Nd-yag laser pulsed welding: Effects on the superduplex stainless steel UNS S32750

Abstract

The use of superduplex stainless steels in industry increases due to their characteristics that combine good mechanical properties and resistance to corrosion. The study of super duplex stainless steels is very important due to the development of activities in the area of oil and natural gas, mainly with the recent discovery of the pre-salt oil in Brazil. These industries operate in critical atmosphere, because of the presence of seawater and oil. The UNS S32750 consists of a biphasic structure with volumetric fractions of 50% ferrite and 50% austenite. Therefore, the development of techniques for improving welding of super duplex steels is necessary in order to ensure that phase balance and properties of the material are not severely damaged in the process. The objective is to characterize joints of UNS S32750 duplex stainless steel welded with the Laser Nd-YAG (Neodymium-Doped Yttrium Aluminium Garnet) pulsed process. Welds were performed in the autogenous condition, varying the heat input introduced by the process. Then, an analysis of the base metal, the weld beads and the heat affected zone, were performed through optical microscopy (OM), corrosion tests (CPT), SEM (Scanning Electron Microscopy), and EDS (Energy Dispersive Spectroscopy). The results obtained were related to the welding parameters used. The success of the research provides knowledge parameters and properties in the welded joints of this superduplex stainless steel.