Tailoring the microstructure and mechanical properties for Hastelloy X alloy by laser powder bed fusion via scanning strategy

Abstract

Irregular large pores induced by laser powder bed fusion (LPBF) are inherent defects, which greatly domain the mechanical properties of as-built components. Laser remelting is an effective method to diminish the porosity and increase the energy input, while excessive heat accumulation is generally at the expense of powder spatter. In the study, LPBF-fabricated Hastelloy X alloy was built by combining laser remelting and five scanning strategies (three meander and two chessboard strategies) to investigate the scanning strategy effects on the related microstructure and mechanical properties via experiment and simulation. In comparison, results showed that the average temperature of the powder model rises from 622.02 K to 880.88 K, and the cooling rate approximately increases from 106 K/s up to 107 K/s for the chessboard strategy. The chessboard strategy with a large scanning island yields the highest density (99.34%). More homogeneous grain also nucleates due to the evident 〈111〉 micro-texture distribution. The refined microstructure achieved by the chessboard strategy with laser remelting leads to a superior combination of tensile strength (∼820 MPa) and elongation (∼30%). Grain boundary strengthening and dislocations hardening are the dominant mechanisms of as-built Hastelloy X alloy.

Keywords

• Laser powder bed fusion
• Hastelloy X superalloy
• Scanning strategy
• Numerical simulation
• Mechanical properties