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Gamagenic elements addition on welding of uns S32750 superduplex steel plates by pulsed Nd: YAG laser

Grant number: 18/17362-6
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): December 01, 2018
Effective date (End): August 31, 2020
Field of knowledge:Engineering - Mechanical Engineering - Manufacturing Processes
Principal Investigator:Vicente Afonso Ventrella
Grantee:Leonardo Vilela de Menezes Carvalho
Home Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil

Abstract

Super duplex steels welded joints have their microstructure modified due to the thermal cycle involved on process, changing their structure from equal volume fractions of austenite and ferrite to a major ferrite structure. This reduces the desirable properties of this steel, such as corrosion resistance, which are very important to the oil and gas industry, known for the application of these steels to their structures and equipment. In this sense, this work seeks to continue the proposed solution of nickel addition for austenite stabilization, and consequent recovery of biphasic balance. At the beginning of this project, the candidate was successful, showing effectivity using nickel as way to improve weld bead properties. Striving to continue the research, a new methodology has now been proposed, with the incorporation of additional metal by the electrodeposition technique, which will treat improvements in the control of added metal, with time reduction and repeatability, mandatory for an industrial application. This methodology will also allow the evaluation of copper and cobalt, as well as nickel, since they are all gamagenic elements. Thus, through the Nd: YAG pulsed laser welding process, UNS S32750 super duplex stainless steel thin sheets will be joined with copper, cobalt or nickel as a way to improve bead characteristics. The gamagenic characteristic of these elements, added to the advantages of laser welding, will be able to make this type of welding possible for the offshore industry. Through mechanical tests and microstructural characterization, it will be possible to judge, at the end of the project, the application of the mentioned elements, as well as the way to add them.