30 Jun 2009
Fraunhofer ILT and its industrial partners have developed an innovative and cost-efficient repair technique for engine components.
A laser cladding technique that exploits a novel design of feed nozzle allows the localized repair of aero-engine components made from titanium and nickel-based alloys, or superalloys, which would previously have had to be replaced in their entirety.
The new process uses a laser to generate a local weld pool on the surface of the component. A specially designed powder-feed nozzle then introduces a metal powder composed of a similar material into the molten metal. Once cooled, the resulting layer possesses very similar mechanical properties to those of the original component.
"What is so innovative is that we can take oxidation-sensitive titanium materials and components that have a tendency to distort, and weld them in a precise and reproducible manner without any distortion," said Andres Gasser, project manager at the Fraunhofer Institute of Laser Technology in Aachen, Germany. "A local gas atmosphere is used to prevent the molten weld pool generated in the cladding process from reacting with the surrounding atmosphere. This method avoids the need for a costly gas chamber."
One key element of this technique is a newly developed system of powder-feed nozzles, which makes powder use more efficient while also preventing oxidation of the layers. According to Gasser, the nozzles' modular configuration means that the range of possible applications is virtually unlimited.
To test the process in an industrial setting, the Fraunhofer team has employed a modified laser cladding machine (based on a system originally produced by TRUMPF). The machine has been operational at Rolls Royce Deutschland for a year, and the engine manufacturer says that the new repair technique has reduced the time required for general overhauls of engines by approximately one third.
The technique will now be developed further by an innovation cluster called TurPro, or "Integrative production technology for energy-efficient turbomachinery". Established by the Fraunhofer-Gesellschaft, TurPro will apply the technique to other turbomachinery components. The intention is to prove its value in repairing land-based turbines, which would open up its use in general engine technologies as well as in other areas of mechanical engineering.