Ablation resistance and mechanism of SiC–LaB6 and SiC–LaB6–ZrB2 ceramics under plasma flame

Abstract

In this study, silicon carbide-lanthanum hexaboride (SiC–LaB6) and silicon carbide–lanthanum hexaboride–zirconium boride (SiC–LaB6–ZrB2) ceramics were fabricated by spark plasma sintering at 1900 °C, and their ablation resistance was tested under plasma flames over 2300 °C. The results indicate that the SiC–LaB6–ZrB2 ceramic exhibits better ablation resistance than the SiC–LaB6 ceramic. After ablation under the plasma flame for 60 s, the mass and linear ablation rates of the SiC–LaB6 ceramic were 15.83 μg/s and 1.08 μm/s, respectively, while those of SiC–LaB6–ZrB2 were -8.42 μg/s and -0.27 μm/s. With the addition of ZrB2, SiC–LaB6–ZrB2 ceramic attained a high density and fewer inner oxygen diffusion channels. Moreover, the ZrO2–La2O3–SiO2 oxide scale with good self-healing ability and excellent stability was formed in the ablation centre, which can retard the further oxidation during ablation.