Long-term Creep Rupture Properties and Microstructure of 12% Cr Heat Resisting Steels

Recent literature indicates that there is a concern regarding the short-term vs. long-term creep rupture base metal properties for Grade 91 material. Evaluations of recent creep rupture data suggest that the material properties degrade more severely than expected and extrapolated creep rupture properties may be very optimistic. One of the approaches to evaluate creep rupture data is with a parameterized master curve such as the Larson-Miller parameter. Evaluations of creep rupture data indicate that the effects of material degradation can be considered with appropriate stress, time and temperature relationships. Using the Larson-Miller parameter methodology, the selected heats of Grade 91 creep rupture data indicate a reasonable relationship that does not appear to degrade rapidly for the longer term data. If even longer term creep rupture data suggest severe aging degradation as compared to current extrapolations, a transition of the Larson-Miller parameter constant from 31 to 20 does not appear to be a good method to calculate the degraded life estimates. As longer term creep rupture data become available, resulting oxide thicknesses should be measured and reported. The adverse effect of oxidation at longer times, resulting in loss of material and effectively higher stress, should be evaluated.

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Long Term Creep Rupture Properties and Microstructure of 12% Cr Heat Resisting Steels

Tetsu-to-Hagane ◽

10.2355/tetsutohagane1955.68.16_2541 ◽

1982 ◽

Vol 68 (16) ◽

pp. 2541-2550

Author(s):

Ik-Min PARK ◽

Toshio FUJITA

Keyword(s):

Creep Rupture ◽

Term Creep ◽

Rupture Properties

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Strength of Materials at Elevated Temperatures. Long Term Creep-Rupture Properties and Microstructure of Weld Metal on 2.25Cr-1Mo Steel Thick Plate.

Journal of the Society of Materials Science Japan ◽

10.2472/jsms.48.122 ◽

1999 ◽

Vol 48 (2) ◽

pp. 122-129 ◽

Cited By ~ 2

Author(s):

Takashi WATANABE ◽

Masayoshi YAMAZAKI ◽

Hiromichi HONGO ◽

Junichi KINUGAWA ◽

Tatsuhiko TANABE ◽

...

Keyword(s):

Weld Metal ◽

Thick Plate ◽

Elevated Temperatures ◽

Creep Rupture ◽

Strength Of Materials ◽

Term Creep ◽

Rupture Properties

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A Postassessment Test of 100,000 h Creep Rupture Strength of Grade 91 Steel at 600 °C

Journal of Pressure Vessel Technology ◽

10.1115/1.4037446 ◽

2017 ◽

Vol 139 (5) ◽

Cited By ~ 4

Author(s):

K. Maruyama ◽

N. Sekido ◽

K. Yoshimi

Keyword(s):

Rupture Strength ◽

Creep Rupture ◽

Creep Rupture Strength ◽

Data Points ◽

Predicted Values ◽

Grade 91 ◽

Term Creep ◽

Term Data ◽

Grade 91 Steel

Predictions as to 105 h creep rupture strength of grade 91 steel have been made recently. The predicted values are examined with long-term creep rupture data of the steel. Three creep rupture databases were used in the predictions: data of tube products of grade 91 steel reported in National Institute for Materials Science (NIMS) Creep Data Sheet (NIMS T91 database), data of T91 steel collected in Japan, and data of grade 91 steel collected by an American Society of Mechanical Engineers (ASME) code committee. Short-term creep rupture data points were discarded by the following criteria for minimizing overestimation of the strength: selecting long-term data points with low activation energy (multiregion analysis), selecting data points crept at stresses lower than a half of proof stress (σ0.2/2 criterion), and selecting data points longer than 1000 h (cutoff time of 1000 h). In the case of NIMS T91 database, a time–temperature parameter (TTP) analysis of a dataset selected by multiregion analysis can properly describe the long-term data points and gives the creep rupture strength of 68 MPa at 600 °C. However, TTP analyses of datasets selected by σ0.2/2 criterion and cutoff time of 1000 h from the same database overestimate the data points and predict the strength over 80 MPa. Datasets selected by the same criterion from the three databases provide similar values of the strength. The different criteria for data selection have more substantial effects on predicted values of the strength of the steel than difference of the databases.

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Effect of Cobalt and Boron on Long-term Creep Rupture Strength of 12Cr Cast Steels

Tetsu-to-Hagane ◽

10.2355/tetsutohagane.96.620 ◽

2010 ◽

Vol 96 (10) ◽

pp. 620-628 ◽

Cited By ~ 4

Author(s):

Masahiko Arai ◽

Kentaro Asakura ◽

Hiroyuki Doi ◽

Hirotsugu Kawanaka ◽

Toshihiko Koseki ◽

...

