Synthesis of Hard Materials by Field Activation: The Synthesis of Solid Solutions and Composites in the TiB ₂ –WB ₂ –CrB ₂ System

Abstract

The synthesis of solid solutions of (Ti,W,Cr)B 2 from elemental reactants using the field‐activated, pressure‐assisted synthesis method and employing the SPS apparatus was investigated. The nature of the products depended on temperature; they were nearly pure solid solutions at 1900°C with minor amounts of β‐WB. The product density and microhardness depended on the temperature of synthesis for the same value of applied pressure (64 MPa). Samples with the highest density (94%) corresponded to a hardness of 22.7 GPa. When annealed at 1500°C, the solid solutions decomposed, precipitating a (W,Ti,Cr)B 2 phase in a spinodal form. In addition, β‐WB precipitates in the form of thin (0.4–5.3 nm) layers were observed. They existed in a 60°/120° orientation to the (Ti,W,Cr)B 2 matrix, in agreement with previous observations. Highly faceted, small (nanosized) pores associated with the β‐WB precipitates were also observed.