Abstract Directed energy deposition (DED) of Ni-based superalloys has wide applications in the fields of aviation, energy and power. However, for the non-weldable superalloys like Inconel 738, cracking frequently occurs during DED and cannot be thoroughly controlled up to now. We propose a novel method to prevent the cracking during Inconel 738 DED, in which a small amount of Inconel 718 is in-situ doped between the deposited layers of Inconel 738. The obtained layered-gradient-material is found to be free of both macro- and micro-cracks. The microstructure shows that doping Inconel 718 cannot interrupt the epitaxial growth of grains, but can modify the precipitation of γ′. In Inconel 718 layers, nano γ′ particles are intensively precipitated only in the inter-dendrites, while in Inconel 738 layers, they are precipitated in both the inter- and inner-dendrites. This modification on γ′ precipitation can effectively decrease the inner stress and alleviate the stress concentration at the grain boundaries, thus the cracking is prevented. The tensile tests, which were conducted at room temperature, 600 °C and 800 °C respectively, demonstrate that the composite deposited workpieces possess promising strength and plasticity. The proposed method has great potential to improve the printability of un-weldable superalloys in additive manufacturing.

中文翻译：

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一种通过原位掺杂 Inconel 718 防止 Inconel 738 定向能量沉积开裂的新方法

摘要 镍基高温合金的定向能量沉积（DED）在航空、能源和电力领域有着广泛的应用。但是，对于Inconel 738等不可焊高温合金，DED过程中经常出现开裂，目前还不能彻底控制。我们提出了一种防止 Inconel 738 DED 开裂的新方法，其中少量 Inconel 718 原位掺杂在 Inconel 738 沉积层之间。 - 和微裂纹。微观结构表明，掺杂 Inconel 718 不能中断晶粒的外延生长，但可以改变 γ' 的析出。在 Inconel 718 层中，纳米 γ' 粒子仅在枝晶间密集析出，而在 Inconel 738 层中，它们沉淀在枝晶间和枝晶内。这种对γ′析出的改性可以有效地降低内应力，减轻晶界处的应力集中，从而防止开裂。分别在室温、600°C 和 800°C 下进行的拉伸试验表明，复合沉积工件具有良好的强度和塑性。所提出的方法在提高不可焊接高温合金在增材制造中的可印刷性方面具有巨大的潜力。证明复合沉积工件具有良好的强度和塑性。所提出的方法在提高不可焊接高温合金在增材制造中的可印刷性方面具有巨大的潜力。证明复合沉积工件具有良好的强度和塑性。所提出的方法在提高不可焊接高温合金在增材制造中的可印刷性方面具有巨大的潜力。