Key Takeaways & Executive Findings
- •• Scanning strategy significantly influences the anisotropy of microstructure and mechanical properties in LPBF-formed GH3536 alloy. • The 67° scanning strategy yields the best combined tensile properties at room temperature and 815 °C, while 0° and contour strategies result in the worst. • Anisotropy is attributed to differences in texture strengthening, grain boundary strengthening, and dislocation strengthening effects. • Modulating the scanning strategy can effectively mitigate mechanical property anisotropy in LPBF-formed GH3536 alloy.
Abstract
The GH3536 (Hastelloy-X) nickel-based superalloy is increasingly applied in the aerospace industry due to its exceptional combination of excellent oxidation resistance and high-temperature strength. Laser powder bed fusion (LPBF) is an additive manufacturing (AM) technology for producing metallic components with complex shapes using layer-by-layer manufacture principle. The debate has long prevailed as to research on eliminating anisotropy in the forming of GH3536 alloy through LPBF technology. In this study, the anisotropy of microstructure and mechanical properties of GH3536 alloy formed by LPBF was investigated using different scanning strategies (0°, 90°, 67°, checkerboard, and contour). The scanning strategy was optimized to reduce the weaving differences between the horizontal and vertical directions of the microstructure of the LPBF formed GH3536 alloy, which in turn reduces the anisotropy of the properties in both directions. The results of the tensile specimens indicate that except for the horizontal specimens produced using the contour scanning strategy, the strength of all other specimens exceeds that of the vertical specimens. Additionally, differences in elongation are observed, demonstrating that the GH3536 alloy fabricated via laser powder bed fusion exhibits anisotropic properties. According to electron backscatter diffraction (EBSD) analysis, the grain boundary strengthening and geometrically necessary dislocations (GNDs) impede dislocation motion during tensile deformation along the horizontal direction. Consequently, this mechanism negatively affects both the tensile strength and ductility in that orientation. The anisotropy in tensile strength and plasticity is attributed to the different crack sensitivities in the two tensile directions. In addition, specimens molded using different scanning strategies exhibit varying degrees of anisotropy, strength, and elongation due to different degrees of texture strengthening, grain boundary strengthening, and dislocation strengthening effects. Regardless of the stretching direction, the combined tensile properties of the 0° and contoured specimens are the worst under the room temperature and 815 °C stretching conditions. The 67° specimens exhibit the best combined tensile properties. Therefore, the anisotropy of the mechanical properties of the LPBF formed GH3536 alloy can be positively mitigated by modulating the scanning strategy.
1. Introduction
GH3536 alloy, also known as Hastelloy-X, is a solid solution strengthened nickel-based superalloy that primarily contains elements such as molybdenum, tungsten, and chromium. This alloy possesses a well-balanced combination of mechanical strength, high-temperature oxidation resistance, corrosion resistance, hot workability, and weldability between 600 °C and 900 °C. Consequently, it is widely used in components of gas turbine engines and high-temperature gas-cooled reactors (HTGR), particularly for manufacturing parts for aircraft engine combustion chambers [1-6].
Laser powder bed fusion (LPBF) is an additive manufacturing process for metals that enables the direct fabrication of complex components through the interaction of high-power lasers with metal powders. This technology boasts high design freedom, simplified processing, and improved forming quality. Due to its use of metal powders and near-zero waste, LPBF technology finds extensive application in fields such as aerospace, medical, automotive, and mold manufacturing [6-10].
Despite these attractive advantages, several technical issues still hinder the widespread application of LPBF technology on GH3536 alloys, mainly facing challenges such as porosity, crack defects, element segregation, and anisotropy behavior. Most researchers modulated the underlying process parameters to reduce internal defects and change the microstructure of alloys. Maria et al. [11] found that laser power significantly affects the microstructure of GH3536 alloy. Under high laser power, the melt pool width increased, and the solidification microstructure exhibited a stronger preferred orientation. At the same time, lowering the laser scanning rate can avoid cracks and holes, and the densities of the specimens were increased from 77% to 99%. However, the elongation showed strong anisotropy.
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Ming-song Hao, Lin Zhou, Kai Wang, Guan Wang, Jing-jing Liang, Jin-guo Li (2025). Influence of scanning strategies on microstructure and properties anisotropy of GH3536 alloy formed by laser powder bed fusion. China Foundry. https://doi.org/10.1007/s41230-025-4207-x
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Frequently Asked Questions
What is the effect of scanning strategy on the anisotropy of GH3536 alloy formed by LPBF?
The scanning strategy significantly influences the anisotropy of microstructure and mechanical properties. The 67° scanning strategy yields the best combined tensile properties, while 0° and contour strategies result in the worst, indicating that modulating the scanning strategy can mitigate anisotropy.
Which scanning strategy provides the best tensile properties for LPBF-formed GH3536 alloy?
The 67° scanning strategy provides the best combined tensile properties at both room temperature and 815 °C, as it balances texture, grain boundary, and dislocation strengthening effects.
What are the main factors contributing to anisotropy in LPBF-formed GH3536 alloy?
Anisotropy is attributed to differences in texture strengthening, grain boundary strengthening, and dislocation strengthening effects, as well as crack sensitivity in different tensile directions.
How does the contour scanning strategy affect the mechanical properties of GH3536 alloy?
The contour scanning strategy results in the worst combined tensile properties, with horizontal specimens showing lower strength compared to vertical specimens, indicating higher anisotropy.
What is the significance of the 67° scanning strategy in reducing anisotropy?
The 67° scanning strategy effectively reduces anisotropy by optimizing the microstructure, leading to more uniform mechanical properties in both horizontal and vertical directions.
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