MACROSCOPIC ASSESSMENT OF HIGH PRESSURE FAILURE OF B_4C AND B_4C/SiC COMPOSITES

摘要

Advanced ceramic materials, such as SiC and B_4C, have long been used in applications that take advantage of their very high hardness, low density, and chemical stability. Example uses are armor, grit blast nozzles, and wear resistant components in mining. In general, B_4C out performs SiC in these applications due to its higher hardness and lower density. However, in cases where the ceramic component is exposed to extremely high pressure (> 20 GPa), the performance of B_4C falls below that of SiC. The present work aims to examine this behavior at the macro-scale using impact testing. First, a series of impact tests were performed on identical samples of B_4C and SiC tiles. Testing over a range of pressures showed a cross-over in performance at nominally 20 GPa. Second, B_4C/SiC composites with a range of B_4C to SiC ratios were fabricated and tested above and below the 20 GPa threshold. Below 20 GPa, the higher B_4C content composites performed best, whereas above 20 GPa, the higher SiC content composites performed best.