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Effects of CoAl2O4 inoculants on microstructure and mechanical properties of IN718 processed by selective laser melting
Additive Manufacturing ( IF 11.0 ) Pub Date : 2020-05-25 , DOI: 10.1016/j.addma.2020.101328
I-Ting Ho , Tzu-Hou Hsu , Yao-Jen Chang , Chen-Wei Li , Kai-Chun Chang , Sammy Tin , Koji Kakehi , An-Chou Yeh

This work investigated the effects of CoAl2O4 inoculants on the microstructure and mechanical properties of a superalloy – Inconel 718 (IN718), processed by selective laser melting (SLM). IN718 powder was blended with 0.2 wt. % of CoAl2O4 particles. After the SLM process, the CoAl2O4 particles reacted with IN718 and formed a dispersion of Al-rich nano-oxide particles in the matrix. These inoculants were observed to facilitate the formation of fine, equiaxed grains and reduce the degree of crystallographic texture in the as-built microstructure. The presence of the nano-oxide particles in the microstructure served to restrict the mobility of grain boundaries during heat-treatment and promoted the formation of a bimodal grain structure with comparatively finer average size. Due to the reduction of crystallographic texture, the elastic anisotropy present in as-built specimens was greatly minimized with the addition of CoAl2O4 inoculants. Specimens containing inoculants were also found to possess improved tensile properties following heat-treatment at both room temperature and 650 °C. Furthermore, creep testing at 650 °C/650 MPa revealed that the steady strain rate of IN718 was lowered from 8.8×10−9 s−1 to 4.9×10−9 s−1, and the creep rupture life was extended by 52 hours in samples that were fabricated with CoAl2O4. These results strongly suggest that the decomposition of CoAl2O4 into Al-rich oxides during SLM processing not only contributes to grain refinement and a reduction in the degree of crystallographic texture but also forms an oxide dispersion that restricts the mobility of dislocations and grain boundaries in IN718.



中文翻译:

CoAl 2 O 4孕育剂对选择性激光熔炼IN718组织和力学性能的影响

这项工作研究了CoAl 2 O 4孕育剂对通过选择性激光熔化(SLM)处理的超合金Inconel 718(IN718)的微观结构和力学性能的影响。将IN718粉末与0.2wt。%共混。%的CoAl 2 O 4颗粒。经过SLM处理后,CoAl 2 O 4颗粒与IN718反应,并在基体中形成了富铝的纳米氧化物颗粒的分散体。观察到这些孕育剂有利于细小等轴晶的形成,并降低了已建成的微结构的晶体织构程度。微观结构中纳米氧化物颗粒的存在起到了限制热处理过程中晶界迁移的作用,并促进了平均尺寸相对较小的双峰晶粒结构的形成。由于降低了晶体织构,加入CoAl 2 O 4可极大地降低铸态试样中的弹性各向异性。孕育剂。在室温和650°C热处理后,还发现含有孕育剂的样品具有改善的拉伸性能。此外,在650°C / 650 MPa的蠕变测试表明,IN718的稳态应变速率从8.8×10 -9 s -1降低至4.9×10 -9 s -1,蠕变断裂寿命延长了52小时在用CoAl 2 O 4制造的样品中。这些结果强烈表明,CoAl 2 O 4的分解 在SLM处理过程中形成富铝氧化物不仅有助于晶粒细化和降低晶体织构度,而且会形成氧化物分散体,从而限制IN718中位错和晶界的迁移率。

更新日期:2020-05-25
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