A group of scientists from Sandia National Laboratories, Ames National Laboratory, Iowa State University and Bruker Corp., all in the USA, used a 3D printer to create a high-performance metal alloy, or superalloy, with an unusual composition that makes it stronger and lighter than state-of-the-art materials currently used in gas turbine machinery.
The findings could have broad impacts across the energy sector as well as the aerospace and automotive industries, and point towards a new class of similar alloys that have yet to be discovered.
"We're showing that this material can access previously unobtainable combinations of high strength, low weight and high-temperature resiliency," Sandia scientist Andrew Kustas said. "We think part of the reason we achieved this is because of the additive manufacturing approach."
Both fossil fuel and nuclear power plants rely on heat to turn turbines that generate electricity. But power plant efficiency is limited by how hot metal turbine parts can get.
Image credit: Craig Fritz, Sandia National Laboratories
If turbines can operate at higher temperatures, then more energy can be converted to electricity while reducing the amount of waste heat released to the environment.
The new superalloy, which is composed of 42 per cent aluminium, 25 per cent titanium, 13 per cent niobium, 8 per cent zirconium, 8 per cent molybdenum and 4 per cent tantalum – was stronger at 800°C than many other high-performance alloys, including those currently used in turbine parts, and still stronger when it was brought back down to room temperature.
"This is therefore a win-win for more economical energy and for the environment," said Sal Rodriguez, a Sandia nuclear engineer who did not participate in the research.
Aerospace researchers seeking out lightweight materials that stay strong in high heat could also benefit from the superalloy.
3D printing is already widely used as a versatile and energy-efficient manufacturing method. It uses a high-power laser to flash-melt a material, usually a plastic or a metal which is then deposited in layers to build an object as the molten material rapidly cools and solidifies.
The researchers repurposed the technology as a fast, efficient way to craft new alloys by using a 3D printer to melt together powdered metals and then immediately produce a sample of it.
"We have a lot of examples of where we have combined two or three elements to make a useful engineering alloy," Kusta said. "Now, we're starting to go into four or five or beyond within a single material. And that's when it really starts to get interesting and challenging from materials science and metallurgical perspectives."
Moving forward, the team is interested in exploring whether advanced computer modelling techniques could help researchers discover more members of what could be a new class of high-performance superalloys produced by additive manufacturing.
"These are extremely complex mixtures," said Sandia scientist Michael Chandross who was not directly involved in the study. "All these metals interact at the microscopic – even the atomic – level, and it's those interactions that really determine how strong a metal is, how malleable it is, what its melting point will be and so forth.
"Our model takes a lot of the guesswork out of metallurgy because it can calculate all that and enable us to predict the performance of a new material before we fabricate it."
