The eutectic high entropy alloy Nb0.73CoCrFeNi2.1 was manufactured by means of arc smelting and the obtained ingots were cut into 300-μm-thick foils, which were used as filler alloys to braze Crofer 22 APU to Hf-metallized yttria-stabilized zirconia (3YSZ). The brazing process was conducted in a vacuum furnace at 1200 °C for 5 min at a vacuum of 4.3·10–4 mbar. In order to minimize the intense diffusion and erosion of the steel substrate, a heating and cooling rate of 50 K/min was applied. Sound joints without any pores or flaws were obtained. The microstructure of the joints consisted of an HfO2 reaction layer at the ceramic interface and the same eutectic structure consisting of a Laves phase and a solid solution that was already detected in the smelted foil. The average hardness of the microstructure in the joint seam amounted to 352 ± 17 HV0.01 and the joints reached strength values up to 97 ± 7 MPa while the fracture area was always located at the ceramic interface in the HfO2 layer. Comparable joints, with AgCuTi3 as filler metal, brazed at 920 °C, only reached a shear strength of ~ 52 ± 2 MPa.

中文翻译：

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Nb 0.73 CoCrFeNi 2.1共晶高熵合金在高温接头中的应用

通过电弧熔炼生产高共熔高熵合金Nb0.73CoCrFeNiNi2.1，将所得铸锭切成300μm厚的箔，用作填充合金，将Crofer 22 APU钎焊至Hf金属化的氧化钇稳定的氧化锆。 （3YSZ）。钎焊过程在真空炉中于1200°C的真空度为4.3·10–4 mbar下进行5分钟。为了使钢基材的强烈扩散和侵蚀最小化，采用了50 K / min的加热和冷却速率。获得了没有任何孔或瑕疵的牢固的接头。接头的微观结构由位于陶瓷界面的HfO2反应层和由Laves相和已在熔融箔中检测到的固溶体组成的共晶结构组成。接缝处显微组织的平均硬度为352±17 HV0。01和接头达到的强度值高达97±7 MPa，而断裂区域始终位于HfO2层的陶瓷界面处。使用AgCuTi3作为填充金属的可比接头在920°C的温度下钎焊，其剪切强度仅为〜52±2 MPa。