December 17, 2020
Organic molecules on a metal surface…a machinist’s best friend
WEST LAFAYETTE, Ind. – How can you improve the cutting of “gummy” metals? Purdue University innovators have come up with an answer – and their findings may help in manufacturing products and reducing component failures.
The researchers previously showed that the application of a permanent marker or Sharpie, glue or adhesive film made it easier to cut metals such as aluminum, stainless steels, nickel, copper and tantalum for industrial applications. Marking the metal surface to be machined with ink or an adhesive dramatically reduced the force of cutting, leaving a clean cut in seconds. Now, they have discovered how these films produce the effect.
“We have found that you only need the organic film from the markers or glue to be one molecule thick for it to work,” said Srinivasan Chandrasekar, Purdue professor of industrial engineering. “This ultra-thin film helps achieve smoother, cleaner and faster cuts than current machining processes. It also reduces the cutting forces and energy, and improves the outcomes for manufacturing across industries such as biomedical, energy, defense and aerospace.”
The research is published in Science Advances. The study involves a collaboration between researchers at Purdue, Osaka University (Japan) and the Indian Institute of Science (India). The research is supported by the National Science Foundation and U.S. Department of Energy.
If a significant improvement can be made to the machinability of gummy metals or alloys – that is how well they cut, drill or grind – then there is potential to lower the cost of products, improve their performance or enable new and improved product designs.
The researchers found, using organic monolayer films created by molecular self-assembly, that the molecule chain length and its adsorption to the metal surface are key to realizing these improvements. By using the “right” organic molecules, the metal is locally embrittled resulting in improved machining.
“We are also learning through our discovery more about how environmental factors influence failure of metals,” said Anirudh Udupa, a lead author on the study and a researcher in Purdue's School of Industrial Engineering. “As we decipher how the organic molecular films improve the machinability of these metals, the better also is our understanding of common environment-assisted failures in metals, such as stress-corrosion cracking, hydrogen embrittlement and liquid metal embrittlement.”
The researchers are looking for partners to continue developing their technology. For more information on licensing and other opportunities, contact OTC at firstname.lastname@example.org and mention track code 2019-CHAN-68634.
About Purdue Research Foundation Office of Technology Commercialization
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Anirudh Udupa, firstname.lastname@example.org
Organic Monolayers Disrupt Plastic Flow in Metals
Tatsuya Sugihara, Anirudh Udupa, Koushik Viswanathan, Jason M Davis
and Srinivasan Chandrasekar
Adsorbed films often influence mechanical behavior of surfaces, leading to well-known mechanochemical phenomena such as liquid metal embrittlement and environment-assisted cracking. Here, we demonstrate a previously unidentified mechanochemical phenomenon wherein adsorbed long-chain organic monolayers disrupt large-strain plastic deformation in metals. Using high-speed in situ imaging and post-facto analysis, we show that the monolayers induce a ductile-to-brittle transition. Sinuous flow, characteristic of ductile metals, gives way to quasi-periodic fracture, typical of brittle materials, with 85% reduction in deformation forces. By independently varying surface energy and molecule chain length via molecular self-assembly, we argue that this “embrittlement” is driven by adsorbate-induced surface stress, as against surface energy reduction. Our observations, backed by modeling and molecular simulations, could provide a basis for explaining diverse mechanochemical phenomena in solids. Additionally, the results have implications for manufacturing processes such as machining and comminution, and wear.