Researchers from Virginia Tech have made a significant discovery regarding a new solid lubrication method that significantly lessens friction in machinery, even at extremely high temperatures. This breakthrough surpasses the breakdown temperature commonly associated with traditional solid lubricants like graphite, and the detailed findings were shared in Nature Communications.
“This innovative solid-state lubricant could revolutionize how we create materials for advanced engines, potentially enhancing their durability and performance in extreme environments,” remarked Rebecca Cai, an associate professor in the Department of Materials Science and Engineering and a co-author of the study. “Despite decades of exploration, only about 20 solid lubricants have been identified.”
Having the right lubricant can prolong a jet engine’s lifespan, leading to savings of millions of dollars; however, most of those identified lubricants deteriorate at temperatures comparable to molten lava. This discovery is crucial given that friction and wear are projected to cost the U.S. economy over $1 trillion in 2023, which is roughly equal to 5 percent of the nation’s gross domestic product.
With the growing significance of materials in innovative sectors like advanced manufacturing, these results establish Virginia Tech as a frontrunner in pioneering technologies and state-of-the-art research, presenting exciting possibilities for interdisciplinary problem-solving.
Challenges with Lubricants
Friction is fundamental to movement; however, in many industrial sectors, including advanced manufacturing, transportation, and aerospace, excessive friction can lead to equipment wear. Lubricants, which are materials that minimize friction between contacting surfaces, play a vital role in ensuring safe operations and peak performance. Nonetheless, creating materials that can resist wear at temperatures exceeding 600 degrees Celsius (1,000 degrees Fahrenheit) is still a considerable challenge.
The path to these groundbreaking discoveries regarding solid lubricants required extensive time, intellectual effort, and institutional collaboration.
“Working collaboratively with other universities allowed many knowledgeable individuals to come together to exchange resources, which is essential in this field,” noted Zhengyu Zhang, who was a Ph.D. student and the primary author of the study. “The future of numerous industries hinges on advances in materials science, and such a broad topic demands diverse expertise.”
The success of this discovery also relied on a high-temperature tribometer, a device that Cai acquired for her lab in 2019. This advanced instrument assesses friction, wear, and other tribological characteristics between two surfaces under high-temperature conditions. At that point, Virginia Tech was a leader in making this technology available to faculty and graduate students, providing the necessary testing capabilities at temperature levels far exceeding conventional equipment.
Solid Results
The research team employed high-temperature trials, sophisticated materials analysis, and computational techniques to demonstrate that layers of spinel oxide—a specific mineral class that serves as a coating—can naturally develop on the surfaces of additively manufactured metals during high-temperature oxidation, allowing for self-lubrication. This is made feasible because of the spinel oxide’s low shear strength, meaning the molecular bonds are weak and can slide past each other under stress, combined with its high stability that preserves its characteristics in challenging high-temperature situations.
Initially, the researchers utilized advanced computational tools to predict which oxides would function optimally. Subsequently, by meticulously altering the metal surface that formed a unique oxide layer, Cai and Zhang confirmed that spinel oxides possess superior resilience at elevated temperatures compared to previously used materials.
Each partner in the collaboration contributed crucial elements to the study:
- The University of Florida utilized 4D transmission electron microscopy to characterize and identify crystal structures of intricate oxidized surfaces.
- Jackson State provided the initial samples of the additively manufactured metals.
- Arizona State assisted in securing funding and performing calculations.
- Iowa State conducted simulations to analyze the mechanical properties of the key oxide.
- Nebraska-Lincoln performed high-temperature harness testing.
- Virginia Tech coordinated the project vision, executed high-temperature tribological tests, analyzed surface characterization, calculated key thermal and mechanical properties for all oxides, and carried out phase prediction analyses.
“This represents a significant scientific accomplishment, and we are grateful to our collaborators for making it happen,” said Cai. “Without the resources of Virginia Tech and robust partnerships with scientists across the nation, we wouldn’t have been able to uncover this new category of solid lubricant. These findings showcase an encouraging direction toward creating self-lubricating alloys for demanding temperatures.”
