Aerospace alloy research is all in a spin
06 November 2012
An ESA research facility is helping to develop an aircraft-grade alloy that is twice as light as conventional nickel superalloys, while offering equally good properties.
Airlines are always looking for ways to save fuel by cutting down on weight without sacrificing safety. Generally, cutting weight by 1 percent will save up to 1.5 percent in fuel. For commercial airlines, this saving quickly adds up, offering cheaper flights and fewer stopovers while reducing the overall impact on the environment.
Current turbine blades
For years, engineers have known that titanium aluminide alloys offer great weight benefits over the nickel superalloys used today in conventional jet engines. Since the newer alloy can withstand extreme temperatures up to 800°C, it is of particular interest to engine manufacturers.
Although it is possible to make the alloy in a laboratory, casting it in the shapes required by industry, such as a turbine blade, is not simple. ESA's Impress Project scientists have been looking into the problem. To understand natural processes, scientists often remove as many external variables as possible, concentrating their observations on core interactions. The Impress Project needed to ‘switch-off’ a factor that was hampering these observations: gravity.
Switching off gravity
Aluminium samples were heated in a small furnace carried in a sounding rocket launched from Kiruna, Sweden. During six minutes of free fall, they were heated to over 700°C and then monitored by X-rays as they cooled.
Looking at the results, the researchers realised that casting titanium aluminides might require looking in the opposite direction: hypergravity.
To help them in this regard, the Impress team turned to ESA’s centrifuge, located at the ESTEC research and technology centre in the Netherlands, to test their theory.
Casting the metals in a centrifuge creating up to 20 times normal gravity helps the liquid metals to fill every part of a mould, producing a perfectly cast alloy, even with complex shapes.
Over a million jet turbine blades will be made over the next eight years, and using titanium aluminide would reduce their weight by 45% over traditional components. The alloy’s benefits are also of interest to the car industry – before long, cars will run on engines using such space-based knowledge.