UNS S32750 superduplex stainless steel welding with pulsed Nd:YAG laser and cobalt addition

• Grant number: 22/08493-5
• Support Opportunities: Regular Research Grants
• Duration: December 01, 2022 - November 30, 2023
• Field of knowledge: Engineering - Mechanical Engineering - Manufacturing Processes
• Principal Investigator: Vicente Afonso Ventrella
• Grantee: Vicente Afonso Ventrella
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil

Abstract

In general, the essential requirements required for a metallic alloy used in industries belonging to the chemical sector are mechanical resistance, in view of the various efforts to which the materials will be subjected, and corrosion resistance, due to the environmental severity to which the materials will be exposed. . Components and equipment in these industries are often subjected to high temperatures and contact with extremely corrosive fluids or fluids containing abrasives. In this sense, in addition to the challenges inherent to this type of industry, there is a need to use materials with high mechanical and corrosion performance, as well as welding processes capable of guaranteeing good quality of the welded joint. Super duplex stainless steel has been gaining more and more space in the chemical sector precisely because it has such requirements mentioned above. In addition, it meets the needs of the traditional austenitic and ferritic in many applications, as the super duplex stainless steel can combine the properties of both ferritic and austenitic. Its high corrosion and mechanical resistance is attributed to its balanced microstructure in approximately 50% ferrite and 50% austenite. The welding of super duplex stainless steels directly interferes with the microstructure of the weld metal and, therefore, only a well-adjusted welding process can generate welded joints with an adequate balance of phases (austenite and ferrite). If this balance is not obtained, the advantages of super duplex steel over traditional stainless steels may be lost. This research work involves the study of the influence of cobalt addition to the weld metal, through electrolytic deposition on the base metal joint face, on the ferrite/austenite phase balance of the UNS S32750 super duplex stainless steel. The laser weld beads will be obtained with different additions of cobalt in the joint to be welded. The results obtained through this proposed study will therefore be compared with experimental results available in the literature and results obtained by the nickel research group. In this way, the role of the laser in the control of the austenite and ferrite phases will be investigated, where it will be demonstrated the feasibility of using the Nd:YAG pulsed laser welding process, with the addition of cobalt, in the control of the phases present in the weld metal, and therefore ensuring good mechanical properties and good corrosion resistance of the welded joint. Microstructural characterization techniques will be used through Optical Microscopy, Scanning Electron Microscopy and X-Ray Diffraction. In addition, a mechanical characterization will be carried out through Vickers microhardness tests, CPT corrosion tests and tensile tests. The contribution intended by this research project should be in the sense of obtaining a greater dissemination of information about the application of a solid-state, pulsed, Nd:YAG laser source in the welding of super duplex stainless steel UNS S32750 with the aid of the addition of a gammagenic element for phase balance control. In this case, the addition will be carried out through electrolytic deposition in the region of the base metal to be fused. duplex, an important constituent of the metallic components of the chemical industry. The results obtained will be able to contribute to the reduction of damages caused by premature failures of components, arising from the unbalance of phases, but mainly to reduce the risks of environmental and operational accidents that can be caused by these failures. (AU)