Beam shaping technology and its application in metal laser additive manufacturing: A review

Laser additive manufacturing (AM) technology is widely applied in manufacturing critical components (e.g., rocket fuel nozzles, satellite antenna mounts and human implants, etc.) in automotive, medical, aerospace and other fields due to the advantages of high manufacturing precision, flexibility and automation. This technology can considerably improve the combination property of printed parts by integrated manufacturing of material structure and performance. Currently, in the focused Gaussian beam, the energy distribution is high in the center and low at the edge is generally employed in laser AM technology. However, it tends to produce a high thermal gradient in the melt pool, resulting in a subsequent generation of porosity and coarse grains. As a new solution to this problem, beam shaping technology can improve printing efficiency and quality by modulating the distribution of laser beam energy. In this paper, the application of beam shaping technology in two mainstream metal laser AM processes (laser powder bed fusion (LPBF) and directed energy deposition (DED)) is systematically reviewed, including the energy distribution, melt pool morphology and part quality of different shaped beams. The effects of different-shaped beams on parts quality mainly depends on their influence on the morphology and internal dynamics of the melt pool. For promoting the application of beam shaping technology in the metal laser AM field, it is necessary to achieve adequate control for the energy input stability of the shaped beam. In addition, how to realize metal laser AM with multi-shaped beams and dynamic beam shaping is also crucial to the future development of metal laser AM technology.