Potentials of Ultrasonically Atomized Cored Wires for Powder Metallurgy and Additive Manufacturing

Powder production for additive manufacturing is currently mainly done by inert gas atomization. A new process is the production of low-oxygen and highly spherical metal powders by ultrasonic atomization from a wire or rod feedstock. As a crucible-free process and because of an electric arc as an energy source, even materials with a high liquidus temperature up to 1800 degrees C can be processed. A limitation of this technique can be found in the continuous processing of high-strength materials, like martensitic hardenable tool steels, from a stiff wired feedstock because of the limited feed ability. This paper investigates the possibility of processing high-strength steel powder using cored wire as the starting material for the ultrasonic atomization process to circumvent the feeding problem of highstrength materials. Thereby, two carbon martensitic hardenable hot work tool steels with a carbon content of 0.12 wt. % and 0.4 wt. % are considered as reference materials. After the atomization process with varying parameters, powders are characterized concerning their morphology, chemical composition, phases formed, and related powder properties. In addition to flowability, the bulk density are also determined. Based on these results, a conclusion will finally be given on the suitability of ultrasonically atomized powders for additive manufacturing and fast sintering techniques.