Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore
doi:10.3850/978-981-18-6021-8_OR-01-0269
Laser Powder Bed Fusion of Grain Refined 316L Stainless Steel through Ti in-situ Alloying
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
2Singapore Centre for 3D Printing, school of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
3Singapore Institute of Manufacturing Technology, 73 Nanyang Drive, 637662, Singapore
ABSTRACT
Laser powder bed fusion (LPBF) is a subset of additive manufacturing process, which has the advantage in the fabrication of geometry-complex components. It features a high thermal gradient because of the intrinsic ultrafast cooling rate (~107 K/s). The high thermal gradient leads to a higher critical nucleation undercooling and the fast cooling rate limits the formation of solutes. Consequently, strong epitaxial grain growth tendency is frequently observed in LPBF-processed alloys. This presentation demonstrates that in-situ alloying with Ti addition can significantly promote grain refinement (from 16.7 to 0.8 μm) without bringing undesirable intermetallic phases in LPBF-processed 316L. The Ti-rich solutes at the solid/liquid interface activated heterogeneous nucleation, thus achieving grain refinement. This method could also be used for the grain refinement of other alloys, such as Al alloys and Ti alloys, in order to tailor their microstructures and mechanical properties to suit specific engineering applications.
Keywords: Additive manufacturing, Laser powder bed fusion, Grain refinement, 316L stainless steel, In-situ alloying, Alloy design
1School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
2Singapore Centre for 3D Printing, school of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore
3Singapore Institute of Manufacturing Technology, 73 Nanyang Drive, 637662, Singapore
ABSTRACT
Laser powder bed fusion (LPBF) is a subset of additive manufacturing process, which has the advantage in the fabrication of geometry-complex components. It features a high thermal gradient because of the intrinsic ultrafast cooling rate (~107 K/s). The high thermal gradient leads to a higher critical nucleation undercooling and the fast cooling rate limits the formation of solutes. Consequently, strong epitaxial grain growth tendency is frequently observed in LPBF-processed alloys. This presentation demonstrates that in-situ alloying with Ti addition can significantly promote grain refinement (from 16.7 to 0.8 μm) without bringing undesirable intermetallic phases in LPBF-processed 316L. The Ti-rich solutes at the solid/liquid interface activated heterogeneous nucleation, thus achieving grain refinement. This method could also be used for the grain refinement of other alloys, such as Al alloys and Ti alloys, in order to tailor their microstructures and mechanical properties to suit specific engineering applications.
Keywords: Additive manufacturing, Laser powder bed fusion, Grain refinement, 316L stainless steel, In-situ alloying, Alloy design
