After the discovery of laser technology in 1960, the precision and fexibility of lasers showed great potential for material and surface processing. Due to the high initial costs and the low effciency of laser beam sources, it took laser cladding until the 1980s to become adopted industry-wide (Corbin et al. 2004). It proved to be a promising alternative to conventional electric arc welding and cladding methods,since the confned heat input results in low dilution and an overall reduction of defects (Morgado and Valente 2018).
At its core, laser cladding is a laser welding process where individual weld beads are aligned and stacked onto a substrate material. In its simplest form, it is used to clad metal surfaces with metals or carbides. Typical applications are the reinforcement of mechanical parts that are used in abrasive or corrosive environments (Lachmayer et al. 2018). The cladding of ductile round stock with a hard and wearresistant metal improves tribological properties of gears and bearings. Compared to other cladding processes, the laser-based process is very fexible and therefore the higher investment for the laser source is often worthwhile. Additive manufacturing with laser cladding evolved with the need for the repair of worn drawing dies for metal stamping (Levy et al. 2003). In addition, reinforcement of structures with increased complexity used in the automobile industry is possible.
Generally, laser cladding process heads exist in two different confgurations, which themselves are distinctive in wire and powder-based fller material. At the same time, both systems can be designed with an off-axis or a coaxial material supply (Lammers et al. 2018).
Laser metal deposition in pure cladding applications is typically set up for maximum deposition rates. Therefore, large amounts of wire or powder fller material are added to the laser processing zone off-axially. For sophisticated additive tasks with higher resolution, a coaxial powder or wire nozzle setup is required.
One of the main advantages of laser cladding for additive manufacturing is the large build volume, where some build-chambers can have the size of multiple cubicmeters.The possibility to add onto existing freeform surfaces allows the combination of high-speed conventional machining and specialized additive manufacturing.
Advances in process development enable not only changing complexity, but also the use of special and even hard to weld materials. Laser cladding is not only limited to metals, even ceramics or carbides can be used to disperse into metal surfaces to functionalize 3D-printed parts.
Leveraged through advanced process monitoring and feedback control loops, even larger objects with longer print durations and ultimately safety-relevant aviation parts can be manufactured and repaired.
