Ablation resistance of HfC(Si, O)-HfB2(Si, O) composites fabricated by one-step reactive spark plasma sintering

Abstract

A dense HfC(Si, O)-HfB2(Si, O) composite was fabricated by reactive spark plasma sintering using HfC and SiB6 as starting reactants. The best ablation resistance was obtained with the composite fabricated with the addition of 15 vol.% SiB6. After ablation under an oxyacetylene flame for 60 s, the mass and linear ablation rates of this composite were −0.007 mg cm−2 s−1 and −0.233 μm s−1, respectively. The negative ablation rates are the result of a slight mass gain/thickness increase, which indicate that the oxidation process was stable and mechanical scouring was limited during ablation. This enhanced ablation resistance was attributed to a unique double-layered oxide formation, which possessed lower oxygen permeability and better mechanical strength. The solid solution nature of the composite and its appropriate phase composition were responsible for the stable oxide structure formation.