The oxidation-resistance mechanisms of multicomponent ultra-high-temperature ceramics at 1700 °C

The oxidation behavior of (HfB 2 ) 1 (ZrB 2 ) 0.5 –20 vol% SiC (HZS) and (HfB 2 ) 1 (ZrB 2 ) 0.5 (CrB 2 ) 0.25 –20 vol% SiC (HZCS) composites, prepared by spark plasma sintering, was investigated at 1700 °C in air. Relative to HfB 2 –20 vol% SiC (HS), both exhibit comparable oxidation resistance and superior spallation resistance. Multi-scale characterization reveals that the (Hf, Zr)O 2 solid solution formed in HZS and HZCS is less inclined to react with SiO 2 to form (Hf, Zr)SiO 4 ; the residual SiO 2 accumulates atop the (Hf, Zr)O 2 layer, producing a dense, multilayered scale that impedes inward oxygen diffusion. The reduced silicate yield also suppresses cracking from thermal-expansion mismatch, while the finer (Hf, Zr)O 2 grains—arising from sluggish grain growth—yield smoother scales less prone to spallation under high-enthalpy, high-shear flow. With ~ 14.5–18.5% lower density and reduced raw-material cost relative to HS, these composites show strong promise for aerospace applications and offer guidance for designing next-generation ultra-high-temperature ceramics (UHTCs).