Electrical discharge machinable intra/inter type B4C composites with enhanced mechanical properties by two-step reactive spark plasma sintering

Intra/inter type super hard B4C-based composites were fabricated by two-step spark plasma sintering at 1600-1800 degrees C with ZrSi2, B4C and C additives under 40 MPa. The ZrSi2 transient liquid and in situ ternary (B4C-SiC-ZrB2) eutectic composition assisted the densification of the B4C matrix. The as-sintered composites had a unique microstructure of inter- and intra- SiC (ZrB2) secondary phases in the B4C matrix with strong bondings. The fully dense B4C-40 wt%(B4C-SiC-ZrB2) composite possessed a Vickers hardness, flexural strength and fracture toughness of 31.2 GPa, 542 MPa and 5.08 MPa<middle dot>m(0.5) respectively, owing to the strengthening and toughening effect of both the inter- and intra- particles. The inter- elongated ZrB2 phase also provided an enhanced electrical conductivity of 230.7 S/m. The composite was facilitated to wire electrical discharge machining with a material removal rate of 2.84 mm(3)/min, which is ten times that of the monolithic B4C ceramic.