The method builds the blades from a titanium powder fused with a beam of electrons accelerated by a 3-kilowatt electron gun.
The gun is 10 times more powerful than laser beams currently used for printing metal parts. This boost in power allows Avio, which is part of GE Aviation, to build blades from layers of powder that are more than four times thicker than those used by laser-powered 3D printers.
As a result, one machine can produce eight stage 7 blades for the low pressure turbine that goes inside the GEnx jet engine in just 72 hours. “This is very competitive with casting, which is how we used to make them,” says Mauro Varetti, advanced manufacturing engineer at Avio.
Avio developed the technology, called electron beam melting or EBM, together with Sweden’s Arcam. The idea was to improve the manufacturing of parts made from an advanced aerospace material called titanium aluminide (TiAl). The material is 50 percent lighter than the nickel-based alloys typically used for low pressure turbine blades.
Blades made from the material can reduce the weight of the entire low pressure turbine by 20 percent. “Although the material is expensive, the weight savings and the fuel consumption savings tied to weight reduction more than pay for it,” Varetti says.
But titanium aluminide is also notoriously hard to work with. Companies normally use lost-wax casting or spin casting to make TiAl parts. However, the material has a very high contraction ratio and can become fragile and prone to cracks as it cools. The EBM printer solves these problems.
The printer builds parts directly from a 3D computer drawing by melting layers of fine powder with an electron beam. The technology allows workers to preheat the powder and better control the part’s properties.
Engineers can also change the shape of the blades and print different blades on the same machine in a quick succession, which would be laborious and expensive with casting.
Later this year, GE will start testing blades printed for the GEnx engine at its test facility in Peebles, Ohio. GE designed the GEnx for Boeing’s Dreamliner and 747-8 aircraft. The parts will also go inside the GE9X, a new jet engine GE is developing for Boeing’s next-generation long-haul plane, the 777X.
EBM machines are now working inside Avio’s new 20,000-foot plant near Turin, Italy. The factory, which is dedicated to additive manufacturing, opened last August.
GE also started building a new factory for making 3D-printed jet engine fuel nozzles in Alabama. Gregg Morris, who runs additive manufacturing programs at GE Aviation, says he can think of dozens of jet engine parts that could be 3D-printed. “The sky is the limit,” he says.