Additive Manufacturing of Carbon Steels Through Direct Ink Write Printing of Oxide Precursors
Stiers, Collin D.
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A method for additive manufacturing of various carbon steels from low cost and stable oxide powders is presented. This method uses direct ink write (DIW) processes to extrude inks composed of oxide powders, plastic binders, and solvents. Oxide powders are synthesized into viscous inks through mechanical mixing with a plastic binder and solvents. Inks are then extruded under ambient conditions into three dimensional (3D) architectures. The 3D printed green bodies solidify on contact with air after which they are subjected to a reducing process at elevated temperatures in hydrogen-rich environments to burn off the polymer binder and reduce the oxide powders, yielding metal alloys with controlled compositions. While this approach has been demonstrated in previous publications for various alloys, adding carbon, an important element in most industrial steels, has been a persistent challenge. This paper demonstrates an approach to introduce carbon during the reduction process, resulting in through-thickness carburization of the final parts. Post-printing, the parts can be heat treated to achieve desirable characteristics through well-established methods.