Influence of sintering and sintering additives on the mechanical and microstructural characteristics of Si sub(3)N sub(4)/SiC wood cutting tools

Si sub(3)N sub(4)/SiC cutting tools were fabricated by industrial near net shape fabrication processes. The samples were consolidated by gas-pressure sintering and pressure less sintering using three different additive systems. The mechanical and microstructural properties were compared to composites made by hot pressing. The composites fabricated by gas-pressure sintering showed 99% density, the Vickers hardness was 17.2 GPa and the fracture toughness reached 4.5 MPa[sqrt]m. Machining trials on wood showed that a post-sintering treatment by hot isostatic pressing increases the integrity of the cutting tip due to a devitrification of the intergranular phase.