Hybrid Additive Manufacturing (AM) enables functionally graded materials by using secondary processes and energy sources to alter specified locations throughout a build. These secondary processes and energy sources can alter the microstructure, reduce the local average grain size, increase dislocation density, as well as impart or relieve residual stress. These changes in properties are not confined within a single layer but can have possible compounding effects on previous layers. The ability to control the material properties within a localized region of a part provides significant advantages in part design and performance but presents unique challenges in the nondestructive evaluation (NDE) of such parts. In this work, 316 low carbon stainless steel samples were created using laser powder bed fusion (LPBF) with varying milled interlayers as hybrid surface treatments. Ultrasonic responses, i.e., wave speed and backscatter measurements, were used to investigate the sensitivity of such measurements for detection of the interlayer spacing and their variability across a set of samples created with the same build parameters.

DOI: 10.32548/RS.2022.032

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