Normal spectral emissivity study for GH3044 alloy and Ti-6Al-4V alloy

Abstract

Changes in normal spectral emissivity during alloy oxidation cause large errors in radiation thermometry for aero-engines and gas turbines. To study the effect of oxidation on the normal spectral emissivity of the alloy surface, GH3044 alloy and Ti-6Al-4V alloy were selected as the research objects in this paper, and the normal spectral emissivity of the two alloys at 1.5–2.1 μm wavelength was experimentally measured during oxidation in the air for 12 h. The two alloys commonly showed an overall increasing trend with oscillation during the oxidation process, but their oscillation characteristics were significantly different. The interference effect caused by the air-oxide film interface was the main reason for the oscillation phenomenon. To explore the changes of normal spectral emissivity caused by oxide film, the composition and micromorphology of alloy surface were analyzed through X-ray diffraction (XRD) and scanning electron microscopy (SEM), and it was found that the change of the alloy surface composition and micromorphology were the main factors for the overall increase on the normal spectral emissivity. In addition, polynomial models of normal spectral emissivity versus oxidation time of the two alloy was established, which was in good agreement with the experimental results.