Effect of h-BN Content on Microstructure and Mechanical Properties of Si<sub>3</sub>N<sub>4</sub>

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doi:2003.40.9.867

J. Korean Ceram. Soc. > Volume 40(9); 2003 > Article

Journal of the Korean Ceramic Society 2003;40(9): 867.
doi: https://doi.org/10.4191/kcers.2003.40.9.867

질화규소의 미세조직과 기계적 성질에 미치는 h-BN 첨가의 영향

김승현, 이영환, 조원승, 김준규¹, 조명우², 이은상², 이재형³

인하대학교 재료공학부
¹인하대학교 소재연구소
²인하대학교 기계공학부
³영남대학교 재료금속공학부

Effect of h-BN Content on Microstructure and Mechanical Properties of Si₃N₄

ABSTRACT

$Si_{3}N_{4}$-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.

Key words: Machinable ceramics, $Si_3$$N_4$, h-BN, Mechanical property, Machinability