Embrittlement Behavior of Isothermally Heat-Treated T/P92 Steel at 350°C

2007 ◽  
Vol 345-346 ◽  
pp. 465-468 ◽  
Author(s):  
Ja Min Koo ◽  
Sung Yong Kim ◽  
Kee Sam Shin ◽  
Yeon Gil Jung ◽  
Sung Kang Hur
Keyword(s):  
Power Plants ◽  
Structural Integrity ◽  
Air Cooling ◽  
Boiler Tube ◽  
P92 Steel ◽  
Heat Treated

P92 steels as well as P91 are widely used as boiler tube materials of ultra super critical (USC) power plants these days. And thus embrittlement is very important for structural integrity of the USC plants. The embrittlement was observed when P92 (Modified 9Cr-1.8W-0.5Mo-V-Nb) steels were quenched to and held at the temperature of 320 to 350°C, which were the temperatures intermediate between Ms and Mf, and then air-cooled. Nearly same kind of the embrittlement had been observed with the T/P91 steels and a theory had been proposed to explain the mechanism of the embrittlement by us. From the theory, the embrittlement might be caused by the brittle martensite which is freshly formed during air-cooling. We tried to apply the theory for the embrittlement of the T/P92 steel. The behaviors of the embrittled T/P92 steel were explained well by the theory.

Crystallographic Differences of Metastable NI2MO in a NI-MO-AL Superalloy

1980 ◽  
Vol 38 ◽  
pp. 158-159
Author(s):  
Michael M. Kersker ◽  
E. A. Aigeltinger ◽  
J. J. IIren
Keyword(s):  
Mechanical Properties ◽  
Air Cooling ◽  
Solution Treated ◽  
Heat Treated ◽  
Metastable Compounds ◽  
Rapidly Solidified

Ni-rich alloys based on approximate ternary composition Ni-8Mo-15A1 (at%) are presently under investigation in an attempt to study the contribution, if any, of the profusion of Mo-rich NixMo metastable compounds that these alloys contain to their excellent mechanical properties. One of the alloys containing metastable NixMo precipitates is RSR 197 of composition Ni-8.96Mo-15.06A1-1.98Ta-.015Yt. The alloy was prepared at Pratt and Whitney Government Products Division, West Palm Beach, Florida, from rapidly solidified powder. The powder was canned under inert conditions and extruded as rod at 1315°C. The as-extruded rod, after air cooling, was solution treated at 1315°C for two hours, air cooled, and heat treated for one hour at 815°C, followed again by air cooling.

scholarly journals Enhancing Graphene Retention and Electrical Conductivity of Plasma-Sprayed Alumina/Graphene Nanoplatelets Coating by Powder Heat Treatment

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 643
Author(s):  
Xiaoyu Wu ◽  
Shufeng Xie ◽  
Kangwei Xu ◽  
Lei Huang ◽  
Daling Wei ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Structural Integrity ◽  
Ceramic Coatings ◽  
Treatment Temperature ◽  
Graphene Nanoplatelets ◽  
Structural Defects ◽  
Temperature Plasma ◽  
Heat Treated ◽  
Plasma Sprayed

Burning loss of graphene in the high-temperature plasma-spraying process is a critical issue, significantly limiting the remarkable performance improvement in graphene reinforced ceramic coatings. Here, we reported an effective approach to enhance the graphene retention, and thus improve the performance of plasma-sprayed alumina/graphene nanoplatelets (Al2O3/GNPs) coatings by heat treatment of agglomerated Al2O3/GNPs powders. The effect of powder heat treatment on the microstructure, GNPs retention, and electrical conductivity of Al2O3/GNPs coatings were systematically investigated. The results indicated that, with the increase in the powder heat treatment temperature, the plasma-sprayed Al2O3/GNPs coatings exhibited decreased porosity and improved adhesive strength. Thermogravimetric analysis and Raman spectra results indicated that increased GNPs retention from 12.9% to 28.4%, and further to 37.4%, as well as decreased structural defects, were obtained for the AG, AG850, and AG1280 coatings, respectively, which were fabricated by using AG powders without heat treatment, powders heat-treated at 850 °C, and powders heat-treated at 1280 °C. Moreover, the electrical conductivities of AG, AG850, and AG1280 coatings exhibited 3 orders, 4 orders, and 7 orders of magnitude higher than that of Al2O3 coating, respectively. Powder heat treatment is considered to increase the melting degree of agglomerated alumina particles, eventually leaving less thermal energy for GNPs to burn; thus, a high retention amount and structural integrity of GNPs and significantly enhanced electrical conductivity were achieved for the plasma-sprayed Al2O3/GNPs coatings.

