Development of carbide intermetallic layer by electric discharge alloying on AISI-D2 tool steel and its wear resistance

Electrical discharge alloying was performed on AISI-D2 steel using Ni-W powder mixed dielectric in order to improve the hardness and to reduce the specific wear rate. The alloyed layer was characterized using optical microscopy, scanning electron microscopy, X-ray diffraction analysis and energy-dispersive spectroscopy. Wear tests were conducted based on L9 orthogonal array in a pin-on-disc tribometer and the alloying parameters were optimized using Taguchi's technique. Hard intermetallics based on Fe7C3, Cr3C2 and Ni2W4C were formed by electric discharge alloying, which primarily contributed to the improvement in hardness up to 600 HV0.5. The specific wear rate of the alloyed layer was subsequently reduced by around a factor of eight compared to that of the base material. The pulse off-time was found to be predominant in obtaining higher hardness and lower specific wear rate among the alloying parameters, peak current, pulse on-time and off-time.