Microstructural Evolution and Mechanical Properties of Nickel-Base Superalloy Brazed Joints Using a MPCA Filler
Microstructural Evolution and Mechanical Properties of Nickel-Base Superalloy Brazed Joints Using a MPCA Filler
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DOI：
10.1007/s11661-019-05386-8
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发表时间：
2019-11-01
影响因子：
2.8
通讯作者：
Yu, Zhenzhen
中科院分区：
文献类型：
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作者：
Gao, Minrui;Schneiderman, Benjamin;Yu, Zhenzhen
设计了一种成分为Fe5Co20 Ni20Mn35Cu20的新型多主成分合金(MPCA)钎料，用于钎焊镍基合金600(Ni-Cr-Fe)。热力学计算，包括原子尺寸差异、混合熵和混合热、价电子浓度和相图计算，以优化MPCA填充材料的组成，目标是面心立方(FCC)晶体结构和适合钎焊的熔点。X射线衍射测试证实了铸态MPCA中存在面心立方结构，差热分析(DTA)结果表明其熔化范围为1080-1150℃。MPCA还表现出值得作为钎料候选的力学性能，其真实压缩屈服应力为286 Mpa，极限压缩强度为591 Mpa，断裂应变为106%。通过对600合金母材的润湿性试验，确定了最佳的钎焊温度为1200℃，此时MPCA的润湿角为14°，铺展性能最佳。将MPCA板材冷轧成300微米的薄片进行钎焊。在研究的整个钎焊时间范围内(15-120分钟)，没有观察到组织缺陷，电子背散射衍射(EBSD)结果表明，在填充材料的凝固组织中存在等轴晶。利用能量色散光谱(EDS)的数据，对MPCA的组成元素进行了动力学分析。虽然在从MPCA扩散到600合金的元素中，Mn是扩散最快的元素，但所有这些元素的扩散系数都在同一个数量级。这一结果表明了与MPCA相关的迟滞扩散理论。研究了钎焊时间对钎焊接头剪切强度的影响。当钎焊时间为90min时，抗剪强度达到最大值，为530 Mpa。当钎焊时间增加到90min时，互扩散距离的增加有利于更强的冶金结合。然而，超过90min后，在填充箔内的晶界上形成了脆性的Cr2Mn3和CrMn3金属间化合物，导致接头的剪切强度降低和脆性断裂。(C)矿物、金属和材料学会和2019年ASM国际
A new multi-principal-component alloy (MPCA) filler metal with the composition Fe5Co20 Ni20Mn35Cu20 was designed for brazing Ni-base Alloy 600 (Ni-Cr-Fe). Thermodynamic calculations, including atomic size difference, mixing entropy and enthalpy, valence electron concentration, and phase diagram calculations were used to optimize the composition of the MPCA filler material, targeting a face-centered cubic (FCC) crystalline structure and a melting point appropriate for brazing. An X-ray diffraction measurement confirmed the presence of an FCC structure in the as-cast MPCA, and differential thermal analysis (DTA) results demonstrated its melting range to be 1080-1150 degrees C. The MPCA also exhibited mechanical properties worthy of a brazing filler candidate, with a true compressive yield stress of 286 MPa, an ultimate compressive strength of 591 MPa, and a fracture strain of 106 pct. The optimum brazing temperature was determined to be 1200 degrees C through a wettability test on the Alloy 600 base material, at which the MPCA exhibited a low wetting angle of 14 deg and optimal spreading behavior. The MPCA plate was cold rolled into 300 mu m foils for brazing. For the full range of brazing times studied (15 to 120 minutes), no microstructural defects were observed, and electron backscatter diffraction (EBSD) results showed equiaxed grains present in the solidification microstructure of the filler material. Using data from energy-dispersive spectroscopy (EDS), a kinetic analysis was performed for the constituent elements in the MPCA. It was determined that althoughMn was the fastest diffusing of the elements that diffused from the MPCA into the Alloy 600, the diffusion coefficients for all of these elements were on the same order of magnitude. This result was indicative of the sluggish diffusion theory associated with MPCAs. The effect of brazing time on the shear strength of the brazed joint was evaluated. A maximum shear strength of 530 MPa was achieved at a brazing time of 90 minutes. As brazing time increased up to 90 minutes, the increasing interdiffusion distance facilitated a stronger metallurgical bond. However, beyond 90 minutes, the formation of brittle Cr2Mn3 and CrMn3 intermetallic compounds at the grain boundaries within the filler foil led to a lower shear strength and brittle fracture in the joint. (C) The Minerals, Metals & Materials Society and ASM International 2019