The microstructure of nickel-based superalloy Inconel 718 prepared by selective laser melting (SLM) has effect on its mechanical performance. In this work, microstructure evolution and tensile properties were studied in as-SLMed state and after various heat treatments, as well as the role of defects on its fracture mechanism at high temperature. The results indicated that the as-SLMed microstructure consisted of dendritic and cellular structure, while small γ′′ phases and acicular δ phases formed after heat treatments. Two types of defects, ‘X-shaped crack’ and ‘central crack’ were formed in the as-SLMed specimens during in-situ high temperature tensile process, which suggested that the melt pool boundaries and the center of melt pools were cracks initiation places because of high density of defects and segregation. Room temperature (RT) tensile strengths of the as-SLMed specimens exceeded the cast standard but were inferior to the wrought standard. Apparently, the standard heat treatment (SHT) and direct aging treatment (AG) specimens showed highest tensile strengths (1430 MPa at RT and 1189 MPa at 650 °C). RT tensile strengths of the SHT specimens were increased by 43.7 % when compared with those of the as-SLMed ones, even 12 % higher than those of wrought standard as a result of precipitation strengthening effect. However, elongation after heat treatments decreased significantly due to dislocation pinning effect from strengthening phases. Furthermore, the strengths and elongations in horizontal and vertical directions showed obvious anisotropy because of strong preferential texture in specimens formed during SLM process. This paper looks at microstructural evolution, mechanical properties evaluation of Inconel 718 fabricated by SLM under various heat treatments, the results showed that the tensile properties can be tuned via proper treatment to suit their application requirements.

通过选择性激光熔化（SLM）制备的镍基高温合金Inconel 718的微观结构对其机械性能有影响。在这项工作中，研究了在SLM状态下以及经过各种热处理后的微观结构演变和拉伸性能，以及缺陷对其在高温下断裂机理的作用。结果表明，as-SLMed组织由树枝状和细胞状结构组成，γ'′相和针状δ小热处理后形成的相。在原位高温拉伸过程中，SLM试样中形成了两种类型的缺陷，即“ X形裂纹”和“中心裂纹”，这表明熔池边界和熔池中心是裂纹产生的场所。由于缺陷和偏析的密度很高。SLM试样的室温（RT）拉伸强度超过铸造标准，但不及锻造标准。显然，标准热处理（SHT）和直接时效处理（AG）标本显示出最高的拉伸强度（室温下为1430 MPa，在650°C下为1189 MPa）。SHT试样的RT拉伸强度与SLM试样相比，提高了43.7％，由于析出物的增强作用，其强度甚至比锻制标准高12％。然而，热处理后的延伸率显着下降，这是由于强化相的位错钉扎效应所致。此外，由于在SLM过程中形成的样品具有较强的优先纹理，因此在水平和垂直方向上的强度和伸长率显示出明显的各向异性。本文研究了SLM在各种热处理条件下制造的Inconel 718的微观结构演变，力学性能评估，结果表明，可以通过适当的处理来调整拉伸性能以适应其应用需求。由于在SLM过程中形成的试样具有很强的优先纹理，因此在水平和垂直方向上的强度和伸长率显示出明显的各向异性。本文研究了SLM在各种热处理条件下制造的Inconel 718的微观结构演变，力学性能评估，结果表明，可以通过适当的处理来调整拉伸性能以适应其应用需求。由于在SLM过程中形成的试样具有很强的优先纹理，因此在水平和垂直方向上的强度和伸长率显示出明显的各向异性。本文研究了SLM在各种热处理条件下制造的Inconel 718的微观结构演变，力学性能评估，结果表明，可以通过适当的处理来调整拉伸性能以适应其应用需求。