Effect of ageing time on microstructure and mechanical properties of SAF 2205 duplex stainless steel

2018 ◽  
Vol 1 (91) ◽  
pp. 23-30
Author(s):  
R.N. Penha ◽  
L.B. Silva ◽  
C.S.P. Mendonça ◽  
T.C. Moreira ◽  
M.L.N.M. Melo
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Impact Toughness ◽  
Stainless Steels ◽  
Sigma Phase ◽  
S Phase ◽  
Duplex Stainless Steels ◽  
Phase Precipitation ◽  
Saf 2205

Purpose: SAF 2205 duplex stainless steels (DSSs) are materials characterized by a favourable combination of the properties of ferritic and austenitic stainless steels. This type of stainless steel presents good weldability, corrosion resistance especially for stress corrosion cracking (SCC). However, this steel presents an unavoidable disadvantage that is its potential microstructural instability. Although duplex stainless steels design idea is to present two main types of microstructure, other phases and carbides or nitrides can precipitate. In the case of DSS SAF 2205, in addition to austenitic and ferritic microstructure, during heat treatment processing, welding or use may occur precipitation of undesirable intermetallic phases such as chi, Widmanstätten austenite, sigma besides carbides and nitrides. The precipitation of s-phase is associated with effects that cause both reduction of toughness and decreases the corrosion resistance on austenitic, ferritic and duplex stainless steels. Design/methodology/approach: This study evaluated the aging treatment effect on hardness, impact toughness and ferrite content of a SAF 2205 duplex stainless steel. Samples were solubilized at 1150°C, quenched in water and aged at 850°C during 1, 5, 10, 30, 60 or 180 minutes. After aging, cooling was to room temperature in air. Findings: Aging time promoted s-phase precipitation and hardness increase. Hardness and ferrite volume measurements, microscopy and the prediction of sigma phase bases the discussion. Impact toughness decreased with time aging and intermetallic phase precipitation. Research limitations/implications: As future work could be performed some corrosion test, vary the cooling rate after aging, and using other techniques to identify phases. Focus the research at lower aging times to try the describe Cr partitioning process to form sigma phase. Practical implications: High aging time should be avoided for SAF 2205 DSS. Originality/value: Usually sigma-phase precipitation on DDS is correlated to welding process. This paper correlates it to aging heat treatment.

Effect of Solubilization Temperature on the Sigma Phase Precipitation of a Superduplex Stainless Steel

2014 ◽  
Vol 805 ◽  
pp. 305-310
Author(s):  
Aline da Silva ◽  
Carlos Alberto Rodrigues ◽  
Antonio Carlos Ancelotti ◽  
Edmilson Otoni Corrêa ◽  
M.L.M. Noronha Melo
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Stainless Steels ◽  
Sigma Phase ◽  
Phase Precipitation ◽  
Volumetric Fraction ◽  
Different Temperatures ◽  
Superduplex Stainless Steel ◽  
Mechanical Properties And Corrosion ◽  
Precipitated Phases

Superduplex stainless steel is an important class of stainless steels because it combines the benefits of ferrite and austenite phases, resulting in steels with better mechanical properties and corrosion resistance. However, a significant problem of this steel is the precipitation of deleterious phases during heat treatment. Among these precipitated phases, the most relevant is the sigma phase, because it causes higher loss of properties. The objective of this work therefore is to study the sigma phase precipitation in the superduplex stainless steel UNS S32520 when submitted to heat treatment of solubilization in three different temperatures (1050 C, 1150o C and 1250° C) and subsequently aged in the temperature of 850oC during 10 minutes, 30 minutes, 60 minutes, 3 hours and 10 hours, followed by water quenching. The results showed that as the solubilization temperature increases, there is a significant grain growth and an increase of the ferrite volumetric fraction, which delays the sigma phase precipitation in this superduplex stainless steel. Moreover, it can be verified that the hardness of the material is directly related to volumetric fraction of sigma present in the steel.

Sigma Phase Precipitation of Duplex Stainless Steel and its Effect on Corrosion Resistance

2009 ◽  
Vol 620-622 ◽  
pp. 391-394 ◽  
Author(s):  
Ying Han ◽  
De Ning Zou ◽  
Wei Zhang ◽  
Rui Huang
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Aging Time ◽  
Corrosion Behavior ◽  
Stainless Steels ◽  
Sigma Phase ◽  
Precipitation Amount ◽  
Aging Treatment ◽  
Phase Precipitation

The present study concerns the influence of aging parameters on the microstructure and corrosion behavior of duplex stainless steel S31803 and S32750. It has been found that the microstructural evolutions were extremely sensitive to sigma phase precipitation during aging treatment, and sigma phase was enhanced with the increase of aging time from 2 min to 120min at its precipitation peak temperature 850 °C for S31803 and 920°C for S32750 steels respectively. The precipitation of sigma phase in S32750 is ahead of that in S31803 steel, within 10min, the sigma phase precipitation rate of S32750 is much faster than that of S31803 steel. The precipitation amount of sigma phases in S32750 steel is noticeable higher than that in S31803 steel during any aging treatment. The corrosion resistance is directly influenced by the abundant sigma phases, especially for the S32750. This result is helpful for practical aging treatment establishment of the S31803 and S32750 duplex stainless steels.

scholarly journals Effect of Sigma Phase on Corrosion Resistance of Duplex Stainless Steels

1996 ◽  
Vol 45 (2) ◽  
pp. 83-89 ◽  
Author(s):  
Shuji Hashizume ◽  
Kaoru Sato ◽  
Masaharu Honda ◽  
Katsumi Masamura ◽  
Jun-ichi Sakai ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Stainless Steels ◽  
Sigma Phase ◽  
Duplex Stainless Steels

