Changes in creep property and precipitates due to aging of T91 steel after long-term service

Lok, Vanno; Le, Thi Giang; Yu, Jong Min; Wha, Young; Nguyen, Vinh Phu; Choi, Seung Tae; Yoon, Kee Bong

doi:10.1007/s12206-020-0720-4

Cited by 8 publications

(8 citation statements)

References 31 publications

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“…The mean area fractions of the precipitates for each tube are computed as the average of the individual area fractions of the precipitates from the five OM images. The ImageJ software was used to measure the area fraction, number, and size of precipitates from the OM images [14][15][16]. The detailed steps using ImageJ software to quantitatively analyze the precipitates were in line with a previously reported method [16,17].…”

Section: Methodsmentioning

confidence: 99%

Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Bang

Kim

et al. 2021

J Mech Sci Technol

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Life assessment predictions of reformer tubes of HP40Nb grade steel used in the petrochemical industry were investigated by quantitative metallographic evaluations of the area fractions of precipitated carbides. Correlations were established between the field-service periods and area fractions of the carbides via microstructural analysis. The microstructures of the virgin and other tubes were examined using optical microscopy (OM) for service periods of 1.8, 6.0, 7.2, 8.5, 9.7, and 16.2 years at 950 °C. The area fractions of the precipitates were measured by image analysis using ImageJ software. The results showed that increase in the area fractions of the precipitates was almost proportional to increase their service times. The relationships between area fractions of the precipitates and service times were also discussed for a 6-year cracked tube and a tube that had been in service for 11.5 years at another furnace. The obtained relationship can thus be used via the surface replication method for on-site residual life assessments.

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Section: Methodsmentioning

confidence: 99%

Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Bang

Kim

et al. 2021

J Mech Sci Technol

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“…Specimens for the microstructural examination of the P91 steel were prepared via standard polishing and etched using Vilella's reagent (1 g of picric acid, 5 ml of HCl, and 100 ml of ethanol) for approximately 20 s 3 . Optical microscopy (OM) and scanning electron microscopy (SEM) were used to investigate the microstructural characteristics of the as‐received specimens and post‐tested specimens.…”

Section: Methodsmentioning

confidence: 99%

“…12 Creep deformation is characterized by a decrease in the creep strain rate in the primary creep (PC) region, followed by a steady-state creep strain rate in the secondary creep (SC), and an increase in the creep strain rate during the tertiary creep leading to failure. 3,13 Modeling creep deformation behavior becomes essential for predicting creep life and safe-life design of Grade 91 steel for applications at high temperature. 17 Because Grade 91 steel exhibits an extended period of the PC region about 30% of the total creep life, the PC must be considered for improving the accuracy of creep rupture life prediction.…”

Section: Introductionmentioning

confidence: 99%

“…Because Grade 91 steel exhibits an extended period of the PC region about 30% of the total creep life, the PC must be considered for improving the accuracy of creep rupture life prediction 18 . Moreover, the strain accumulation in the PC and SC stages is considerable compared to that in the tertiary creep stage 3 . The PC and SC deformation behavior of Grade 91 can be described by coupling constitutive equations, which indicate the kinetics of the process and the evolution of the internal variables 17 .…”

Section: Introductionmentioning

confidence: 99%

“…P91 martensitic steel has been widely used in the fabrication of steam pipes, tubes, and other components in steam turbines of fossil power plants, and petrochemical plants because of various advantages in mechanical properties at elevated temperature. It has high thermal conductivity, low thermal expansion rate, high steam corrosion resistance, 1 high creep resistance, good weldability, 2 and precipitate stability 3 . The use of P11(1.25Cr‐0.5Mo) steel is limited to the temperature lower than 538°C 4,5 due to the lower creep resistance than P22(2.25Cr‐1Mo) steel.…”

Section: Introductionmentioning

confidence: 99%

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Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Lok

Yoon

2022

Fatigue Fract Eng Mat Struct

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Creep deformation and rupture behavior of welded joints from service‐exposed P91 steel were investigated by creep tests and microstructure examination. A series of miniature tensile creep tests were conducted at 569°C under applied stresses ranging from 182.5 to 286 MPa for the heat‐affected zone (HAZ), base metal, and weld metal. Creep deformation behavior was modeled using the experimentally measured creep strain data as the primary creep‐secondary creep (PC‐SC) model and fitting closely with the measured creep curves of each metal. Power‐law type creep equations were employed to describe the primary and secondary creep behavior. The creep rupture life of the cross‐weld specimen was predicted using the PC‐SC model with HAZ properties. An accurate prediction was possible if the stress in estimation was increased to 1.14 times of the actual applied stress. The creep test results with the cross‐weld specimens were used for verification. Applying the Monkman–Grant relationship and the creep damage tolerance factors to the cross‐weld joint life prediction are also discussed.

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Ferritic–Martensitic Steels in Power Industry: Microstructure, Degradation Mechanism, and Strengthening Methods

Jiang,

Huang,

Feng

et al. 2024

steel research int.

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Ferritic–martensitic (F–M) steels are widely used for high‐temperature pressure vessels and reactor cladding structures in power plants. The high operating temperatures and pressures, as well as the radiation environment, significantly challenge the mechanical stability of these steels. Here, the degradation mechanisms in F–M steels during creep and thermal aging under these harsh environments are reviewed. The exceptional mechanical properties of F–M steels are mainly attributed to their well‐constructed microstructures and chemical compositions. Microstructural barriers such as dislocations, solid solution atoms, and precipitates play key roles in resisting degradation. During the long‐term service, the microstructures undergo gradual evolution, resulting in a deterioration of mechanical properties at the macrolevel. In addition to the degradation mechanisms, some recent advancements in strengthening methods, including microalloying strengthening, thermomechanical treatment (TMT), and oxide dispersion strengthening, are summarized, aimed at the development of next‐generation F–M steels. The strengthening of the F–M steels is mainly achieved by enhancing the thermal stability of their microstructures. Insight into both the deterioration mechanisms and strengthening methods of F–M steels may pave the way for new approaches in developing high‐performance steels for applications in next‐generation power plants operating at ultrahigh operating temperatures and pressures.

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Changes in creep property and precipitates due to aging of T91 steel after long-term service

Cited by 8 publications

References 31 publications

Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Quantitative study on area fraction of precipitated carbides of HP40Nb steel as a function of service period

Creep life estimation of a service‐exposed P91 cross‐weld joint based on a primary‐secondary creep deformation model

Ferritic–Martensitic Steels in Power Industry: Microstructure, Degradation Mechanism, and Strengthening Methods

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