and 18mm in length approximately by compacting in different pressure (50~200 MPa) and sintering temperature (300~900 ℃). The EDM condition is 1~12A discharge current, 25~500μs pulse time, and 50% duty factor. The electrical discharge machining is proceeding in kerosene with tool electrode as cathode and workpiece as anode. The result is as following.
It can be concluded that the best condition to fabricate the sintered powder compacted electrode is 1:1 in weight ratio between WC/Co and Fe powders; with 200Mpa compacting pressure and sintering temperature at 900℃, which results in lowest electrical resistivity. Under such condition, the area covered ratio can reach 100% at best EDM condition, which is pulse time τon = 50 μs, rest time τoff = 50 μs, 8A in current and 1.5 min in machining time.
The surface hardness of workpiece increases with machining time. The surface hardness dramatically increases to Hv1500 as machining time over 1.5 min. The hardness of modification layer equals to the WC/Co particle itself which brings to the best wear ability. Moreover, the hardness of under surface in between 48 μm is much higher than it of the SKD11 work steel. The hardness in between 30 μm can reach up to Hv1200 in particular. The hardness of surface modification layer increases linearly with machining time. However, the limit of surface modification layer is about 30 μm, and the needed time is below 5 min.

總目錄
論文審定書 I
誌謝 II
中文摘要 III
英文摘要 IV
總目錄 V
圖次 VII
表次 XII
符號說明 XIII

第一章 緒論 1
1-1 研究動機 1
1-2 文獻回顧 3
1-2-1 放電加工之起源 3
1-2-2 混合粉末放電加工法 4
1-2-3 混合粉末放電被覆法 8
1-2-4 壓粉體電極放電被覆法 12
1-3 研究目的 19

第二章 基本理論 20
2-1 放電現象之基本理論 20
2-2 放電加工之基本理論 22
2-3 放電加工之材料移除機制 23
2-4 放電加工之變質層特徵 26
2-5 放電加工之參數設定 27

第三章 實驗設備與實驗方法 32
3-1 實驗設備 32
3-1-1 CNC放電加工機 32
3-1-2封閉式表面放電被覆裝置 32
3-1-3量測設備 37
3-2 實驗方法 38
3-2-1 實驗材料 38
3-2-2 試片前處理 42
3-2-3 實驗條件設定 43
3-2-4 實驗步驟 44

第四章 結果與討論 46
4-1 工件表面被覆硬質層的預備實驗結果 46
4-2 壓粉體棒材的電阻率 48
4-3 脈衝放電時間與加工時間對被覆層面積覆蓋率的影響 50
4-4 放電電流與脈衝放電時間對被覆層面積覆蓋率的影響 70
4-5 工件表面之被覆層硬度 87
4-6 工件表面之被覆層厚度 90

