| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 94 === In this research, titanium alloy is machined by electric discharge machining (EDM) with different kinds of aqueous solutions addition in deioned water. During the EDM process, the oxygen is produced from the working fluid due to electrolysis phenomenon and then combined with Ti. As the result of this reaction, titanium oxide is generated on the surface of the workpiece. Besides, the machined zone shows different color tone, which can be influenced by the peak current, pulse duration, and duty factor.
The experimental results revealed that aqueous solutions addition can not only improve the surface roughness but also affect the color tone. The workpiece machined in deioned water or hydrogen peroxide solution has evident color which changes with the peak current under the pulse duration 1μs. The color tone turn red to yellow when the peak current is increased from 1A to 8A. However, if the pulse duration is enlarged, color become muddy even in the case of small peak current. On the contrary, when using sodium bicarbonate or sodium hydroxide solution as working fluid, the color tone of the workpiece shows muddy without any color tone until 1000μs.
By mean of this novel method, the surface coloring treatment could be carried out during the machining process, therefore the efficiency of procedure would be enhanced greatly.
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