New aluminum, nickel superalloy promises 100% hydrogen combustion engines

University of Alberta Engineering researcher Meifeng Li. (Image courtesy of the U of A).

A new superalloy composed of metals such as aluminum and nickel has been developed by an engineering team at the University of Alberta with the goal of targeting high-temperature applications.

Known as a ‘complex concentrated alloy,’ the new material is ideal for coating surfaces such as those in gas turbines, power stations, vehicles and airplane engines.

In a paper published in the journal Materials Today, the researchers note that the alloy — AlCrTiVNi5 — has superior thermomechanical properties that include high stability, low expansion, fracture tolerance, and a valuable combination of strength and ductility — which make it able to stand up in high-heat and high-pressure environments. Thus, it could prove important for use in hydrogen engines.

“If you would like to use a 100% hydrogen fuel combustion engine, the flame temperature is extremely high,” Jing Liu, senior author of the study, said in a media statement. “Until now, none of the existing metallic coatings have been able to work in a 100% hydrogen combustion engine.”

Hydrogen burns at temperatures ranging from 600 to 1500 degrees Celsius. This means that any mechanical components involved in hydrogen combustion must be able to withstand high heat as well as resist corrosion from steam.

Currently, most hydrogen combustion engines in commercial applications run on a mix of fuels — natural gas and hydrogen, or diesel and hydrogen, for instance — but as more industries work to adopt hydrogen as a primary fuel source, Liu sees a need to prepare for the ultra-high temperature conditions of a fully hydrogen-fuelled engine.

“As we move toward a 100% hydrogen combustion engine, we want to know which alloys can withstand the conditions. None of the existing ones did, but we learn valuable insights from these failures,” she said.

The research team identified the strengths and weaknesses of each existing commercially available alloy, then used theoretical simulations to identify potential new combinations that might have the strength and durability they were looking for.

“We understand how things react when they heat up,” Hao Zhang, co-author of the study, said. “So we use these simulations and calculations to understand how the interface between the matter and the environment changes if we change the composition.”

After identifying AlCrTiVNi5, the team put the new alloy through the same high-temperature tests used on existing commercially available alloys. All of the existing alloys failed after 24 hours or less in the hot, corrosive environment, but the new complex concentrated alloy stood up to the challenge.

“We did our experiment on these corrosive environments for up to 100 hours at 900 degrees Celsius and it survived, so that’s a big improvement,” Zhang said.

Although the alloy offers promise to withstand the heat of a high-percentage hydrogen combustion engine, further studies are necessary before it can be widely adopted.

“This alloy outperforms anything else on the market right now,” Liu said. “It opens the door for new possibilities and will hopefully advance the Canadian hydrogen economy.”