Microstructural, Mechanical, and Electrochemical Analysis of Duplex and Superduplex Stainless Steels Welded with the Autogenous TIG Process Using Different Heat Input

Abstract

Duplex Stainless Steels (DSS) and Superduplex Stainless Steels (SDSS) have a strong appeal in the petrochemical industry. These steels have excellent properties, such as corrosion resistance and good toughness besides good weldability. Welding techniques take into account the loss of alloying elements during the process, so this loss is usually compensated by the addition of a filler metal rich in alloying elements. A possible problem would be during the welding of these materials in adverse conditions in service, where the operator could have difficulties in welding with the filler metal. Therefore, in this work, two DSS and one SDSS were welded, by autogenous Tungsten Inert Gas (TIG), i.e., without addition of a filler metal, by three different heat inputs. After welding, microstructural, mechanical, and electrochemical analysis was performed. The microstructures were characterized for each welding condition, with the aid of optical microscopy (OM). Vickers hardness, Charpy-V, and cyclic polarization tests were also performed. After the electrochemical tests, the samples were analyzed by scanning electron microscopy (SEM). The SDSS welded with high heat input kept the balance of the austenite and ferrite, and toughness above the limit value. The hardness values remain constant in the weld regions and SDSS is the most resistant to corrosion.

Effects of Local Heat Input Conditions on the Thermophysical Properties of Super Duplex Stainless Steels (SDSS)

“…Furthermore, the computer code used has been continuously updated by the authors and applied for different materials and welding conditions 3,6,[9][10][11][12] . In this paper we introduce new features to improve the model capability such as routines for kinetics of phase transformations for super duplex stainless steels 7,8 .…”

“…Microstructure plays a decisive role on both 1,2 . The accurate determination of the residual stresses during the steels welding and corrosion resistance during service are, therefore, subjects that need better attention due to their technological importance [3][4][5][6] . The super duplex stainless steels (SDSS) are enhanced materials that could be used in several applications that need higher performance 3 .…”

Optimizing the Mechanical Properties in the Repair Zone of 5Cr5MoV by Controlling Welding Heat Input

“…The variation of the dendrite size can be attributed to the changes of heat input, which significantly influence the cooling rate. In this aspect, a high heat input means a low cooling rate [24], which can effectively reduce the growth time of dendrite, and it can provide enough time for the dendrite growth into the fusion zone. These columnar dendrites are the major microstructure in the weld.…”

Sigma Phase: Nucleation and Growth

“…The precipitation of phase σ is of significant interest for DSS and SDSS. The presence of sigma phase worsens the mechanical properties and the corrosion resistance of these steels [1][2][3]. The sigma phase presents the most significant volume when compared to the other intermetallic phases observed in the DSS/SDSS microstructures.…”

“…They possess a high mechanical strength, good tenacity, adequate corrosion resistance in various media, and excellent resistance to stress corrosion cracking. These steels are widely used in the chemical industry and in offshore applications that require high corrosion resistance and great mechanical strength [1][2][3][4][5][6][7][8][9][10]. The continuous development of DSS resulted in the composition of complex steels containing considerable amounts of alloying elements.…”