Microstructure and Thermal Shock Properties of SiC Materials

doi:2011.25.3.28

J. Ocean Eng. Technol. > Volume 25(3); 2011 > Article

J. Ocean Eng. Technol. 2011;25(3):28-33.
DOI: https://doi.org/10.5574/KSOE.2011.25.3.028

Lee Sang-Pill,Cho Kyung-Seo,Lee Hyun-Uk,Son In-Soo,Lee Jin-Kyung

Department of Mechanical Engineering Dong-Eui University,Department of Mechanical Engineering graduate school of Dong-Eui University,Department of Mechanical Engineering graduate school of Dong-Eui University,Department of Mechanical Engineering Dong-

SiC 재료의 미세조직 및 열충격 특성

이상필,조경서,이현욱,손인수,이진경

동의대학교 기계공학과,동의대학교 일반대학원 기계공학과,동의대학교 일반대학원 기계공학과,동의대학교 기계공학과,동의대학교 기계공학과

Keywords: Flexural strength, Liquid phase sintering, Microstructure, SiC, Thermal shock property

핵심용어: 굽힘강도, 액상소결, 미세구조, 탄화규소, 열충격 특성

Abstract

The thermal shock properties of SiC materials were investigated for high temperature applications. In particular, the effect of thermal shock temperature on the flexural strength of SiC materials was evaluated, in conjunction with a detailed analysis of their microstructures. The efficiency of a nondestructive technique using ultrasonic waves was also examined for the characterization of SiC materials suffering from a cyclic thermal shock history. SiC materials were fabricated by a liquid phase sintering process (LPS) associated with hot pressing, using a commercial submicron SiC powder. In the materials, a complex mixture of $Al_2O_3$ and $Y_2O_3$ powders was used as a sintering additive for the densification of the microstructure. Both the microstructure and mechanical properties of the sintered SiC materials were investigated using SEM, XRD, and a three point bending test. The SiC materials had a high density of about 3.12 Mg/m3 and an excellent flexural strength of about 700 MPa, accompanying the creation of a secondary phase in the microstructure. The SiC materials exhibited a rapid propagation of cracks with an increase in the thermal shock temperature. The flexural strength of the SiC materials was greatly decreased at thermal shock temperatures higher than $700^{circ}C$, due to the creation of microcracks and their propagation. In addition, the SiC materials had a clear tendency for a variation in the attenuation coefficient in ultrasonic waves with an increase in thermal shock cycles.