Making Metals That Can Beat The Heat

Japanese researchers have identified an alloy that can withstand ultra-high temperatures and pressure.

AsianScientist (Oct. 9, 2018) – A research group in Japan has identified a metal capable of withstanding constant forces at ultrahigh temperatures. Their findings are published in Scientific Reports.

Heat engines are key to the future of harvesting energy from fossil fuels. Creep behavior—or a material’s ability to withstand forces under ultrahigh temperatures—is an important factor for heat engines since increased temperatures and pressures lead to deformation. Understanding a material’s creep can help engineers construct efficient heat engines that can withstand extreme temperature environments.

In the present study, scientists led by Professor Kyosuke Yoshimi of Tohoku University, Japan, developed a titanium carbide (TiC)-reinforced, molybdenum-silicon-boron (Mo-Si-B)-based alloy, or MoSiBTiC, whose high-temperature strength was identified under constant forces in the temperature ranges of 1,400-1,600 degrees Celsius.

The researchers assessed the alloy’s creep in a stress range of 100-300 megapascals for 400 hours. All experiments were performed in a computer-controlled test rig under vacuum in order to prevent the material from oxidizing or reacting with the any potential air moisture, which could ultimately result in rust formation.

“Our experiments show that the MoSiBTiC alloy is extremely strong compared with cutting-edge Nickel-based single crystal superalloys, which are commonly used in hot sections of heat engines such as jet engines of aircrafts and gas turbines for electric power generation,” said Yoshimi.

They also found that, contrary to previous studies, the alloy experiences larger elongation with decreasing forces. This behavior has so far only been observed with superplastic materials that are capable of withstanding unexpected premature failure.

These findings suggest that MoSiBTiC is suitable for use in systems that function at extremely high temperatures, such as energy conversion systems in automotive applications, power plants and propulsion systems in aircraft engines and rockets. However, the researchers noted that several additional microstructural analyses are required to fully understand the alloy’s mechanics and its ability to recover from high stress exposure.

“Our ultimate goal is to invent a novel ultrahigh-temperature material superior to Nickel-based superalloys and replace high-pressure turbine blades made of Nickel-based superalloys with new turbine blades of our ultrahigh-temperature material,” said Yoshimi. “To achieve that, as the next step, the oxidation resistance of the MoSiBTiC must be improved by alloy design, without deteriorating its excellent mechanical properties.”

The article can be found at: Kamata et al. (2018) Ultrahigh-temperature Tensile Creep of TiC-reinforced Mo-Si-B-based Alloy.


Source: Tohoku University.
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