Engineering research groups at the University of Alberta have discovered a new coating material that is expected to be used in high-temperature applications such as hydrogen-fired engines. This coating is made from a new superalloy of metals such as aluminum and nickel, and the new material is called a composite concentrated alloy, which is ideal for surface coatings that must withstand high temperatures, such as gas turbines, power stations, automobile and aircraft engines. The newly developed AlCrTiVNi5 alloy has excellent thermomechanical properties, including high stability, low expansion, fracture tolerance, and a valuable combination of strength and ductility, which allows it to withstand high thermal and high-pressure environments.
Project Leader Jing Liu, Assistant Professor in the Department of Chemical and Materials Engineering, said the new coating material performs better than existing commercial alloys used as coatings for high-temperature applications. It turned out to be very important for the use of hydrogen engines. Hydrogen is considered one of the cleanest energy sources because it produces only water when burned or used in fuel cells. It plays an important role in the emission reduction goals of Canada and Alberta and is used in a wide range of applications, including transportation, home heating, and heavy industry.
However, one of the challenges of adopting hydrogen is its high combustion temperature, ranging from 600 degrees Celsius to 1,500 degrees Celsius. These extreme temperatures mean that any mechanical parts involved in the combustion of hydrogen must be able to withstand high temperatures and resist the corrosion of steam. Professor Jing Liu said that if you want to burn an engine with 100% hydrogen fuel, the flame temperature will be very high. Until now, none of the existing metal coatings have been able to function in 100% hydrogen-fueled engines.
Currently, most hydrogen-fueled engines in commercial applications use blended fuels, such as natural gas and hydrogen, or diesel and hydrogen, but as more and more industries use hydrogen as their primary fuel source, Professor Jing Liu believes it is necessary to prepare for the ultra-high temperature conditions of fully hydrogen-fueled engines. As we move towards 100% hydrogen-fueled engines, we want to know which alloys can withstand these conditions. None of the existing alloys can withstand it, but we have learned valuable lessons from these failures.
The research team identified the strengths and weaknesses of each existing commercially available alloy, then used theoretical simulations to identify new combinations of strength and durability that might have the strength and durability they were looking for, and computer modeling to understand the properties of each potential new alloy. Simulations and calculations are used to understand how the interface between matter and the environment changes if the composition is changed.
After identifying AlCrTiVNi5, the team conducted the same high-temperature tests on the new alloy as existing commercial alloys. All existing alloys failed after 24 hours or less in a corrosive environment at high temperatures, but this new composite concentrated alloy withstood the challenge.
While this new alloy is expected to withstand a high proportion of the heat of hydrogen-burning engines, further research is needed before widespread adoption, opening the door to new possibilities that are expected to drive Canada's hydrogen economy. The study, titled "Novel Entropy-Stabilized Oxide Coatings Thermally Grown from Valve Metal-Based Composite Concentrated Alloys," has been published in Materials Today.