No abstract

Binder jet metallic additive manufacturing (AM) is a popular alternative to powder bed fusion and directed energy deposition because of lower costs, elimination of thermal cycling, and lower energy consumption. However, like other metallic AM processes, binder jetting is prone to defects like porosity, which decreases the adoption of binder-jetted parts. Binder-jetted parts are sometimes infiltrated with a low melting temperature metal to fill pores during sintering; however, the infiltration is impacted by the part geometry and infiltration environment, which can cause infill nonuniformity. Furthermore, using an infiltration metal creates a complicated multiphase microstructure substantially different than common wrought materials and alloys. To bring insight to the binder jet/infiltration process toward part qualification and improved part quality, spatially dependent ultrasonic wave speed and attenuation techniques are being applied to help characterize and map porosity in parts made by binder jet AM. In this paper, measurements are conducted on binder-jetted stainless steel and stainless steel infiltrated with bronze samples. X-ray computed tomography (XCT) is used to provide an assessment of porosity.

No abstract

Advancements in manufacturing processes, such as metal 3D printing, are deeply reliant on our understanding of the resulting internal features and microstructures that dictate material behavior. Microstructure characterization is often relegated to techniques that require extensive sample sectioning and surface preparation, which are inherently limited to a small portion of the bulk material. In this presentation, I will show how elastic wave propagation methods (namely, ultrasonic testing) can be combined with physics-based models to extract microstructural parameters in fit-for-service parts. Example results are given for binder jet printed metals (namely, stainless steel 316 and SS316 infiltrated with bronze) where microstructure is characterized over large volumes nondestructively. These methods are correlated to both destructive metrics of microscale features and mechanical properties, which are linked to processing conditions and sample geometry. Finally, I will provide a broader outlook for the impact these techniques may have on the development and implementation of quality assurance protocols for additively manufactured parts.

Binder jet printing (BJP) is a promising additive manufacturing method with benefits in sustainability, material selection, and geometric design freedom. However, issues related to part quality persist, necessitating reliable inspection and characterization strategies. Traditional protocols involving sectioning and extensive sample preparation may miss crucial information about a components’ microstructure due to volumetric variations. This study explores ultrasonic inspection of binder jet SS316L tensile specimens containing spatially varying grain size and porosity by measurement of longitudinal wave speed and attenuation. The ability of ultrasound to detect porosity is evaluated by cross referencing wave speed and attenuation data with porosity data gathered from x-ray computed tomography (XCT). Three-dimensional pore volumes were collapsed into two-dimensional maps such that ultrasound and XCT could be compared in a point-by-point fashion. After tensile testing, the location of failure was compared against wave speed and attenuation extremes. The results show the potential of ultrasound as well as important considerations related to the inspection of additively manufactured parts with complex microstructures.