Hot pressing and oxidation behavior of ZrB2–SiC–TaC composites

Abstract

A ZrB2–20 vol% SiC–5 vol% TaC ceramic was sintered through the hot pressing process. By sintering for 60 min at 1850 °C under 40 MPa in a vacuum atmosphere, an almost fully dense specimen with a relative density of 97.5% was achieved. The phase and microstructural investigations revealed that alongside the ZrB2, SiC and TaC as the starting materials, two new phases of ZrC and TaSi2 were synthesized in-situ during the hot pressing. The oxidation behavior of as-sintered hybrid composites was investigated at three temperatures in an atmospheric furnace for 1-, 4- and 10-h cycles. Parabolic oxidation rate constants of 2.25, 30.69 and 1309.70 mg2/cm4.h were calculated for the samples oxidized at the temperatures of 1000, 1400 and 1700 °C, respectively. The activation energy of 178.7 kJ/mol was kinetically calculated for the oxidation of ZrB2–SiC–TaC ceramics. Four oxidized layers on the unaffected ZrB2–SiC–TaC matrix were also detected and microstructurally characterized.