Keyword(s):

Rupture Strength ◽

Creep Rupture ◽

Creep Rupture Strength ◽

Cast Steels ◽

Term Creep

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Prediction of Breakdown Transition of Creep Strength in Advanced High Cr Ferritic Steels by Hardness Measurement of Aged Structures at High Temperature

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.345-346.553 ◽

2007 ◽

Vol 345-346 ◽

pp. 553-556 ◽

Cited By ~ 8

Author(s):

Hassan Ghassemi Armaki ◽

Kouichi Maruyama ◽

Mitsuru Yoshizawa ◽

Masaaki Igarashi

Keyword(s):

Power Plants ◽

Rupture Strength ◽

Hardness Measurement ◽

Creep Rupture ◽

Ferritic Steels ◽

Creep Rupture Strength ◽

Cr Concentration ◽

Reduction Of Area ◽

Term Creep

Recent researches have shown the premature breakdown of creep rupture strength in long term creep region of advanced high Cr ferritic steels. As safe operation of power plants becomes a serious problem we should be able to detect and predict the breakdown transition of creep rupture strength. Some methods for detecting the breakdown transition have been presented till now like the measurement of reduction of area after creep rupture and particle size of laves phase. However it will be more economic if we make use of non-destructive tests, for example, hardness testing. In this paper 3 types of ferritic steels with different Cr concentration have been studied. The results suggest that the hardness of aged structures is constant independently of exposure time in short term region, whereas the hardness breaks down in long term region. The boundary of breakdown in hardness coincides with that of breakdown in creep rupture strength.

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Novel Concept of Creep Strengthening Mechanism using Grain Boundary Fe2Nb Laves Phase in Austenitic Heat Resistant Steel

MRS Proceedings ◽

10.1557/opl.2011.558 ◽

2011 ◽

Vol 1295 ◽

Cited By ~ 20

Author(s):

Imanuel Tarigan ◽

Keiichi Kurata ◽

Naoki Takata ◽

Takashi Matsuo ◽

Masao Takeyama

Keyword(s):

Grain Boundary ◽

Strengthening Mechanism ◽

Local Deformation ◽

Creep Rupture ◽

Laves Phase ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Term Creep

ABSTRACTThe creep behavior of a new type of austenitic heat-resistant steel Fe-20Cr-30Ni-2Nb (at.%), strengthened by intermetallic Fe2Nb Laves phase, has been examined. Particular attention has been given to the role of grain boundary Laves phase in the strengthening mechanism during long-term creep. The creep resistance increases with increasing area fraction (ρ) of grain boundary Laves phase according to equation ε/ε = (1−ρ), where ε0 is the creep rate at ρ = 0. In addition, the creep rupture life is also extended with increasing ρ without ductility loss, which can yield up to 77% of elongation even at ρ = 89%. Microstructure analysis revealed local deformation and well-developed subgrains formation near the grain boundary free from precipitates, while dislocation pile-ups were observed near the grain boundary Laves phase. Thus, the grain boundary Laves phase is effective in suppressing the local deformation by preventing dislocation motion, and thereby increases the long-term creep rupture strength. This novel creep strengthening mechanism was proposed as “grain boundary precipitation strengthening mechanism” (GBPS).

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Creep–rupture model of aluminum alloys: Cohesive zone approach

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406214543413 ◽

2014 ◽

Vol 229 (8) ◽

pp. 1343-1347 ◽

Cited By ~ 1

Author(s):

Kyungmok Kim

Keyword(s):

Aluminum Alloys ◽

Cohesive Zone ◽

Rupture Life ◽

Stress Rupture ◽

Creep Rupture ◽

Time Dependent ◽

Element Analysis ◽

Rupture Model ◽

Term Creep

In this article, a creep–rupture model of aluminum alloys is developed using a time-dependent cohesive zone law. For long-term creep rupture, a time jump strategy is used in a cohesive zone law. Stress–rupture scatter of aluminum alloy 4032-T6 is fitted with a power law form. Then, change in the slope of a stress-rupture line is identified on a log–log scale. Implicit finite element analysis is employed with a model containing a cohesive zone. Stress–rupture curves at various given temperatures are calculated and compared with experimental ones. Results show that a proposed method allows predicting creep–rupture life of aluminum alloys.

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