Electrolytic machining system

Abstract

A workpiece consisting essentially of sintered tungsten carbide alloy having added thereto titanium carbide and/or tantalum carbide is electrolytically machined using an aqueous electrolyte solution consisting essentially of 5% to saturated value by weight of an alkali metal chloride selected from the group consisting of sodium chloride and potassium chloride, and an alkali metal compound selected from the group consisting of 3.6%-5.3% by weight of sodium hydroxide, up to 7.5% by weight of potassium hydroxide, up to 7.1% by weight of sodium carbonate, up to 9.2% by weight of potassium carbonate, up to 11.2% by weight of sodium bicarbonate, and up to 13.3% by weight of potassium bicarbonate. The workpiece is positioned opposite a machining electrode with a small machining gap therebetween and an alternating electric current is passed serially through the electrolyte solution in the machining gap, through the workpiece and through the machining electrode to render the workpiece anodic during part of the alternating current cycle so as to form oxides including water-insoluble tungsten oxide and titanium oxide and/or tantalum oxide on the workpiece surface and to render the workpiece cathodic during the reverse part of the alternating current cycle so as to cause the water-insoluble oxides to react with alkali metal ions in the electrolyte solution to form reaction products which are soluble in water to thereby dissolve the oxides and prevent oxide accumulation on the workpiece surface.