Abstract

This study investigated the fatigue crack propagation (FCP) behavior of different regions (base metal (BM), heat-affected zone (HAZ) and weld metal (WM)) of dissimilar metal welded joints of L360MS pipeline steel with Inconel 625 welding wire as the filler material. The effect of the microstructure on FCP was discussed. The results indicated that the fatigue crack growth rates (da/dN) for the WM were lower than those for the BM and the HAZ under the same stress ratio. The microstructures of these regions had different characteristics, such as equiaxed austenite, ferrite and pearlite, which could explain the observed differences in properties. For instance, the FCP path revealed that the existence of ductile equiaxed grains and coarse columnar grains caused the WM to have higher fatigue crack growth resistance and a more tortuous crack propagation path than the BM and the HAZ. The microstructure, grain orientation, strain distribution and grain boundaries around the fatigue crack in the HAZ specimens that propagated through the WM and the fusion line were analyzed by electron backscatter diffraction (EBSD). The results showed that the fatigue cracks followed a zigzag path into the HAZ along the high-angle Type II boundary and Type I boundary in the WM.

Graphic Abstract

中文翻译：

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Inconel 625焊接金属的L360MS管线钢焊接接头的疲劳裂纹扩展行为研究

摘要

本研究以Inconel 625焊丝为基础，研究了L360MS管线钢异种金属焊接接头不同部位（母材（BM），热影响区（HAZ）和焊缝金属（WM））的疲劳裂纹扩展（FCP）行为。填充材料。讨论了微观结构对FCP的影响。结果表明，疲劳裂纹扩展速率（d a / d N在相同的应力比下，WM低于BM和HAZ。这些区域的微观结构具有不同的特征，例如等轴奥氏体，铁素体和珠光体，这可以解释所观察到的性能差异。例如，FCP路径表明，与BM和HAZ相比，延性等轴晶粒和粗柱状晶粒的存在使WM具有更高的抗疲劳裂纹扩展性和更曲折的裂纹扩展路径。通过电子反向散射衍射（EBSD）分析了通过WM和熔合线传播的热影响区试样的疲劳裂纹周围的组织，晶粒取向，应变分布和晶界。

图形摘要