In-situ Sensing and Post-production Inspection for Additive Metal Parts Using Eddy Current Arrays

This presentation describes a leap in capability for the application of Eddy Current Testing Arrays (ET-Arrays) for both in-situ and post-production inspection of additive manufactured (AM) metal parts. For in-situ layer-by-layer inspection, prototype demonstrations have been completed for both laser powder bed fusion (LPBF) and electron beam direct energy deposition (EB-DED). For post-production, volumetric inspection for surface and far-side cracks, as well as weld material characterization, has been demonstrated for thin components and for features that are accessible post-production or machined. This technology is currently in use commercially for weld inspection.

To deliver practical in-situ ET-Array capabilities for LPBF, several technology advances were required, including: fully parallel electronics to acquire digital complex impedance data at three frequencies simultaneously for all channels; large channel count systems to support over 300 sensing element channels simultaneously (typical sensing element size of 1mm); sensor array designs that can be modeled accurately to enable layer-by-layer recalibration and absolute conductivity estimation; methods to account for variable lift-off (proximity of each sensing element to metal surfaces); data analytics including physics model-based inverse methods and intelligent filtering in the x, y and z (build) directions; and integration of the system into AM machines. Note that for nonferrous alloys the ET-Arrays can see through the powder to inspect the processed metal for defects, geometry, and metallurgical conditions. Furthermore, multiple frequencies provide sensitivity to both surface and subsurface flaws. LPBF sensitivity is through several layers, which helps determine whether a defect was remelted by the next processing pass or remains in the finished component. JENTEK Sensors, Inc. has developed each of these elements including a powder model that enables characterization of powder properties. This presentation describes the key technologies and provides details of the in-situ EB-DED and LPBF implementations as well as a brief description of the post-weld inspection capabilities.