The additive manufacturing (AM) process has numerous advantages in comparison to conventional subtractive machining technologies. Monitoring techniques and non-destructive evaluation (NDE) is relied upon to provide monitoring, material property measurements, and geometry layer-by-layer in real time. Array eddy current (AEC) is one of the techniques that has capabilities to directly scan the component without physical contact with the powder and fused layer surfaces at low and high temperatures. Two types of materials were used for demonstration of AEC capabilities: typical carbon ferromagnetic steel 4140 and nonmagnetic alloy Inconel 625. Artificial and process induced discontinuities such as notches and holes were fabricated with electrical discharge machining process, machining, and by varying the laser fusion parameters. The AEC technology demonstrated very good sensitivity and resolution to surface and subsurface discontinuities and conditions. Powder and solid AM material electromagnetic properties were measured to enable further development of technology. Several scans were conducted inside a laser powder bed fusion chamber. A 4140 steel specimen with machined, AM process-induced, and natural defects was tested. The technique was able to detect lack of fusion process-induced defects as small as one layer thickness or 0.04 mm height.

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