scholarly journals Impact of Thermomechanical Fatigue on Microstructure Evolution of a Ferritic-Martensitic 9 Cr and a Ferritic, Stainless 22 Cr Steel

2020 ◽  
Vol 10 (18) ◽  
pp. 6338 ◽  
Author(s):  
Bernd Kuhn ◽  
Jennifer Lopez Barrilao ◽  
Torsten Fischer
Keyword(s):  
Material Selection ◽  
Fatigue Loading ◽  
Thermomechanical Fatigue ◽  
Power Engineering ◽  
Microstructural Stability ◽  
Damage And Failure ◽  
Trade Name ◽  
Energy Conversion Systems ◽  
Grade 91 ◽  
Grade 91 Steel

The highly flexible operation schemes of future thermal energy conversion systems (concentrating solar power, heat storage and backup plants, power-2-X technologies) necessitate increased damage tolerance and durability of the applied structural materials under cyclic loading. Resistance to fatigue, especially thermomechanical fatigue and the associated implications for material selection, lifetime and its assessment, are issues not considered adequately by the power engineering materials community yet. This paper investigates the principal microstructural evolution, damage and failure of two steels in thermomechanical fatigue loading: Ferritic-martensitic grade 91 steel, a state of the art 9 wt % Cr power engineering grade and the 22 wt % Cr, ferritic, stainless Crofer® 22 H (trade name of VDM Metals GmbH, Germany; under license of Forschungszentrum Juelich GmbH) steel. While the ferritic-martensitic grade 91 steel suffers pronounced microstructural instability, the ferritic Crofer® 22 H provides superior microstructural stability and offers increased fatigue lifetime and more forgiving failure characteristics, because of innovative stabilization by (thermomechanically triggered) precipitation of fine Laves phase particles. The potential for further development of this mechanism of strengthening against fatigue is addressed.

Microstructural stability and long term creep strength of grade 91 steel

2009 ◽  
Vol 4 (4) ◽  
pp. 176-183 ◽  
Author(s):  
K Kimura ◽  
K Sawada ◽  
H Kushima ◽  
Y Toda
Keyword(s):  
Creep Strength ◽  
Microstructural Stability ◽  
Grade 91 ◽  
Term Creep ◽  
Grade 91 Steel

Causes of heat-to-heat variation of creep strength in grade 91 steel

2017 ◽  
Vol 696 ◽  
pp. 104-112 ◽  
Author(s):  
K. Maruyama ◽  
J. Nakamura ◽  
N. Sekido ◽  
K. Yoshimi
Keyword(s):  
Creep Strength ◽  
Grade 91 ◽  
Grade 91 Steel

Influence of Stress on Degradation and Life Prediction of High Strength Ferritic Steels

2004 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Kota Sawada ◽  
Kiyoshi Kubo ◽  
Hideaki Kushima
Keyword(s):  
Yield Stress ◽  
Elastic Limit ◽  
High Strength ◽  
Time To Rupture ◽  
Limit Stress ◽  
Creep Resistant Steels ◽  
Grade 91 ◽  
Term Creep ◽  
Grade 91 Steel

Influence of stress on creep deformation and degradation behavior has been investigated. Corresponding to inflection of stress vs. time to rupture curve, difference in recovery phenomena, that was homogeneous in short-term and inhomogeneous in long-term, was observed. Inflection of stress vs. time to rupture curve took place at the stress condition corresponding to half of 0.2% offset yield stress at the temperature. Elastic limit stress of Grade 91 steel was evaluated to be 150MPa at 600°C and 100MPa at 650°C, by means of stress abrupt change test. These stresses were found to be almost the same as half of 0.2% offset yield stress at the temperatures. Inflection of stress vs. time to rupture curve is caused by transient of applied stress from higher level than elastic limit to within elastic range. It has been concluded that long-term creep strength of ferritic creep resistant steels should be predicted from the selected creep rupture data under the stresses lower than elastic limit by considering half of 0.2% offset yield stress at the temperature, by means of Larson-Miller parameter with a constant of 20.

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

2017 ◽  
Vol 139 (5) ◽  
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.

A comparative study on atmospheric oxidation of reduced activation ferritic martensitic steel and grade 91 steel

2018 ◽  
Vol 135 ◽  
pp. 204-215 ◽  
Author(s):  
N. Sreevidya ◽  
Sinu Chandran ◽  
C.R. Das ◽  
Shaju K. Albert ◽  
S. Rangarajan
Keyword(s):  
Comparative Study ◽  
Martensitic Steel ◽  
Atmospheric Oxidation ◽  
Grade 91 ◽  
Grade 91 Steel
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