A Study on Accuracy of Micro-Holes Drilled in Ti-6Al-4V Alloy by Using Electrical Discharge Machining Process

Abstract

Thermophysical properties of the Ti-6Al-4V titanium alloy make it difficult to process with electro discharge machining (EDM) process. The aim of this experimental work was to investigate manufacturing of micro-holes in titanium alloy by means of EDM . Further investigation the accuracy of drilled holes was performed in order to improve the EDM drilling method in this alloy. As a part of the research, the impact of four EDM process parameters on performance factors such as: material removal rate (MMR), linear tool wear (LTW) was verified in parallel to accuracy metrics of the micro-hole: radial overcut (ROC), cylindricity(CYL), recast layer thickness (RLT). The analysis of the obtained relationships showed that the properties of the Ti-6Al-4V alloy, such as low thermal conductivity, and low electrical conductivity significantly affect the EDM process efficiency. It is clearly visible through increased electrode wear, as well as the accuracy and quality reduction of the drilled holes. When analyzing the accuracy of the hollow micro-holes, it was observed that the highest current amplitude resulted in a smaller amount of microcracks in the layer around the hole entrance. The optimal process parameters to obtain a satisfactory geometry of micro-holes have been found such as: current amplitude 3.33 – 4.65 A, pulse time duration 550 – 1000 µs, open voltage 100 V, and tool rotation speed 300 rpm.

Keywords

• ti-6al-4v alloy
• micro-hole
• edm-drilling
• difficult-to-cut mateial