ADVANCED MATERIALS & PROCESSES | MARCH 2025 23 is fed into the system and melted with a plasma torch in a water-cooled copper crucible. The molten material is then atomized with an argon gas jet, allowed to cool in the flight, and extracted through two cone-shaped cyclones into environmentally isolated collection containers. The process cycles repeatedly and rapidly, going from melting to powder while producing throughputs of more than 20 tons per month. Scrap such as bar ends, machining chips, discarded and end-of-life parts, and castings can be used as a feedstock for such systems. This stream of reclaimed metal materials lays the foundation for establishing an economical, sustainable, and lean business-and-environmental model, from both a production and supply chain perspective. The system is able to control the overall particle size distribution (PSD) and yield. It can also take in non-yielded or coarse powder back through the cycle, creating specific powder sizes for different AM, MIM, HIP, and cladding usage. For example, within four runs, this proprietary system can yield approximately 50% of the original material placed in it in laser powder bed fusion (LPBF) PSD. And that cycle quickly continues to whatever specification of PSD is demanded internally or by an outside market. For example, binder jetting consumes powder of 0-25 microns, LPBF 15-45 and 15-63 microns, electron beam melting 45-90 microns, and directed energy deposition 45-106 microns; HIP uses coarser powders of 45-250 microns. These diverse particle sizes, depending on the make-up of the alloy needed, can be met efficiently through the system’s fast and continuous runs. THE PRACTICAL MEANING Sustainability initiatives are on the rise worldwide and efforts are being made to reduce net carbon footprint of the products. No matter what one thinks are the origins of rising atmo- spheric carbon levels in the environment, many homeowners, businesses, and most insurance companies are planning for the consequences. From a business perspective, there are benefits to meeting ESG standards for reasons related to forecasting, risk management, investor review, and tax credits. There is also the long-standing mandate of returning shareholder value by maximizing use of assets such as metals. And there are practical engineering reasons for complying with the principles of lean, waste reduction, and recycling. According to an article in Waste Management: • Metal recycling reduces greenhouse emissions by requiring significantly less energy to manufacture products from recyclables than virgin materials and by avoiding landfills. • Energy saved using recycled materials is up to 95% for aluminum, 75% for copper, and 60% for steel. • Scrap metal recycling conserves natural resources. Recycling one ton of steel conserves 2500 lbs of iron ore, 1400 lbs of coal, 120 lbs of limestone, and 2 tons of CO2 emissions. • Aluminum (recycling) conserves more than 4 metric tons of bauxite ore. Yet, in contrast to these incentives, according to Statista Research Department’s 2022 data: • Despite the relatively high value of scrap metal, 29% of discarded (i.e., recycled, incinerated, or landfilled) nonferrous metal and 54% of discarded ferrous metal ends up in a landfill (EPA 2021a, EPA 2021b). • In the U.S., metals are recycled at varying rates: lead (76%), titanium (60%) magnesium (52%), aluminum (51%), nickel (51%), iron and steel (47%), tin (35%), copper (34%), and chromium (27%). That is a significant amount of metal alloy resource left behind during the processing of goods. Until now, this has been due to the lack of a process that will convert these scrap alloys into usable metal units in an economical way. The plasma-assisted, gas-atomization system overcomes this hurdle by using various forms of scrap alloys to produce premium-grade spherical powders. MANUFACTURING IN THE CIRCULAR METAL ECONOMY Imagine a leading industrial gas turbine manufacturer with massive in-house machining operations that is creating waste bins of various alloys (say, Mar M247, Haynes 282, and Inconel 718) on a weekly basis—but is also using those same alloys in powder form as a feedstock for its integrated fleets of additive machines that are printing components for the turbines. Such a manufacturer is an ideal candidate for either externally sourced, low-carbon metal alloy powders—or for powders produced from the scrap Fig. 3 — A well-utilized 3D-printed part (left) used in the oil and gas industry, transformed through precision machining (right) to meet exacting specifications. Courtesy of Knust-Godwin.
RkJQdWJsaXNoZXIy MTYyMzk3NQ==