Surface integrity, fatigue performance and dry sliding wear behaviour of Si3N4-TiN after wire-electro discharge machining

Silicon nitride-titanium nitride (Si3N4-TiN) ceramic composite was machined by wire-electro discharge machining (WEDM) to characterize the surface integrity and to investigate its effect on fatigue performance. Dry sliding wear behaviour of Si3N4-TiN sliding against EN32 steel was also tested. The polished and machined surfaces were examined for finding the hardness. The wire-EDM cut surface was examined with scanning electron microscope (SEM) for obtaining its microstructure. The wire-EDM of silicon nitride-titanium nitride produced a rough recast surface with different types of defects like micro-cracks, micro-pores, globules, droplets and surface craters. The material deposition to work specimen after machining was scrutinized by EDAX composition analyzer. The polished surface and wire-EDM cut surface were examined for determining the fatigue performance and it was observed that a deficiency of 25-35% in fatigue life in wire-EDM cut surface than that of the polished surface. Also, the wire-EDM cut surface exerts very high tensile residual stress compared to the polished surface. From the results, it is evident that the polished surface exhibits better surface finish and fatigue life, higher wear resistance and micro-hardness than that of the machined surface.