Microstructure Characterization of Duplex Stainless Steel Welding Joint with Different Solution and Aging Treatment

2010 ◽  
Vol 658 ◽  
pp. 376-379
Author(s):  
Jun Yang ◽  
Tuo Yan Zhang ◽  
Jun Hui Yu ◽  
Wei Zhang ◽  
Jiao Li
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Volume Fraction ◽  
Optical Microscope ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Solution Temperature ◽  
Eutectoid Reaction ◽  
Σ Phase ◽  
Stainless Steel Welding

The microstructural evolutions of 2205 duplex stainless steel welding joints were investigated in this paper. The specimens were solution treated at 1100°C and 1200°C for 1 h, water quenched and then isothermal aged for various durations at 850°C, followed by water cooling. The volume fraction of ferrite phase in HAZ, weld and base metal of the steel were measured by the ferrite scope detector. The changes of microstructure in sigma (σ) phase, ferrite and austenite phase were analyzed by optical microscope and energy dispersive spectrum. The results show that the volume fraction of ferrite phase increases and the ferrite grain becomes coarse when solution temperature enhances from 1100°C to 1200°C. During the aging, σ phase precipitates at γ/δ phase boundary and grows into the ferrite phase, and a eutectoid reaction of δ→σ+γ2 occurs. With extending of the aging time, the amount of ferrite phase decreases, σ phase increases and thin needle secondary austenite phase distributes across ferrite grains. In addition, high solution temperatures can delay the procedure of σ phase precipitation.

Effect of The Sigma Phase on the Mechanical Properties of a Cast Duplex Stainless Steel during the Ageing Treatment at 850°C

2013 ◽  
Vol 684 ◽  
pp. 325-329 ◽  
Author(s):  
Tian Liang ◽  
Xiao Qiang Hu ◽  
Xiu Hong Kang ◽  
Dian Zhong Li
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Nuclear Power ◽  
Power Plants ◽  
Sigma Phase ◽  
Volume Fraction ◽  
Optical Microscope ◽  
Eutectoid Reaction ◽  
Secondary Austenite

With about equal amount of austenite and ferrite in volume fraction, duplex stainless steel (DSS) is in advantage of mechanical properties and corrosive behaviors. Hence it is widely applied to the heavy castings for nuclear power plants inshore, such as impellers, pumps and valves. However, lots of cracks usually occur in these castings during manufacturing processes, because it is susceptible to precipitate the brittle intermetallic compound of sigma phase when the castings are exposed from 600 to 1000oC. In this work, the precipitation of sigma phase was observed by optical microscope (OM) and scanning electron microscope (SEM) in a cast DSS named as MAS/6001, which aged at 850oC from 5 to 300 minutes. The effect of sigma phase on the mechanical properties was analyzed by the tensile at room temperature and impact tests at -10°C. The results show that sigma phase in the MAS/6001 steel precipitated simultaneously with the secondary austenite, which obeyed the eutectoid reaction. The interfaces between austenite or secondary austenite and sigma phase were the locations where cracks generated from the void aggregation. Cracks are susceptible to propagate along or cross these interfaces, and to promote the sigma phase breaking-off, which severely deteriorated the mechanical properties.

Effect of Thermal Cycle on Microstructure and Corrosion Behavior of Duplex Stainless Steel SAF 2205 Electron Beam Welded Joint

2018 ◽  
Vol 786 ◽  
pp. 119-127
Author(s):  
Sameh M. Khafagy ◽  
Morsy Amin Morsy ◽  
H.M. El Sherbini ◽  
Y.F. Barakat
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Thermal Cycle ◽  
Welded Joint ◽  
Volume Fraction ◽  
Holding Time ◽  
Σ Phase ◽  
Phase Volume Fraction ◽  
Saf 2205

It is known that heat treatment (HT) highly affects the properties of base metal (BM) and fusion zones (FZ) of duplex stainless steel (DSS). In fact, it may give unwanted structure changes. Duplex stainless steels SAF 2205 welded joint was subjected to thermal cycle at temperature of 850◦C at holding times 1, 3, 5 and 7 hours. The influence of heating cycles and concentration of corrosive medium on the corrosion properties and microstructure of 2205 alloy was the objective of this work. It was found that process led to noticeable decrease in the corrosion resistance of BM and FZ specimens; moreover the decrease was large in BM than FZ. It was also found that sigma phase (σ) precipitated in the different zones of the structure. σ phase volume fraction was found to increase with increasing the holding time of HT, and its increase is larger in BM. Corrosion resistance was found to be oppositely related to σ phase formation. Secondary austenite phase (γ2) was also precipitated and its volume fraction in FZ was found to increase with increasing the holding time of HT and decreased in BM.

