The role of overlap region width in multi-laser powder bed fusion of Hastelloy X superalloy

Abstract

During the multi-laser powder bed fusion (ML-PBF) process, the quality of the overlap region is essential to ensure the integrity between different laser scanning areas. Here, six different overlap region widths (ORWs) are selected to systematically investigate the effect of ORWs on densification, metallurgical defects, crystalline microstructure, and mechanical performance of the Hastelloy X samples processed by multi-laser powder bed fusion. ORWs are set to 0, 50, 100, 150, 200, and 250 μm, respectively. With an increment in ORW, the porosity gradually increases from 0.01% to 7.08%. Inversely, microcracks are reduced with increasing the ORWs due to the smaller width-to-depth ratio of the melt pools and the increased degree of recrystallisation. All the samples display equivalent ultimate tensile strength of ∼880 MPa, while the elongations at break of the overlap samples are 3.5%−10.5% lower than that of the single-laser processed one (28.4%). The inferior ductility is ascribed to the decreased densification in the overlap regions, of which the adverse effect can be minimised when an ORW of 150 μm is utilised. This work is anticipated to provide efficient reference and theoretical guidance for the large-size nickel-based superalloy components fabricated by ML-PBF.

Keywords

• multi-laser powder bed fusion
• selective laser melting
• overlap region
• nickel-based superalloy
• mechanical properties