Additive Manufacturing

JUL 2018

ADDITIVE MANUFACTURING is the magazine devoted to industrial applications of 3D printing and digital layering technology. We cover the promise and the challenges of this technology for making functional tooling and end-use production parts.

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Page 33 of 60

AM / Toward Tailored Materials 31 materials knowledge and capacity to provide not just feedstock for additive manufacturing today, but also the next generation of AM materials. More on that in a moment. Working with the Known If the use and development of 3D printing materials is following that same three-stage trajectory as design thinking, then today manufacturers are largely in the first stage, relying on known alloys that can be applied for additive manufacturing. In the near term, therefore, these users need to understand how to optimize the AM processing of these existing materials. "Today, there are about 5 to 10 alloys that we see being ordered 90 percent of the time," says Will Herbert, director of corporate development for Carpenter Technology. These alloys are familiar from the cast-wrought world, compatible with 3D printing and known to be effective. Final part properties are one reason for the limited number of alloys used in AM today. "When you're forging, you work the material and can confer additional properties to the alloy, such as strength or fatigue resistance for example," Herbert says. In the 3D printing process, where the material is formed simultaneously with part geometry, "We've been fairly limited in the universe of alloys because we have to select metals that you can strengthen without putting in this additional energy after the process." Yet even these existing alloys are still not perfectly understood. "We've translated those directly to additive manu- facturing, but I don't think those materials have necessarily been tailored accordingly to the new technology," Murtagh says. "They've kind of been force-fit to some degree, because that's what we know today." In its own AM materials research and through collaboration with CalRam, Car- penter is exploring how material properties translate to the final part, and how factors such as particle size, shape and distribution affect the build. This research is already expanding material options for metal 3D printing by encouraging a revisiting of what Herbert calls "back catalog" alloys—materials that are difficult to forge as large billets or to investment cast, for example, but may be good candidates for laser sintering or another AM process. "When you wrought process these materials, the material composition can change very widely from the center of the billet to the outside," Herbert says. "You can mitigate these types of seg- regation issues when you start with a powder, and your particle size is on the order of 30 microns, and your freezing rates can be very high. Suddenly we have all these 'new' alloys we can try out." Update and Innovate Carpenter is also beginning to optimize materials specifically for additive, creating variants that meet existing standards while being at least somewhat customized to the 3D printing process. "In the medium term we can continue to take existing alloys within the industry standard specifications and tweak them, find- ing a way to optimize the chemistry, the particle shape and size, in Carpenter's materials research has involved revisiting "back catalog" alloys—materials that are difficult to forge or cast, but that may be a good fit for laser sinter- ing or another additive process. In early 2018, Carpenter acquired CalRam, a California-based company that specializes in metal 3D printing of production parts such as this landing gear knuckle, 3D printed from Ti-6Al-4V. (The blue insert is the digital model of the component.)

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