Laser Beam Shaping and Laser Beam Oscillations – Local and Temporal Modulation of the Energy Input as the Solution for Hard-to-weld Materials?

Additive manufacturing (AM), especially the process of Powder Bed Fusion using a laser-based system (PBF-LB/M), is nowadays a well-established technology that is already used for the manufacture of industrial parts, especially in the aerospace sector. As the processed materials mainly originate from the casting technology, severe process faults like hot cracking (solidification and liquation cracking), cold cracking, and, often still, residual porosity emerge during laser processing of the materials. Nevertheless, materials like highly alloyed aluminum (e.g., 2xxx, 6xxx, and 7xxx series), Ni-based superalloys, as well as refractory metals like tungsten, are of high interest for several industry sectors like aerospace, automotive, high-performance lightweight applications, plasma-facing environments (nuclear fusion), heat exchangers, and more. Especially for such high-end materials and applications, AM can play an essential role in manufacturing extremely complex and application-specific parts. This presentation provides an approach for the crack-free processing of hard-to-weld materials like highly alloyed aluminum and refractory metals like tungsten in process-based approaches, such as laser beam shaping and laser beam oscillations, that can be applied to every modern PBF-LB/M machinery. Such processing strategies tackle the root cause of hot or cold cracking – namely, the rapid cooling rate, with a locally and temporally adapted laser intensity distribution. With the application of both strategies – laser beam shaping and laser beam oscillations (with and without a combination) – severe crack reduction, up to a reproducible crack elimination at crack-prone materials like Al2024, Al6013, and tungsten, can be achieved. The experiments were conducted on bare metal sheets with a thickness of 2 mm, a laser wavelength of 1070 nm, and a variation of the laser power, scan speed, oscillation amplitude, oscillation frequency, laser beam profile, and spot diameter. An analysis of the top-view as well as the cross sections of the specimens gives detailed information about the cracking behavior and the microstructure depending on the adjusted parameter settings.