Determination of the maximum surface chromia thickness for the nondestructive identification of internal alumina scales on a heat-resistant alloy using cathodoluminescence

Abstract

To develop a nondestructive analytical method for identifying internal α-Al2O3 scales formed in heat-resistant alloys, the maximum thickness of surface Cr2O3 scales for identifying internal α-Al2O3 scales via cathodoluminescence (CL) spectroscopy was estimated using CL-peak intensity at 695 nm for Cr2O3 film-deposited sapphires and α-Al2O3 scales formed on the surface of Fe-Cr-Al alloys. The estimated maximum Cr2O3 thickness was validated by measuring the CL peak intensities of Ni-25Cr-5Al alloys heated at 1000°C under oxygen. Therefore, internal α-Al2O3 scales can be identified nondestructively by acquiring the surface CL spectra up to ~ 3-µm surface Cr2O3 thickness.