Samples of glass pieces welded to metal with high-speed lasers (NASA/W. Hrybyk)
2 Nov. 2018. The federal government’s space agency is supporting two projects for improving the capabilities of astronauts to create and repair their equipment during space travel. NASA awarded a grant to QuesTek Innovations in Evanston, Illinois and University of Pittsburgh’s engineering school to apply principles of custom-designed materials for 3-D printing, and is advancing the use of lasers to assemble parts in space made from dissimilar materials.
The Questek-Pittsburgh initiative aims to systematize the tuning of high-performance materials for additive manufacturing, the term for industrial-scale 3-D printing in space. The $750,000 Small Business Technology Transfer award focuses on Inconel 718, a nickel-iron alloy, considered a super-alloy for its ability to withstand high temperatures, and a favorite material for aerospace applications. When using Inconel 718 in space travel for additive manufacturing, however, the material’s properties need to be altered to meet the special rigors of that environment, and these adjustments are often made ad hoc to meet specific needs.
The results, says Questek’s project leader Jiadong Gong, is greater uncertainty in the parts being created by additive manufacturing or AM, in space. “For as promising as AM is to modern manufacturing,” says Gong in a Pittsburgh statement, “its acceptance by major commercial or government industries like NASA comes down to a lack of confidence in the quality of the part. The majority of systems are based largely on hand-tuned parameters determined by trial-and-error for a limited set of materials, which is ineffective, costly and can contribute to mission failure.”
The Questek-Pittsburgh team is developing a more systematic approach to materials design, applying the company’s approach known as Integrated Computational Materials Engineering. With this process, the researchers plan to provide materials designers with quantitative tools to forecast adjustments in properties needed for materials like Inconel 718 when configured for additive manufacturing in space environments. The result, say the researchers, is more reliability in 3-D printed engine parts and spacecraft components that can be produced by flight crews on demand. The team believes the technology can be extended to other aerospace, industrial and automotive industries.
Welding glass to metal
A second initiative also aims to improve performance of materials in space environments, in this case assembling parts made of different materials. Researchers from NASA’s Goddard Space Flight Center in Greenbelt, Maryland is experimenting with high-speed lasers to fuse components of glass and metal. A team led by Goddard physicist Robert Lafon is testing ultra high-speed femtosecond lasers — measured in one quadrillionths of a second — to weld small pieces of glass to metal, glass to glass, and to drill tiny pin holes in materials.
The researchers are also extending that capability to larger pieces of materials used in equipment and systems used in space. Those materials include exotic glass such as sapphire and Zerodur, an industrial ceramic, as well as metals like titanium. Their advances are expected to make it easier and safer to affix glass to metal. As Lafon explains in a NASA statement, “You have to use epoxy, which outgases and deposits contaminants on mirrors and other sensitive instrument components. This could be a serious application. We want to get rid of epoxies.”
Drilling tiny hair-size holes with lasers is also a potentially useful innovation. “The ability to remove small volumes of material without damaging the surrounding matter allows us to machine microscopic features,” notes Lafon. The technology, say the researchers, can be applied to etching microscopic channels or waveguides through which light could travel in photonic integrated circuits, as well as producing channels in microfluidic, or lab-on-a-chip, devices for drug and chemical analysis in space.
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