ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 64 3D PRINTSHOP TWO-METAL PRINTING CREATES STRONGER PARTS A new hybrid setup created by Washington State University scientists uses two welding heads to 3D print two metals at the same time. The resulting bimetallic material proved 33% to 42% stronger than either metal alone, thanks in part to pressure caused between the metals as they cool together. In a demonstration, the two welding heads worked one right after the other on a circular layer to print two metals, each with specific advantages. A corrosion-resistant, stainless-steel core was created inside an outer casing of cheaper “mild” steel like that used in bridges or railroads. Because the metals shrink at different rates as they cool, internal pressure was created— essentially clamping the metals together. “This method deposits the metals in a circle instead of just in a line. By doing that, it fundament- ally departs from what’s been possible,” says Lile Squires, a WSU mechanical engineering doctoral student and the study’s first author. “Going in a circle essentially allows one material to bear hug the other material, which can’t happen when printing in a straight line or in sandwiched layers.” The capability to strengthen 3D-printed metal parts layer-by-layer could give automotive shops new options soon with the ability to quickly create strong, customized steel parts. Bimetallic, torque- resistant axle shafts, for instance, or cost-effective, high-performance brake rotors could be developed. wsu.edu. DED TECHNIQUE JOINS DISSIMILAR MATERIALS Researchers at Oak Ridge National Laboratory (ORNL) are developing a technique to design compositionally graded composite parts that have variable properties. These components transition from high-strength super- alloys to refractory alloys that can withstand extremely high temperatures. The scientists used powders of Inconel 718, a nickel-based alloy, and C103, a niobium-based alloy. These alloys—one high strength and the other high-temperature resistant—do not want to join and tend to create cracks when they do. But by using a blown-powder directed energy deposition beam machine and changing the rate at which the powders flow, the scientists can change the composition of the joined metals so that it has the beneficial properties of both. ORNL scientists designed the actual nonlinear gradient pathway by coupling state-of-the-art computational thermodynamics with experimental data gathered via multiscale, high- throughput characterization tools. By doing so, they successfully circum- vented welding issues and joined normally nonweldable superalloys with refractory alloys. The team analyzed the stress states of these integrated builds with neutron diffraction-based studies at ORNL, validating the computational alloy design. Currently, melt pool, thermal and strain models are being generated based on the experimental data. Among the applications for this technology are rocket engines for space, aerospace manufacturing, fusion and fission reactor fabrication, marine- related uses, renewable energy systems—anywhere an extreme environment exists, researchers say. ornl.gov. A hybrid setup creates parts using precise computer programming and two welding heads. Courtesy of Washington State University. Using 3D printing in conjunction with polymer-derived ceramics, researchers from Penn State created a turbine component that can withstand higher temperatures than parts made with conventional metals. “We found that with the right design for the part, the ceramic airfoil shape that we 3D printed can perform just as well as the metal components,” says associate professor Stephen Lynch. “Our hope is that this technology could be used to develop ceramic parts that perform similarly to metallic parts in gas turbine engines but can tolerate higher temperatures for greater fuel efficiency.” Lynch notes that the team also used the design freedom of additive manufacturing to create internal features that dramatically improve the effectiveness of the cooling air inside the blade. psu.edu. BRIEF
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