Ablation behavior of (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-SiC-Si ceramics via reactive melt infiltration

(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B 2 -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 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B 2 -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 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2 )B 2 occurred. The uphill diffusion of Ti atoms transited (Ti,Zr,Hf,Nb,Ta)O x to Ti(Nb x Ta 1-x ) 2 O 7 while Zr 0.5 Hf 0.5 O 2 continuously precipitated. A multicomponent oxide layer of (Ti,Zr,Hf,Nb,Ta)O x along with (Zr,Hf) 6 Ta 2 O 17 , (Hf,Zr)(TiO 4 ) 2 , and (Zr,Hf) x (Ti,Ta) 1-x O embedded in SiO 2 melt was eventually formed on the ceramic surface. This oxide layer was spread above the high melting point Zr 0.5 Hf 0.5 O 2 , Ti(Nb x Ta 1-x ) 2 O, and low oxygen content (Ti,Zr,Hf,Nb,Ta)O x to form a stable, dense, and high viscosity protective layer.