• Journal of the Korean Ceramic Society
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• v.40 no.9
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• pp.867-873
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• 2003

$Si_{3}N_{4}$-BN based machinable ceramics were fabricated by hot-pressing at $1800^{\circ}C$ for 2 h under a pressure of 25 MPa. The microstructure, mechanical properties, and machinability were investigated. With increasing h-BN content from 5 vol% to 30 vol%, three point flexural strength decreased from 1000 MPa of monolithic S $i_3$ $N_4$ to 720～400 MPa. The fracture toughness, $K_{IC}$ , was decreased from 7.6 MPaㆍ$m^{1/2}$ of monolithic S $i_3$ $N_4$ to 6.5～4.1 MPaㆍ$m^{1/2}$. The grain size and aspect ratio of $\beta$-S $i_3$ $N_4$ slightly decreased with increasing h-BN content. S $i_3$ $N_4$ monolith could not be machined due to brittle fracture, but S $i_3$ $N_4$-BN based machinable ceramics could be machined without fracture, showing excellent machinability. With increasing h-BN content, the thurst force during cutting and micro-drilling process was decreased.