Effect of short duration solution treatment at temperatures below 1000 °C on σ -phase precipitation in a super duplex stainless steel alloy

2018 ◽  
Vol 49 (5) ◽  
pp. 530-537 ◽  
Author(s):  
V.D. Cojocaru ◽  
N. Şerban ◽  
M.L. Angelescu ◽  
E.M. Cojocaru ◽  
I. Cinca ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Short Duration ◽  
Solution Treatment ◽  
Steel Alloy ◽  
Super Duplex Stainless Steel ◽  
Phase Precipitation ◽  
Σ Phase ◽  
Stainless Steel Alloy

Effect of Solution Treatment on Microstructure and Properties of the SAF2507 Super Duplex Stainless Steel

2012 ◽  
Vol 724 ◽  
pp. 3-6 ◽  
Author(s):  
Jin Ming Liu ◽  
Jie Liu ◽  
Guang Wei Fan ◽  
Dong Fang Du ◽  
Guo Ping Li ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Solution Treatment ◽  
Tensile Tests ◽  
Treatment Temperature ◽  
Solution Treatment Temperature ◽  
Super Duplex Stainless Steel ◽  
Phase Precipitation ◽  
Σ Phase ◽  
Solution Treated

Effect of solution treated temperature at 5001100°C on ferrite/austenite ratio and σ phase precipitation has been studied in this paper, and the tensile properties after solution treatment at 950°C and 1050°C is compared. The results shows that the ferrite/austenite ratio treated 1050~1100°C is about 1:1; and the formation of σ phase occurs in the ferrite or at ferrite - austenite boundary. The quantity of the σ phase precipitation increases firstly and then decreases with increase of the solution treatment temperature, reaching the maximum at 900°C, and disperse at above 1050°C. Tensile tests show that the fracture is brittle divided and stretched by ductile belt at 950°C, and ductile at 1050°C.

Influence of Sigma Phase Precipitation on Pitting Corrosion of 2507 Super-Duplex Stainless Steel

2010 ◽  
Vol 658 ◽  
pp. 380-383 ◽  
Author(s):  
Ying Han ◽  
De Ning Zou ◽  
Wei Zhang ◽  
Jun Hui Yu ◽  
Yuan Yuan Qiao
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Ambient Temperature ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Super Duplex Stainless Steel ◽  
Phase Precipitation ◽  
Pitting Potential ◽  
Σ Phase ◽  
Pitting Corrosion Resistance

Specimens of 2507 super-duplex stainless steel aging at 850°C for 5 min, 15 min and 60 min were investigated to evaluate the pitting corrosion resistance in 3.5% NaCl solution at 30°C and 50°C. The results are correlated with the microstructures obtained with different aging time. The precipitation of σ phase remarkably decreases the pitting corrosion resistance of the steel and the specimen aged for 60 min presents the lowest pitting potential at both 30°C and 50°C. With increasing the ambient temperature from 30°C to 50°C, the pitting potential exhibits a reduction tendency, while this tendency is less obviously in enhancing the ambient temperature than in extending the isothermal aging duration from 5 to 60 min. SEM analysis shows that the surrounding regions of σ phase are the preferable sites for the formation of corrosion pits which grew up subsequently. This may be attributed to the lower content of corrosion resistance elements in these regions formatted with σ phase precipitation.

scholarly journals Effect of Solution Treatment Temperature on Microstructural Evolution, Precipitation Behavior, and Comprehensive Properties in UNS S32750 Super Duplex Stainless Steel

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1481
Author(s):  
Junhe Li ◽  
Wei Shen ◽  
Ping Lin ◽  
Fuming Wang ◽  
Zhanbing Yang
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Solution Treatment ◽  
Element Distribution ◽  
Treatment Temperature ◽  
Solution Treatment Temperature ◽  
Super Duplex Stainless Steel ◽  
Σ Phase ◽  
Comprehensive Properties

The changes of microstructures, element distribution, and comprehensive properties were studied to explore their interactions with each other, induced by solution treatment of UNS S32750 super duplex stainless steel. The results showed that the ferrite content improved, while the austenite content declined as the temperature increased. From 900 to 1000 °C, the σ phase existing at α/γ grain boundaries and in ferrite grains gradually dissolved. At 1050 °C, the microstructures consisted of only ferrite and austenite. From 1050 to 1300 °C, the Cr2N precipitated in ferrite and gradually grew and coarsened. The impact energy and pitting potential of UNS S32750 first improved and then weakened, while the hardness is the opposite, owing to the combined effects of element distribution, microstructures, and precipitates. In the presence of the σ phase, the corrosion resistance and mechanical properties of UNS S32750 correspond directly to the σ phase fraction. Subsequently, the rise in temperature promoted γ → α phase transformation, and the elements partitioning ratios of Cr and Mo declined, resulting in reduced toughness and corrosion resistance and a rise in hardness. Consequently, when the solution treatment temperature is 1050 °C, the α/γ ratio of UNS S32750 approached 1:1, with excellent overall properties.

