Nondestructive, Rapid Identification of Aluminum Nitride and Internal Alumina Scales on a Heat-Resistant Alloy Using Cathodoluminescence

A nondestructive method to rapidly identify AlN precipitates and internal Al₂O₃ scales on Ni–Cr–Al alloy via cathodoluminescence (CL) analysis is proposed. AlN could be instantly distinguished from Al₂O₃, Cr₂O₃, and CrN based on the detection of violet luminescence in CL images. Moreover, an Al₂O₃ scale beneath a surface Cr₂O₃ scale with the thickness below 3.2 μm can be rapidly identified based on a peak at 695 nm in the CL spectra of the alloy surface with no requirement for a destructive cross-sectional analysis. The exposure time for the CL images and the acquisition time for the CL spectra were within 1 min. Therefore, CL analysis may provide a rapid, nondestructive, analytical method for identifying AlN precipitates and internal Al₂O₃ scales in heat-resistant alloys.