Microstructure Evolution in Isothermal Heat Treatment of 0Cr32Ni7Mo4NDuplex Stainless Steel

2014 ◽  
Vol 789 ◽  
pp. 314-319
Author(s):  
Yu Lai Chen ◽  
Hong He ◽  
Fei Fang
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Microstructure Evolution ◽  
Volume Fraction ◽  
Decomposition Reaction ◽  
Optical Microscope ◽  
Isothermal Heat Treatment ◽  
Σ Phase ◽  
Temperature Range ◽  
Δ Phase

The microstructure evolution of as-cast 0Cr32Ni7Mo4N hyper duplex stainless steel during the isothermal heat treatment in the temperature range of 800°C-1300°Cwas studied in the present investigation. The morphologies and precipitates were observed and determined by using optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results show that eutectoid decomposition reaction (δ→σ+γ2) take place in ferrite (δ) phase during isothermal heat treatment in the temperature range of 800°C-1000°C. Sigma (σ) phase and secondary austenite (γ2) phase coexist as cellular structure. Lamellar Cr2N precipitates in δ phase mostly when isothermal heat treatment at 800°Cand 850°C, while it only appears in γ phase between 900°C and 1050°C. As the annealing temperature rising, the quantity of σ phase, Cr2N and γ2 phase decreases. The volume fraction ratio of ferrite and austenite is stable between 1100°C and 1300°C, and γ → δ transformation is hard to occur.

scholarly journals Mechanical Properties of a Thermally-aged Cast Duplex Stainless Steel by in Situ Tensile Test at the Service Temperature

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 317 ◽  
Author(s):  
Qingdong Zhang ◽  
Sida Ma ◽  
Tao Jing
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Thermal Aging ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Service Temperature

Z3CN20.09M cast duplex stainless steel (CDSS) has been used for primary coolant water pipes in pressurized water reactors due to its excellent mechanical properties. Such pipes operate at an elevated service temperature (~320 °C) and experience issues of thermal aging embrittlement. In situ tensile tests were conducted to investigate the deformation mechanisms of Z3CN20.09M CDSS after long-term thermal aging at 475 °C for up to 2000 h in both optical microscope and scanning electron microscope at 320 °C. For the 320 °C tests, the tensile stress and other mechanical properties, e.g. the yield stress and the ultimate tensile strength, increase during the thermal aging process and recover to almost the same level as the unaged condition after annealing heat-treatment, which is caused by the formation and dissolution of precipitation during aging and anneal heat-treatment, respectively. For the slip mechanism, straight slip lines form first in the austenite phase. When these slip lines reach the austenite/ferrite interface, three kinds of slip systems are found in the ferrite phase. During the fracture process, the austenite phase is torn apart and the ferrite phase shows a significant elongation. The role of the ferrite phase is to hold the austenite matrix, thus increasing the tensile strength of this steel.

Effect of Solution Temperature on Microstructure of 2205 Duplex Stainless Steel Welded Joints

2010 ◽  
Vol 658 ◽  
pp. 432-435
Author(s):  
Yuan Yuan Qiao ◽  
De Ning Zou ◽  
Jiao Li ◽  
Ying Han
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Arc Welding ◽  
Solution Treatment ◽  
Optical Microscope ◽  
Solution Temperature ◽  
2205 Duplex Stainless Steel ◽  
Manual Arc Welding ◽  
Temperature Solution ◽  
Steel Joints

The various temperature solution experiments were carried out in this paper, which for 2205 duplex stainless steel joints welded by manual arc welding. The evolutions of microstructure in pre/post solution treatment and the contents of ferrite phase were conducted by using optical microscope and ferrite scope detector. The analysis results in the welded, the heat affected and the base metal regions show that suitable solution treatment is effective to adjust the welded microstructure condition. The austenite in each region transformed into ferrite when the temperature enhanced from 1050 to 1200°C. This resulted in increasing the volume of ferrite and coarsening the grain. All microstructure characteristics of the three regions were taken into account, it deduced that the feasible solution temperature range was 1050~1100°C for 2205 duplex stainless steel welded joint.

