Parameter and Microstructure Research on LPBF M50NiL steel

M50NiL bearing steel specimens are produced by the powder bed fusion-laser beam technology (PBF-LB), and the machinability and microstructural characteristics of bearing steel for PBF-LB have been investigated. Within a reasonable range, the relative density of specimens is positively correlated with the laser power while negatively with the scanning speed. In particular, it is easy to induce premature hump effect in the melt channel by using the high power and low speed process parameters, which promotes the generation of defects and is not conducive to the improvement of the density. The scanning spacing should be reasonably set according to the melting width of the single melt track and the accumulated heat effect during the printing process. The strip scanning strategy should take into account the size effect of the printed entity on the density. Through the single-factor variable approach, based on the influence of the laser power, scanning speed, hatching space and scanning strategy on the relative density, the desirable process parameters window can be obtained as follows: 210-280 W of laser power, 500-800 mm/s of scanning speed, hatching space between 0.08-0.12 mm, layer thickness of 0.04 mm, and strip-zoning scanning strategy with a rotation of 67°between layers. Thus, the relative density of the sample can reach as high as 99.64%.