LENS Technology Used in New One-Step Process for 3D Printing Multimaterial Structures

Laser engineering net shaping (LENS), a patented, hybrid additive manufacturing technology developed by Optomec, is most often used for high-value metal 3D printing. It can also be added onto existing CNC equipment, to repair parts using 3D printing. Now, a research team from Washington State University (WSU) is using LENS technology in a one-step process developed to 3D print multimaterial structures.

Amit Bandyopadhyay, the Herman and Brita Lindholm Endowed Chair Professor in the university’s School of Mechanical and Materials Engineering, said, “This is a step towards the next level of manufacturing and the next generation of design, validation, optimization and manufacturing using 3D printing.”

Amit Bandyopadhyay displays 3D printed bimetallic sample.

Not only has 3D printing overhauled many industrial practices, but it’s also been a major influence on product design processes. But, most 3D printers can only use one material at a time to 3D print parts – not the case for the WSU team’s new process. The researchers, led by Bandyopadhyay, have been able to use their new technique to 3D print structures out of both metal and ceramic, and a bimetallic tube that’s magnetic at one end and not in the other.

Multimaterial 3D printed designs.

This month, the team published a paper on their work, titled “Additive manufacturing of Inconel 718-Copper alloy bimetallic structure using laser engineered net shaping (LENS),” in the Additive Manufacturing journal.

The research was funded by the Joint Center for Aerospace Technology Innovation, the National Science Foundation, and NASA’s Marshall Space Flight Center; co-authors of the paper include WSU graduate students Bonny Onuike and Bryan Heer, and Bandyopadhyay. 

The abstract reads, “To understand processing ability and measure resultant interfacial and thermal properties of Inconel 718 and copper alloy GRCop-84, bimetallic structures were fabricated using laser engineering net shaping (LENS), a commercially available additive manufacturing technique. It was hypothesized that additively combining the two aerospace alloys would form a unique bimetallic structure with improved thermophysical properties compared to the Inconel 718 alloy. Two approaches were used: the direct deposition of GRCop-84 on Inconel 718 and the compositional gradation of the two alloys. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray Diffraction (XRD), Vickers microhardness and flash thermal diffusivity were used to characterize these bimetallic structures to validate our hypothesis. The compositional gradation approach showed a gradual transition of Inconel 718 and GRCop-84 elements at the interface, which was also reflected in the cross-sectional hardness profile across the bimetallic interface. SEM images showed columnar grain structures at the interfaces with Cr₂Nb precipitate accumulation along grain boundaries and the substrate-deposit interface. The average thermal diffusivity of the bimetallic structure was measured at 11.33 mm²/s for the temperature range of 50 °C–300 °C; a 250% increase in diffusivity when compared to the pure Inconel 718 alloy at 3.20 mm²/s. Conductivity of the bimetallic structures increased by almost 300% compared to Inconel 718 as well. Such structures with designed compositional gradation and tailored thermal properties opens up the possibilities of multi-material metal additive manufacturing for next generation of aerospace structures.”

Graphical abstract

With the ability to use more than a single material at once during 3D printing jobs, manufacturers can better control material properties such as corrosion protection, environmental adaptation, and heat conduction. This could help lower the number of manufacturing steps, and allow manufacturers to make complex products with multiple parts using just one machine, in a single operation.

Additionally, multimaterial 3D printing negates the use of adhesives or joint connections that are currently needed to make multimaterial products.

“You could be joining two very strong materials together, but their connection will only be as strong as their adhesive. Multimaterial, additive manufacturing helps get rid of the weak point,” Bandyopadhyay explained.

A LENS system was used to join two materials in one step, and successfully 3D printed a structure of copper and Inconel 718, which is a nickel-chromium alloy used in liquid-fueled rockets; it’s also used to make sheet metal parts for airplane engines.

Closeup of 3D printed multimaterial sample object.

This material can hold up well under high temperatures, but cools very slowly, which was a bonus for this project. When the copper was added to the 3D printing process, the part could be cooled 250% faster, which equals higher fuel efficiency and a longer life for airplane engines.

This research has also opened up additional design options. The researchers worked with WSU graduate students Tom Gualtieri and Yanning Zhang to 3D print a metal-ceramic material in just one operation.

“This allows us to vary the composition and add functionality to a product during 3D printing that is traditionally very difficult to achieve. And we can do this in a single process with a single machine,” Bandyopadhyay said.

“Multimaterial additive manufacturing has opened the doors to so many different possible creations. It has allowed us to be bolder and be more creative.”

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