Sandia scientists 3D print new superalloy

In the emerging field of additive manufacturing, researchers from Sandia National Laboratories in Albuquerque, N. M., have developed a material that could significantly reduce carbon emissions from electricity-generating power plants.

The Sandia scientists, collaborating with researchers at Ames National Laboratory, Iowa State University, and Bruker Corp., used metal 3D printing, also called additive manufacturing, 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 turbines used to generate electricity.

Sandia's experiments showed that the new superalloy – 42% aluminum, 25% titanium, 13% niobium, 8% zirconium, 8% molybdenum, and 4% tantalum – was stronger at 800 degrees Celsius (1,472 degrees Fahrenheit) 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.

"We're showing that this material can access previously unobtainable combinations of high-strength, low-weight and high-temperature resiliency," said Sandia scientist Andrew Kustas. "We think part of the reason we achieved this is because of the additive manufacturing approach."

The new material also represents a fundamental shift in alloy development because no single metal makes up more than half of the material. By comparison, steel is about 98% iron combined with carbon, among other elements.

"Iron and a pinch of carbon changed the world," said Kustas, who supervised the project and authored the research paper. "We have a lot of examples of where we have combined two or three elements to make a useful engineering alloy. 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."

3D printing offers advantages

Metal 3D printing is a versatile and energy-efficient manufacturing method that is gaining popularity, especially in cost-effective, high-tech applications. This printing technique typically uses a high-power laser to flash-melt a material deposited in layers, building an object as the molten material rapidly cools and solidifies.

Sandia's researchers have found metal printing can also serve as a fast and efficient way to craft new materials by quickly melting together powdered metals and then immediately printing a sample.

In an article titled "Extreme hardness at high temperature with a lightweight additively manufactured multi-principal element superalloy," published in the December 2022 edition of the journal Applied Materials Today, the Sandia team describes the advantages and potential applications for the new 3D printed alloy.

"Compositionally, the present alloy is expected to be significantly less dense than refractory-rich multi-principal-element alloys (MPEA), while also retaining higher strength and more refined microstructure achievable with the rapid solidification of additive manufacturing," the researchers penned in the article. "This highlights the value proposition of combining advanced alloys with advanced manufacturing methods to achieve unusual materials properties."

They said the ability to shape a superalloy into nearly its end-use form offers multiple opportunities to accelerate the development of next-generation lightweight structural aerospace alloys by using more conventional gas-atomized feedstock powders.

"This would enable more direct comparisons of strength and toughness at similar part geometry length scales with other additive manufacturing process results using the superalloy powders," the researchers said.

Moving forward, the team is interested in exploring whether advanced computer modeling techniques could assist in the discovery of more members of what could be a new class of high-performance, additive manufacturing-forward superalloys.

"These are extremely complex mixtures," according to Sandia scientist Michael Chandross, an expert in atomic-scale computer modeling 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 enables us to predict the performance of a new material before we fabricate it."

Kustas said challenges lie ahead. For one, it could be difficult to produce the new superalloy in large volumes without microscopic cracks, which is a general challenge in additive manufacturing. He also said the materials that go into the alloy are expensive. So, the new metallic material might not be appropriate for consumer goods, for which keeping costs down is a primary concern.

"With all those caveats, if this is scalable, and we can make a bulk part out of this, it's a game changer," he added.

More alloys, applications

Sandia's scientists said the new 3D-printed alloy could have a major impact on the energy sector and be an important new material for the aerospace and automotive industries.

About 80% of electricity in the United States and 73% percent of the world's electricity comes from fossil fuel or nuclear power plants, according to the U.S. Energy Information Administration. Both types of facilities rely on heat to turn turbines that generate electricity. Engineers say power plant efficiency is limited by how hot the metal turbine parts can get. 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.

Energy is not the only industry that could benefit from the findings. Aerospace researchers also seek out lightweight materials that stay strong in high heat.

Additionally, Ames Lab scientist Nic Argibay said Ames and Sandia are partnering with the automotive industry to explore how alloys like this could be used in next-generation vehicles.

Ames is also assisting in research that could lead to the development of a new class of 3D-printed metallic materials.

"Electronic structure theory led by Ames Lab was able to provide an understanding of the atomic origins of these useful properties, and we are now in the process of optimizing this new class of alloys to address manufacturing and scalability challenges," Argibay said.

The U. S. Department of Energy and Sandia's research and development program funded the research.