Duplex Stainless Steels: A Dozen of Significant Phase Transformations

Padilha, Angelo Fernando; Aguiar, Denílson José Marcolino de; Plaut, Ronald Lesley

doi:10.4028/www.scientific.net/ddf.322.163

Cited by 21 publications

(28 citation statements)

References 19 publications

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“…Addition of alloying elements influences the composition, microstructure and can improve mechanical properties [18]. One limitation of using DSS is the numerous phase transformations occurring in broad temperature range from 300 • C to 1300 • C [19,20]. The intermetallic phases precipitate and induce a negative effect on the toughness and performance of DSS [21,22].…”

Section: Introductionmentioning

confidence: 99%

Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates

Saeidi

Alvi

Lofaj

et al. 2019

Metals

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Duplex stainless steel, 71 wt.% austenite, 13 wt.% ferrite and 16 wt.% sigma, was made upon heat treating of fully ferritic as-built selective laser melted (SLM) 2507 stainless steel at 1200 °C. Formation of sigma phase in the heat treated SLM 2507 was investigated using optical microscopy and scanning electron microscopy (SEM). The heat treated SLM 2507 demonstrated a yield strength of 686 MPa, ultimate tensile strength of 920 MPa and an elongation of 1.8% at room temperature with a brittle fracture morphology. Precipitation of sigma phase during heat treatment and slow cooling improved the mechanical and wear properties at high temperatures (1200 °C and 800 °C, respectively). The tensile strength and elongation of the heat treated SLM 2507 was measured 400 MPa and 20% as compared to casted duplex steel with 19 MPa and 30% elongation at 1200 °C. The 20 times higher mechanical strength as compared to casted duplex steel was attributed to sigma precipitates. Tribological behaviour of heat treated duplex SLM 2507 containing sigma at 800 °C showed very low wear rate of 4.5 × 10−5 mm3/mN compared to casted duplex steel with 1.6 × 10−4 mm3/mN.

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Section: Introductionmentioning

confidence: 99%

Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates

Saeidi

Alvi

Lofaj

et al. 2019

Metals

View full text Add to dashboard Cite

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“…Fast cooling rates during heat treatment can influence the formation of intermetallic sigma phase. Studies carried out [48] and shown by TTT diagrams indicate cooling rates (higher Stainless Steels and Alloys than 250°C/hr) can completely avoid sigma precipitation. The test instrument for the high temperature mechanical testing is Gleeble 3800 .…”

Section: Mechanical Performance and Microstructural Studies Of Slm Stmentioning

confidence: 95%

Microstructure-Tailored Stainless Steels with High Mechanical Performance at Elevated Temperature

Saeidi¹,

Akhtar²

2019

Stainless Steels and Alloys

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Stainless steels are widely used in chemical, structural and automotive applications due to their high room-temperature mechanical properties, toughness, corrosion resistance and low cost. However, tendency and rise in industrial demands for components to be used at high temperature with good mechanical performance and corrosion resistance limit their usage in many applications and narrow down their service criteria. Tailoring the microstructure, tuning the chemistry, adjusting the phase composition and introducing a dense 3D network of dislocations can tailor and develop stainless steels with high performance for extreme conditions, such as elevated temperatures. In this chapter, the effect of the microstructure of additively manufactured and thermo-mechanically processed stainless steels on the high temperature mechanical performance is discussed and a comparison is made with conventional steels. Moreover, new mechanisms are introduced and discussed co-relating the microstructure and properties.

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“…Além disso, nos aços inoxidáveis duplex a ferrita é termodinamicamente metaestável entre 600 e 1000 ºC e possui teores altos de elementos como cromo e molibdênio formadores de fase sigma. Portanto, a precipitação da fase sigma ocorre principalmente pela decomposição da ferrita e resulta no empobrecimento do cromo e do molibdênio em regiões próximas as da formação dessa fase deletéria, reduzindo a resistência a corrosão desses aços [16] [17].…”

Section: Figuraunclassified

Avaliação da susceptibilidade de precipitação da fase sigma na soldagem do aço inoxidável duplex SAF2205

et al. 2019

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RESUMO A soldagem de aços inoxidáveis duplex é uma operação crítica, devido aos ciclos térmicos aos quais o material é submetido, que podem favorecer a precipitação de fases deletérias. Nesse contexto, objetivo dessa pesquisa é analisar a influência da energia de soldagem na susceptibilidade à formação de fase sigma no aço duplex SAF2205. As chapas de SAF2205 foram soldadas pelo processo de soldagem GMAW, variando a energia de soldagem em 0,5kJ/mm, 1,0kJ/mm, 1,5 kJ/mm. O material foi analisado por microscopia óptica, DRX e microdureza Vickers. A análise da microestrutura das chapas evidenciou que quanto maior o aporte térmico utilizado na soldagem, maior é a quantidade de austenita e maior o tamanho do grão austenítico e ferrítico. Por meio do perfil de microdureza verificou-se que ocorre a redução da dureza na ZTA. Através do DRX foi determinada a presença de fase sigma nas regiões de solda para amostras soldadas com energia de soldagem de 1,0kJ/mm e 1,5 kJ/mm. Concluiu-se que pode-se utilizar nos processos de soldagem GMAW de aços inoxidáveis duplex SAF2205 com 4 mm de espessura aporte térmico próximo de 0,5 kJ/mm quando o objetivo for evitar a formação de fase sigma e aproximadamente igual a 1,5 kJ/mm quando o objetivo for manter percentual das fases na ZTA e ZF próximo ao do metal.

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Duplex Stainless Steels: A Dozen of Significant Phase Transformations

Cited by 21 publications

References 19 publications

Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates

Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates

Microstructure-Tailored Stainless Steels with High Mechanical Performance at Elevated Temperature

Avaliação da susceptibilidade de precipitação da fase sigma na soldagem do aço inoxidável duplex SAF2205

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