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Appication of pulsed Nd: YAG laser in uns s 32750 super duplex stainless steel welding used in oil and natural gas industry

Abstract

In general, the essential requirements required for an alloy used in the industries belonging to the Oil and Natural Gas are mechanical strength, in view of the various efforts which will be submitted materials, and corrosion resistance, due to the severity with which environmental materials will be exposed. The components and equipment in these industries are often subjected to high temperatures and contact with fluids containing highly corrosive or abrasive. In this sense, beyond the challenges of petroleum exploration of increasingly aggressive existing sources, the new findings called pre-salt represent another group of operations that require use of materials with high mechanical performance and corrosion resistance, and also welding processes capable of ensuring good quality of the weld. The super duplex stainless steel has been gaining more space in the petrochemical industry precisely because it has such requirements mentioned above. In addition, it meets the needs of the traditional austenitic and ferritic steels in many applications because the super duplex stainless steel is able to combine the properties of both ferritic and austenitic. Is attributed to its high corrosion resistance and mechanical its balanced microstructure by approximately 50% to 50% ferrite and austenite. The welding of super duplex stainless steels directly interferes in the microstructure of the weld metal and therefore only a welding process can generate well-adjusted welded joints with a suitable balance of the phases (austenite and ferrite) and with minimal precipitation of intermetallic phases deletéreis. If this balance is not achieved can lose the advantages of super duplex stainless steels on the traditional. This work involves the study of the influence of welding pulse energy Nd: YAG laser on the balance of phase ferrite / austenite super duplex stainless steel UNS S32750. The laser weld beads are obtained with varying intensity of the laser beam (W/cm2) with temporal width (ms), and different depths of focus. The results obtained from this study suggested will therefore be compared with experimental results available in the literature, which are generated by other welding processes. Thus, the role of laser control of austenite and ferrite phases will be investigated, where it is shown the feasibility of using the welding process by pulsed laser Nd: YAG laser in this control phase in the weld metal and thus guaranteeing a good toughness and good resistance to corrosion of the weld. Microstructural characterization techniques will be used by Optical Microscopy, Scanning Electron Microscopy, X-Ray Diffraction and if necessary will be used Transmission Electron Microscopy to characterize the very fine carbides in the matrix. In addition a mechanical characterization will be performed by Vickers hardness microhardness tests, corrosion tests, micro scale abrasion tests and tensile tests. The contribution required by this project should be in order to achieve greater dissemination of information about the application of a solid state laser source, pulsed Nd: YAG laser welding of super duplex stainless steel UNS S32750. The project has great potential for innovation in the field of lasers, through the application of pulsed solid state laser (Nd: YAG) in super duplex stainless union, an important constituent of the metallic components of the industries of Petroleum and Natural Gas. The results could help in reducing losses caused by premature failure of components, but mainly to reduce the risk of environmental accidents and operations which may be caused by these failures. (AU)