Effect of Repeated Thermal Shock on Mechanical Properties of ZrB2-SiC-BN Ceramic Composites

Gang Li,Hongbo Chen

doi:10.1155/2014/419386

Abstract

ZrB2-20 vol.% SiC-10 vol.% h-BN (particles) ceramic composites (ZSB) were fabricated by hot pressing under inert gas protected. ZSB samples with mean size 75 × 55 × 40 mm3 were heated using current heating method and then cooled down to low temperature by circulating water. ZSB samples repeatedly went through thermal shock with 10–50 times under various conditions, respectively. Diverse effects on residual strength of ZSB at different experiment conditions (temperatures, thermal shock times, and heating rates) were investigated. The test results indicated that the residual strength of specimen materials all reached the maximum while the temperature was 1600°C and thermal shock number was less than 50 times. Because ZSB samples could not stand the extremely serious hyperoxidation at very high temperature (1800°C), the residual strength of samples decreased sharply. At 1600°C, when the thermal shock times was 20, ZSB samples' residual strength reached the maximum, but it decreased to the lowest point while the thermal shock times was 30. So we argued that the sensitive thermal shock number was 30. Finally, we analyzed the influences on samples residual strength generated by different heating rates at the same temperature and thermal shock number; the results showed that when heating rate was equal to cooling rate, the residual strength of specimen materials reached the maximum.

Highlights

Zirconium diboride (ZrB2) ceramic matrix composites are attractive candidates for hypersonic vehicles’ structure members
We analyzed the influences on samples residual strength generated by different heating rates at the same temperature and thermal shock number; the results showed that when heating rate was equal to cooling rate, the residual strength of specimen materials reached the maximum
ZSB sample materials were subjected to thermal shock several times (10 times, 20 times, 30 times, 40 times, and 50 times) by current heating, respectively at four different temperature points (1200∘C, 1400∘C, 1600∘C, and 1800∘C), testing the residual strengths of sample materials and observing the changes of sample materials surface morphology and cross-section morphology before and after the thermal shock

Summary

Introduction

Zirconium diboride (ZrB2) ceramic matrix composites are attractive candidates for hypersonic vehicles’ structure members In application process, they have to support the high temperature difference or the thermal shock due to the highheat flow produced in reentry and flight, for during the highspeed flight course, the aircraft will have friction with the air and produce the transient state high temperature and highheat flow [1,2,3,4]. ZrB2-SiC-BN composites’ residual strength after thermal shock was tested under rapid heating conditions, testing the influences on the thermal shock resistance of sample materials at diverse temperature difference, heating rates, and cycle index, analyzing the reason of material failure and investigating the thermal shock resistance mechanism of ZrB2-SiC-BN ceramic composites

Experimental

Results and Discussion

Conclusions