Tantalum, added composite molybdenum silicides helps boost material resilience of turbine blades, as tested by scientists at Kyoto University. Advanced compositions of molybdenum silicides improve the strength of blade materials at temperatures around 1,400 degrees Celsius (°C ). By contrast, nickel-based turbine blades, used in similar combustion systems, already melt at temperatures 200°C, or lower, and require significant air-cooling.
But the operating temperatures of modern gas turbine combustion systems can occasionally exceed 1,600 degrees Celsius, researchers pointed out. Kyoto University found that fabricating molybdenum silicide-based composite - by pressing and heating their powders (powder metallurgy) - improves resistance to fracturing at ambient temperatures. But this process also lowers the material’s high-temperature strength, owing to the inclusion of silicon dioxide layers within the material.
Using ‘directional solidification’, the team managed to fabricate their molybdenum silicide-based materials. The team found that a homogeneous material could be formed by controlling the solidification rate of the composite during fabrication, and by adjusting ternary elements added to the composite.
Tantalum increases material strength
“The new material only starts to deform plastically under uniaxial compression above 1,000 degrees Celsius,” researchers said, adding the material's high-temperature strength increases through microstructure refinement.
“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,” they pointed out.
In a report, published in the Journal Science and Technology of Advanced Materials, the researchers pointed out that alloys fabricated at Kyoto University are “much stronger at high temperatures than modern nickel-based super-alloys as well as recently developed ultrahigh-temperature structural materials.”