Jul. 21--OAK RIDGE -- A new class of stainless steels developed at Oak Ridge National Laboratory could have broad applications in the energy sector, and ORNL already has signed three collaborative research agreements with companies interested in pushing the development for commercial uses.

The alumina-forming austenitic stainless steels -- known as AFAs -- resist corrosion at high temperatures while maintaining their strength, and their cost is reportedly low compared to other high-performance alloys. That makes them potentially applicable for a broad range of uses, from components in gas turbines to tubing in the petrochemical industry.

"What's different is most stainless steels use chromium to make them corrosion resistant," said Mike Brady, a senior researcher in ORNL's Materials Science and Technology Division. "That's where the stainless aspect comes from. This alloy uses aluminum instead of chromium."

There are nickel-based alloys on the market with some of the same properties, but they are much more expensive, Brady said.

"What we've done is get these aluminum additives to work in an iron-based material, which is much cheaper than a nickel-based material," he said. Typically that would weaken the iron at higher temperatures, but the Oak Ridge research team was able to overcome those inherent problems, he said.

The invention came in 2007, when the first paper was published in the journal Science, but the growing involvement of private industry could speed commercial use of these new alloys.

"We think there's a chance there'll be a pretty wide applicability," Brady said.

Higher operating temperatures -- in fossil fuel power plants, heat exchanges in engines, gas turbines, and fuel cells -- can result in greater energy efficiency and reduced emissions of greenhouse gases. That's why researchers are pushing development of alloys for use at the highest temperatures possible.

ORNL has active CRADAs (cooperative research and development agreements) with two small turbine engine makers -- Capstone Turbine Corp.and Solar Turbines Inc. -- and an alloy producer, Carpenter Technology Corp.

"We're also talking with chemical and petrochemical companies," Brady said.

The lab currently is working with alloy producers to do small castings of 40 to 50 pounds of materials, using commercial processes to make sure the AFAs can be done the same way as standard stainless steels, and working with engine companies on development and testing of prototype parts.

Senior writer Frank Munger may be reached at 865-342-6329.

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