Normal spectral emissivity of GH536 (HastelloyX) in three surface conditions

Abstract

The normal spectral emissivity of GH536, a nickel-based superalloy, is measured using a FT-IR spectrometer in the wavelength range 1–15μm at moderate and high temperature (400–1200K), as well as the samples with partially oxidized and flame treatment processed. It is found that the emissivity of GH536 decreases with the increasing of emission wavelength, which is well predicted by the electromagnetic wave theory, and increases linearly when the temperature rises. The emissivity of the other two samples with partially oxidized and flame treatment processed is also investigated in details. The results of the partially oxidized sample indicate that oxidation can enhance the emissivity significantly and alter the wavelength dependence trend. And the results of the flame treatment processed sample shows that the impurities and defects caused by the fire treatment process moderately increase the emissivity. The experimental data of GH536 is compared with the results calculated using Hagen-Rubens equation, which shows an inconsistence at high temperature condition. Therefore, a modified emissivity model is proposed, which has a good agreement in measured wavelength range at moderate and high temperature condition.