Wire Arc Additive Manufacturing (WAAM) Component with Integrated Substrate for Subsea Tee Branch Application

Abstract In a pioneering effort to optimize subsea infrastructure design and installation, Saipem launched an R&D program [Ref. 1] to produce a Wire Arc Additive Manufacturing (WAAM) Tee Branch (TB) component with an integrated substrate and a novel square base design. This project, developed in cooperation with Vallourec, aimed to investigate the feasibility and advantages of using WAAM technology to create complex subsea components that meet stringent industry standards. The methodology involved printing the TB component at manufacturer's facility, followed by comprehensive characterization at its own R&D center in France. Adhering to the DNV-ST-B203 guidelines, the component was qualified to meet contractor's specific requirements. The base pipe, a seamless pipe, was prepared and used as a substrate for WAAM deposition. Post-printing, the component underwent precise machining to facilitate non-destructive testing (NDT) inspections, including Liquid Penetrant Inspection (LPI) and Ultrasonic Testing (UT). The innovative square base design allowed for thorough inspection of the interface between the base pipe and the WAAM addon ensuring the detection of any potential defects. The NDT results were crucial in confirming the integrity of the component. An accurate inspection could be performed thanks to the square base design and shown no defect. Following NDT, a series of destructive tests were conducted in both the WAAM region and at the interface between the base pipe and the WAAM material. These tests included chemical analysis, tensile testing, hardness measurement, Charpy impact testing, macro and microstructural analysis, porosity rate assessment and bend testing. The results were promising, demonstrating that the TB component globally fulfilled contractor's specifications. The innovative square base design facilitated comprehensive NDT inspection and could contribute to the overall structural integrity of the component. Destructive testing revealed interesting mechanical properties, confirming the robustness and reliability of the WAAM-produced TB. This project provides significant insights into the application of WAAM technology for subsea infrastructure, showcasing its potential to improve the manufacturing of complex components. The successful integration of the substrate with the WAAM underlines the feasibility and advantages of the WAAM, such as the complexity of the geometry and the cost/benefit advantage coming from the optimization of the size and weight of the produced component. From a contractor point of view, the initiative represented a first step toward the industrialization of the innovative manufacturing process for subsea applications.