Creep fracture behaviour of SUS304H steel with vanadium addition based on small punch creep testing

Htun, Nyein Chan Zan; Nguyen, Thanh Tuan; Won, Dooil; Nguyen, Manh Hung; Yoon, Kee Bong

doi:10.1080/09603409.2016.1227909

Cited by 10 publications

(1 citation statement)

References 18 publications

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“…Bai et al [8] and Tan et al [9] also reported similar results. The precipitated phases improve resistance to steam oxidation and creep at high temperatures-the Cu-rich phase and Nb(C,N) precipitates enhance high-temperature stability and creep resistance [10][11][12][13][14]. Moreover, the Cr-rich M 23 C 6 precipitates increase the susceptibility to intergranular corrosion at grain boundaries [15].…”

Section: Introductionmentioning

confidence: 99%

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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