Fabrication and Mechanical Properties of Hot-Pressed TiB₂-TiN_xC_y High-Strength Composite by the Solid Phase Reaction of TiN with B₄C Powder

Abstract

TiB₂-TiN_xC_y composite ceramics with high density, mechanical strength and electrical conductivity were prepared by the hot-pressing method with the solid phase reaction of TiN with B₄C powder. The TiN powder containing 0-20 mass%B₄C-additives was hot-pressed at 1950°C for 3.6ks under a pressure of 31.2MPa in ambient Ar gas. The 42.9 mass%TiB₂-TiN_xC_y composite derived by the addition of 16 mass%B₄C to TiN had a relative density of 98.9%, hardness of 25.4GPa, flexural strength of 850MPa, fracture toughness (K_IC) of 9.5MPa⋅m^1/2, Young's modulus of 505GPa and electrical conductivity of 5.4MS⋅m^-1. This composite showed excellent mechanical properties comparable with those of hot-pressed Si₃N₄ or SiC ceramics and an electrical conductivity comparable with metal. The composite is expected to be used as a ceramic mold material that can be machined by electrical discharge, corrosion-resistant electrode components, and electro-conductive high-temperature structural materials.