Optimization of fog inlet air cooling system for combined cycle power plants using genetic algorithm

2015 ◽  
Vol 76 ◽  
pp. 449-461 ◽  
Author(s):  
Mehdi A. Ehyaei ◽  
Mojtaba Tahani ◽  
Pouria Ahmadi ◽  
Mohammad Esfandiari
Keyword(s):  
Genetic Algorithm ◽  
Power Plants ◽  
Cooling System ◽  
Combined Cycle ◽  
Air Cooling ◽  
Air Cooling System

Comparison of the Limit Loads Between Defected Pressure Pipes With an Internal Pit and an External Pit at High Temperature

2013 ◽  
Author(s):  
Changyu Zhou ◽  
Bo Wang ◽  
Zhigang Sun ◽  
Jilin Xue ◽  
Xiaohua He
Keyword(s):  
High Temperature ◽  
Power Plants ◽  
Structural Integrity ◽  
Load Condition ◽  
Relative Length ◽  
Limit Load ◽  
Relative Depth ◽  
Corrosive Media ◽  
Pressure Pipe ◽  
Pressure Pipes

High temperature pressure pipes are widely used in power stations, nuclear power plants, and petroleum refinery, which always bear combined effects of high temperature, high pressure, and corrosive media, so the local pits are the most common volume defects in pressure pipe. Due to various reasons, the defects usually appear on the internal or external wall of pipe. In this paper, the dimensions of a defect were characterized as three dimensionless factors: relative depth, relative gradient and relative length. The main objects of study were the pipe with an internal pit and pipe with an external pit. Orthogonal array testing of three factors at four different levels was applied to analyze the sequence of the influence of three parameters. In present study, when the maximum principal strain nearby the location of the defects reaches 2%, the corresponding load is defined as the limit load, which is classified as two kinds of load type: limit pressure and limit bending moment. According to this strain criterion and isochronous stress strain data of P91 steel, the limit load of high temperature pipe with a local pit was determined by using ABAQUS. And in the same load condition of the pipe with the same dimensionless factors, the limit load of the internal defected pipe was compared with that of the external defected pipe. The results of this study can provide a reference for safety assessment and structural integrity analysis of high temperature creep pressure pipe with pit defects.

Compressed Air Energy Storage System Exergy Analysis and its Combined Operation with Nuclear Power Plants

2013 ◽  
Vol 448-453 ◽  
pp. 2786-2789 ◽  
Author(s):  
Jin Li ◽  
Chu Fu Li ◽  
Yan Xia Zhang ◽  
Hui Guo Yue
Keyword(s):  
Energy Storage ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Exergy Analysis ◽  
Compressed Air ◽  
Air Cooling ◽  
Compressed Air Energy Storage ◽  
Tracking Mode ◽  
Combined Operation

Nuclear plants are facing more and more peaking pressure, and combined operation with compressed air energy storage (CAES) systems is an effective approach to improve its peaking capacity. This work first simulates and conducts the exergy analysis for the CAES system. The results show that exergy efficiency of the CAES system is about 51.7%, as well as the exergy loss are primary in the fuel combustion and compressed air cooling processes, accounted for 25.4% and 11.3% of total exergy, respectively. Subsequently, three combined operation modes between CAES system and nuclear power plants for power grid peaking are investigated, which shows that three section tracking mode and incomplete tracking mode can achieve the balance between peaking effects and peaking cost.

