Nb对PREP法制备内燃机用IN718粉末合金组织和温拉伸性能的影响

采用等离子旋转电极法制备了包含γ'相的镍基粉末高温合金,并对合金中含有不同Nb比例时显微组织结构的改变进行分析,同时对其处于650℃下力学性能进行了测试。研究结果表明:经过热处理后,在γ相内形成了γ'相,当Nb比例从0%提高至3.0%时,γ'相的微观形貌始终保持方形的结构,添加Nb之后形成了更加粗大的γ'相。相对于未加Nb,当在合金内添加Nb之后,试样拉伸强度增大了120MPa以上。试样拉伸强度随Nb含量增加而逐渐增加。Nb能够显著提升合金高温强度,存在一个最优Nb含量使试样获得最佳高温塑性。含3.0%Nb的合金组织发生了塑性断裂,合金中形成了明显延伸的断口,存在众多小尺寸等轴韧窝。当Nb含量增大后,合金发生了塑性降低。含3.0%Nb的合金在拉伸过程中形成了孪晶并降低了滑移带的数量,增加Nb含量后有助于生成层错组织。

Tensile Strength and Microstructures of Samples Made of Nb-Doped IN718 Alloy Powder

The Nb-doped IN718 super-alloy powder,an advanced Ni-based aircraft engine material,was synthesized by plasma rotating electrode atomization.The influence of the Nb-doping on the microstructures and tensile behavior of the blanks,fabricated with the Nb-doped IN718 alloy powder,was investigated with scanning electron microscopy,transmission electron microscopy and tensile strength measurement at 650℃.The preliminary results show that the Nb-doping had a major impact.Specifically,the Nb-doping significantly affected the tensile properties,measured at 650℃,possibly because of formation of the cubic γ′-phase grains among γ-phased grains; as the Nb-content increased from 0.0% to 4.5%(wt),the tensile-strength/yield-strength increased by 120 MPa/170 MPa,respectively; the contraction-area at fracture changed in a decrease-increase-decrease mode and the elongation-ratio,varying in the similar manner,maximized at 3 wt.%,and the plasticity continuously decreased.We found that ductile fracture mechanism dominated.