| Abstract Scope |
Laser welding, cutting, and additive manufacturing processes are dominated by the use of ytterbium-doped fiber lasers. These systems operate in both single and multi-modes at a 1 µm wavelength, which is similar to that of Nd:YAG solid state lasers. Advances in their fiberoptic delivery in fiber laser systems have also allowed for rapid beam deflection and scanning over large regions, thus further increasing their application space across different metalworking processes. Even though these systems are widely used, the absorptivity of the 1 µm wavelength is typically only on the order of 0.3 for common stainless steels and nickel alloys. Absorptivity levels fall to levels of 0.1 and below when processing highly reflective materials, such as Al and Cu, thus limiting the utility of current fiber lasers. New blue light diode lasers that operate at wavelengths between 400-500 nm increase these absorptivity levels by more than 50% over current 1 µm wavelength systems. Little is known concerning the effect of these increasing absorptivity levels on the resulting weld dimensions or on the formation and stability of the keyhole formed during the laser welding process, introducing significant uncertainty into process development and process parameter selection. Given the higher absorptivity of the lower laser wavelengths and the uncertainty that will develop in the calculation of energy density and other critical beam-material interactions, process maps developed from experimental design of experiments and numerical modeling for these 1 m lasers will not be applicable. An in-depth knowledge of laser-material interactions is needed to provide process engineers with the tools to predict weld processing parameters and properties. Using selected high reflectivity materials and a baseline austenitic stainless steel, the performance of blue light and single mode 1 µm lasers will be compared with a standard 1 µm multi-mode fiber laser system. |