6K Additive
A plume of microwave-based plasma is engaged. Powder particulates previously loaded into hoppers are injected from two points. And the particles flow into the heat zone, melting quickly before the surface tension of the molten metal causes it to form a perfect sphere.
“Microwave-based plasma – that’s basically the secret sauce,” says 6K Additive President Frank Roberts. “With the UniMelt [process], you’re using microwaves as your energy source. Energy is passing through a waveguide, and they’ll intersect a torch stack. In the torch stack, that’s where we’re applying gas. The result is, instead of having your electric field be concentrated on the OD (optical density), the electric field gets dispersed pretty evenly through the core of your plasma.”
After TCT visited 6K Additive’s facilities in Pittsburgh earlier this year, there will be a deeper dive into the company’s UniMelt process – the central piece in a process that is delivering high-quality metal powders to additive manufacturing (AM) users – in a later issue of the magazine. But here, the focus is on how 6K Additive is ensuring its method of material manufacture is as sustainable as it can be. Not just in the control of energy as it spheroidises its powders, but in the way it procures raw material at the front end and recycles it at the back end. For while quality is the top priority for 6K Additive, sustainability of its products is a close second. It has been since day dot.
To underscore the company’s sustainability claims, 6K Additive commissioned a third party – Foresight Management – to conduct lifecycle assessments on its nickel and titanium powders. These powders currently represent around 95% of what flows through the company’s factories, and as detailed in a TCT Magazine cover story last year, were shown to use much less energy and emit much less carbon than conventional techniques. With nickel, 6K Additive was using 6,265MJ of energy and produced 301kg C02-eq for every 100kg delivered – a 91% energy reduction and 92% carbon emissions reduction. Titanium, meanwhile, was using 56,268MJ of energy and produced 2,748kg C02-eq for every 100kg delivered – a 74% energy reduction and 78% carbon emissions reduction.
“This is twofold,” Roberts says of how 6K is able to deliver these numbers.
“It’s the efficiency of UniMelt, so how effective we’re able to put energy into that machine and generate plasma – it’s highly efficient from 99% coupling power into plasma creation – and then the other big mover is yield. You only put in what you want to get out. All that energy goes into prime product, not in waste. That’s what makes this meaningful data.”
6K Additive is keen to point out that, thanks to UniMelt, its yield tends to be much higher than the 25-50% yield delivered by conventional atomisation processes. That 6K can save so much material from going straight to landfill is a good start, but 6K is also incentivising its customers to recycle material once used, bringing the front and back end of its processes together to close the circle.
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Treating customers as its suppliers, 6K offers buyback agreements as part of its long-term supply contracts that means, as long as the user has good traceability on their parts, 6K will take back their scrap and offer, for example, 15% off their next order. There are also strategic relationships in place with some of the US’s largest processing facilities to upcycle material from failed builds, support structures, condensate, and out of spec or used powders to turn them into powder or ingot.
Before a decision is made on whether 6K uses the incoming metals for its powder business or its alloy business, it goes through a ‘complicated decision tree’ that considers quality, economics, and efficiency. Since powder is the company’s biggest value stream, 6K will hope to get most incoming scrap metal through that business, but the alloy side of the company will pick whatever isn’t feasible for the powder side.
“Let’s say you had nickel 718 solid, some sort of big ring out of a jet engine, it will never make sense to take something that large and turn it into turnings and then the turnings into powder,” Roberts explains. “The most efficient thing you can do with that is immediately take it to some wrought product or application. The goal is nothing that was on any one of these value streams leaves this site and goes to a landfill. We’re looking at ways of upcycling everything.”
As of this summer, that looks set to include materials previously used in hip, knee, and shoulder joint replacement surgeries in partnership with Surgical Metal Recycling.
“If you generate a used powder, chances are we will be able to rejuvenate it,” assesses Roberts. “You can really see true scrap-to-powder-to-part-to-scrap-to-powderto-part, and just continuing this infinite loop without the need for things like ore coming from Russia, [for example.]”
Reshoring the production of metal materials is also on the agenda at 6K Additive. Its Pittsburgh facilities currently boast four UniMelt bays, but the company is in the process of expanding that to ten. At the point at which those bays are operational and 6K Additive is manufacturing a wider range of materials at the volumes its producing nickel and titanium, expect more lifecycle assessments to follow, and more incentives for its customers to recycle their material.
