Ultrasonic diagnostic for in situ control in metal additive manufacturing

This paper presents a study on an in situ ultrasonic measurement technique used to measure a part’s height and for defect tracking during the Laser Powder Bed Fusion process. The ultrasonic wave speed is determined for LPBF manufactured 100Cr6 samples with a pulse echo configuration and a 10 MHz ultrasonic wave. Measurements of the propagation speed show a value of 5660 ± 100 m/s in every direction, which confirms the isotropy of LPBF samples. The pulse echo technique is used to monitor the evolution of the part’s height during the process, based on the measured propagation velocity. This method shows that the melted layer’s thickness oscillates in the range of ±30% of the theoretical layer thickness. Defect tracking was tested on three L-PBF samples with designed cavities 1, 2 and 5 mm3. A numerical model is proposed to understand the detection limitations of ultrasonic monitoring.