PROCESSING AND PROPERTIES OF BORON CARBIDE WITH HAFNIUM DIBORIDE ADDITION

This article presents the results of investigations on densification, mechanical and electrical properties of boron carbide (B₄C) with the addition of HfB₂. High dense B₄C-HfB₂ (2.5-30 wt.%) composites were prepared by hot pressing at a temperature of 2173 K with 40 MPa mechanical pressure. The B₄C-HfB₂ composite mixture exhibited a better sintering aptitude compared with monolithic B₄C. Hardness and elastic modulus of B₄C-HfB₂ composites were measured to be in the range 36-28GPa and 465-525GPa respectively. Indentation fracture toughness of B₄C increased with HfB₂ content and obtained a maximum of 7 MPa.m 1/2 at 30 wt.% HfB₂, which is ∼3 times higher than the monolithic B₄C. Crack deflection was identified to be the major toughening mechanism in the developed composite. B₄C-10wt.% HfB₂ composite exhibited a maximum electrical conductivity of 7144 Ω-1m-1 which is 26% higher than the conductivity of monolithic B₄C (5639 Ω-1m-1) at 1373 K