Evaluation of productivity scaling approaches for laser powder bed fusion of nickel-base alloy 625

Abstract

In recent years, Laser Powder Bed Fusion (L-PBF) has become an industrially established manufacturing technique due to the possibility to manufacture highly complex parts without additional tools. State-of-the-art L-PBF machines use single-mode fiber lasers in combination galvanometer scanners due to their broad availability, high dynamic capability and excellent focusability. To increase system productivity the manufacturing task is parallelized by the utilization of multiple laser-scanner-systems leading to increased machine costs. Alternative approaches for the scaling of L-PBF productivity such as beam shaping and variable laser beam diameters for the use of higher laser powers (PL < 400 W) are hardly used in L-PBF machines. In consequence the high peak intensities of Gaussian intensity distribution with d_s = 50 – 100 μm of state-of-the-art L-PBF machines limit the usable laser powers due to the risk of part defects resulting from keyhole formation. Hence, non-Gaussian intensity distribution such as ring-mode laser beams as well as laser beam diameter variation exhibit great potential for high-power L-PBF systems. As part of the Digital Photonic Production (DPP) Research Campus funded by the BMBF L-PBF machine setups with a switchable ring-mode fiber laser and a defocused Gaussian laser intensity distribution were developed, validated and compared for the processing nickel-base alloy 625. By implementation of these approaches build-up rates up to 150% higher than those of conventional L-PBF machines were achieved while maintaining relative densities above 99.9%.