Mechanical properties and electrical discharge machinability of SPS sintered Y-TZP- and YGd-TZP-titanium nitride composites

Electrical discharge machining (EDM) of ceramics provides an opportunity to manufacture complex shape components from sintered blanks provided the material has a sufficiently high electrical conductivity. In this study yttria and yttria-gadolinia co-stabilized zirconia powders (Y-TZP, YGd-TZP) were produced by intensive co -milling. Fully dense composite ceramics with TZP matrix and 28-32 vol% titanium nitride dispersion were manufactured by spark plasma sintering and subsequently ED-machined by die sinking in oil based dielectric. The materials offer high strength of 1200-1450 MPa coupled with an attractive fracture resistance of 7-7.8 MPa root m. The ceramics exhibit a high electric conductivity of 21-74 kS/m with the highest values observed for the co-stabilized matrix and the higher TiN content. ED machining can be carried out at high machining rates of >1 mm(3)/min. The dominant material removal mechanism is melting. ED-machining leaves only a very thin glass-like process zone at the surface, the bulk material stays widely unaffected.