In this research, additively manufacturing a functionally graded material (FGM) with a compositional range of Ni-based Inconel superalloy (Inconel 718) and Fe-based stainless steel (SS 316L) via directed energy deposition (DED) was examined. The microstructural transformation, defect behavior, and Vickers hardness of the material were each determined as a function of the discrete chemical composition of the FGM varied in steps of 10 wt% of the two materials across its length. In particular, for the specific compositions of 30 wt% Inconel 718/70 wt% SS 316L and 20 wt% Inconel 718/80 wt% SS 316L, critical pores and cracks (defects) initiated by ceramic oxides occurred due to the presence of intermetallic and carbide compounds. In addition, the results of electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) analyses of the FGM demonstrate that the thermal and residual stresses due to constitutional supercooling and columnar-to-equiaxial transition (CET) became concentrated at the grain boundaries, thereby further contributing to the formation of the defects. The measured Vickers hardness was inevitably found to be minimal near the defective compositional range regardless of laser parameter optimization due to the reduced generation of segregants in the inter-dendritic regions and the increased formation of precipitates at the grain boundaries. The results of microstructural and mechanical analyses indicate that deliberate and strategic removal of the defective compositional range helped obtain a robust FGM composed of Inconel 718 and SS 316L without noticeable defects.

在这项研究中，研究了通过定向能量沉积 (DED) 对成分范围为 Ni 基 Inconel 高温合金 (Inconel 718) 和 Fe 基不锈钢 (SS 316L) 的功能梯度材料 (FGM) 进行增材制造。材料的微观结构转变、缺陷行为和维氏硬度均被确定为 FGM 的离散化学成分的函数，这两种材料在其长度上以 10 wt% 的步长变化。特别是，对于 30 wt% Inconel 718/70 wt% SS 316L 和 20 wt% Inconel 718/80 wt% SS 316L 的特定成分，由于金属间化合物的存在，陶瓷氧化物引发了临界孔隙和裂纹（缺陷）。和碳化物。此外，FGM 的电子背散射衍射 (EBSD) 和 X 射线衍射 (XRD) 分析结果表明，由于结构过冷和柱状到等轴转变 (CET) 导致的热应力和残余应力集中在晶界处，从而进一步促进缺陷的形成。由于枝晶间区域中偏析物的产生减少和晶界处析出物的形成增加，无论激光参数如何优化，都不可避免地发现在有缺陷的组成范围附近测得的维氏硬度是最小的。微观结构和机械分析的结果表明，有意和战略性地去除有缺陷的成分范围有助于获得由 Inconel 718 和 SS 316L 组成的坚固 FGM，没有明显的缺陷。