Quantitative evaluation of the effect of process-induced defects on the fatigue limit of additively manufactured Ni-based superalloy in a hydrogen environment

氢环境下工艺缺陷对增材制造镍基高温合金疲劳极限影响的定量评估

• 批准号: 22J12181
• 负责人: PARK SUNGCHEOL
• 金额: $ 0.58万
• 依托单位: Kyushu University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2022
• 资助国家: 日本
• 起止时间: 2022-04-22 至 2023-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-22J12181/
• 关键词: Additive manufacturing; Ni-based superalloy 718; Fatigue limit; Small crack; Fatigue threshold

During this year, I have examined the fatigue limit of an additively-manufactured, Ni-based superalloy 718 in terms of the small, fatigue-crack growth-threshold, using samples with various small defects and microstructures. Based on the macro- and microscopic analyses, the determining mechanism of the fatigue limit, the effects of small defects and the factors impacting fatigue resistance were all thoroughly explored. The principal conclusions are summarized as follows:1) Fatigue tests revealed that small-crack behavior was governed by maximum shear stress under both cyclic torsional loading and push-pull loading. This implied that the fatigue limit of all the samples was the threshold condition of a shear-mode, small fatigue-crack propagation, similar to the findings related to wrought materials.2) In each case, the shear-mode, small fatigue-crack growth-threshold was estimated to quantify the effects of small defects. As a result, the relationship between the fatigue threshold and defect size was acquired, showing not only a crack-size dependence consistent with the results of wrought materials, but also a substantially low fatigue resistance of additively-manufactured materials.3) Through the comprehensive examination of the effects of potential determining factors on small fatigue crack-growth resistance, it was concluded that the twist angle between two favorable slip planes in neighboring grains was the most influential factor in the inferior fatigue threshold of the additively-manufactured material.

在今年，我研究了使用具有各种小缺陷和微观结构的样品的小型疲劳裂缝生长阈值来检查成型制造的，基于NI的Superaly 718的疲劳极限。基于宏观和显微镜分析，彻底探索了疲劳极限，小缺陷和影响疲劳抗性的因素的决定机制。主要结论总结如下：1）疲劳测试表明，在循环扭转载荷和推力负载下，小裂纹行为受最大剪切应力的控制。这意味着所有样品的疲劳极限是剪切模式的阈值条件，小疲劳裂缝的传播，类似于与锻造材料相关的发现。2）在每种情况下，剪切模式，小疲劳片估计生长阈值可以量化小缺陷的影响。结果，获取了疲劳阈值和缺陷尺寸之间的关系，不仅表明裂纹大小的依赖性与锻造材料的结果一致，而且还表明，加上添加材料的疲劳耐药性基本低。3）通过综合性。3）检查潜在决定因素对小疲劳裂纹增长耐药性的影响，得出的结论是，相邻晶粒中两个有利的滑动平面之间的扭角是增材制造材料下疲劳阈值的最具影响力因素。

项目成果

Shear-mode threshold of small fatigue crack in Ni-based superalloy 718 fabricated by additive manufacturing

增材制造镍基高温合金718小疲劳裂纹的剪切模式阈值

• 发表时间: 2022
• 作者: 陳思楠;中村匡秀;Sinan Chen and Masahide Nakamura;Sinan Chen and Masahide Nakamura;Sungcheol Park
• 通讯作者: Sungcheol Park