A major improvement makes porous intermetallics five times more oxidation resistant

An interdisciplinary research team from Tomsk Scientific Center of the Siberian Branch of the Russian Academy of Sciences has proposed an effective method for boosting the performance of high-temperature burners by modifying the composition of intermetallics they’re made of. Microalloying of base metal powders with small amounts of dysprosium and yttrium allowed for even distribution of rare-earth elements (REE) throughout the entire volume of the material obtained via self-propagating high-temperature synthesis (SHS). Such an approach enhances the alloys’ oxidation resistance by up to five times. These findings have been published in high-impact journals Vacuum and International Journal of Alloys and Compounds .

"Porous intermetallic alloys that can withstand high temperatures without corroding or breaking apart is a major trend in materials science right now. These materials are essential to modern power generation and chemical reactors. Rare-earth elements like dysprosium, yttrium, or gadolinium are known for their ability to enhance the properties of alloys – even a tiny amount of 0.05 atomic percent can significantly boost their resistance to harsh oxidative environments. This means the burners can operate at temperatures above 1,000 ℃ for much longer without breaking down," explains Nikita Pichugin, a junior researcher at the Laboratory of Technological Combustion.

These porous materials are mostly powder-based. However, the lack of commercially available metal powders containing REE in Russia necessitated the development of a special technique to coat common powdered metals with a thin layer of dysprosium and yttrium. To prove the viability of the proposed approach, the powders were evaluated in the making of a porous material with improved properties.

Using an electron-beam setup – courtesy from the colleagues from the Laboratory of Advanced Technologies –, the researchers fused the magnetron sputtered REE coating onto the powder particles, thus creating a powder masteralloy with core-shell type particles with aluminum and chromium "cores" and dysprosium and yttrium "shells".

This modified powder was then used to create porous intermetallics via the SHS. The process is much like lighting a large sparkler: a mixture of nickel, aluminum, and masteralloy powders slowly burns at temperatures above 1,500–1,600 ℃, forming porous structures. The scientists studied how to properly use the new master alloys to ensure that the micro-concentration of REE is evenly distributed throughout the material. Tests showed that the high-temperature oxidation resistance of microalloyed porous materials is 2–5 times higher than that of conventional intermetallics. Their use in the production of burners, including infrared ones, will significantly extend the lifespan of these products at high temperatures.