Characterizing the As-Fabricated State of Additively Fabricated IN718 Using Ultrasonic Nondestructive Evaluation

This article reports on the characterization of the as-fabricated state of Inconel 718 samples fabricated using laser directed energy deposition (DED). Laser-DED is known to produce complex metastable microstructures that can significantly influence the baseline ultrasonic response compared to conventional processing methods. The present work uses three parameters to characterize the samples: (a) ultrasonic velocity, (b) an attenuation coefficient, and (c) a backscatter coefficient. The baseline ultrasonic response from the DED sample was compared against the ultrasonic properties of conventional IN718 samples reported in the literature. The results suggest that strong grain boundary scattering from large macrograins can lead to attenuation and backscatter values that are significantly higher than conventional samples. Additionally, the results including velocities, attenuation and backscatter coefficients were found to be dependent on the fabrication direction, with the build direction being different from the transverse directions. Finally, destructive analysis was used to develop conjectures to explain the experimentally observed ultrasonic response.

Automated summary

This article characterizes the as-fabricated state of Inconel 718 samples fabricated using laser directed energy deposition (DED) and compares its ultrasonic properties with conventional IN718 samples. The results show that the complex metastable microstructures of laser-DED samples can significantly influence the baseline ultrasonic response, with higher attenuation and backscatter values caused by strong grain boundary scattering from large macrograins. Additionally, the ultrasonic response is found to be dependent on the fabrication direction, different from the transverse directions.