Discovery could create superior alloys with many applications

Discovery could create superior alloys with many applications
Concentrated solar power is just one technology that urgently needs alloys with superior abilities to withstand high temperature corrosion.

Many current and future technologies require alloys that can withstand high temperatures without corroding. Researchers at Chalmers University of Technology, Sweden, have seen a breakthrough in creating superior alloys.

The Chalmers team have made a breakthrough in understanding how alloys behave at high temperatures, pointing the way to significant improvements in many technologies, with the discovery potentially leading to the creation of superior alloys with many applications.

Developing alloys that can withstand high temperatures without corroding is a major challenge in many fields, such as:

  • Renewable and sustainable technologies;
  • Aviation;
  • Materials processing; and
  • Petrochemistry.

Why are superior alloys so important?

According to Chalmers University, at high temperatures alloys can react violently with their environment, causing the materials to fail by corrosion. To protect against this, all high temperature alloys are designed to form a protective oxide scale, usually consisting of aluminium oxide or chromium oxide.

Oxide scale plays a key role in preventing the metals from corroding. Therefore, research on high temperature corrosion is focused on these oxide scales – how they are formed, how they perform at high heat, and how they sometimes fail.

Nooshin Mortazavi, a materials researcher at Chalmers’ Department of Physics, said: “Adding reactive elements to alloys results in a huge improvement in performance – but no one has been able to provide robust experimental proof why.

“Likewise, the role of water, which is always present in high-temperature environments, in the form of steam, has been little understood. Our paper will help solve these enigmas.”

How are these elements linked?

Researchers show how these two elements are linked by demonstrating how the reactive elements in the alloy promote the growth of an aluminium oxide scale.

The presence of these element particles causes the oxide scale to grow inward, rather than outward, thereby facilitating the transport of water from the environment towards the alloy substrate. Reactive elements and water combine to create a nanocrystalline, oxide scale.

Further to their discoveries, the Chalmers researchers suggest a practical method for creating more resistant alloys. They demonstrate that there is a critical size for the reactive element particles. Reactive element particles cause cracks in the oxide scale when above a certain size, which then provides an easy route for corrosive gases to react with the alloy substrate, causing rapid corrosion.

This ground-breaking research from Chalmers University of Technology points the way to stronger, safer, more resistant alloys in the future.

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