Structural Integrity Research for Reactor Pressure Vessel Under In-Vessel Retention of a Core Melt

2016 ◽  
Author(s):  
Yongjian Gao ◽  
Yinbiao He ◽  
Ming Cao ◽  
Yuebing Li ◽  
Shiyi Bao ◽  
...  
Keyword(s):  
Pressure Vessel ◽  
Material Properties ◽  
Power Plants ◽  
Structural Integrity ◽  
Plastic Material ◽  
Plastic Region ◽  
Reactor Pressure Vessel ◽  
Elastic Plastic ◽  
Elastic Plastic Material ◽  
Reactor Pressure

In-Vessel Retention (IVR) is one of the most important severe accident mitigation strategies of the third generation passive Nuclear Power Plants (NPP). It is intended to demonstrate that in the case of a core melt, the structural integrity of the Reactor Pressure Vessel (RPV) is assured such that there is no leakage of radioactive debris from the RPV. This paper studied the IVR issue using Finite Element Analyses (FEA). Firstly, the tension and creep testing for the SA-508 Gr.3 Cl.1 material in the temperature range of 25°C to 1000°C were performed. Secondly, a FEA model of the RPV lower head was built. Based on the assumption of ideally elastic-plastic material properties derived from the tension testing data, limit analyses were performed under both the thermal and the thermal plus pressure loading conditions where the load bearing capacity was investigated by tracking the propagation of plastic region as a function of pressure increment. Finally, the ideal elastic-plastic material properties incorporating the creep effect are developed from the 100hr isochronous stress-strain curves, limit analyses are carried out as the second step above. The allowable pressures at 0 hr and 100 hr are obtained. This research provides an alternative approach for the structural integrity evaluation for RPV under IVR condition.

Inlet Air Cooling Applied to Combined Cycle Power Plants: Influence of Site Climate and Thermal Storage Systems

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Nicola Palestra ◽  
Giovanna Barigozzi ◽  
Antonio Perdichizzi
Keyword(s):  
Power Output ◽  
Parametric Analysis ◽  
Power Plants ◽  
Cooling System ◽  
Thermal Storage ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Air Cooling ◽  
Ambient Conditions ◽  
Cooling Systems

The paper presents the results of an investigation on inlet air cooling systems based on cool thermal storage, applied to combined cycle power plants. Such systems provide a significant increase of electric energy production in the peak hours; the charge of the cool thermal storage is performed instead during the night time. The inlet air cooling system also allows the plant to reduce power output dependence on ambient conditions. A 127MW combined cycle power plant operating in the Italian scenario is the object of this investigation. Two different technologies for cool thermal storage have been considered: ice harvester and stratified chilled water. To evaluate the performance of the combined cycle under different operating conditions, inlet cooling systems have been simulated with an in-house developed computational code. An economical analysis has been then performed. Different plant location sites have been considered, with the purpose to weigh up the influence of climatic conditions. Finally, a parametric analysis has been carried out in order to investigate how a variation of the thermal storage size affects the combined cycle performances and the investment profitability. It was found that both cool thermal storage technologies considered perform similarly in terms of gross extra production of energy. Despite this, the ice harvester shows higher parasitic load due to chillers consumptions. Warmer climates of the plant site resulted in a greater increase in the amount of operational hours than power output augmentation; investment profitability is different as well. Results of parametric analysis showed how important the size of inlet cooling storage may be for economical results.

