Ablation behavior of (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-SiC-Si ceramics via reactive melt infiltration

(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-SiC ceramics with an open porosity of only 0.49 % were successfully fabricated in this work by the reactive melt infiltration (RMI) method. Air plasma flame ablation behavior of (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂-SiC ceramics under 2300 °C temperature exhibited excellent resistance with mass and linear ablation rates of 3.66 mg/s and 0.88 μm/s, respectively. During ablation, the transition from continuous melting sublimation of Si and oxidation of SiC to oxidation of (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂ occurred. The uphill diffusion of Ti atoms transited (Ti,Zr,Hf,Nb,Ta)O_x to Ti(Nb_xTa_1-x)₂O₇ while Zr_0.5Hf_0.5O₂ continuously precipitated. A multicomponent oxide layer of (Ti,Zr,Hf,Nb,Ta)O_x along with (Zr,Hf)₆Ta₂O₁₇, (Hf,Zr)(TiO₄)₂, and (Zr,Hf)_x(Ti,Ta)_1-xO embedded in SiO₂ melt was eventually formed on the ceramic surface. This oxide layer was spread above the high melting point Zr_0.5Hf_0.5O₂, Ti(Nb_xTa_1-x)₂O, and low oxygen content (Ti,Zr,Hf,Nb,Ta)O_x to form a stable, dense, and high viscosity protective layer.