Electrochemical Drilling of Inconel Superalloy with Acidified Sodium Chloride Electrolyte

The performance of modern air engine components such as turbine rotor and stator assemblies depends on a very large number of small holes, with diameters and aspect ratios in the range of 1–4 mm and 40–200, respectively. These high-temperature components are made of difficult-to-machine superalloys such as inconel. Shaped tube electrolytic machining (STEM) appears to be the preferred technique for drilling cooling holes in turbine blades. A review of the literature shows that the dynamics of STEM for deep hole drilling have not been sufficiently investigated. Guidelines for the selection of operating parameters such as voltage, electrolyte flowrate, and tool feedrate are not available. The objective of the present investigation has been to optimise the operating parameters of STEM such as voltage and tool feedrate using high-speed steel (HSS). The optimised parameters have then been used for drilling holes in inconel. Experiments show that good holes can be obtained by a combination of low voltage and comparatively high feedrate which results in low values of equilibrium inter-electrode gap. A good, uniform hole with an aspect ratio of 11 was obtained in inconel at voltage and tool feedrate of 17 V and 1.0 mm min

_1 , respectively. Results also point to the need for using dummy workpieces above and below the workpiece for obtaining uniform hole diameter, specifically at the ends.