Crack monitoring during plasma spraying of ceramic coatings by non-contact acoustic emission method

Abstract

Atmospheric plasma spraying (APS) is an effective process to make ceramic coatings. However, several types of cracks are inherently present in the coatings and among them, delamination cracks within the coatings or at the interface with the underlying layer are believed to reduce their durability and reliability. In this study, non-contact laser acoustic emission (AE) method and original AE measurement system successfully detected the cracks during APS in real time, which was very difficult because of noise from the APS system. AE waveform was sampled and recorded continuously during the testing time. AE events due to delamination cracks were successfully detected from noisy waveform by this system. Influences of the scanning speed and the power of the plasma jet to the delamination were also confirmed. © 2010 The Japan Institute of Metals.