Long Term High-Temperature Environmental Effect on Impact Toughness in Austenitic Alloys

2014 ◽  
Vol 627 ◽  
pp. 205-208
Author(s):  
Mattias Calmunger ◽  
Guo Cai Chai ◽  
Sten Johansson ◽  
Johan Moverare
Keyword(s):  
High Temperature ◽  
Impact Toughness ◽  
Stainless Steels ◽  
Power Plants ◽  
Austenitic Stainless Steels ◽  
Alloy 617 ◽  
Temperature Environment ◽  
The Impact ◽  
High Temperature Environment

Structural integrity is crucial for the safety of power plants with higher efficiency to meet the increasing global energy consumption. High-temperature environment will demand not only improved high-temperature corrosion resistance but also a maintained sufficient toughness. This study investigates how long term high-temperature environment influence the impact toughness of two austenitic stainless steels (AISI 304 and Sandvik SanicroTM 28) and one nickel-bas alloy (Alloy 617). Alloy 617 has shown increasing impact toughness with both increasing temperature and time, up to 700°C and 3 000 hours, while the two austenitic stainless steels have shown the opposite for the same conditions. At 10 000 hours the impact toughness of Alloy 617 has decreased but the alloy still possess great toughness. Both austenitic stainless steels show embrittlement due to brittle σ-phase and Alloy 617 seems to gain good impact toughness performance from small evenly distributed precipitates.

Effect of PWHT Cycles on Impact Toughness of Austenitic Stainless Steel Weldments

2009 ◽  
Author(s):  
M. M. Ibrahim ◽  
H. G. Mohamed ◽  
Y. E. Tawfik
Keyword(s):  
Impact Toughness ◽  
Impact Energy ◽  
Stainless Steels ◽  
Nuclear Power ◽  
Power Plants ◽  
Plate Thickness ◽  
Austenitic Stainless Steels ◽  
Aisi 304L ◽  
Stress Relieving ◽  
The Impact

Austenitic stainless steels are widely used welding materials in nuclear reactors and power plants because of their high strength, good ductility, excellent corrosion resistance and a reasonable weldability. These properties make austenitic stainless steels attractive candidate materials for use in the fabrication of piping systems, automotive exhaust gas systems and in a variety of equipment associated with the chemical and nuclear power industries. PWHT is a stress relieving process whereby residual stresses are reduced by typically heating to 550–650 °C for a set time depending upon plate thickness. It concerns have emerged about possible effects on the mechanical properties of the base (parent) and weld plates (PM and WM). The 6 mm AISI 304L, 316L, and 347 austenitic stainless steels were used for this work. These welds were produced by SMAW and GTAW techniques using a single vee preparation and multiple weld beads, and welded by various types of consumables. The fracture surfaces of the Charpy V-notch PM and WM (before and after PWHT) samples were examined by SEM. Scanning electron fractographs was critical in this study, in that valuable information regarding the mechanism and nature of failure could be determined. This paper reports work on the impact toughness of the three types of austenitic stainless steels. The parent and weld regions were examined for all types of steels used, and then exposed to temperature in the PWHT range. The effect of exposure to multiple PWHT cycles on these properties is discussed. A decrease in impact energy and fracture toughness with an increase in the number of heat treatments was evident in the parent metal. Similary, the weld metal showed a decrease in impact energy after two PWHT cycles.

Investigation of Impact Compressive Mechanical Properties of Sandstone After as well as Under High Temperature

2014 ◽  
Vol 33 (6) ◽  
pp. 585-591 ◽  
Author(s):  
Shi Liu ◽  
Jinyu Xu
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Critical Temperature ◽  
High Temperatures ◽  
Experimental Studies ◽  
Practical Significance ◽  
Temperature Environment ◽  
Shpb Test ◽  
The Impact ◽  
High Temperature Environment

AbstractConducting experimental studies on the impact compressive mechanical properties of rock under the high temperature environment is of both theoretical value and practical significance to understanding the relationship between the rock under the effect of impact loads and the high temperature environment. Based on the Φ100 mm SHPB and the self-developed Φ100 mm high-temperature SHPB test devices, the impact compressive tests on the sandstone, whether cooling after high temperatures or under real-time high temperatures are carried out. As the test results indicate that since the two high-temperature ways of loading are different from each other, the impact compressive properties of sandstone, after as well as under high temperatures, show different variations along with changes in temperature. Under the effect of the same impact loading rate, there exists a clear critical temperature range in the impact compressive mechanical properties of sandstone after high temperature, and, near the critical temperature, there occurs a significant mutation in the impact compressive mechanical properties. Under high temperatures, however, the impact compressive mechanical properties follow an overall continuity of change except that there are slight fluctuations at individual temperatures.

Pitting Studies Under Anoxic Conditions on Candidate Container Materials AISI 316L hMo and UHB 904L for The Disposal of HLW in Argillaceous Formations

2003 ◽  
Vol 807 ◽  
Author(s):  
Bruno Kursten ◽  
Frank Druyts
Keyword(s):  
Stainless Steel ◽  
Stainless Steels ◽  
Near Field ◽  
Austenitic Stainless Steels ◽  
Aisi 316L ◽  
Progressive Change ◽  
Anoxic Conditions ◽  
The Impact ◽  
Container Material

