Micro-hardness evaluation for surface alloying of H11 die steel with Cu-Cr-Ni powder metallurgy tool in electrical discharge machining

摘要

Electrical discharge machining is a non-conventional material removal process; recently, efforts have been made to use it as a surface alloying/modifying method. This study investigates and compares the micro-hardness of the surface machined by electrical discharge machining process using composite tool electrode (copper-chromium-nickel) manufactured by powder metallurgy and conventional copper tool. Design of experiment is used to find the best level of process parameters in order to achieve high micro-hardness. The machined surfaces are subsequently analyzed using different techniques like scanning electron microscopy, X-ray diffraction and energy-dispersive spectroscopy to ascertain the surface characteristics. Results indicate that the micro-hardness of the alloyed surface formed by powder metallurgy tool electrode is improved by 96.3% as compared to base material and 65.7% as compared to the surface machined by conventional copper electrode. Energy-dispersive spectroscopy of the surface machined using powder metallurgy electrode confirms significant material migration from tool and dielectric to the machined surface. The X-ray diffraction shows the formation of cementite (Fe3C), intermetallic compound of iron, chromium and nickel (FeCrNi) and chromium carbide (Cr7C3) on the surface machined using powder metallurgy electrode.