Nitriding of the Ti-6Al-4V alloy using electrical discharge machining with addition of SiC abrasive powder in the dielectric fluid

ABSTRACT The nitriding process using Electric Discharge Machining is a method that associates the ability to process complex surfaces with the obtaining of thermochemical treatment of nitriding. The titanium alloy Ti-6Al-4V has a wide applicability in the market, mainly because it presents excellent mechanical properties like high tensile strength, corrosion as well as low density. However, the alloy does not have good resistance to sliding wear, which prevents it from being applied as a raw material for parts subject to these conditions. Therefore, electrical discharge nitriding can significantly improve the slip wear resistance of the titanium alloy. The equipment used in this research was a conventional sink EDM machine. Adequations in the machine were necessary so that the dielectric fluid used did not contaminate the mineral oil, original equipment fluid. The graphite electrode was used as a tool electrode. SiC silicon carbide abrasive powder of 600 mesh granulometry was added to the aqueous solution formed by deionized water and urea, used as dielectric fluid. The samples were characterized by optical microscopy, X-ray diffraction (XRD), SEM, Vickers microhardness test and surface roughness measurements. The results obtained showed the formation of superficial layers enriched by electrolytic plasma with nitrogen, forming the ceramic compound TiN of high hardness. This layer has an average thickness of 104µm and its formation is present on every surface of the sample. It was observed an increase of the surface hardness in relation to the base material around 52% and a reduction of the roughness around 31% when compared to the nitriding process by electric discharges, without addition of the abrasive powder.