Role of Boundary Strengthening on Prevention of Type IV Failure in High Cr Ferritic Heat-Resistant Steels

Liu, Yuan; Tsukamoto, Shiro; Sawada, Kota; Abe, Fujio

doi:10.1007/s11661-013-2072-5

Cited by 36 publications

(23 citation statements)

References 22 publications

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“…This is shown in Figure 14, together with the results on the other 9 to 12Cr steels of Gr.92, [47] Gr.122, [48] 9Cr-boron steel, [46] 9Cr-oxide dispersion strengthened (ODS) steel (9Cr-0.13C-2W-0.2Ti-0.35Y 2 O 3 ), [49] 9Cr-1W steel [19] subjected to tempering and cold rolling, and A C3 -HAZ specimens of Gr.92, [50,51] Gr.122 [48] , and 9Cr-boron steel, [51] where HAZ means the heat-affected-zone of welded joints. The A C3 -HAZ specimens were subjected to rapid heating to A C3 temperature and then raid cooling to room temperature followed by post-weld heat treatment at around 1013 K (740°C), which simulates the microstructure of HAZ of welded joints.…”

Section: B Creep Life Prediction Based On Time To Minimum Creep Ratementioning

confidence: 99%

Creep Behavior, Deformation Mechanisms, and Creep Life of Mod.9Cr-1Mo Steel

Abe

2015

Metall Mater Trans A

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The creep behavior, deformation mechanisms, and the correlation between creep deformation parameters and creep life have been investigated for Mod.9Cr-1Mo steel (Gr.91, 9Cr-1Mo-VNb) by analyzing creep strain data at 723 K to 998 K (450°C to 725°C), 40 to 450 MPa, and t r = 11.4 to 68,755 hours in NIMS Creep Data Sheet. The time to rupture t r is reasonably correlated with the minimum creep rate _ e min and the acceleration of creep rate by strain in the acceleration region dln_ e/de, as t r = 1.5/[_ e min (dln_ e/de)], where _ e min and dln_ e/de reflect the creep behavior in the transient and acceleration regions, respectively. The _ e min is inversely proportional to the time to minimum creep rate t m , while it is proportional to the strain to minimum creep rate e m , as _ e min = 0.54 (e m /t m ). The e m decreases with decreasing stress, suggesting that the creep deformation in the transient region becomes localized in the vicinity of prior austenite grain boundaries with decreasing stress. The duration of acceleration region is proportional to the duration of transient region, while the dln_ e/de is inversely proportional to the e m . The t r is also correlated with the t m , as t r = g t m , where g is a constant. The present creep life equations reasonably predict the degradation in creep rupture strength at long times. The downward deviation takes place in the t r vs _ e min curves (Monkman-Grant plot). At the same _ e min , both the e m and t m change upon the condition of t m µ e m . The decrease in e m with decreasing stress, corresponding to decreasing _ e min , causes a decrease in t m , indicating the downward deviation of the t r vs _ e min curves.

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Section: B Creep Life Prediction Based On Time To Minimum Creep Ratementioning

confidence: 99%

Creep Behavior, Deformation Mechanisms, and Creep Life of Mod.9Cr-1Mo Steel

Abe

2015

Metall Mater Trans A

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“…One problem that causes the premature failure of P92 steel is the type IV failure. For this mode of failure, the weld joint fractured at the fine-grained heat affected zone where the peak temperature reaches around A c3 during the welding thermal cycle [5,6]. Another concern with regard to the failure of P92 steel weld joint is the weld metal which is often characterized by a dramatic reduction in fracture toughness.…”

Section: Introductionmentioning

confidence: 99%

Microstructure evolution of P92 steel weld metal after service for 8000 h

Zhang¹,

Du²,

Li³

et al. 2017

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Microstructure characterization and impact toughness test were performed on the P92 steel weld metal which was sectioned from the component of the main steam pipe of an ultrasupercritical unit after 8000 h exposure at high temperature. Precipitates of M23C6, MX, and Laves phase were detected in the weld metal. The weld metal after long-term service possessed much lower impact toughness compared with the as-fabricated weld metal. Micro-cracks were also found in the weld metal which formed during the welding process. Impact toughness reduction in the weld metal was correlated with the microstructure evolution. K e y w o r d s : P92 steel, weld metal, microstructure, impact toughness, precipitates

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“…Type III cracking occurs in the coarse-grained heat affected zone (CGHAZ). Type IV cracking [1,[13][14][15][16] is a pernicious form of cracking that occurs in the FGHAZ or inter-critically heat affected zone (ICHAZ). Past decades' research has shown that types I-III cracking are associated with the fabrication of a joint and may be hydrogen, reheat, temper embrittlement and occasionally long-term creep-related cracks.…”

Section: Introductionmentioning

confidence: 99%