Pit Morphology and Its Relation to Microstructure of 850°C Aged Duplex Stainless Steel

Magnabosco, Rodrigo; Alonso-Falleiros, Neusa

doi:10.5006/1.3278167

Cited by 50 publications

(32 citation statements)

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“…Some of these elements, which are added as an alloying element in austenite, can precipitate and lead to pitting corrosion [13] [14].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, they may be more susceptible to localized corrosion, such as pites [13] [14]. What characterizes the resistance to pitting corrosion is the capability of a metal to passivate, form a continuous film and adherent of oxides able to prevent the penetration of oxygen into the matrix [15].…”

Section: Introductionmentioning

confidence: 99%

“…This corrosive process is known as an extremely localized attack, initiated by the breakage of the passive film in regions that presents defects such as inclusions, dislocations, grain boundaries or interfaces [15]. The alloying elements that dictate the resistance to pitting corrosion and the formation of the passivating layer in a stainless steel are Cr, Mo and N [14].…”

Section: Introductionmentioning

confidence: 99%

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Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints

Lopes¹,

Rodrigues²,

Silva³

et al. 2018

MSA

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The main objective of this research is to better understand the correlation between the constituent phases presented in the super-duplex steel SAF 2507 when it is under welding process by arc shielding gas MIG-MAG (Metal Inert Gas-Metal Active Gas). Conventional short circuit transfer and derivative STT (Surface Tension Transfer) using the 2594 welding wire as a filler metal and the effects on welding power in hardness, toughness and pitting corrosion are considered here. The results showed that the welding energy (Ew) changed the α/γ-phase's balance and occasionally formed σ-phase in ferrite grain boundaries which led to changes in hardness, toughness and pitting corrosion resistance in molten zone (MZ), heat activated zone (HAZ) and metal base regions (MB). Furthermore, the increased amount of γ-phase improved the pitting corrosion resistance index (PRENγ) mainly in the MZ. This is due to decrease of α-phase fraction and formation of coarser grains, for higher welding energy. The toughness in the MZ decreased with less formation of γ-phase, coalescence of ferritic grains and localized formation of σ-phase, raising the hardness in the HAZ when the welding energy was lower.

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“…Some of these elements, which are added as an alloying element in austenite, can precipitate and lead to pitting corrosion [13] [14].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints

Lopes¹,

Rodrigues²,

Silva³

et al. 2018

MSA

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“…Os mecanismos de formação de fase sigma em aço inoxidável dúplex UNS S31803 são explorados em alguns trabalhos, (1)(2)(3)(4) onde se constata, de forma geral, que em até 0,1 horas de envelhecimento entre 700°C e 900°C a fase sigma se forma em interfaces ferrita/ferrita ou ferrita/austenita, por meio da transformação da ferrita presente por decomposição eutetóide, gerando também austenita secundária. A partir de 0,1 horas de envelhecimento, as frações volumétricas de ferrita e de austenita decrescem, indicando que o crescimento da http://dx.doi.org/10.4322/tmm.2012.027…”

