Abstract
Evaluation of cracks in the ceramic coatings is very important to insure the reliability of the coating itself and the coated materials, parts and whole systems. Laser acoustic emission (AE) method was applied to enable a non-contact and in-situ monitoring of cracks in the ceramic coating immediately after plasma spraying. In this study, originally developed Continuous Wave Memory (CWM) was used as an AE measurement system to enable the continuous waveform recording during plasma spraying process. AE signals due to cracks could be successfully distinguished from large noise components such as mechanical vibration and laser scattering during the process. The AE events during plasma spraying revealed correlation with the dynamic temperature fluctuation on the surface of the specimen which was generated by the scanning of the plasma torch. Furthermore, the larger temperature fluctuation brought higher active AE signals.
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