Influence of the laser source pulsing frequency on the direct laser deposited Inconel 718 thin walls

Abstract The Direct Laser Deposition (DLD) process has shown significant results in manufacturing due to its relevant flexibility to refurbish high-performance components (e.g. turbine blades or disks) or fabricating complex shaped parts. The solidification microstructure during the DLD process, is known to be controllable using different process parameters that induce changes in the grain structure, micro-segregation, and phase transformations. This work focuses on the effect the frequency of the pulsed laser has on the metallurgical characteristics of deposited thin walls. More specifically, the effect of three different pulsing rates (10 Hz, 100 Hz, 1000 Hz) during the deposition of the Nickel-based superalloys Inconel 718 has been studied and the results compared with parts produced by continuous wave laser mode. This work highlights how the pulsing rate significantly affected the thermal history, melt pool shape, grain size and its morphology, segregation region (Nb-enriched), and hardness. Finally, the microhardness was also evaluated and a correlation between the metallurgical characteristics and the pulsing rate was established.