Development of silicon nitride/silicon carbide composites for wood-cutting tools

Industrial wood-cutting inserts were produced from both Si3N4- and Si3N4-based ceramic matrix composites (CMC), subjected to industrial wood-cutting conditions and compared to tungsten carbide (WC). Relevant material properties for this particular application were collected and compared to the results obtained from the cutting tests. The results show that Si3N4/30 wt.% SiC gives the best balance between fracture toughness and wear. An yttria/lanthana sintering aid system allows the production of a very fine-grained microstructure without decreasing the fracture toughness. Post-hipping and crack-healing operations have been shown to be of paramount importance for the survivability of the cutting edges. An extrapolation from the lifetime prediction test gives a potential lifetime for the CMC material three times that obtained from the WC.