Mechanical and Electrical Properties of Strong TiB₂-B₄C Ceramic System by Hot-Pressing

Abstract

TiB₂-B₄C ceramic composites containing no additives were hot-pressed from a mixture of TiB₂ and B₄C powders containing 0 up to 100mol% B₄C (20mol%). Hot-pressing was conducted at 1950°C for 3.6ks under a pressure of 31.2MPa in an Ar gas atmosphere. The mechanical and electrical properties were examined as a function of compositional change from TiB₂ to B₄C. TiB₂-B₄C composites containing 20-60mol% B₄C had a relative density of 97.4-98.9%, Vickers hardness of 23.8-27.2GPa, flexural strength of 589-705MPa, Young's modulus of 490-568GPa, fracture toughness (K_IC) of 6.46-8.05MPa·M^1/2. The mean surface roughness (R_a) was 25.6-30.5nm and the electrical conductivity 0.30-3.96MS·m^-1. Thus, these composites possessed a high electrical conductivity and a smooth surface. Their mechanical properties were 1.5 times higher than those of pure TiB₂ or B₄C ceramics, and comparable to those of SiAlON or hot-pressed Si₃N₄ ceramics. The present composites are suitable as ceramic mold materials, machinable by electric discharge, corrosion-resistant electrode components, tool materials and high-temperature structural materials.