Verification of Probabilistic Fracture Mechanics Analysis Code for Reactor Pressure Vessel

2021 ◽  
Vol 143 (4) ◽  
Author(s):  
Yinsheng Li ◽  
Genshichiro Katsumata ◽  
Koichi Masaki ◽  
Shotaro Hayashi ◽  
Yu Itabashi ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Working Group ◽  
Power Plants ◽  
Structural Integrity ◽  
Pressure Vessels ◽  
Irradiation Embrittlement ◽  
Energy Agency ◽  
Probabilistic Fracture Mechanics ◽  
Integrity Assessments ◽  
Reactor Pressure

Abstract Nowadays, it has been recognized that probabilistic fracture mechanics (PFM) is a promising methodology in structural integrity assessments of aged pressure boundary components of nuclear power plants, because it can rationally represent the influencing parameters in their inherent probabilistic distributions without over conservativeness. A PFM analysis code PFM analysis of structural components in aging light water reactor (PASCAL) has been developed by the Japan Atomic Energy Agency to evaluate the through-wall cracking frequencies of domestic reactor pressure vessels (RPVs) considering neutron irradiation embrittlement and pressurized thermal shock (PTS) transients. In addition, efforts have been made to strengthen the applicability of PASCAL to structural integrity assessments of domestic RPVs against nonductile fracture. A series of activities has been performed to verify the applicability of PASCAL. As a part of the verification activities, a working group was established with seven organizations from industry, universities, and institutes voluntarily participating as members. Through one-year activities, the applicability of PASCAL for structural integrity assessments of domestic RPVs was confirmed with great confidence. This paper presents the details of the verification activities of the working group, including the verification plan, approaches, and results.

Elastic-Plastic Fracture Mechanics Analysis of Cast Stainless Steel Pipes (Influence of Axial Load on Z-Factor of Pipes With Circumferential Crack Under Bending Load)

2013 ◽  
Author(s):  
Masayuki Kamaya ◽  
Kiminobu Hojo
Keyword(s):  
Stainless Steel ◽  
Axial Load ◽  
Power Plants ◽  
Structural Integrity ◽  
Term Operation ◽  
Steel Pipes ◽  
Integrity Assessment ◽  
Plastic Failure ◽  
Elastic Plastic ◽  
Bending Load

Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of cracked pipes. In the ASME Section XI, the load multiplier (Z-factor) is used to derive the elastic-plastic failure of the cracked components. The Z-factor of cracked pipes under bending load has been obtained without considering the axial load. In this study, the influence of the axial load on Z-factor was quantified through elastic-plastic failure analyses under various conditions. It was concluded that the axial load increased the Z-factor; however, the magnitude of the increase was not significant, particularly for the main coolant pipes of PWR nuclear power plants.

Numerical Simulation to Study the Effect of Arc Travelling Speed and Welding Sequences on Residual Stresses in Welded Sections of New Ferritic P92 Pipes

2016 ◽  
Vol 35 (2) ◽  
pp. 121-128 ◽  
Author(s):  
Xiaowei Wang ◽  
Jianming Gong ◽  
Yanping Zhao ◽  
Yanfei Wang ◽  
Zhiqiang Ge
Keyword(s):  
Residual Stresses ◽  
Power Plants ◽  
Small Diameter ◽  
Good Combination ◽  
Thick Wall ◽  
P92 Steel ◽  
Welding Technology ◽  
Symmetrical Distribution ◽  
Mechanical And Physical Properties ◽  
Welding Sequences

AbstractNew ferritic P92 steel is widely used in modern power plants due to its good combination of mechanical and physical properties. However, cracks are often formed in the welded sections during the fabrication or service. In order to ensure the structure integrity, the effects of residual stresses need to be considered. The objective of this paper is to investigate the influence of arc travelling speed and welding sequences on the residual stresses distribution in the welded sections of P92 pipes by finite element method (FEM). Results show that arc travelling speed and welding sequences have great effects on residual stresses distribution. With the arc travelling speed increasing, the residual stresses increase. Meanwhile, welding sequences of case B present smaller residual stresses and more symmetrical distribution of residual stresses at the weld centre line. Therefore, using slower arc travelling speed and case B welding sequences can be useful to decrease the residual stresses, which provides a reference for optimizing the welding technology and improving the fabrication process of new ferritic P92 welded pipes with small diameter and thick wall.

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