Monster Machines: This Electron Gun Turns Titanium Powder Into Turbine Blades For Planes

Monster Machines: This Electron Gun Turns Titanium Powder Into Turbine Blades For Planes

Titanium aluminide is a 3D-printable metal compound that holds great promise for lighter, stronger aircraft turbines but is notoriously difficult to work. That is, it was notoriously difficult to work with, until additive manufacturing firm Avio developed this metal-melting 3 kW electron gun.

Titianium aluminide (TiAl) is an intermetallic alloy developed beginning in the early 1970s for use in automotive and aircraft engines. Its light weight, strength, and resistance to both heat stress and oxidation make it ideal for these applications. It’s also 50 per cent lighter than the nickel superalloys currently employed.

For aircraft turbine blades, for example, using TiAl rather than conventional alloys has shown to boost the engine’s thrust to weight ratio by as much as 20 per cent. “Although the material is expensive, the weight savings and the fuel consumption savings tied to weight reduction more than pay for it,” Mauro Varetti, an advanced manufacturing engineer at Avio, the GE subsidiary that developed the new electron gun. However, TiAl tends to contract, shrink, and crack as it cools in a conventional lost-wax or spin-casting mould, leading to lots of wasted precursor and even higher production costs.

The EBM (electron beam melting) printer from Avio avoids this issue entirely. The system works by drafting the component in a vacuous three dimensional space from a stockpile of molten TiAl powder using a 3kW electron beam 10 times more powerful than any existing 3D metal-printing laser. Because the laser is so much more powerful than existing options, engineers can better control the properties of the TiAl and produce components from layers up to four times thicker (and sturdier) than existing Ni superalloys.

What’s more, the EBM can produce components in a fraction of the time needed by traditional casting. The new system can spit out as many as seven fan blades for the GE GEnx turbine engine every three days, in fact. That’s roughly the same speed as traditional casting — but with a fraction of the loss.

GE is already working with its Italian subsidiary to scale up the printing technology and begin incorporating the blades in its GE9x (for the new 777x) and its Genx engine used in the Dreamliner and 787. The company plans to begin testing engines with these new components at its Peebles, OH, test facility later this year. [GE ReportsARCAMWiki]