Investigation on the Fatigue Crack Propagation Behavior of L360MS Pipeline Steel Welded Joints with Inconel 625 Weld Met
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ORIGINAL ARTICLE
Investigation on the Fatigue Crack Propagation Behavior of L360MS Pipeline Steel Welded Joints with Inconel 625 Weld Metal Yunfeng Hu1 • Bin Wang1,2 • Yingchao Xu1 • Liang Wang3 • Wenqin Cheng1
Received: 10 April 2020 / Accepted: 12 July 2020 Ó The Indian Institute of Metals - IIM 2020
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.
& Bin Wang [email protected] 1
School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China
2
Welding Engineering Technology Research Center in Sichuan Province, Chengdu 610500, China
3
School of Engineering, Southwest Petroleum University, Nanchong 637800, China
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Trans Indian Inst Met
Graphic Abstract
Keywords Dissimilar metal welded joint Fatigue crack propagation Bimetallic composite pipe EBSD
1 Introduction As energy consumption is increasing worldwide, energy resources are facing depletion, and it is increasingly difficult to exploit traditional energy resources such as oil and
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natural gas. Extreme extraction and transport environments have imposed strict requirements on transport pipelines, wherein the general aim is to minimize cost while ensuring the transport quality. Bimetallic composite pipes (BCPs) have become a research focus because of their good corrosion resistance, mechanical properties and processability, which can significantly improve the service life of pipelines [1–3]. The combination of low cost and superior performance has led to the wide adoption of BCPs in oil and gas transport, the chemical industry, the nuclear industry and other fields [4–8].
Trans Indian Inst Met
For BCPs, stainless steel or nickel-based alloys mainly provide corrosion resistance and are used as the cladding layer. Carbon steel or high-strength low-alloy steel as the base layer mainly provide
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