Effect of Secondary Phase Precipitation on Impact Toughness of Duplex Stainless Steel

2017 ◽  
Vol 889 ◽  
pp. 138-142 ◽  
Author(s):  
Amit Powar ◽  
Amol Gujar ◽  
Niketan Manthani ◽  
Vinayak Pawar ◽  
Rajkumar Singh
Keyword(s):  
Stainless Steel ◽  
Impact Toughness ◽  
Duplex Stainless Steel ◽  
Solution Treatment ◽  
Secondary Phase ◽  
Phase Precipitation ◽  
X Ray Diffraction ◽  
Σ Phase ◽  
Material Solution ◽  
The Impact

Duplex Stainless Steel (DSS) combines good mechanical strength and ductility with moderate to good corrosion resistance in a variety of environments. DSS are prone to the formation of various intermetallic phases (σ, χ, π, R), carbides (M23C6) and nitrides (Cr2N), when it exposed to temperatures lower than 1000°C. This study focuses on effect of secondary phase precipitation on impact toughness of ASTM A182 DSS. Cylindrical bar of DSS was open die forged in the temperature range of 1200-1050°C. After the forging, the bar was slow cooled by covering it with ceramic wool. This leads to the formation of σ phase at the ferrite/austenite interfaces and significantly reduced the impact toughness of the material. Solution treatment was done at different temperature and effect on toughness studied. The microstructural changes produced as consequences of the distinct test condition have been analyzed by means of optical and electron microscopy, X-ray diffraction.

Microstructure Evolution and σ-Phase Precipitation Kinetics of 2507 Duplex Stainless Steel Aging at 850°C

2013 ◽  
Vol 711 ◽  
pp. 87-90
Author(s):  
Yin Hui Yang
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Aging Time ◽  
Solution Treatment ◽  
Treatment Temperature ◽  
Solution Treatment Temperature ◽  
Phase Precipitation ◽  
Σ Phase ◽  
Phase Precipitate ◽  
Δ Ferrite

A commercial 2507 duplex stainless steel with different solution treatments followed by aging at 850°C has been investigated. At the early aging time of 850°C, the σ-phase precipitate was predominantly distributed at the δ/γ interface, as the isothermal aging time was increased to 150 min, more σ-phase precipitate formed in ferrite and became coarser by a eutectoid reaction δσ+γ2. The amount of δ-ferrite decreased rapidly at the beginning of aging for 80 minutes, increasing solution treatment temperature from 1060°C to 1230°C delayed decomposition of δ-ferrite due to lowering σ-phase formation element (Cr). The reaction rate K and σ-phase precipitation rate were lowered by increasing solution treatment temperature from 1060°C to 1230°C.

The Study on Welding HAZ Microstructure of SAF 2507 Duplex Stainless Steel by Simulation Tests

2014 ◽  
Vol 804 ◽  
pp. 277-280 ◽  
Author(s):  
Ren Long Tao ◽  
Jie Liu ◽  
Guang Wei Fan ◽  
Xu Chang
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Cooling Rate ◽  
Significant Influence ◽  
Thermal Simulation ◽  
Cooling Time ◽  
Phase Precipitation ◽  
Σ Phase

Thermal simulation by GLEEBLE3800 is adopted to obtain the simulated welding HAZ microstructures in SAF 2507 duplex stainless steel with the GLEEBLE3800 thermal simulation machine. The simulation peak temperatures are 800oC, 900oC, 950oC, 1000oC, 1050oC and 1100oC, The cooling velocities are t12/8=3.6s, 7s, 20s and 40s (t12/8 is cooling time of 1200oC to 800oC which is used to describe the cooling rate). The results indicate that the peak temperatures have significant influence on the microstructures of austenite and ferrite. At 900oC, the content of σ phase precipitation reaches the maximum, which is distributed mainly in α or at α/γ junction. When the temperature is set above 1050oC, the σ phase disappears. A faster cooling rate passing through 800~1050oC is required to avoid brittle σ phase precipitation.

Heat Treatment Effect on Pitting Corrosion of Super Duplex Stainless Steel UNS S32750 GTA Welds

2013 ◽  
Vol 746 ◽  
pp. 467-472 ◽  
Author(s):  
In June Moon ◽  
Bok Su Jang ◽  
Jin Hyun Koh
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Pitting Corrosion ◽  
Super Duplex Stainless Steel ◽  
Σ Phase ◽  
Gas Tungsten Arc ◽  
Weld Metals ◽  
Pitting Corrosion Resistance ◽  
Heat Treated

The purpose of this study was to investigate the effect of heat treatment (930°C, 1080°C, 1230°C) followed by quenching on the pitting corrosion resistance, sigma phase precipitation, and microstructural change of a super duplex stainless steel (UNS S32750) welds made by gas tungsten arc (GTA). Based on the microstructural examination, the σ phase was formed in welds heat treated at 930°C while there were little σ phases formed in welds experienced the relatively fast cooling from 1080°C and 1230°C. Accordingly, the most weight loss due to pitting corrosion occurred in the as received base and weld metals heat treated at 930°C. It was confirmed that the pitting corrosion occurred in the phase boundaries of ferrite/sigma and austenite/sigma.

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