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

Abstract

Abstract In this work, MoAlB samples for plasma exposure test were condensed by spark plasma sintering at 1200\u2009°C for 10\u2009minutes. Ablation resistance of MoAlB ceramic was investigated in a plasma torch facility for about 30\u2009seconds at high temperature range of ∼1670-2550\u2009°C, which provided a quasi-real hypersonic service environment. The results showed that the linear ablation rate was increased from 0\u2009µm/s at ∼1670\u2009°C to 86.4\u2009µm/s at ∼2550\u2009°C. At ∼1670\u2009°C, the ablated surface of MoAlB ceramic was covered by Al2O3 layer, presenting excellent ablation resistance. At ∼2220\u2009°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\u2009°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.