Objective 1
A comprehensive weldability study will investigate three advanced pipeline materials: API 5L X-80, X-100 and Alloy 625-cladded X-65. The study aims to identify process parameter fields for defect-free welds and establish relationships between FSW process parameters, microstructure and mechanical properties. A combined modelling and experimental approach will define and validate welding parameters sets through microstructural analysis and mechanical testing. The resulting database and validated model will enable accurate prediction of weld microstructures and properties under varying thermomechanical conditions.
Objective 2
In the project FSW tool wear and failure mechanisms will be investigated and related to the conditions in the shear layer, i.e. the interface between the tool and base material, including temperature, viscosity and geometry. Models of the shear layer will be combined with systematic NDT monitoring of the tool and comprehensive process data, including tool and base material temperatures. The results will support the development of a real-time tool monitoring concept that can trigger the process controller when shear layer conditions threaten tool integrity.
Objective 3
Developing an adaptive loop control for the FSW process based on three major developments:
A real-time NDT and quality monitoring module using adapted sensors, software and AI to detect defect formation during orbital welding and provide information to the process controller.
A dedicated study of root and surface defect formation and their dependence on process parameters, enabling knowledge-based parameter adjustments to prevent defects or limit their growth.
Evaluation of defect criticality based on the toughness behavior of the joints, crack resistance curves and failure assessment models to determine critical crack lengths.
Objective 4
Developing an in-operando repair capability to correct defects caused by temporary process instabilities during FSW. The concept exploits the unique ability of FSW to re-weld affected areas directly, without requiring prior treatment or preparation of the defective region before the repair operation.
Objective 5
Developing an FSW process controller that integrates the knowledge generated throughout the project to ensure stable operation and the required microstructure and material properties. If a defect occurs, the controller will detect it and automatically adjust the process parameters to prevent further growth. The detected defect size will be compared with the critical crack length. If the critical value is exceeded, an in-operando repair operation will be initiated to restore the weld.
This project is funded by the Research Fund for Coal and Steel, a programme managed by the European Commission, under Grant Agreement no. 101296202
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