scholarly journals On the microstructure and mechanical properties of silver-bearing antibacterial CD4MCu duplex stainless steels: Solid solution temperature

2019 ◽  
Vol 9 (9) ◽  
pp. 1067-1075
Author(s):  
Hongliang Xiang ◽  
Dong Liu ◽  
Xueping Chen ◽  
Huatang Cao ◽  
Xuanpu Dong
Keyword(s):  
Solid Solution ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Duplex Stainless Steel ◽  
Volume Fraction ◽  
Antibacterial Properties ◽  
Solution Treatment ◽  
Solution Temperature ◽  
Ion Release ◽  
Solid Solution Treatment

The Ag-bearing antibacterial stainless steel has attracted substantial attention in the field of bacterial proliferation prevention. In this study, a Cu–Ag alloy was incorporated into a CD4MCu duplex stainless steel (DSS) to produce a good antibacterial property. The Ag-bearing CD4MCu duplex stainless steel samples were conducted solid solution treatment at various temperatures. The effects of the solid solution temperature on the microstructure, mechanical and corrosion properties, as well as silver ion release characteristics and antibacterial properties were investigated. Results show that apart from the original α, γ phases, Ag-bearing phases were formed in all samples after solid solution at different temperatures. The volume fraction of α and Ag-bearing phases decrease with increasing solution temperature. The tensile strength, hardness, elongation, and corrosion resistance first decrease and then increase along with the increase in the solid solution temperature. The heat treatment conducted at 1150 °C increases the strength, the hardness, the pitting corrosion resistance, and the antimicrobial capability simultaneously. The antibacterial rates of all the Ag-bearing CD4MCu duplex stainless steel samples after solid solution treatment are above 99%, indicating their good anti-bacterial capabilities.

Study of Micro Deformation of Austenitic-Ferrite Duplex Stainless Steel by Nanoindentation Method

2016 ◽  
Vol 725 ◽  
pp. 316-321
Author(s):  
Su Juan Guo ◽  
Yuan Yuan Cui ◽  
Fu Zhen Xuan ◽  
Xiao Wang
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Cyclic Deformation ◽  
Deformation Behavior ◽  
Load Level ◽  
Austenite Phase ◽  
Ferrite Phase ◽  
Indentation Creep ◽  
Evolution Rule

Based on the technology of the nanoindentation, the basic mechanical properties and cyclic deformation behavior of the austenite phase and ferrite phase in an austenitic-ferritic duplex stainless steel was studied. Firstly, from the displacement monotonic indentation experiment, the differences between the basic mechanical properties (e.g. hardness and elastic modulus) of austenite phase and ferrite phase are compared. Then, with the incremental load controlled loading-unloading conditions applied, the indentation depth evolution rule and the indentation creep behavior was studied. Finally, with the load controlled cyclic indentation experiments being conducted, the cyclic evolution rule of displacement into surface were observed, and the influence of different load level on the micro cyclic deformation behavior of each phase were discussed.

Effects of Solution Temperature on Microstructure and Tensile Properties of Casting Duplex Stainless Steel

2010 ◽  
Vol 146-147 ◽  
pp. 818-824
Author(s):  
Hong Liang Xiang ◽  
Dong Liu ◽  
Fu Shan He
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Tensile Properties ◽  
Energy Dispersive Spectrometer ◽  
Solution Treatment ◽  
Optical Microscope ◽  
Treatment Temperature ◽  
Solution Temperature ◽  
Solution Treatment Temperature ◽  
Super Duplex Stainless Steel

In this paper, effects of solid solution treatment temperature on microstructure and tensile properties of casting SAF 2507 super duplex stainless steel were researched by means of optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and tensile test. The results indicate that the amount of γ phase increases according to a linear relationship f(g ) = -0.134T +159.94 during the temperatures from 1100°C to 1250°C. Tensile properties of casting SAF 2507 super duplex stainless steel fluctuate with solution temperature change. Austenitic grain size and morphology are the most important factors on tensile property. The tensile strength is the highest owing to the finest austenitic grain at the solution temperature of 1150°C. The elongation is related to the fracture mode. At 1100 , elongation ration is highest because of the ductile fracture.

