Components of the offshore industry have to withstand high mechanical loads under extreme conditions. Thus, noble metals have been used for manufacturing of pipes, with materials as corrosion resistant alloys (CRA). Nevertheless, fusion welding for CRA still lacks of reproducibility, looking for more effective processes. In this context, friction stir welding is suitable for CRA. Therefore, this study focuses on mechanical and corrosion properties of friction stir welds in UNS N06625 and UNS S32760. At first, the weld microstructure and its corresponding heat input were analysed. Besides, microhardness measurements were performed. Moreover, the pitting resistance was studied according ASTM G48A. The results showed that friction-stir-welded alloy 625 had greater pitting resistance than friction-stir-welded super duplex.
The advent of mechanically lined pipes represented a new turning point for the oil industry in terms of performance and cost for fluids transportation. However, the implementation of this technology demanded the development of new improvements such as reel-lay techniques and joining methods to ensure the reliable and safe operation of the pipeline. It also posed new challenges for inspection and flaw assessment by non-destructive testing (NDT) methods, especially of the joining region formed at the pipe termination by the interface between liner, steel substrate and the weld overlay used for sealing of the assembly. This region, commonly referred to as the triple point, is formed by a dissimilar weld joint with high metallurgical complexity. As a consequence, many conventional NDT techniques have failed in providing trustworthy indications of the defects. Thus, in order to find an alternative for NDT inspection to fulfil the international security standards, this paper reports the use of guided waves generated by an electromagnetic acoustic transducer (EMAT) to interrogate the integrity of the triple point. The present research focused on the performance evaluation of shear horizontal waves to interrogate a test piece simulating a lined pipe structure which had artificially inserted discontinuities at the triple point region. The findings documented in this paper were achieved by the means of finite element analysis (FEA) and experimental validation of a transducer design and wave propagation in the triple point area.
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