Sintering of TiB₂-W Cermets by HIP and their Properties

Abstract

The purpose of this study is to investigate the formation of a new phase in TiB₂-W cermets during HIP sintering and to evaluate the influence of this new phase on the mechanical properties. Green compacts of TiB₂-W with compositions between 5 and 40vol%W were densified by HIP at a pressure of 200MPa and temperatures above 2023K, which yielded the cermets with a relative density of more than 99%. Analysis of these semples by XRD, EPMA and Auger, showed the presence of TiB₂, β-WB and WTiB₂, however no metallic W was detected between 5 and 30vol%W. The Vickers hardness, fracture toughness and Young's modulus increased with the formation of the WTiB₂ phase, and its volume fraction increased at W-rich compositions. The highest fracture toughness of 7.8MPam_1/2 and Young's modulus of 571GPa, were obtained for the TiB₂-25vol%W composition. The Vickers hardness value of all specimens was above 20GPa. The fracture toughness values of the higher W compositions were greater than those of the lower W compositions.