Coloring of titanium alloy by EDM (2nd report) - Analysis of coloring mechanism

摘要

In the previous report, we proposed a new coloring method for titanium alloy by Electrical Discharge Machining (EDM) in dielectric water and discussed the coloring mechanism for titanium alloy. The colored surface could be caused by an interference phenomenon in the anodic oxide film formed with electrolytic affection during EDM. In this study, further investigation of the coloring mechanism on the EDM surface was carried out by calculating the spectral reflectance of interference light based on the "multiple beam interference" theory. As a result, it was shown that the color of the EDM surface strongly resembled the interference color of spectral reflectance. It was therefore confirmed that the surface coloring by EDM was caused by an interference phenomenon in the anodic oxide film. Moreover, the oxide film thickness depended on the average working voltage.