Creep Deformation Analyses for Grade 91 Steels Considering Heat-to-Heat Variation

2018 ◽  
Author(s):  
Haruhisa Shigeyama ◽  
Yukio Takahashi ◽  
John Siefert ◽  
Jonathan Parker
Keyword(s):  
Creep Strain ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Power Plants ◽  
Primary Creep ◽  
Heat Resistant ◽  
Large Heat ◽  
Reasonable Prediction ◽  
Materials Used ◽  
Grade 91

In order to evaluate creep life of heat-resistant materials used in power plants, it is important to estimate variation of stress distribution caused by creep deformation appropriately. For achieving this, creep strain equations which can express the creep deformation behavior with good accuracy are indispensable. Additionally, a lot of heat-resistant steels show large heat-to-heat variations in creep properties. Therefore, it is also important to take into account of the heat-to-heat variations in the creep analyses. In this study, existing creep strain equations for Grade 91 steel were applied to six heats with a variety of creep strength and creep deformation behavior. Furthermore, some modification was made in order to obtain better agreement with test data in primary creep stage. It was found that reasonable agreements were obtained between the measured creep deformation behavior and predictions obtained by these equations only by changing creep rupture property depending on the particular heats. This suggests that reasonable prediction for creep deformation can be made even for the materials lacking the information of creep deformation as long as their rupture properties are known.

Investigation on Creep Behavior of Grade 91 Heat-Resistant Steel at 923K

2016 ◽  
Vol 853 ◽  
pp. 163-167
Author(s):  
Fa Cai Ren ◽  
Xiao Ying Tang
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Grade 91

Creep deformation behavior of SA387Gr91Cl2 heat-resistant steel used for steam cooler has been investigated. Creep tests were carried out using flat creep specimens machined from the normalized and tempered plate at 973K with stresses of 100, 125 and 150MPa. The minimum creep rate and rupture time dependence on applied stress was analyzed. The analysis showed that the heat-resistant steel obey Monkman-Grant and modified Monkman-Grant relationships.

Characterisation of the Microstructure Evolution of Aged Grade 91 Steel

2020 ◽  
Author(s):  
Chang Che ◽  
Xiang Liu ◽  
Youqiao Huang ◽  
Qingchuan Pan ◽  
Gong Qian
Keyword(s):  
Microstructural Evolution ◽  
Microstructure Evolution ◽  
Power Plants ◽  
Optical Microscope ◽  
Laves Phases ◽  
Transmission Electron ◽  
Materials Used ◽  
Grade 91 ◽  
Grade 91 Steel

Abstract Grade 91 steel has high creep strength and has been used as the material of piping in 600°C USC power plants in China. The Grade 91 materials used in actual power plants are useful in estimating the changes of material properties caused by long-term aging and damage at low stress conditions. An understanding of the long-term microstructural evolution under actually used conditions is a key for the improvement of these heat resistant steels. In this article, microstructural evolution of Grade 91 steel under different service conditions in Chinese power plants was studied using optical microscope (OM), transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) techniques. The results show, M23C6, MX (V-rich particles; Nb-rich particles), and Laves phases were found to precipitate. A quantitative characterisation of microstructure evolution was evaluated during long-term exposure, focusing on the size of precipitates (M23C6 carbides, Laves phase, MX phase) for the Grade 91 steel after long-term service.

Effect of Simulated Heat Affected Zone Thermal Cycle on the Creep Deformation and Damage Response of Grade 91 Steel Including Heat-to-Heat Variation

2018 ◽  
Author(s):  
Yukio Takahashi ◽  
Haruhisa Shigeyama ◽  
John Siefert ◽  
Jonathan Parker
Keyword(s):  
Weld Metal ◽  
Base Metal ◽  
Creep Strength ◽  
Creep Deformation ◽  
Heat Affected Zone ◽  
Thermal Cycle ◽  
Power Plants ◽  
Temperature History ◽  
Wide Range ◽  
Grade 91

Grade 91 and other creep strength enhanced ferritic steels are widely used in fossil power plants as the structural materials of high temperature piping and components. As the operating temperature of these plants is as high as 600°C, creep deformation and accompanying damage cannot be neglected in evaluating their integrity. In particular, creep damage tends to concentrate in the softened heat-affected zone in welded joints and often caused so-called type-IV cracking, in advance of failure in base metal or weld metal. In evaluating the likelihood of such a failure, it is important to understand the mechanical property of such region in comparison with base metal and weld metal. Previous studies have shown that considerable degradation of creep strength brought by thermal cycles simulating the temperature history experienced by such a zone. In order to strengthen the understanding, thermal cycle was given to six Grade 91 heats encompassing a wide range of creep properties and their creep behavior was evaluated in this study. As a result, it was found that resistance for creep deformation and rupture life of six heats showed different trend than what was observed in the original metal but the heat-dependency of the ductility seems to be inherited.

