Consolidation via spark plasma sintering of HfB 2/SiC and HfB 2/HfC/SiC composite powders obtained by self-propagating high-temperature synthesis

Abstract

HfB 2–SiC and HfB 2–HfC–SiC dense composites have been prepared by self-propagating high-temperature synthesis (SHS) followed by spark plasma sintering (SPS) without the addition of any sintering aid. Starting from Hf, B 4C, Si, and, when synthesizing the ternary system, also graphite powders, it was found that the SHS technique leads to the complete conversion of reactants to the desired products and the SPS allows for the full consolidation under the following optimal operating conditions: maximum dwell temperature (1800 °C), total processing time (30 min) and applied pressure (20 MPa). The obtained ternary composite displayed relatively low resistance to oxidation while the binary product exhibited low and thermally stable oxidation rate up to 1450 °C. In addition, the mechanical properties of both products are comparable to, and, in some cases better than, those related to analogous HfB 2-based composites prepared with other processing routes. Moreover, the required consolidation conditions (processing time, temperature, and pressure) resulted to be milder in this investigation.