Corrosion Characterization: Use of Raman Spectroscopy for Failure Analysis
A self-locking nut was received for inspection as part of the IAF’s standard quality assurance procedure. A metallurgical cross section was taken, and upon optical microscopic observation, crack-like defects filled with what appeared to be oxides were observed close to the surface of the nut. In order to determine if the defects are folds created during forging, Raman spectroscopy was used to analyze the oxides. The analysis was based on two important properties of Iron oxides: Different oxides are created at different temperatures, each having distinct Raman spectrum. By comparing Raman spectrums from the literature to the ones obtained experimentally, it was determined that the defects originated in the manufacturing process, most likely during forging.
KeywordsAerospace fasteners Alloy steel Characterization Corrosion Corrosion failure analysis Failure analysis Fatigue failure
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