Effect of the Heat Treatment on the Corrosion Resistance of Duplex Stainless Steels

2018 ◽  
Vol 27 (8) ◽  
pp. 3859-3868 ◽  
Author(s):  
Luca Pezzato ◽  
Mattia Lago ◽  
Katya Brunelli ◽  
Marco Breda ◽  
Irene Calliari
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Stainless Steels ◽  
Duplex Stainless Steels

Sigma phase precipitation on welded SAF 2205 Duplex Stainless Steels after isothermal heat treatment

2014 ◽  
Vol 1611 ◽  
pp. 177-182
Author(s):  
A. F. Miranda Pérez ◽  
R. Sandström ◽  
I. Calliari ◽  
F. A. Reyes Valdés
Keyword(s):  
Corrosion Resistance ◽  
Stainless Steels ◽  
Duplex Stainless Steels ◽  
Austenitic Steels ◽  
Isothermal Treatment ◽  
Ferromagnetic Behavior ◽  
Isothermal Heat Treatment ◽  
Σ Phase ◽  
Δ Ferrite ◽  
Saf 2205

ABSTRACTDuplex stainless steels are commonly used for various applications owing to their superior corrosion resistance and/or strength. They have ferromagnetic behavior together with a good thermal conductivity and a lower thermal expansion as a result of higher ferrite content than austenitic steels. Their ferrite matrix suffers a decomposition process during aging in the temperature range 650-950° C producing precipitation of austenite, σ and χ, carbides and nitrides. These intermetallic phases are known to be deleterious for corrosion resistance and mechanical properties.In this work the effect of aging time during isothermal treatment at 850°C and 900°C on the microstructure of SAF 2205 Duplex Stainless Steels welded plates has been investigated. The aim of this work is to determine the morphology of σ phase, and perform a quantitative analysis of the precipitation process.Submerged Arc Welding is used for processing. It produces a high content of δ ferrite in the heat affected zone and low content of austenite in the weld. Microstructural examination shows that the σ phase precipitates at δ ferrite/γ interphases. Longer aging treatments give rise to an increase of volume fraction together with a coarser morphology.

scholarly journals Austenitic-ferritic stainless steel containing niobium

2013 ◽  
Vol 66 (4) ◽  
pp. 467-471
Author(s):  
André Itman Filho ◽  
Wandercleiton da Silva Cardoso ◽  
Leonardo Cabral Gontijo ◽  
Rosana Vilarim da Silva ◽  
Luiz Carlos Casteletti
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Charge Transfer ◽  
Ferritic Stainless Steel ◽  
Stainless Steels ◽  
Sigma Phase ◽  
Charge Transfer Resistance ◽  
Chemical Compositions ◽  
Transfer Resistance ◽  
Ferritic Stainless Steels

The austenitic-ferritic stainless steels present a better combination of mechanical properties and stress corrosion resistance than the ferritic or austenitic ones. The microstructures of these steels depend on the chemical compositions and heat treatments. In these steels, solidification starts at about 1450ºC with the formation of ferrite, austenite at about 1300ºC and sigma phase in the range of 600 to 950ºC.The latter undertakes the corrosion resistance and the toughness of these steels. According to literature, niobium has a great influence in the transformation phase of austenitic-ferritic stainless steels. This study evaluated the effect of niobium in the microstructure, microhardness and charge transfer resistance of one austenitic-ferritic stainless steel. The samples were annealed at 1050ºC and aged at 850ºC to promote formation of the sigma phase. The corrosion testes were carried out in artificial saliva solution. The addition of 0.5% Nb in the steel led to the formation of the Laves phase.This phase, associated with the sigma phase, increases the hardness of the steel, although with a reduction in the values of the charge transfer resistance.

scholarly journals Duplex Stainless Steels—Alloys for the 21st Century

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 836
Author(s):  
Roger Francis ◽  
Glenn Byrne
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
21St Century ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Cost Benefit ◽  
Industrial Applications ◽  
Carbon Steels ◽  
Duplex Stainless Steels ◽  
Corrosion Resistant

Duplex stainless steels were first manufactured early in the 20th century, but it was the introduction in the 1970s of the argon-oxygen decarburisation (AOD) steel making process and the addition of nitrogen to these steels, that made the alloys stronger, more weldable and more corrosion resistant. Today, duplex stainless steels can be categorised into four main groups, i.e., “lean”, “standard”, “super”, and “hyper” duplex types. These groups cover a range of compositions and properties, but they all have in common a microstructure consisting of roughly equal proportions of austenite and ferrite, high strength, good toughness and good corrosion resistance, especially to stress corrosion cracking (SCC) compared with similar austenitic stainless steels. Moreover, the development of a duplex stainless-steel microstructure requires lower levels of nickel in the composition than for a corresponding austenitic stainless steel with comparable pitting and crevice corrosion resistance, hence they cost less. This makes duplex stainless steels a very versatile and attractive group of alloys both commercially and technically. There are applications where duplex grades can be used as lower cost through-life options, in preference to coated carbon steels, a range of other stainless steels, and in some cases nickel alloys. This cost benefit is further emphasised if the design engineer can use the higher strength of duplex grades to construct vessels and pipework of lower wall thickness than would be the case if an austenitic grade or nickel alloy was being used. Hence, we find duplex stainless steels are widely used in many industries. In this paper their use in three industrial applications is reviewed, namely marine, heat exchangers, and the chemical and process industries. The corrosion resistance in the relevant fluids is discussed and some case histories highlight both successes and potential problems with duplex alloys in these industries. The paper shows how duplex stainless steels can provide cost-effective solutions in corrosive environments, and why they will be a standard corrosion resistant alloy (CRA) for many industries through the 21st century.

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