SURFACE MODIFICATION OF TITANIUM NITRIDE ON TOOL STEEL BY ELECTRICAL DISCHARGE MACHINING IN UREA SOLUTION

The recast layer of surface modification is studied by electrical discharge machining (EDM) on tool steel. An experiment is carried out using a titanium electrode grade 1 and dielectric media of urea solution, containing nitrogen element. The morphology, microstructure, element composition and compound of recast layer are characterized by scanning electron microscopy, electron dispersion spectroscopy and X-ray diffraction. It is composed of dark grey and light grey layer. Titanium nitride (TiN) layer is formed on dark grey layer, while light grey layer is composed of titanium, chromium, iron and carbon elements. The results reveal t thickness of recast layer is composed of 15 - 25- layer thickness are studied for relationship, including average surface roughness and EDM current. The microhardness of recast layer and substrate are also investigated and compared.