In a joint project, experts from the Siemens gas turbine manufacturing plant in Berlin and the Fraunhofer Institute for Laser Technology (ILT) in Aachen, Germany, have developed a laser-based technology that speeds up the manufacturing process for turbine vanes slated for the hot gas area of an engine. A modular manufacturing process has also been introduced to overcome problems that were encountered when producing delicate vane structures.
The new technology uses selective laser melting (SLM) and works similarly to a 3D printer. Special alloys are melted by laser on a powder bed, and the vane components are then built up layer by layer.
The Clean Energy Center commissioned by Siemens last year plays a major role in developing and refining gas turbines as a facility for conducting realistic tests on various turbine components with liquid or gaseous fuels. During the tests, individual turbine parts are exposed to temperatures of 1,500 degrees Celsius or more. Such components are usually manufactured from superalloys in a precision casting process, in which each iterative loop may last several months and incur significant costs.
Guide vanes consist of two massive platforms and an airfoil which has a delicate cooling structure that has presented a major manufacturing challenge in the past. Despite using SLM technology, the production of the cooling structure still required additional internal supports.
A modified process chain has solved the problem: both the airfoil and the two massive platforms that turbine vanes consist of are manufactured separately and then subsequently brazed together. This makes it possible to not only eliminate the supports in the blade, but also to improve the surface quality. The result is a fully functional component that can be used in hot path rig testing in order to deliver quick feedback to the design engineers.
This modular production of turbine blades offers significant potential for other components as well. It would make it possible to connect cast and SLM-made parts, leaving just the complex or variable parts to be produced using SLM. At the same time, it would also facilitate the production of parts with difficult geometries that are currently too large for the SLM process.