Effect of long-term service on the precipitates in P92 steel

Yanping, Zeng; Jia, Jie; Cai, Wenhe; Dong, Shaohua; Wang, Zhichun

doi:10.1007/s12613-018-1640-5

Cited by 14 publications

(4 citation statements)

References 45 publications

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“…Kipelova, Belyakov, and Kaibyshev (2012) confirmed that fine Laves phase particles are formed on the lath boundaries of the crept specimen by 1% strain at 650 °C (𝑡 = 374 h) of P911(3Co) steel. Moreover, Zeng, Jia, Cai, Dong, and Wang (2018) recently reported that the Laves phase not only forms on the PAGB and lath boundaries but also finely precipitates inside the lath martensite at a scale of 100 nm order for a reheater tube of P92 which served for 9854 h in an actual power plant operated at 603 °C and under 5.87 MPa.…”

Section: Grade 92 Steelmentioning

confidence: 99%

“…MX particles composed of fine NbX type and very fine VX type with a size below few 10s of nm are distributed uniformly in Grade P92 before the creep test (Hasegawa et al, 2004;Sawada et al, 2006;Danielsen et al, 2007;Zeng et al, 2018). However, MX particles are coarsened after creep deformation at 600 °C for 𝑡 = 39 534 h and especially, coarse MX particles with a size over 100 nm are observed in the vicinity of the PAGBs (Sawada et al, 2006).…”

Section: Grade 92 Steelmentioning

confidence: 99%

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Analysis of the Degradation in the Creep Strength of High-Cr Martensitic Steels

Tamura¹,

Abe²

2021

JMSR

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To investigate the formation process of the Z-phase, which lowers the long-term rupture strength of high-Cr martensitic steel, the creep curves of Grades T91, T92, and P92 were analyzed along with the experimental steels of 9Cr-1W and 9Cr-4W by applying an exponential law to the temperature, stress, and time parameters. The activation energy (Q ), activation volume (V ), and Larson-Miller constant (C ) were obtained as functions of creep strain. At the beginning of creep, sub-grain boundary strengthening occurs due to dislocations that are swept out of the sub-grains, which is followed by strengthening due to the rearrangement of M23C6 and the precipitation of the Laves phase. After Q  reaches a peak, heterogeneous recovery and subsequent heterogeneous deformation begin at an early stage of transient creep in the vicinity of several of the weakest boundaries due to coarsening of the precipitates. This activity triggers an unexpected degradation in strength due to the accelerated formation of the Z-phase. Stabilization of M23C6 and the Laves phase is important for mitigating the degradation of the long-term rupture strength of high-strength martensitic steel. The stabilization of the Laves phase is especially important for the Cr-Mo systems because Fe2Mo is easily coarsened at ~600 °C as compared to Fe2W. Lowering the hardness and Si content also prevents excess hardening due to the Laves phase, which also mitigates the degradation. The online monitoring of creep curves and the QVC  analysis render it possible to detect signs of long-term degradation under targeted conditions within a relatively short period.

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Section: Grade 92 Steelmentioning

confidence: 99%

Section: Grade 92 Steelmentioning

confidence: 99%

Analysis of the Degradation in the Creep Strength of High-Cr Martensitic Steels

Tamura¹,

Abe²

2021

JMSR

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“…Hence, Laves-phase precipitates at the grain boundaries maintaining a semi-coherent interface with one of the adjacent grains. On the other hand, in the surroundings of M C 23 6 carbides, chromium-depleted zones are generated promoting the enrichment of tungsten and molybdenum, thus enhancing the nucleation rate of Laves phase [53]. In both cases, precipitation is controlled by the diffusion of elements that are part of the precipitate phase.…”

Section: Precipitation Kineticsmentioning

confidence: 99%

Laves phase formation in Fe-based alloys from strengthening particle to self-healing agent: a review