Effects of ternary additions on the deformation behavior of single crystals of MoSi2

2000 ◽  
Vol 646 ◽  
Author(s):  
Haruyuki Inui ◽  
Koji Ishikawa ◽  
Masaharu Yamaguchi
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Single Crystals ◽  
Creep Strain ◽  
High Temperatures ◽  
Low Temperatures ◽  
Deformation Behavior ◽  
Creep Strain Rate ◽  
Compression Creep ◽  
Ternary Additions

ABSTRACTEffects of ternary additions on the deformation behavior of single crystals of MoSi2 with the hard [001] and soft [0 15 1] orientations have been investigated in compression and compression creep. The alloying elements studied include V, Cr, Nb and Al that form a C40 disilicide with Si and W and Re that form a C11b disilicide with Si. The addition of Al is found to decrease the yield strength of MoSi2 at all temperatures while the additions of V, Cr and Nb are found to decrease the yield strength at low temperatures and to increase the yield strength at high temperatures. In contrast, the additions of W and Re are found to increase the yield strength at all temperatures. The creep strain rate for the [001] orientation is significantly lower than that for the [0 15 1] orientation. The creep strain rate for both orientations is significantly improved by alloying with ternary elements such as Re and Nb.

A Research on Laser Cladding Co-Based Alloy to Repair Heat Resistant Steel of the Valves Used in Ultra-Super Critical Nuclear Power Plants

2021 ◽  
Vol 58 (5) ◽  
pp. 0514007-514007220
Author(s):  
刘福广 Liu Fuguang ◽  
李勇 Li Yong ◽  
杨二娟 Yang Erjuan ◽  
米紫昊 Mi Zihao ◽  
王博 Wang Bo ◽  
...  
Keyword(s):  
Laser Cladding ◽  
Nuclear Power ◽  
Power Plants ◽  
Nuclear Power Plants ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant

Creep Deformation of Particle-Strengthened Metal-Matrix Composites

1989 ◽  
Vol 111 (1) ◽  
pp. 99-105 ◽  
Author(s):  
Z. G. Zhu ◽  
G. J. Weng
Keyword(s):  
Constitutive Equation ◽  
Metal Matrix Composites ◽  
Creep Strain ◽  
Creep Deformation ◽  
Creep Resistance ◽  
Metal Matrix ◽  
Order Approximation ◽  
Stress Redistribution ◽  
Matrix Composites ◽  
The Matrix

A multiaxial theory of creep deformation for particle-strengthened metal-matrix composites is derived. This derivation is based on the observation that there are two major sources of creep resistance in such a system. The first, or metallurgical effect, arises from the increased difficulty of dislocation motion in the presence of particles and is accounted for by a size- and concentration dependent constitutive equation for the matrix. The second, or mechanics effect, is due to the continuous transfer of stress from the ductile matrix to the hard particles and the corresponding stress redistribution is also incorporated in the derivation. Both power-law creep and exponential creep in the matrix, each involving the transient as well as the steady state, are considered. The constitutive equations thus derived can provide the development of creep strain of the composite under a combined stress. The multiaxial theory is also simplified to a uniaxial one, whose explicit stress-creep strain-time relations at a given concentration of particles are also given by a first- and second-order approximation. The uniaxial theory is used to predict the creep deformation of an oxide-strengthened cobalt, and the results are in reasonably good agreement with the experiment. Finally, it is demonstrated that a simple metallurgical approach without considering the stress redistribution between the two constituent phases, or a simple mechanics approach without using a modified constitutive equation for the metal matrix, may each underestimate the creep resistance of the composite, and, therefore, it is important that both factors be considered in the formulation of such a theory.

scholarly journals Investigation of Corrosion Resistance of Alloys with Potential Application in Supercritical Water-cooled Nuclear Reactors

2019 ◽  
Vol 63 (2) ◽  
pp. 328-332 ◽  
Author(s):  
Ákos Horváth ◽  
Attila R. Imre ◽  
György Jákli
Keyword(s):  
Corrosion Resistance ◽  
Supercritical Water ◽  
Power Plants ◽  
Fuel Cladding ◽  
Pressurized Water ◽  
Water Reactors ◽  
Reactor Types ◽  
Materials Used ◽  
Supercritical Water Cooled Reactor ◽  
Nuclear Applications

The Supercritical Water Cooled Reactor (SCWR) is one of the Generation IV reactor types, which has improved safety and economics, compared to the present fleet of pressurized water reactors. For nuclear applications, most of the traditional materials used for power plants are not applicable, therefore new types of materials have to be developed. For this purpose corrosion tests were designed and performed in a supercritical pressure autoclave in order to get data for the design of an in-pile high temperature and high-pressure corrosion loop. Here, we are presenting some results, related to corrosion resistance of some potential structural and fuel cladding materials.

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