Effect of heat treatment on the microstructure and mechanical properties of 2.4 GPa grade maraging steel fabricated by laser powder bed fusion

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Effect of heat treatment on the microstructure and mechanical properties of 2.4 GPa grade maraging steel fabricated by laser powder bed fusion
Title:
Effect of heat treatment on the microstructure and mechanical properties of 2.4 GPa grade maraging steel fabricated by laser powder bed fusion
Journal Title:
Additive Manufacturing
Keywords:
Publication Date:
03 October 2022
Citation:
Wei, S., Kumar, P., Lau, K. B., Wuu, D., Liew, L.-L., Wei, F., Teo, S. L., Cheong, A., Ng, C. K., Zhang, B., Tan, C. C., Wang, P., & Ramamurty, U. (2022). Effect of heat treatment on the microstructure and mechanical properties of 2.4 GPa grade maraging steel fabricated by laser powder bed fusion. Additive Manufacturing, 59, 103190. https://doi.org/10.1016/j.addma.2022.103190
Abstract:
The effects of three different heat treatments (direct aging, austenitizing–aging, and solutionizing–austenitizing–aging) on the meso-/micro-structures and the mechanical properties of the 18 wt% Ni-350 maraging steel (M350), specifically designed for ultra-high strength, additively manufactured using the laser powder bed fusion (LPBF) are studied. In both the as printed and directly aged conditions, the dendritic growth induced cellular structures constitute the unit microstructural features of the martensite; the martensitic transformation in these conditions occurs within the cell matrix and the cell boundaries act as the preferred sites for the austenite retention/reversion. The cell structures partially dissolve upon the austenitizing–aging heat treatment, while solutionizing fully erases them; both these heat treatments can facilitate the formation of the conventional packet–block–lath hierarchy, which is absent in the as printed and directed aged samples. Uniaxial tensile and mode I fracture toughness measurements reveal that the presence of the austenite in the directly aged M350 maraging steel lowers its strength but increases the fracture toughness. The absence of austenite in the other two heat treatment conditions results in high strength, but lower toughness. These findings shed light on understanding fundamental relationship between the unique features of the LPBF process and the martensitic transformation in maraging steels.
License type:
Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)
Funding Info:
This research / project is supported by the A*star - Structural Metal Alloys Programme
Grant Reference no. : A18B1b0061
Description:
ISSN:
2214-8604
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