Effect of Pre-Strain and Aging Heat Treatment on the Corrosion Behavior for 2205 Duplex Stainless Steel in 6% FeCl3 Solution

2019 ◽  
Author(s):  
Chengsi Zheng ◽  
Qingnan Fei ◽  
Weihai Kong ◽  
Zhibin Ai
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Aging Time ◽  
Corrosion Behavior ◽  
Volume Fraction ◽  
Physical Metallurgy ◽  
Σ Phase ◽  
2205 Duplex Stainless Steel ◽  
Fecl3 Solution ◽  
Δ Ferrite

Abstract A 2205 duplex stainless steel (DSS) was pre-stretched to 5% and subsequently aged at 850 °C for 0–120 minutes, to explore the effects of pre-strain and aging treatment on the corrosion behavior of the DSS in 6% FeCl3 solution at 50 °C for 72 hours. The microstructure, hardness and corrosion behavior of the pre-strained and aged DSS were investigated based on statistical data and physical metallurgy in comparison with the counterparts without pre-strain. The results showed that the sigma (σ) phase precipitated firstly in δ-ferrite grain boundaries and then in δ-ferrite/γ-austenite (δ/γ) phases boundaries by consuming the volume fraction of δ-ferrite. The volume fraction of σ phase in the DSS with and without pre-strain increased with increasing aging times following a classical Johnson-Mehl-Avrami (JMA) relationship, and the kinetics of the precipitation of σ phase was accelerated by pre-strain throughout the aging time of 60–120 min. The hardness of the non-pre-strained DSS (NP-DSS) was lower than that of pre-strained DSS (P-DSS) throughout 0–120 min at 850 °C. The hardness of NP-DSS increased continuously with increasing aging time, and the hardness of P-DSS decreased firstly and then increased continuously with increasing aging time. The aged NP-DSS displayed a gradually serious pitting with increasing aging time, and the corresponding corrosion behavior of the aged P-DSS exhibited pitting firstly and then mainly cracking, and the pitting occurred in the vicinity of δ/σ and γ/σ boundaries.

Characterization of Duplex Stainless Steel Weldments

2006 ◽  
Author(s):  
Mona A. El-Demellawy
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Intergranular Corrosion ◽  
Volume Fraction ◽  
Solution Treatment ◽  
Ferrite Content ◽  
Pressurized Water ◽  
Great Loss ◽  
Σ Phase ◽  
The Impact

Duplex Stainless Steels (DSS) have found widespread use in a range of industries, because of their high strength with high resistance to stress corrosion cracking and resistance to sensitization-induced intergranular corrosion. The more high alloyed grades [super DSS] are resistant to oxygenated or chlorinated seawater. Consequently, due to the stable mechanical and corrosion properties after thermal aging for long term service at temperatures below 400°C, duplex stainless steel is used in pipes and components in the primary cooling systems in the PWRs (Pressurized Water Reactors). The investigated material was DSS of grade {UNS S31803 (ASTM A790, ASTM 2205)} in the form of pipe. Each weldment specimen was heat treated at one of the following temperatures: 475°C, 600°C, 700°C, 850°C, 1050°C and 1150°C for 1 hour. The ferrite content and hardness tests were performed along the weldment. The impact test was performed according to the ASTM E23 and the examination of intergranular corrosion susceptibility was performed (ASTM A262 - Practice B). The microstructure investigation was carried out by using the light optical microscopy for etched specimens. The SEM with EDAX was used to detect the microstructural changes due to the heat treatment and after corrosion as well as within the fracture surface of the impact specimens. Slight changes were observed at 475 and 600 °C/1 h conditions as compared to the as received condition, while a little loss in ferrite content was observed at 700°C aging condition. This may be the result of precipitation of different types of secondary phases such as χ-phase, ζ-phase, carbides and nitrides. At 850°C, the observed great loss in ferrite content may be attributed to precipitation of σ-phase with large volume fraction. The solution treatment at 1050 °C/1h condition improved the ferrite content values as a result of decomposition of σ-phase. But the ferrite % value does not return back to its original value at the as received condition. On the other hand, when the solution treatment was done at 1150 °C/1h condition, the ferrite content continued to increase to the as received condition as a result of recovery of δ-ferrite inside the structure.

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