The characterization of corrosion resistance, which is essential to estimate the lifetime of brazed joints in corrosive environments, is of central importance for many industrial applications and a basic requirement for the reliable and economic operation of brazed components. High temperature vacuum brazing with thin amorphous-crystalline foils is used for numerous applications such as exhaust gas heat exchangers. In this study one industrial BNi-5a® and two experimental rapidly solidified filler metal foils of Ni7Cr7.5Si4Fe1.5B and Ni20Cr7.5Si4Fe4Mo1.5B wt% were used to braze joints of AISI 304L. In addition, two holding times at 1160 °C were chosen to investigate the effect of the resulting microstructural differences on corrosion resistance. Especially the amount and distribution of borides and silicides within the brazing seam could be changed by the time-dependent diffusion processes, as could be shown by metallographic cross sections. Accelerated intercrystalline corrosion tests were carried out to evaluate the influence of the microstructure on the corrosion depth and damage mechanisms. Additionally, potentiodynamic polarization measurements in synthetic exhaust gas condensate as an application-oriented corrosion medium were performed for a comparative evaluation of corrosion properties and rate. The combination of high chromium-containing filler metal and increased holding time, which led to a more homogeneous microstructure, resulted in a more than five times improved corrosion resistance within both investigations.

Graphic Abstract

中文翻译：

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显微组织对 AISI 304L/NiCrSiB 钎焊接头耐腐蚀性能的影响

耐腐蚀性的表征对于估计腐蚀环境中钎焊接头的寿命至关重要，对许多工业应用至关重要，也是钎焊部件可靠和经济运行的基本要求。带有薄非晶晶箔的高温真空钎焊用于多种应用，例如废气热交换器。在这项研究中，一种工业 BNi-5a® 和两种实验性快速凝固的 Ni7Cr7.5Si4Fe1.5B 和 Ni20Cr7.5Si4Fe4Mo1.5B wt% 填充金属箔被用于钎焊 AISI 304L 的接头。此外，还选择了 1160 °C 下的两个保温时间来研究由此产生的微观结构差异对耐腐蚀性的影响。特别是钎焊缝中硼化物和硅化物的数量和分布可以通过随时间变化的扩散过程而改变，如金相横截面所示。进行了加速晶间腐蚀试验以评估微观结构对腐蚀深度和损伤机制的影响。此外，还对作为应用导向腐蚀介质的合成废气冷凝液进行动电位极化测量，以比较评估腐蚀特性和速率。在两项研究中，高含铬填充金属和增加的保持时间相结合，导致更均匀的微观结构，导致耐腐蚀性提高了五倍以上。如金相横截面所示。进行了加速晶间腐蚀试验以评估微观结构对腐蚀深度和损伤机制的影响。此外，还对作为应用导向腐蚀介质的合成废气冷凝液进行动电位极化测量，以比较评估腐蚀特性和速率。在两项研究中，高含铬填充金属和增加的保持时间相结合，导致更均匀的微观结构，导致耐腐蚀性提高了五倍以上。如金相横截面所示。进行了加速晶间腐蚀试验以评估微观结构对腐蚀深度和损伤机制的影响。此外，还对作为应用导向腐蚀介质的合成废气冷凝液进行动电位极化测量，以比较评估腐蚀特性和速率。在两项研究中，高含铬填充金属和增加的保持时间相结合，导致更均匀的微观结构，导致耐腐蚀性提高了五倍以上。对作为应用导向腐蚀介质的合成废气冷凝液进行动电位极化测量，以比较评估腐蚀特性和速率。在两项研究中，高含铬填充金属和增加的保持时间相结合，导致更均匀的微观结构，导致耐腐蚀性提高了五倍以上。对作为应用导向腐蚀介质的合成废气冷凝液进行动电位极化测量，以比较评估腐蚀特性和速率。在两项研究中，高含铬填充金属和增加的保持时间相结合，导致更均匀的微观结构，导致耐腐蚀性提高了五倍以上。

图形摘要