Ablation behavior of an Ir-Hf coating: A novel idea for ultra-high temperature coatings in non-equilibrium conditions

Abstract A novel Ir-Hf diffusion coating was prepared on iridium through modified pack cementation to improve the non-equilibrium ablation property while maintaining the oxygen diffusion resistance. The Ir-Hf coating consisted of Ir3Hf, IrHf and IrHf2 sublayers with a total thickness of ∼20 μm. During ablation testing in a plasma wind tunnel, the Ir-Hf coating remained intact after 60 s ablation at a heat flux of 4.23 MW/m2 when the surface temperature reached 2320 °C. The coating also passed a 2000 s ablation test at a heat flux of 4.03 MW/m2 without damage. Through comparison, the Ir-Hf coating has a higher maximum tolerable heat flux than pure iridium, Ir-Al coating and C/SiC-HfC composite, showing a promising potential for ultra-high temperature thermal protection applications.