ABSTRACTStainless steel is being envisaged as the primary candidate container material for the final disposal of vitrified HLW in deep geological argillaceous formations in Belgium. The impact of an evolving underground repository environment, i.e. a progressive change from oxic to anoxic conditions (due to the consumption of entrapped oxygen), on the pitting behaviour of austenitic stainless steels AISI 316L hMo and UHB 904L was studied. CPP-experiments were performed in synthetic solutions, which are representative for the near-field chemistry of an underground repository. The solutions contained various amounts of Cl- (100–50,000 mg/L) at near-neutral pH. Experiments were conducted at 16 and 90°C.AISI 316L hMo and UHB 904L will not be subjected to immediate pitting problems neither under oxic, nor under anoxic conditions. However, AISI 316L hMo could present long-term pitting problems under oxic conditions. Pits are much easier initiated on AISI 316L hMo, for both oxic and anoxic conditions. The pits propagate in a rather similar manner under oxic conditions for both alloys, whereas under anoxic conditions the pits formed on AISI 316L hMo are much deeper. AISI 316L hMo is more susceptible to crevice attack.

scholarly journals High Temperature Fatigue of Aged Heavy Section Austenitic Stainless Steels

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 84
Author(s):  
Hugo Wärner ◽  
Guocai Chai ◽  
Johan Moverare ◽  
Mattias Calmunger
Keyword(s):  
High Temperature ◽  
Reference Material ◽  
Structural Stability ◽  
Stainless Steels ◽  
Power Plants ◽  
Electron Backscatter Diffraction ◽  
Niobium Carbide ◽  
Austenitic Stainless Steels ◽  
Dislocation Motion ◽  
Heavy Section

This work investigates two austenitic stainless steels, Sanicro 25 which is a candidate for high temperature heavy section components of future power plants and Esshete 1250 which is used as a reference material. The alloys were subjected to out-of-phase (OP) thermomechanical fatigue (TMF) testing under strain-control in the temperature range of 100 ∘C to 650 ∘C. Both unaged and aged (650 ∘C, 3000 h) TMF specimens were tested to simulate service degradation resulting from long-term usage. The scanning electron microscopy methods electron backscatter diffraction (EBSD) and energy dispersive spectroscopy (EDS) were used to analyse and discuss active failure and deformation mechanisms. The Sanicro 25 results show that the aged specimens suffered increased plastic straining and shorter TMF-life compared to the unaged specimens. The difference in TMF-life of the two test conditions was attributed to an accelerated microstructural evolution that provided decreased the effectiveness for impeding dislocation motion. Ageing did not affect the OP-TMF life of the reference material, Esshete 1250. However, the structural stability and its resistance for cyclic deformation was greatly reduced due to coarsening and cracking of the strengthening niobium carbide precipitates. Sanicro 25 showed the higher structural stability during OP-TMF testing compare with the reference material.

scholarly journals Analysis of Platen Superheater Tube Degradation in Thermal Power Plants via Destructive/Non-Destructive Characteristic Evaluation

Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 581
Author(s):  
Se-Beom Oh ◽  
Jongbeom Kim ◽  
Soon-Woo Han ◽  
Kyung-Mo Kim ◽  
Dong-Seok Yun ◽  
...  
Keyword(s):  
High Temperature ◽  
Ultrasonic Wave ◽  
Wave Velocity ◽  
Power Plants ◽  
Thermal Power ◽  
Microstructural Analysis ◽  
Electromagnetic Acoustic Transducer ◽  
Ultrasonic Wave Velocity ◽  
Temperature Environment ◽  
High Temperature Environment

Coal-fired power plants operating under Korea’s standard supercritical pressure operate in a high-temperature environment, with steam temperatures reaching 540 °C. A standard coal-fired power plant has a 30-year design life, and lifespan diagnosis is performed on facilities that have operated for more than 100,000 h or 20 years. Visual inspection, thickness measurements, and hardness measurements in the field are used to assess the degree of material degradation at the time of diagnosis. In this study, aging degradation was assessed using an electromagnetic acoustic transducer to measure the change in transverse ultrasonic propagation speed, and the results were compared to microstructural analysis and tensile test results. Based on the experimental results, it was found that the boiler tube exposed to a high-temperature environment during long-term boiler operation was degraded and damaged, the ultrasonic wave velocity was reduced, and the microstructural grains were coarsened. It was also confirmed through tensile testing that the tensile and yield strengths increased with degradation. Our findings prove that the degree of change in mechanical properties as a function of the material’s degradation state is proportional to the change in ultrasonic wave velocity.

scholarly journals Improvement of Strength and Impact Toughness for Cold-Worked Austenitic Stainless Steels Using a Surface-Cracking Technique

Metals ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 932 ◽  
Author(s):  
Kwangyoon Kim ◽  
Minha Park ◽  
Jaeho Jang ◽  
Hyoung Kim ◽  
Hyoung-Seok Moon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Impact Toughness ◽  
Stainless Steels ◽  
Low Temperatures ◽  
Austenitic Stainless Steels ◽  
High Strength ◽  
Surface Cracks ◽  
Surface Cracking ◽  
Cold Worked ◽  
The Impact

For cryogenic applications, materials must be cautiously selected because of a drastic degradation in the mechanical properties of materials when they are exposed to very low temperatures. We have developed a new technique using a cold-working and surface-cracking process to overcome such degradation of mechanical properties at low temperatures. This technique intentionally induced surface-cracks in cold-worked austenitic stainless steels and resulted in a significant increase in both strength and fracture at low temperatures. According to the microstructure observations, dissipation of the crack propagation energy with surface-cracks enhanced the impact toughness, showing a ductile fracture mode in even the cryogenic temperature region. In particular, we obtained the high strength and toughness materials by a surface-cracking technique at 5% cold-worked specimen with surface-cracks.

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