Acting as engines in power generation plants, gas turbines operate in temperatures exceeding 1,600°C. But the nickel-based turbine blades used in the plants melt at temperatures 200°C lower and need air-cooling to operate.
To develop turbines with materials that can withstand higher temperatures and reduce CO2 emissions, Kyoto University’s materials scientists examined the properties of various compositions of molybdenum silicides, with and without additional ternary elements.
Earlier investigations carried out to fabricate molybdenum silicide-based composites by pressing and heating their powders resulted in improving their resistance to fracturing at ambient temperature.
But the fabrication proved to be lowering their strength at high temperatures due to formation of silicon dioxide layers within the material.
To address the issue, the Kyoto University team fabricated their molybdenum silicide-based materials using a method known as "directional solidification.”
The method allows the molten metal to progressively solidify in a certain direction.
The team discovered that by controlling the solidification rate of the molybdenum silicide-based composite during fabrication and by adjusting the amount of the ternary element added to the composite could lead to formation of a homogeneous material.
The material has been found to begin deforming plastically under uniaxial compression above 1000°C.
The research has also found that adding tantalum to the composite is more effective than adding vanadium, niobium or tungsten for improving the strength of the material at temperatures around 1400 degrees Celsius.
The alloys fabricated by the university team are expected to be much stronger at high temperatures than modern nickel-based superalloys as well as recently developed ultrahigh-temperature structural materials.
