Pressureless sintering of ZrC-based ceramics by enhancing powder sinterability

The sinterability of ZrC was enhanced by high-energy ball milling as well as introduction of graphite and SiC as sintering additives. Densification process and microstructure development were investigated for ZrC-based ceramics densified by pressureless sintering. As-received ZrC powder showed poor sinterability. After high-energy ball milling. ZrC powder can be sintered to 98.4% theoretical density at 2100 degrees C. The obtained ceramic had fine microstructure and fewer entrapped pores. Introduction of 2 wt.% graphite combined with high-energy ball milling lowered the densification temperature of ZrC. The relative density of obtained ceramic reached up to 95% at 1900 degrees C. Introduced SiC inhibited ZrC grain growth during sintering and consequently avoided the entrapped pores within the grains. The relative density of ZrC-SiC reached up to 96.7% at 2100 degrees C. ZrC-SiC composite formed an interesting intragranular structure and had high fracture strength at room temperature. (C) 2011 Elsevier Ltd. All rights reserved.