Laser deposition welding
Laser cladding part of the cladding (cladding), an almost arbitrary material takes place in which a workpiece a surface application by means of melting and simultaneous application. This can be in powder form e.g. B. done as metal powder or with a welding wire or band. In laser deposition welding, a high-power laser , primarily a diode laser or fiber laser , previously also CO 2 and Nd: YAG lasers , serves as the heat source .
The method can be used to create layers as well as free-form 2.5D structures ( laser generation ). In the latter case, it can be assigned to the 3D printing process.
With laser deposition welding with powder, the laser usually de- focussed the workpiece and melts it locally. At the same time, an inert gas mixed with fine metal powder is fed in. The metal / gas mixture is supplied to the effective area via drag or coaxial nozzles . At the heated point, the metal powder melts and bonds with the metal of the workpiece. In addition to metal powder, ceramic powder materials, especially hard materials , can also be used. Laser deposition welding with wire or tape works in the same way as the process with powder, but with wire or tape as filler material.
With the correct setting of the parameters laser power, feed , mass flow of the powder or, alternatively, the wire or band feed and the focus position, a material application is created on the workpiece, which can be formed into a surface or wall with repeated passes - next to each other or one above the other. The generation of free-form structures without undercuts is also possible with appropriate process management. The connection to the base material can, for. B. can be influenced by the formation of an intermediate layer via the parameters. Subsequent post-processing steps such as milling or turning are usually necessary.
In industrial applications, powder laser deposition welding is mainly used in a fully automated manner, while wire laser deposition welding is mainly used in manual laser welding systems.
The process is used wherever expensive, mostly large components have to be repaired, as they cannot be replaced inexpensively. In addition to forming tools, engine parts and turbine parts such as blades , disks and blisks are among the best-known repair parts. In addition, the process is also used to build functional layers (e.g. wear protection layers).
With standard processing heads, there are always difficulties when processing components with small inner diameters such. B. transmission components or engine interiors, as these cannot penetrate into the corresponding depth. The first miniaturized heads for bore diameters between 25 and 80 mm are currently being tested in practice. They reach depths of up to 500 mm, areas that conventional processing heads cannot reach due to their design.
Micro cladding is a special form of the process for the micro range. It uses either continuously radiating fiber lasers that are strongly focused and fast axis systems or, alternatively, high-repetition pulsed fiber lasers that are also strongly focused, and fast laser scanners for beam deflection . The powder used has a grain diameter of less than 10 μm. Micro walls with a width of 30 µm have already been created. Applications are increasingly aimed at the flexible generation of structures for electronic applications and the texturing of surfaces.
literature
- Ehsan Toyserkani, Amir Khajepour, Stephen F. Corbin: Laser Cladding . CRC, Boca Raton 2004.