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The ablation behaviors of an as-annealed aluminized Ir (IrAl/Ir) coating sample and two aluminized Ir (IrAl 2.7(3) /IrAl/Ir) coating samples were investigated in a plasma wind tunnel for up to 2000s. The IrAl/Ir and IrAl 2.7(3) /IrAl/Ir coating samples showed quite different thermal responses, with ablation resistance limits of ~3.35 MW/m2 and ~3.75 MW/m2, respectively, due to their different oxidation mechanisms. The failure mechanisms of both Ir Al intermetallic coating samples were closely related to the melting of Al 2 O 3 coating due to over-temperature. The results indicated that the Ir Al is a promising non-ablative thermal protection coating material used in non-equilibrium oxidizing environment up to 2000 °C. Unlabelled Image • The ablation resistance of Ir Al coating was investigated in a plasma wind tunnel. • Ir Al intermetallic coating is a non-ablative coating for up to 2000 °C. • The oxidation mechanism of Ir Al coating is determined by the contents of Al. • The failure of Ir Al coating is resulted from the melting of Al 2 O 3 coating. [ABSTRACT FROM AUTHOR]

Abstract The ablation and surface heating behaviors of iridium and Ir-Al coatings on graphite substrates under non-equilibrium conditions were investigated in a plasma wind tunnel. The results showed that the iridium coating had a much higher thermal response than the Ir-Al coating in non-equilibrium conditions. The iridium coating melted at a heat flux of 2.03 MW/m2 with the surface temperature up to 2494 °C, while the surface temperature of the Ir-Al coating was only 1330 °C at this condition. When the heat flux rose to 3 MW/m2, the surface temperature of the Ir-Al coating stayed at ~1520 °C. After continuous ablation at this condition for 500 s, the Ir-Al coating remained intact. It can be concluded that the Al alloying modification could largely improve the ablation resistance of an iridium coating. The present research proposed a novel idea for ultra-high temperature coating for hypersonic applications. Highlights • Pure iridium coating had a heat response of over 2440°C at a heat flux of 3MW/m2 in plasma wind tunnel • Ir-Al coating could withstand a heat flux of more than 3 MW/m2 in plasma wind tunnel • Surface temperature of Ir-Al was about 1000°C lower than iridium coating at the same condition [ABSTRACT FROM AUTHOR]