High-Temperature service stability of antireflective truncated cone structures

Abstract

The study addresses the failure of conventional antireflective coatings in high-temperature fighter jet exhaust nozzles by fabricating antireflective truncated cone structures (depth: 260 μm, groove width: 90 μm, period: 140 μm) on GH4099 nickel-based superalloy substrates using femtosecond laser processing. The investigation systematically evaluates the service stability of these structures under isothermal exposure (550–1100 °C for 1–10 h) and thermal cycling (6–12 cycles), while finite-difference time-domain (FDTD) simulations elucidate the anti-reflection mechanism. Results demonstrate excellent stability of the micron-scale cone structures at 550–850 °C, with only nanoscale oxide particles forming after prolonged exposure. In contrast, obvious oxide coarsening, cracking and morphological degradation take place on the structural surface at 1100 °C, which reduces structural stability. The oxygen content increases to 42.40% with extended thermal exposure, and dense oxide layers effectively suppress further oxidation. The lowest average reflectivity (4.45%) appears after six thermal cycles at 850 °C, while reflectivity increases at 1100 °C. FDTD simulations reveal that 200 nm pyramidal oxide structures provide optimal antireflective performance, exhibiting the lowest reflectivity at 45° incidence. A preliminary lifetime projection based on 6–12 cycle data suggests extended durability, though longer-term validation is required. These results provide insights for stealth nozzle design under static thermal conditions.