Italian aerospace company Avio has worked with Swedish additive manufacturing specialist Arcam to produce metal turbine blades for GE's GEnx jet engine, used on the Boeing 787 and 747-8.
Arcam technology uses electron beams rather than the laser sources favoured by other additive manufacturing equipment makers, calling its process electron beam melting or EBM. The high power process can build blades from layers of powder that are more than four times thicker than those used by laser-powered 3D printers.
Using a 3 kW electron beam gun, said to be 10 times more powerful than the alternative laser beams, eight stage seven blades for the low pressure turbine element of the GEnx engine were produced 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, which is owned by GE.
The key focus of the project was to improve the manufacturing of parts made from titanium aluminide (TiAl), a material that is 50% 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%. "Although the material is expensive, the weight savings and the fuel consumption savings tied to weight reduction more than pay for it," Varetti says.
Titanium aluminide is notoriously hard to work with - companies normally using lost-wax casting or spin casting to make such parts. A problem is that the material has a very high contraction ratio, meaning it can become fragile and is prone to cracks as it cools. The EBM printer method solves these problems.
GE will start testing blades printed for the GEnx engine at its test facility in Peebles, Ohio, USA, later this year. The parts will also go inside the company's GE9X, a new jet engine for Boeing's next-generation long-haul plane, the 777X.
EBM machines are now working inside Avio's new 20,000 sq ft plant near Turin, Italy. Dedicated to additive manufacturing, the factory opened last August.
GE is building a new factory in the US for making 3D-printed jet engine fuel nozzles for its LEAP engine. The factory will eventually make up to 40,000 parts per annum.
Avio 3D-printed LPT blades for the LEAP, GEnx, GE90 and GE9X jet engines
Author: Andrew Allcock