氏名　Muttamara　Apiwat
学位の種類　博士（工学）
学位記番号　博甲第321号
学位授与の日付　平成16年9月30日
学位論文題目　Electrical Discharge Machining of Oxide Insulating Ceramics Using the Surface Modification Phenomena of Electrical Discharge　（放電表面改質現象を用いた絶縁性酸化物セラミックスの放電加工）
論文審査委員
　主査　教授　福澤　康
　副査　教授　大里　有生
　副査　助教授　田辺　郁男
　副査　長岡工業高等専門学校　高田　孝次
　副査　毛利　尚武

• 論文目次
• 論文要旨

［平成16（2004）年度博士論文題名一覧］ ［博士論文題名一覧］に戻る．

TABLE OF CONTENTS

Chapter1
introduction
1.1 Introduction　p.1
1.2 Purpose of this research　p.1
1.3 History of EDM　p.2
1.4 Background of Surface Discharge Modification Phenomena　p.2
1.5 EDM process for Al2O3 ceramics　p.5
1.6 Discharge waveform for insulating ceramics　p.6
1.7 Structure of the dissertation　p.7
　References　p.9

Chapter2
EDM ON POLYCRYSTALLINE AND MONOCRYSTALLINE OF ALUMINA CERAMICS MATERIALS
2.1 Introduction　p.11
2.2 EDM on polycrystalline Al2O3 ceramic materials　p.12
　2.2.1 Experimental procedure　p.12
　2.2.2 Results and Discussions　p.13
　2.2.2.1 EDM circuit for Al2O3 machining　p.13
　2.2.2.2 Machining properties of Al2O3　p.14
　2.2.2.3 Main factors of removal EDM process　p.19
　2.2.2.4 Machining of Aluminium nitrode　p.21
　2.2.2.5 Effects of physical properties to machining properties　p.23
　2.2.3 Machining properties of Al2O3 with pipe electrode　p.24
　2.2.3.1 Basic principle of pipe electrode　p.24
　2.2.3.2 Effect of pipe electrode on Al2O3　p.25
　2.2.3.3 Example of deep hole by pipe electrode　p.27
2.3 EDM on mono-crystalline alumina ceramic materials　p.32
　2.3.1 Machining of noble materials of ruby and sapphire　p.32
　2.3.2 Experimental procedure　p.35
　2.3.3 Results and Discussions　p.35
　2.3.3.1 Machining of noble materials for sapphire and ruby　p.35
　2.3.3.2 Effects of crystallographic planes to conductive layer generation　p.37
　2.3.3.3 Discharge waveform observation　p.39
　2.3.3.4 Effects of atomic density　p.41
　2.3.3.5 Cracks propagation in sapphires　p.42
　2.3.3.6 Fracture toughness of sapphires　p.42
　2.3.3.7 Effects of fracture toughness on EDM removal mechanism　p.45
2.4 Conclusions　p.47
　References　p.48

Chapter3
A NEW SURFACE MODIFICATION ON STEEL IN LIQUID NITORGEN
3.1 Introduction　p.51
　3.1.1 Background of the electrical discharge coationg（EDC）technology　p.53
3.2 Experimental procedure　p.54
3.3 Results and Discussions　p.56
　3.3.1 Effect of polarity of electrode　p.58
　3.3.2 Effect of electrode materials　p.61
　3.3.3 Machining conditions　p.61
　3.3.4 Characteristics of modified layer　p.64
　3.3.5 EDM on pure iron　p.67
　3.3.6 EDM on cast iron　p.68
　3.3.7 XRD analysis　p.71
　3.3.8 Adherence of modified layer analyzed by scratch tests　p.73
　3.3.9 Wear test for modifined layer　p.76
　3.3.10 Corrosion Properties　p.77
3.4 Surface modification in powder mixed liquid nitrogen　p.78
　3.4.1 Effects of Ti and TiN powder mixed liquid nitrogen　p.79
　3.4.2 Effects of discharge current　p.85
3.5 Conclusions　p.91
　References　p.92

Chapter4
Conclusions
4.1 Overall conclusions　p.95
4.2 Recommendation and future research　p.96

Acknowledgements　p.99
List of Author's Publications
　Jornal articles　p.101
　Conference proceedings　p.102

Appendixes
Micro EDM on Insulating Si3N4 Ceramics using a new assisting electrode
A1 Effect of a new assisting electrode material on Si3N4　p.103
A2 Characterisitcs comparison between EDM on steel and ceramic　p.105
A3 Effect of electrode diameter　p.107
A4 Effect of EDM conditions　p.108
A5 Effect of tool electrode materials　p.112
A6 Effect of workpiece material to electrode wear rate　p.114
A7 Effect of discharge waveform to machining properties　p.116
A8 Manufacturing of micro-electrodes（Φ{0.1mm）　p.118
A9 Effect of electrode polarity on micro-EDM　p.121
A10 Machining properties for S45C and Si3N4　p.122
A11 Effect of open circuit voltage　p.126
A12 Effect tool electrode materials　p.129
A13 Discharge waveform observation　p.132
A14 References　p.135

Recently, insulating materials such as Si3N4, SiC and ZrO2 have been succeeded to machine by EDM with the assisting electrode method （AEM） that was proposed by Y.Fukuzawa and N.Mohri. This method was considered that the surface modification phenomena simultaneously occur during machining process. The EDM characteristics vary with physical thermal properties of workpiece and electrode materials, machining conditions and atmosphere. However, some insulating materials such as insulating ceramics of Al2O3 were difficult to machine even if using this method. The formation mechanism of the electrical conductive layer on the Al2O3 surface is much different compared with that of other ceramics such as Si3N4 and ZrO2 etc. To achieve the machining of EDM for oxide insulating ceramics using the surface modification phenomena of electrical discharge, many experiments were carried out under the following terms with the view points of surface modified phenomena; （1） EDM for polycrystalline and mono-crystalline Al2O3 using a carbon baked layer as an assisting electrode material, and （2） Surface Fabrication of modified layer in liquid nitrogen. The experiments were carried out by the commercial EDM machine. The following results were obtained on each experiment.
（1） When discharges occur on a colloidal carbon baked layer, it is assumed that the dissolute carbon elements assist the adhesion phenomenon on the discharge surface. A carbon-baked layer was useful material as an assisting electrode for the machining of Al2O3 materials. Using the new assisting electrode, the high purity of Al2O3 ceramics materials were considered as the hard machining workpiece by EDM. So, some trials were carried out on polycrystalline Al2O3 with different purities, 92%, 99.5%, 99.99% and single crystal of sapphires. The better machining properties of the polycrystalline Al2O3 were obtained on the lower impurities materials that has small thermal conductivity value. The effects of crystalline orientation were investigated using 3 crystallographic sapphire planes. On the polycrystalline