ANALYSIS OF ERODED TI-6AL-4V SINGLE CRATERS AND SURFACES IN OIL BY ELECTRON MICROSCOPY AND OPTICAL EMISSON SPECTROSCOPY

Abstract

The comprehension of the metallurgical transformations of the workpiece can contribute with valuable data for simulation models and for a better understanding of surface creation in electrical discharge machining (EDM). This is necessary to improve the process in the scope of zero defect manufacturing. This work aims to investigate the influence of EDM on the often used but difficult to machine alloy Ti-6Al-4V. Single and multiple sparks in oil are performed and subsequently analyzed with advanced electron microscopy methods and optical high-speed emission spectroscopy. The microscopic analysis of recast layer and heat affected zones in addition to the plasma analyses provides deep insight into the process and contributes with new information about EDM. Results showed that, with the employed machining conditions, phase transformations occur at the surface of the material. Also, a superficial carbide layer was observed exclusively during multi sparks experiments. The performed analyses of metallurgical and topographic aspects of EDM describe its surface integrity, i.e., the condition of a surface generated by this manufacturing process. The emission spectroscopy analysis shows that the erosion plasma consists mostly of the dielectric elements with a high amount of hydrogen, which comes from the breaking of the dielectric hydro-carbon chains. This spectrum suggests the plasma takes part in the formation of the carbide layer.