Surface defect detection from additive manufacturing components at elevated temperatures using laser-generated Rayleigh waves

Online monitoring is a critical issue for additive manufacturing components layer by layer to ensure the integrity of the structure. However, the rough surface and high temperature make it difficult to use conventional non-destructive testing methods to carry out. In this work, the laser ultrasonic technique, as a non-contact nondestructive testing method, is applied to detect defects in a 316L stainless steel specimen manufactured using selective laser melting at elevated temperatures. The unreported phenomenon of phase evolution of Rayleigh waves for different excitation locations and temperatures is observed and systematically explored using the finite element method and experiments.