Wackerling,

Rojas,

Oñate

et al. 2023

Mater. Res. Express

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In this study, were extensively reviewed the hardening and self-healing properties of Laves-phase in Fe-based alloys. First, the microstructural features of different polytypes of the Laves-phase, focusing on the thermodynamics and kinetics of formation in ferritic and martensitic steels were revised. C14 was identified as the dominant polytype in steels, providing strengthening by precipitation, anchoring of dislocation, and interphase boundaries, thereby increasing the creep resistance. Although the Laves phase is widely known as a reinforcement particle (or even a detrimental phase in some systems) in martensitic/ferritic and ferritic steels, recent findings have uncovered a promising property. Particles with self-healing characteristics provide creep resistance by delaying creep cavities formation. In this regard, different elements such as tungsten and molybdenum are known to provide this feature to binary and tertiary ferrous alloys due to their ability to diffuse into the creep cavities and form Laves-phase Fe(Mo,W)2. To date, self-healing by precipitation has only been reported in commercial stainless steel AISI 312, 347, and 304 modified with boron, nevertheless with a little contribution to creep rupture life. Although, commercial computational tools with thermodynamic and kinetic databases are available for researchers, to tackle the self-healing process with exactitude, genetic algorithms arise as a new tool for computational design. The two properties of Laves phase reported in the literature, precipitation hardening and self-healing agent, is a mix that can bring out a new research field. Therefore, it is not unreasonable to think of tailor-made high chromium creep-resistant steels reinforced by Laves-phase coupled with self-healing properties. However, owing to the characteristic of Laves-phase seems to be a complex challenge, mainly due to the crystallographic features of this phase in comparison with the host matrix, available computational tools, and databases.

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“…Kipelova, Belyakov, and Kaibyshev (2012) confirmed that fine Laves phase particles are formed on the lath boundaries of the crept specimen by 1% strain at 650 °C (𝑡 = 374 h) of P911(3Co) steel. Moreover, Zeng, Jia, Cai, Dong, and Wang (2018) recently reported that the Laves phase not only forms on the PAGBs and lath boundaries but also finely precipitates inside the lath martensite at a scale of 100 nm order for a reheater tube of P92 served for 9854 h in an actual power plant operated at 603 °C and under 5.87 MPa. These facts indicate that creep strength of Grade 92 steel at around 650 °C is superior to that of Grade 91.…”

Section: Comparison Between Grade 91 and Grade 92 Steelsmentioning

confidence: 99%

Root Cause of Degradation in the Creep Strength of Martensitic Steel

Tamura¹

2021

JMSR

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Creep curves of Grade 91 and 92 steels were analyzed by applying an exponential law to the temperature, stress, and time parameters to investigate the formation process of the Z-phase, which lowers the long-term rupture strength of high-Cr martensitic steel. The activation energy (Q), activation volume (V), and Larson–Miller constant (C) were obtained as functions of creep strain. At the beginning of creep, sub-grain boundary strengthening occurs because of dislocations that are swept out of the sub-grains, and this is followed by strengthening owing to the rearrangement of M23C6 and the precipitation of the Laves phase. Heterogeneous recovery and subsequent heterogeneous deformation start at an early stage of transient creep near several of the weakest boundaries because of the coarsening of the precipitates; this results in the simultaneous decreases in Q, V, and C even in transient creep. Further, this activity triggers an unexpected degradation in strength because of the accelerated formation of the Z-phase even in transient creep. The stabilization of M23C6 and the Laves phase is important to mitigate the degradation of the long-term rupture strength of high-strength martensitic steel. The stabilization of the Laves phase is especially important for Cr-Mo systems because Fe2Mo is easily coarsened at approximately 600 °C compared to Fe2W in Grade 92 steel.

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Effect of long-term service on the precipitates in P92 steel

Cited by 14 publications

References 45 publications

Analysis of the Degradation in the Creep Strength of High-Cr Martensitic Steels

Analysis of the Degradation in the Creep Strength of High-Cr Martensitic Steels

Laves phase formation in Fe-based alloys from strengthening particle to self-healing agent: a review

Root Cause of Degradation in the Creep Strength of Martensitic Steel

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