Section: Introductionunclassified

Influência Do Trabalho a Frio Na Formação De Fase Sigma Em Aço Inoxidável Dúplex

Magnabosco¹,

Ávila²,

Rabechini³

2012

TMM

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ResumoA formação de fase sigma em aços inoxidáveis dúplex durante envelhecimento isotérmico é extensamente relatada na literatura, mas a influência de encruamento prévio ao envelhecimento na cinética de formação dessa fase não foi alvo de estudos sistemáticos até então. Deste modo, o objetivo deste trabalho é estudar a influência do grau de encruamento e do tempo de envelhecimento a 650°C e 850°C, na microestrutura do aço UNS S31803. Foi realizado encruamento em laminador de planos, obtendo-se quatro séries de amostras, com 0%, 10%, 30% e 80% de redução de área transversal. A seguir, conduziu-se envelhecimento isotérmico a 650°C ou 850°C por tempos variando de 10 minutos a 96 horas, seguido de resfriamento em água. Para a quantificação de fase sigma foi utilizado ataque eletrolítico seletivo com solução 10% KOH, e a fração volumétrica de ferrita foi obtida com o auxílio de ferritoscópio. Observa-se que o aumento do encruamento aumenta a possibilidade de nucleação heterogênea de fase sigma no interior dos grãos de ferrita, o que leva a aumento da taxa de formação de sigma e de consumo de ferrita com o aumento do tempo de envelhecimento nas duas temperaturas estudadas. Palavras-chave: Fase sigma; Aço inoxidável dúplex; Cinética de formação. INFLUENCE OF COLD WORK ON SIGMA PHASE FORMATION IN DUPLEX STAINLESS STEEL AbstractThe formation of sigma phase in duplex stainless steels during isothermal aging is widely reported in the literature, but the influence of strain hardening prior to aging on the kinetics of formation of this phase was not a subject of systematic studies so far. The objective of this paper is to study the influence of cold work degree and aging time in aging at 650°C or 850°C of an UNS S31803 steel. Cold rolling was conducted, resulting in four sets of samples with 0%, 10%, 30% or 80% cross sectional area reduction. Those samples were submitted to isothermal aging between 10 minutes and 96 hours, followed by water quenching. Sigma phase quantification is possible after selective electrolytic etching with 10% KOH solution, and the volume fraction of ferrite is obtained with the aid of ferritscope. It is observed that increasing the strain hardening increases the possibility of heterogeneous nucleation of sigma phase within the ferrite grains, leading to increased rate of formation of sigma and consumption of ferrite with increasing aging time at both temperatures studied. Key words: Sigma phase; Duplex stainless steel; Transformation kinetics. INTRODUÇÃOOs mecanismos de formação de fase sigma em aço inoxidável dúplex UNS S31803 são explorados em alguns trabalhos, (1)(2)(3)(4) onde se constata, de forma geral, que em até 0,1 horas de envelhecimento entre 700°C e 900°C a fase sigma se forma em interfaces ferrita/ferrita ou ferrita/austenita, por meio da transformação da ferrita presente por decomposição eutetóide, gerando também austenita secundária. A partir de 0,1 horas de envelhecimento, as frações volumétricas de ferrita e de austenita decrescem, indicando que o crescimento da http://dx

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“…Sigma phase depends on the temperature and time. Aging between 650°C and 950°C promotes the formation of sigma phase by eutectoid decomposition of ferrite or by nucleation and growth from ferrite and austenite 6,7 . Solution annealed at 1080°C and water quenched showed the presence of sigma phase in the ferrite/austenite interfaces 8 .…”

Section: Introductionmentioning

confidence: 99%

Microstructural Transformation in a Root Pass of Superduplex Stainless Steel Multipass Welding

Villalobos-Vera

Mendoza-Bravo

2017

Mat. Res.

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The microstructure of the root pass in a superduplex stainless steel multipass welding was investigated. Results showed that the welding metal has an austenite matrix with particles of sigma phase formed in the ferrite/austenite interface and intragranularly.Eventhough the filler metal is intended to keep the phase balance after welding,the welding metal presented a considerable decrease in the ferrite content and a high proportion of sigma phase. Despite the exposition to thermal cycles on every pass, the heat affected zone presented a microstructure consisting of ferrite and austenite with a small proportion of sigma phase.Therefore,the thermal cycles of every welding pass allowed the decomposition of ferrite into austenite and sigma phase in points close to the heat source, changing the final microstructure.

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Pit Morphology and Its Relation to Microstructure of 850°C Aged Duplex Stainless Steel

Cited by 50 publications

References 1 publication

Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints

Influence of MIG/MAG Welding Process on Mechanical and Pitting Corrosion Behaviors on the Super-Duplex Stainless Steel SAF 2507 Welded Joints

Influência Do Trabalho a Frio Na Formação De Fase Sigma Em Aço Inoxidável Dúplex

Microstructural Transformation in a Root Pass of Superduplex Stainless Steel Multipass Welding

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