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.
Recently, airplane travel has become more affordable and thus more common. This has required engineers and scientists to spend thousands of hours on the development of new material and production technologies. High-pressure turbine (HPT) components are the most heavily loaded parts from the thermal, mechanical, and corrosion points of view. Therefore, both the material from which blades and vanes are cast as well as protective coatings are being constantly developed. Better material translates into longer and safer engine operation. Coatings maintain material structures within aggressive environments. However, despite the wide scope of development, there are areas that have not been investigated, one of which is electro-discharge drilling (EDD) machined cooling holes surface and its influence on environmental coating durability. In this paper, the EDD process impact on coating durability is shown. Process residuals, such as redeposited material and recast layers, result in coating inclusions. Oxidation testing also shows the relationship between the cooling hole diameter and coating durability.
Abstract. The thermophysical properties of the electrodes material significantly impact performance of the electrical discharge machining (EDM). The aim of this article was to investigate the influence of thermophysical properties of selected materials on the EDM process. The effect of the thermophysical properties of these materials on process efficiency factors (material removal rate, linear tool wear) and hole geometry (aspect ratio, radial overcut) was analyzed. The results showed that selected thermophysical properties of the workpiece, such as thermal conductivity, melting point, have the most significant impact on the electro-erosion process. Optimal result parameters (material removal rate: 2.58 mm3/min, linear tool wear: 4.95 mm, aspect ratio: 8.00, radial overcut: 0.046 mm) and no presence of “bottom cone” were obtained for EDM drilling in Inconel 718 and similarly for AISI 1045 steel. On the other end were high resistance alloys such as tungsten carbide and copper alloy.
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