Enhanced Oxidation Resistance of ZrB2–SiC–WC Composite below 1800 °C

Abstract

The effect of 3.6 vol% WC addition to ZrB2–20 vol% SiC (ZSW) on oxidation resistance is studied over a broad range of oxidation temperatures, 1000–1800 °C. Non‐WC‐containing samples (ZS) show significant surface damage and degradation during oxidation, losing protective B2O3 and SiO2‐based surface layers and exposing a porous ZrO2 layer and base material for further oxidation. ZSW samples preserve their surface protective layers during oxidation up to 1800 °C while the underlying ZrO2 scale remains dense. The appearance of convection cells on the surface of ZSW samples during oxidation above 1600 °C is reported. This confirms the presence of boron‐rich phases, suppressing oxygen permeation into the material and enhancing oxidation resistance of ZSW samples. During exposure of the samples to 1800 °C for 15 min, ZS and ZSW samples gain 11.1 ± 1.5 and 7.8 ± 0.3 mg cm−2, respectively, due to oxidation. Exposure of the composites for 5 h at 1600 °C results in weight gains of 10.5 and 7.0 mg cm−2 for ZS and ZSW samples, respectively. Cross sections of oxidized samples at 1800 °C show a tight zirconia layer below a glassy surface in ZSW and complete loss of surface glass in ZS, demonstrating the effectiveness of WC addition.