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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]

In order to improve the high-temperature service property of Ir, a well-bonded single-layer pure IrAl intermetallic coating was prepared on Ir by pack cementation followed by vacuum annealing treatment. The oxidation behavior of the IrAl coating was investigated by cyclic oxidation tests at 1400–2000 °C and compared with that of pure Ir. The results showed that the IrAl coating, although containing many cracks, exhibited excellent oxidation resistance over the whole experimental temperature range. The reasons were deduced to be the in situ formation of Al2O3 and the sintering of the cracks in the IrAl layer. The excellent oxidation protective effect of the single-layer IrAl coating can be ascribed to its stable and unique as-oxidized microstructure, i.e., double-layer structure of Al2O3/Ir′, which showed excellent compatibility and comprehensive property. [ABSTRACT FROM AUTHOR]

Iridium (Ir) does not form a protective oxide barrier in high-temperature oxidizing environments, leading to a limited lifetime at high temperatures. To improve the oxidation resistance, pure Ir was modified by pack cementation to produce a double-layer iridium-aluminum (Ir-Al) coating. The oxidation behavior investigation on the Ir-Al coatings at temperatures from 1400 °C to 2000 °C demonstrated that the oxidation resistance of the Ir were significantly enhanced after the pack cementation treatment. Further detailed studies showed that the morphology and mass loss of the oxidized Ir-Al coating are considerably affected by the melting and oxidation of the IrAl 2.7(3) . [ABSTRACT FROM AUTHOR]