Microstructural and corrosion properties of cold rolled laser welded UNS S32750 duplex stainless steel

Claudio Gennari, Mattia Lago, Balint Bögre, I. Mészáros, Irene Calliari, Luca Pezzato

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The main goal of this work was to study the effect of plastic deformation on weldability of duplex stainless steel (DSS). It is well known that plastic deformation prior to thermal cycles can enhance secondary phase precipitation in DSS which can lead to significant change of the ferrite-austenite phase ratio. From this point of view one of the most important phase transformation in DSS is the eutectoid decomposition of ferrite. Duplex stainless steels (DSSs) are a category of stainless steels which are employed in all kinds of applications where high strength and excellent corrosion resistance are both required. This favorable combination of properties is provided by their biphasic microstructure, consisting of ferrite and austenite in approximately equal volume fractions. Nevertheless, these materials may suffer from several microstructural transformations if they undergo heat treatments, welding processes or thermal cycles. These transformations modify the balanced phase ratio, compromising the corrosion and mechanical properties of the material. In this paper, the microstructural stability as a consequence of heat history due to welding processes has been investigated for a super duplex stainless steel (SDSS) UNS S32750. During this work, the effects of laser beam welding on cold rolled UNS S32750 SDSS have been investigated. Samples have been cold rolled at different thickness reduction (ε = 9.6%, 21.1%, 29.6%, 39.4%, 49.5%, and 60.3%) and then welded using Nd:YAG laser. Optical and electronical microscopy, eddy’s current tests, microhardness tests, and critical pitting temperature tests have been performed on the welded samples to analyze the microstructure, ferrite content, hardness, and corrosion resistance. Results show that laser welded joints had a strongly unbalanced microstructure, mostly consisting of ferritic phase (~60%). Ferrite content decreases with increasing distance from the middle of the joint. The heat-affected zone (HAZ) was almost undetectable and no defects or secondary phases have been observed. Both hardness and corrosion susceptibility of the joints increase. Plastic deformation had no effects on microstructure, hardness or corrosion resistance of the joints, but resulted in higher hardness of the base material. Cold rolling process instead, influences the corrosion resistance of the base material.

Original languageEnglish
Article number1074
JournalMetals
Volume8
Issue number2
DOIs
Publication statusPublished - Jan 1 2018

Fingerprint

Stainless Steel
Stainless steel
Corrosion
Ferrite
Lasers
Corrosion resistance
Hardness
Plastic deformation
Microstructure
Austenite
Welding
Weldability
Laser beam welding
Cold rolling
Heat affected zone
Pitting
Microhardness
Volume fraction
Microscopic examination
Welds

Keywords

  • Corrosion
  • Deformation
  • Duplex stainless steel
  • Microstructure
  • Welding

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Microstructural and corrosion properties of cold rolled laser welded UNS S32750 duplex stainless steel. / Gennari, Claudio; Lago, Mattia; Bögre, Balint; Mészáros, I.; Calliari, Irene; Pezzato, Luca.

In: Metals, Vol. 8, No. 2, 1074, 01.01.2018.

Research output: Contribution to journalArticle

Gennari, Claudio ; Lago, Mattia ; Bögre, Balint ; Mészáros, I. ; Calliari, Irene ; Pezzato, Luca. / Microstructural and corrosion properties of cold rolled laser welded UNS S32750 duplex stainless steel. In: Metals. 2018 ; Vol. 8, No. 2.
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