Microstructural Degradation Assessment in Pressure Vessel Steel by Harmonic Generation Technique

KIM, Chungseok; PARK, Ikkeun

doi:10.3327/jnst.45.1036

Cited by 6 publications

(4 citation statements)

References 21 publications

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“…The lattice parameter of the M 23 C 6 phase increased slightly from 1.0650 nm for the material service-exposed for 54,750 h to 1.0660 nm for the material exposed for 68,550 h. The diffusion of the alloying element Cr led to its replacement of Fe within the M 23 C 6 phase, which increased the lattice parameter of the M 23 C 6 phase as service time increased. Changes in the M 23 C 6 lattice parameter as a function of aging time have also been reported for other steels, including 2.25Cr-1Mo [30] and P91 [31]. However, the peaks of specific precipitated phases were difficult to record because of their low intensity and overlap with the peaks of other phases.…”

Section: Phase Changesmentioning

confidence: 66%

Metal Temperature Estimation and Microstructure Evaluation of Long-Term Service-Exposed Super304H Steel Boiler Tubes

Yoon

Wha

2020

Met. Mater. Int.

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The reliability of service-life assessments for the boiler tubes in thermal power plants depends on the prediction of metal temperatures and the evaluation of microstructure changes. Three tubes-one as-received tube and two tubes service-exposed for 54,750 h and 68,550 h-were used to study metal temperature and microstructure characteristics. First, the average metal temperature was estimated (based on accelerated creep rupture test data for the tubes) using the Larson-Miller parameter. The average metal temperature of the tube experienced during its operational period was estimated to be 616 °C, which is 16 °C higher than the steam temperature of 600 °C. Next, the microstructure characteristics were investigated to evaluate precipitation behavior and creep damage. The results demonstrated that the prominent precipitates in the as-received tube sample included coarse primary Nb(C,N) precipitates at the grain boundaries and fine primary Nb(C,N) precipitates (maximum 200 nm) occasionally observed at dislocations. After long-term service, the size and shape of the Nb(C,N) precipitates were relatively stable. In contrast, string M 23 C 6 precipitates and Cu-rich phase particles were identified at the grain boundaries and within the austenitic matrix, respectively. Increasing the aging time from 54,750 to 68,550 h caused strings of M 23 C 6 precipitates to increase rapidly from 60 to 200 nm and the Cu-rich phase particles to increase from 12 to 32 nm. Finally, creep cavities were observed in both service-exposed tubes. However, creep damage characterized by creep cavities that link and grow into microcracks was observed only in the tube sample service-exposed for 68,550 h.

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Section: Phase Changesmentioning

confidence: 66%

Metal Temperature Estimation and Microstructure Evaluation of Long-Term Service-Exposed Super304H Steel Boiler Tubes

Yoon

Wha

2020

Met. Mater. Int.

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“…The ultrasonic NDE technique has been broadly applied to characterize materials, with many theoretical and experimental investigations in the literature. 5,6 When an ultrasonic sinusoidal wave is introduced into an anharmonic solid, the fundamental wave may be distorted as it propagates so that the second and higher harmonics of the fundamental frequency will be generated. The contact nonlinearity is caused by the nonlinearity in the stress-strain relation across the interface (i.e., voids, cracks, delamination and disbonds) due to the difference of reflection and transmission in the interface region.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Stainless Steel Fiber Reinforced Aluminum Composite Using Ultrasonic Nonlinearity

Kim

Jhang

Hyun

2010

Int. J. Mod. Phys. B

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A 304 stainless steel short fiber reinforced aluminum composite was fabricated and investigated for matrix voids as well as interfacial reaction using ultrasound. The aluminum composite was made by a hot isostatic pressing technique at a temperature of 600°C and subsequent aging at 120°C. The tensile strength significantly increased with the addition of 5% stainless steel fiber. The interfacial reaction evolved and grew with aging time due to generation of intermetallic FeAl2. The ultrasonic nonlinearity (β/β0) increased with the volume fraction of fiber and aging heat treatment because of the generation of microvoids resulted from localized fibers and matrix precipitation. This study demonstrates the potential for characterization of reinforced composite materials fabricated by the powder metallurgy technique.

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“…However, the changes in nonlinearity are not well understood, nor is the cause of the embrittling effects during the aging process [14]. Kim and Park reported that variation in ultrasonic nonlinearity results from microstructural evolution of 2.25Cr-1Mo steel, and this conclusion was supported by the results of electron microscopy and X-ray diffraction in addition to the Vickers hardness and ductile-brittle transition temperature [15].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic characterization for directional coarsening in a nickel-based superalloy during creep exposure

Kim

Hyun

Park

et al. 2012

Journal of Nuclear Science and Technology

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The effects of directional coarsening of g 0 precipitates in nickel-based superalloy on ultrasonic attenuation coefficient and nonlinearity during creep exposure were investigated in this study. The cuboidal g 0 precipitates coarsened preferentially in the direction perpendicular to the applied stress axis during the creep deformation. The length (a) of the g 0 precipitates increased with creep time, while the width (b) increased slightly. Here, the increase in ultrasonic attenuation coefficient and nonlinearity with increasing creep time is discussed in relation to the directional coarsening of g 0 precipitates, which was closely related to the scattering and distortion of the ultrasonic waves. We suggest that ultrasonic attenuation coefficient and nonlinearity can potentially be used for characterization of creep damage in nickel-based superalloys.

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Microstructural Degradation Assessment in Pressure Vessel Steel by Harmonic Generation Technique

Cited by 6 publications

References 21 publications

Metal Temperature Estimation and Microstructure Evaluation of Long-Term Service-Exposed Super304H Steel Boiler Tubes

Metal Temperature Estimation and Microstructure Evaluation of Long-Term Service-Exposed Super304H Steel Boiler Tubes

Characterization of Stainless Steel Fiber Reinforced Aluminum Composite Using Ultrasonic Nonlinearity

Ultrasonic characterization for directional coarsening in a nickel-based superalloy during creep exposure

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