Optimizing laser additive manufacturing (LAM) scanning strategies is crucial for improving the quality and performance of metallic parts formed by laser powder bed fusion (LPBF), particularly for alloys with high susceptibility to cracking. However, there is limited research on the effects of unidirectional and unidirectional-remelting strategies on the temperature field and forming quality of LPBF-manufactured Hastelloy X (HX), a nickel-based superalloy highly susceptible to cracking. This study focused on the temperature field, surface roughness, crack occurrence, and mechanical and thermal properties of LPBF-manufactured HX, employing four different laser scanning strategies: chessboard, bidirectional, unidirectional, and unidirectional-remelting. Specimens manufactured using the unidirectional-remelting strategy showed the lowest surface roughness (4.12 μm), highest density (99.64 %), superior tensile properties (tensile strength of 1068.29 MPa and elongation of 16.82 %), lowest coefficient of friction (0.65), highest thermal conductivity (9.77 W/m·K), and lowest specific heat capacity (0.38 J/g/K) compared to other strategies. This can be attributed to the unidirectional-remelting strategy resulting in specimens with equiaxed grains, the most uniform elemental and residual stress distributions, as well as the strongest grain boundary and dislocation strengthening. Moreover, it exhibited compressive residual stress in HX specimens. Interestingly, the tensile properties of the unidirectional-formed HX parts ranked second only to the unidirectional-remelting formed parts, owing to the efficacy of texture strengthening. These findings provide insights into the underlying mechanisms of optimizing laser scanning strategies for LPBF fabrication of HX, offering essential references for the LAM of crack-sensitive alloys, especially nickel-based superalloys.

中文翻译：

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通过优化策略增强性能的增材制造 Hastelloy X


优化激光增材制造 (LAM) 扫描策略对于提高激光粉末床熔合 (LPBF) 形成的金属零件的质量和性能至关重要，特别是对于高裂纹敏感性的合金。然而，单向和单向重熔策略对 LPBF 制造的哈氏合金 X (HX)（一种极易开裂的镍基高温合金）的温度场和成形质量的影响的研究有限。本研究重点研究 LPBF 制造的 HX 的温度场、表面粗糙度、裂纹发生情况以及机械和热性能，采用四种不同的激光扫描策略：棋盘、双向、单向和单向重熔。使用单向重熔策略制造的样品显示出最低的表面粗糙度 (4.12 μm)、最高的密度 (99.64%)、优异的拉伸性能（拉伸强度为 1068.29 MPa，伸长率为 16.82%）、最低的摩擦系数 (0.65)、最高的摩擦系数与其他策略相比，热导率（9.77 W/m·K）和最低的比热容（0.38 J/g/K）。这可以归因于单向重熔策略导致样品具有等轴晶粒、最均匀的元素和残余应力分布以及最强的晶界和位错强化。此外，HX 样品中还表现出残余压应力。有趣的是，由于织构强化的功效，单向成形 HX 零件的拉伸性能仅次于单向重熔成形零件。 这些发现为优化 HX LPBF 制造激光扫描策略的潜在机制提供了见解，为裂纹敏感合金（尤其是镍基高温合金）的 LAM 提供了重要参考。