Normal spectral emittance of Inconel 718 aeronautical alloy coated with yttria stabilized zirconia films

► Emittance of Inconel 718 coated with plasma sprayed yttria stabilized zirconia. ► The coating is opaque for λ > 9 μm and semi-transparent for λ < 9 μm. ► In the semi-transparent region the emittance decreases with coating thickness. ► 300 μm thick coatings are still semi-transparent. ► In the opaque region the surface roughness determines the emittance level.