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.

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.

Effect of Reversion Heat Treatment on the Mechanical Properties of Thermally Embrittled UNS S32760 Duplex Stainless Steel

2015 ◽  
Vol 830-831 ◽  
pp. 127-130
Author(s):  
Mogra Natesh ◽  
V. Shamanth ◽  
K.S. Ravishankar
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Duplex Stainless Steels ◽  
Nuclear Industry ◽  
Holding Time ◽  
Limiting Factor

Duplex Stainless Steels contain very high chromium contents (19-30% by weight) and exhibit excellent corrosion resistance and extremely good mechanical properties. Embrittlement of duplex stainless steels due to precipitation of αʹ upon prolonged exposure in the temperature range of 280°C to 500°C has been a serious limiting factor for its long term usage in the nuclear industry, where the operating temperatures of cooling pipes is around 300°C. In this investigation, the effect of reversion heat treatment on the mechanical properties of a thermally embrittled duplex stainless steel has been studied. The specimens were solutionized, aged and then reversion treated for varying periods. The aged specimens showed significant increase in tensile strength and decrease in ductility in comparison to the ones in solutionized condition. The specimens which were reversion treated showed marginal decrease in tensile strength and significant increase in ductility after 5 minutes of holding time. As the holding time increased, the tensile strength rapidly decreased and ductility increased initially up to 30 minutes of reversion, after which there was no significant change in strength and ductility.

Microstructure and Mechanical Properties of TiB2/ Al-Si Composites Fabricated by TIG Wire and Arc Additive Manufacturing

2019 ◽  
Vol 944 ◽  
pp. 64-72
Author(s):  
Qing Feng Yang ◽  
Cun Juan Xia ◽  
Ya Qi Deng
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Additive Manufacturing ◽  
Yield Strength ◽  
Filler Wire ◽  
T6 Heat Treatment ◽  
Microstructure And Mechanical Properties ◽  
Before And After

Bulky sample was made by using TIG wire and arc additive manufacturing (WAAM) technology, in which Ф1.6 mm filler wire of in-situ TiB2/Al-Si composites was selected as deposition metal, following by T6 heat treatment. The microstructure and mechanical properties of the bulky sample before and after heat treatment were analyzed. Experimental results showed that the texture of the original samples parallel to the weld direction and perpendicular to the weld direction was similar consisting of columnar dendrites and equiaxed crystals. After T6 heat treatment, the hardness of the sample was increased to 115.85 HV from 62.83 HV, the yield strength of the sample was 273.33 MPa, the average tensile strength was 347.33 MPa, and the average elongation after fracture was 7.96%. Although pore defects existed in the fracture, yet the fracture of the sample was ductile fracture.

Effect of post-weld heat treatment on thermal diffusivity in UNS S32304 duplex stainless steel welds

2017 ◽  
Vol 2 (88) ◽  
pp. 49-58
Author(s):  
E.G. Betini ◽  
C.S. Mucsi ◽  
T.S. Luz ◽  
M.T.D. Orlando ◽  
M-N. Avettand-Fènoël ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Stainless Steel ◽  
Thermal Diffusivity ◽  
Duplex Stainless Steel ◽  
Welding Process ◽  
Austenite Phase ◽  
Shielding Gas ◽  
Heat Treated ◽  
Steel Welds ◽  
Weld Heat

Purpose: The thermal diffusivity variation of UNS S32304 duplex stainless steel welds was studied after pulsed GTA welding autogenous process without filler addition. This property was measured in the transverse section of thin plates after welding process and post-heat treated at 750°C for 8 h followed by air-cooling. Design/methodology/approach: The present work reports measurements of thermal diffusivity using the laser-flash method. The thermal cycles of welding were acquired during welding by means of k-type thermocouples in regions near the weld joint. The used shielding gas was pure argon and 98% argon plus 2% of nitrogen. The temperature profiles were obtained using a digital data acquisition system. Findings: It was found an increase of thermal diffusivity after welding process and a decrease of these values after the heat treatment regarding the solidified weld pool zone, irrespective of the welding protection atmosphere. The microstructure was characterized and an increase of austenite phase in the solidified and heat-affected zones was observed for post-weld heat-treated samples. Research limitations/implications: It suggests more investigation and new measurements about the influence of the shielding gas variation on thermal diffusivity in the heat-affected zone. Practical implications: The nuclear industry, especially, requests alloys with high thermal stability in pipes for power generation systems and safe transportation equipment’s for radioactive material. Thus, the duplex stainless steel grades have improved this stability over standard grades and potentially increase the upper service temperature reliability of the equipment. Originality/value: After heat treatment, the welded plate with 98%Ar plus 2%N2 as shielding gas presented a thermal diffusivity closer to the as received sample. By means of 2%-nitrogen addition in shielding gas during GTAW welding of duplex stainless steel may facilitate austenite phase reformation, and then promotes stability on the thermal diffusivity of duplex stainless steels alloys.

scholarly journals Effect of the Addition of Nickel Powder and Post Weld Heat Treatment on the Metallurgical and Mechanical Properties of the Welded UNS S32304 Duplex Stainless Steel

2016 ◽  
Vol 21 (2) ◽  
pp. 197-208 ◽  
Author(s):  
Ali Tahaei ◽  
Argelia Fabiola Miranda Perez ◽  
Mattia Merlin ◽  
Felipe Arturo Reyes Valdes ◽  
Gian Luca Garagnani
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Nickel Powder ◽  
Welding Process ◽  
Post Weld Heat Treatment ◽  
Gtaw Process ◽  
Welding Properties ◽  
Weld Heat

Abstract In this research, the effect of the addition of nickel powder and the application of a post weld heat treatment (PWHT) on the welding properties of the UNS S32304 lean duplex stainless steel were investigated in order to improve the microstructure and mechanical properties. Nickel powder was directly poured inside the joint gap and mixed with the filler metal during the Gas Tungsten Arc Welding (GTAW) process; moreover, the solution heat treatment was performed at 1100 °C for 10 min. The joints were characterized by optical microscopy (OM) and the evolution of the phase percentages in the different zones was studied by means of the image analysis technique. Tensile and hardness tests were carried out on the joints in order to evaluate the improvement of the mechanical properties. The results showed that both the addition of nickel powder during the welding process and the post weld heat treatment made it possible to improve the mechanical properties of the weld joints. PWHT had the best effect in restoring the equal percentage of ferrite and austenite compared to the addition of nickel powder.

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.

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