Microstructural Coarsening During Sintering of Boron Carbide

Abstract

The sintering behavior of boron carbide was investigated with particular attention given to microstructure development at various stages in the sintering process. Hot‐pressing and pressureless sintering techniques were employed and the effects of heating rate, firing atmosphere, and composition were used to characterize the sintering behavior. Pressureless sintering at temperatures up to 2300°C produces only limited densification. Microstructural coarsening is responsible for this since it leads to conditions where densification is slow. Hot‐pressing and carbon additions suppressed coarsening and permitted densification to >95% of theoretical density.

Mechanical Properties of Injection Molded B4C–C Ceramics

“…In general, the final density increases with increasing sintering temperature and is hardly affected by the amount of free carbon. This observation agrees well with the results of Dole and Prochazka (10,11) who found that the density of B C becomes independent of the carbon addition above &4 wt% C. As shown in Fig. 3, post-densification by HIP to 100% of the theoretical density was possible with 2150 and 2175°C sintered materials having a sintered density *96% TD.…”

“…The role of carbon as a sintering aid in solid state sintering of B C is therefore twofold. First, during the early sintering stage, amorphous carbon inhibits coarsening, brought about by surface-to-surface matter transport (2), e.g., by suppressing vapor-phase transport via deoxidation (11).…”

Pressureless sintering of boron carbide ceramics

“…10) Several previous studies have used reducing agents such as C 3),4) or He-H2 11) to react with and remove oxide impurities from the surface of boron carbide powder. According to the thermodynamic data, 12) Al gas is a reducing agent for boron oxide on B4C starting powder superior to carbon and/or He-H2.…”

Processing and Mechanical Properties of Boron Carbide–Titanium Diboride Ceramic Matrix Composites

“…Significant improvement in sinterability was observed when a small amount of carbon was added before hot pressing [1][2][3][4][5][6][7][8][9][10][11][12]. Other additives such as Al, Fe, Ti, B and SiC have also been used, with various degrees of improvement in sintering behavior and mechanical properties.…”