Experimental investigation of the EDM tools coated with nano-alumina film

Abstract

During electrical discharge machining (EDM) drilling of small high-aspect-ratio holes, abnormal discharges between tool flank and workpiece will result in high process instability and poor shape accuracy. In order to solve this problem, dense nano-alumina insulating film is plated on the tool flank based on atomic layer deposition (ALD) to suppress the secondary discharge for the benefit of the tool's integrity and shape accuracy. Drilling experiments on nickel base superalloy GH4099 workpiece were conducted to test machining effect of the coated brass tool. Experimental results show that it can enhance the process stability and improve the surface topography of the machined holes. The tool wear is reduced by about 21.7%, and the discharge craters and carbon black film along the tool flank are significantly reduced.