第五章 結論 91

參考文獻 93

參考文獻

1. Kunieda M., Lauwers B., Rajurkar K. P., Schumacher B. M., “Advancing EDM through fundamental insight into the process”, CIRP Annals - Manufacturing Technology, 54 (2005), p64 – 87.
2. 邱源成、李榮宗、蕭惟隆，「表面放電被覆裝置」，中華民國發明專利 I335849 號 (2011/01/11 – 2027/12/03)。
3. 倉藤尚雄、鳳誠三郎 原著，鄒大鈞 譯，「放電加工」，復漢出版社，1998。
4. Jeswani M. L., “Effect of the addition of graphite powder to kerosene used as the dielectric fluid in electrical discharge machining”, Wear, 70 (1981), p133-139.
5. Quan Y. M., Liu Y. H., “Powder-suspension dielectric fluid for EDM”, Journal of Materials Processing Technology, 52 (1995), p44 – 54.
6. Uno Y., Okada A., “Surface generation mechanism in electrical discharge machining with silicon powder mixed fluid”, International Journal of Electrical Machining, 2 (1997), p13 – 18.
7. Chow H. M., Yan B. H., Huang F. Y., Hung J. C., “Study of added powder in kerosene for the micro-slit machining of titanium alloy using electro-discharge machining”, Journal of Materials Processing Technology, 101 (2000), p95 – 103.
8. Tzeng Y. F., Lee C. Y., “Effects of powder characteristics on electro discharge machining efficiency”, The International Journal of Advanced Manufacturing Technology, 17 (2001), p586 – 592.
9. 斎藤長男、毛利尚武、大竹広定、吉田敏之，「放電加工による表面処理」，精密工学春季大会学術講演会論文集，G34 (1988)，p560 – 561。
10. Okada A., Uno Y., Hirao K., Takagi T., “Formation of hard layer by EDM with carbon powder mixed fluid using titanium electrode”, Proceedings of 5th International Conference on Progress of Machining Technology (2000), p464 – 469.
11. 林炎成，「放電加工表面改質與精修效果之研究」，國立中央大學機械工程學系博士論文 (2001)。
12. Furutani K., Shiraki K., “Deposition of lubricant layer during finishing process by electrical discharge machining with molybdenum disulphide powder suspended in working fluid”, JSME/ASME International Conference on Materials and Processing (2002), p468 – 473.
13. 劉彥孝，「以創新的放電被覆法對鋼表面改質效果之研究」，國立中山大學機械與機電工程學系碩士論文 (2008)。
14. 馬嘉南，「封閉式放電被覆法之操作條件對鋼表面改質之影響」，國立中山大學機械與機電工程學系碩士論文 (2009)。
15. Crookall J. R., Khor B. C., “Electro discharge machined surface”, Proceeding of 15th International Machine Tool Design and Research Conference (1974), p373 – 383.
16. Gangadhar A., Shunmugam M. S., Philip P. K., “Surface modification in electrodischarge processing with a powder compact tool electrode”, Wear, 143 (1991), p45 – 55.
17. Shunmugam M. S., Philip P. K., “Improvement of wear resistance by EDM with tungsten carbide P/M electrode”, Wear (1994), 171 p1 – 5.
18. 斎藤長男、毛利尚武、高鷲民生、古谷政典 合著，「放電加工技術」，日刊工業新聞社出版 （1997），p198。
19. Wang Z. L., Fang Y., Wu P.N., Zhao W.S., Cheng K., “Surface modification process by electrical discharge machining with a Ti powder green compact electrode”, Journal of Materials Processing Technology, 129 (2002), p139 – 142.
20. Simao J., Aspinwall D., El-Menshawy F., Meadows K., “Surface alloying using PM composite electrode materials when electrical discharge texturing hardened AISI D2”, Journal of Materials Processing Technology, 127 (2002) p211 – 216.
21. Fukuzawa Y., Kojima Y., Tani T., Sekiguti E., Mohri N., “Fabrication of surface modification layer on stainless steel by electrical discharge machining”, Materials and Manufacturing Process, 10 (1995), p195 – 203.
22. Mohri N., Fukusima Y., Fukuzawa Y., Tani T., Saito N., “Layer generation process on work-piece in electrical discharge machining”, CIRP Annuals-Manufacturing Technology, 52 (2003), p157 – 160.
23. Matsukawa K., Satoh K., Goto A., Saito N., Mohri N., “Wear properties of surface modified hard layers using electrical discharge machine”, Journal of Advanced Mechanical Design, Systems, and Manufacturing, 2 (2008), p629 – 639.
24. Erden A., Arinc F., Kogmen M., “Comparison of mathematical models for electric discharge machining”, Journal of Materials Processing and Manufacturing Science, 4 (1995), p163 – 175.
25. Petrofes N. F., Gadalla A. M., “Processing aspects of shaping advanced materials by electrical discharge machining”, Materials and Manufacturing Processes, 3 (1988), p127 – 157.
26. Kobayashi K., Magara T., Ozaki Y., Yatomi T., “The present and future developments of electrical discharge machining”, Proceedings of 2nd International Conference on Die and Mould Technology (1992), p35 – 47.
27. Simao J., Lee H. G., Aspinwall D. K., Dewes R.C., Aspinwall E.M., ”Workpiece surface modification using electrical discharge machining ”, International Journal of Machine Tools & Manufacture, 43 (2003), p121 – 128.
28. Moro T., Mohri N., Otsubo H., Goto A., Saito N., “Study on the surface modification system with electrical discharge machine in the practical usage”, Journal of Materials Processing Technology, 149 (2004), p 65 – 70
29. 于劍平，「放電加工表面特性之研究」，國立成功大學機械工程學系博士論文 （2002）。
30. 陳世昌，「對工具鋼放電加工面之改善效果」，國立中央大學機械工程學系碩士論文（2003）。