Issues in replacing Cr–Mo steels and stainless steels with 9Cr–1Mo–V steel

Swindeman, R.W.; Santella, Michael L; Maziasz, P.J.; Roberts, Barry C.; Coleman, Kent

doi:10.1016/j.ijpvp.2003.12.009

Cited by 115 publications

(44 citation statements)

References 2 publications

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“…The state of damage can be observed indirectly from changes in effective elastic modulus as shown in Eq (8). With the knowledge of cyclic yield strength (k+R) from the previous section, a linear region within a cycle of a fatigue test (line BC in Fig.…”

Section: Determination Of Damage Initiation Parametersmentioning

confidence: 99%

“…This material was originally developed to achieve high creep strength at high temperature for maximum thermal efficiency [7,8] (this is beneficial for the traditional baseline operating conditions of fossilfuel power plants). Corrosion resistance of P91 steel for steam environment has also been shown to be better than more conventional austenitic steels [9].…”

Section: Introductionmentioning

confidence: 99%

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Determination of material parameters for a unified viscoplasticity-damage model for a P91 power plant steel

Kyaw

Rouse

et al. 2016

International Journal of Mechanical Sciences

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The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractSocietal pressures are mounting on electricity operators to operate traditional fossil-fuel power plants in an efficient and flexible manner in conjunction with renewable power plants. This requires the uses of high frequency start up -shut down load profiles in order to better match market demands. As such, high temperature/pressure components such as steam pipe sections and headers experience fluctuating mechanical and thermal loads. There is therefore an industrial need for the accurate prediction of fatigue and creep damage in order to estimate remnant component life. In the present work, a continuum damage model has been coupled with a Chaboche unified viscoplastic constitutive model in order to predict stress-strain behaviour of a P91 martensitic steel (a material used for power plant steam pipes) due to cyclic plasticity and damage accumulation. The experimental data used here are from the previous work [1]. Cyclic fully reversed strain controlled experiments (±0.4%, ±0.25% and ±0.2% strain ranges) and cyclic test with a dwell period (±0.5% strain ranges) for a P91 martensitic steel under isothermal conditions (600°C) are utilised. The physically relevant material parameters are determined and optimised using experimental results. Although many material parameter identification procedures can be found in the literature [1][2][3][4][5][6], there are uncertainties in determining the limits for the parameters used in the optimisation procedure. This could result in unrealistic parameters while optimising using experimental data. The issue is addressed here by using additional dwell test to identify the limits for stress relaxation parameters before using Cottrell's stress partition method to identify the limits for strain hardening parameters. Accumulated stored energy for damage initiation criterion and damage evolution parameters are also extracted from the experimental results. The estimated failure lifetimes for ±0.4%, ±0.25% and ±0.2% cases are 1600, 4250 and 9500 cycles, respectively, as opposed to 1424, 3522 and 10512 cycles as given by experiments.

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Section: Determination Of Damage Initiation Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Determination of material parameters for a unified viscoplasticity-damage model for a P91 power plant steel

Kyaw

Rouse

et al. 2016

International Journal of Mechanical Sciences

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“…Grade P91 steel, a 9Cr martensitic steel developed at Oakridge National Laboratory (ORNL) [1], is used extensively in fossil-fuel based power plant due to its high creep strength and low coefficient of thermal expansion. However, modern and next generation power plants are subjected to thermomechanical fatigue (TMF) due to a rapid rise in the number of start-up cycles to accommodate renewable sources of energy.…”

Section: Introductionmentioning

confidence: 99%

A Unified Viscoplastic Model for High Temperature Low Cycle Fatigue of Service-Aged P91 Steel

Barrett

Farragher

Hyde

et al. 2014

Journal of Pressure Vessel Technology

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The finite element (FE) implementation of a hyperbolic sine unified cyclic viscoplasticity model is presented. The hyperbolic sine flow rule facilitates the identification of strain-rate independent material parameters for high temperature applications. This is important for the thermo-mechanical fatigue of power plant where a significant stress range is experienced during operational cycles and at stress concentration features, such as welds and branch connections. The material model is successfully applied to the characterisation of the high temperature low cycle fatigue behaviour of a service-aged P91 material, including isotropic (cyclic) softening and non-linear kinematic hardening effects, across a range of temperatures and strain-rates.KEYWORDS: service-aged P91, strain-rate independence, unified viscoplasticity, high temperature low cycle fatigue, material Jacobian. INTRODUCTIONGrade P91 steel, a 9Cr martensitic steel developed at Oakridge National Laboratory (ORNL) [1], is used extensively in fossil-fuel based power plant due to its high creep strength and low coefficient of thermal expansion. However, modern and next generation power plants are subjected to thermomechanical fatigue (TMF) due to a rapid rise in the number of start-up cycles to accommodate renewable sources of energy. This results in premature failure of plant components, including plant header and piping systems. Thus, there is a greater requirement to be able to characterise the advanced materials of modern and next generation plants under realistic loading conditions and accurately predict failure at the component level.The high strength of such 9Cr steels may be attributed to its complex microstructure, consisting of prior austenite grains, packets and blocks in a hierarchical format [2]. The blocks contain long martensitic laths and more equi-axed subgrains [2,3]. The martensitic laths contain MX type precipitates which resist motion of mobile dislocations and M 23 C 6 carbonitrides are dispersed along boundaries to increase the resistance of the material to creep deformation [4]. Although 9Cr steels have a high creep strength, fatigue loading results in a coarsening of this microstructure, leading to the cyclic softening phenomenon observed in such materials [2,3,5] and to a reduction in creep strength.

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“…P91 steel is a 9Cr martensitic steel typically used for plant header and piping systems due to its high creep strength [3]. A number of material models capable of simulating the constitutive behaviour of candidate materials already exist, including the unified Chaboche model [4][5][6][7] and the twolayer viscoplasticity model [8,9].…”

Section: Introductionmentioning

confidence: 99%

Multiaxial cyclic viscoplasticity model for high temperature fatigue of P91 steel

Barrett

Farragher

O’Dowd

et al. 2014

Materials Science and Technology

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This paper presents a novel multiaxial, cyclic viscoplasticity material model for high temperature low cycle fatigue of P91 power plant steel. The model incorporates mechanisms-based variable strain-rate sensitivity and the key high temperature cyclic deformation phenomena of cyclic softening and non-linear kinematic hardening. The model has been calibrated to accurately represent the cyclic high temperature constitutive behaviour of ‘as received’ P91 steel. Details on the material Jacobian, with the consistent tangent stiffness for finite element implementation, are presented. The multiaxial implementation is applied to a notched specimen under strain-controlled loading at 600°C and a thin walled pipe under representative pressurised thermomechanical fatigue loading conditions. It is shown that the model for variable strain-rate sensitivity of the present paper predicts significantly different Coffin–Manson notch fatigue life compared to the Chaboche power law model. Ratchetting is shown to be a key candidate failure mechanism for next generation thermomechanical power plant loading conditions, for thin walled pressurised pipes.

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Issues in replacing Cr–Mo steels and stainless steels with 9Cr–1Mo–V steel

Cited by 115 publications

References 2 publications

Determination of material parameters for a unified viscoplasticity-damage model for a P91 power plant steel

Determination of material parameters for a unified viscoplasticity-damage model for a P91 power plant steel

A Unified Viscoplastic Model for High Temperature Low Cycle Fatigue of Service-Aged P91 Steel

Multiaxial cyclic viscoplasticity model for high temperature fatigue of P91 steel

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