Ablation behavior and mechanism of bulk MoAlB ceramic at ∼1670–2550 °C in air plasma flame

In this work, MoAlB samples for plasma exposure test were condensed by spark plasma sintering at 1200 °C for 10 min. Ablation resistance of MoAlB ceramic was investigated in a plasma torch facility for about 30 s at high temperature range of ∼1670−2550 °C, which provided a quasi-real hypersonic service environment. The results showed that the linear ablation rate was increased from 0 μm/s at ∼1670 °C to 86.4 μm/s at ∼2550 °C. At ∼1670 °C, the ablated surface of MoAlB ceramic was covered by Al2O3 layer, presenting excellent ablation resistance. At ∼2220 °C, the macroscopic cracks were induced by thermal stress, which opened up channels for the inward diffusion of oxygen and deteriorated the ablation resistance of the substrate. Above ∼2400 °C, the volatile MoO3 and B2O3 and the erosion of viscous oxides by the high shearing force of plasma stream were the main ablation mechanisms.