Scientists at the GE Global Research labs (GRC) and the Polytechnic University of Bari, Italy have developed a method of cold spraying metal powder onto repair parts.
It involves using particles that leave a cold spray nozzle at four times the speed of sound. ‘The tiny bits of material fly so fast then they essentially fuse together when they hit the target,’ said Gregorio Dimagli, materials scientist at GE subsidiary Avio Aero. ‘Unlike welding, you don’t need to apply heat to make them stick. The bond happens on the atomic level.’
The method, called cold spray or ‘3D painting’, will allow Avio Aero and its parent, GE Aviation, to repair turbine and compressor blades without changing their highly complex underlying crystal structure. It could build whole new parts with walls as thick as one inch or more. According to Dimagli, possible applications range anywhere from heavy-duty gear boxes for oil and gas machinery, to gas turbine rotors and jet engine blades. ‘These methods are the future,’ he says. ‘Compared to what we are using now, you get better quality for less money and you are also done faster.’
Optimal deposition
The 3D painting gun uses pressurized carrier gas zipping through a de Laval nozzle to accelerate powder particles as small as 5 microns to supersonic velocities. The speed causes localized high energy collisions when the particles hit the surface, the micro version of bullets hitting a steel bar. Cold spray operators are using a computer-controlled robot to manipulate the gun. Like 3D printers, the computer works with a 3D image of the part. Engineers program the robot so that it moves in an optimal way to deposit the powder.
The new lab will employ three Avio Aero scientists and six researchers from the university. They will use thermography and other scientific disciplines to look for the best applications of the new methods.
This story is reprinted from material from GE, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier.
