Creep Deformation Parameters and Creep Life of Gr.91

2013 ◽  
Author(s):  
Fujio Abe
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Creep Data ◽  
Creep Life ◽  
Deformation Parameters ◽  
Austenite Grain ◽  
Strain Data ◽  
Downward Deviation ◽  
Prior Austenite Grain

The correlation between the creep deformation parameters and creep life has been investigated for Gr.91 by analyzing creep strain data at 450 to 725 °C, 40 to 450 MPa and tr = 11.4 to 68,755 h in the NIMS Creep Data Sheet. The creep life tr is correlated with the time to minimum creep rate tm as t r = 3.7 t m . Taking the stress dependence of tm / tr into account, the creep life could be predicted more reliably. The minimum creep rate ε̇min depends on both the tm and the strain to minimum creep rate εm as ε . min = 0.54 ε m / t m . The εm is evaluated to be 0.02 to 0.03 at high stresses at each temperature but it decreases with decreasing stress at temperatures above 550 °C, suggesting that the creep deformation in the transient region becomes more inhomogeneous with decreasing stress probably due to localized creep deformation within 1 μm in the vicinity of prior austenite grain boundaries. The downward deviation takes place in the the tr versus ε̇min curves (Monkman-Grant plot). At the same ε̇min, both the εm and tm change upon the condition of tm ∝ εm as can be seen from the above equation. The decrease in εm with decreasing stress, corresponding to decreasing ε̇min, causes a decrease in tm, indicating the downward deviation of the tr versus ε̇min curves.

Evaluation of Creep Deformation Property of Grade 91 Steels

2015 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Kota Sawada ◽  
Hideaki Kushima
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Deformation Property ◽  
Time Dependent ◽  
Tertiary Creep ◽  
Total Strain ◽  
Dominant Factor ◽  
Creep Equation ◽  
Time To Rupture

Creep deformation property of Grade T91 steels over a range of temperatures from 550 to 625°C was analyzed by means of the empirical creep equation reported in the previous study [1]. The creep equation consists of four time dependent terms and one constant and time to rupture is estimated as a time to total strain of 10%. Accuracy of the creep equation to represent creep curve and to predict time to rupture and minimum creep rate was indicated. Times to minimum creep rate, total strain of 1%, initiation of tertiary creep and rupture were evaluated by the creep equation. Stress dependence of strains at minimum creep rate and the initiation of tertiary creep were analyzed. Contribution of four time dependent terms to the strains at minimum creep rate, total strain of 1% and initiation of tertiary creep was investigated. Three parameters to determine a temperature and time-dependent stress intensity limit, St, were compared and a dominant factor of St was examined. Heat-to-heat variation of the creep deformation property was investigated on two heats of T91 steels contain low and high nickel concentrations.

Investigation on Creep Behavior of Grade 91 Heat-Resistant Steel at 923K

2016 ◽  
Vol 853 ◽  
pp. 163-167
Author(s):  
Fa Cai Ren ◽  
Xiao Ying Tang
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Resistant Steel ◽  
Creep Tests ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Grade 91

Creep deformation behavior of SA387Gr91Cl2 heat-resistant steel used for steam cooler has been investigated. Creep tests were carried out using flat creep specimens machined from the normalized and tempered plate at 973K with stresses of 100, 125 and 150MPa. The minimum creep rate and rupture time dependence on applied stress was analyzed. The analysis showed that the heat-resistant steel obey Monkman-Grant and modified Monkman-Grant relationships.

Creep Deformation Behavior and Microstructural Degradation During Creep of Pre-Strained 25Cr-20Ni-Nb-N Steel

2007 ◽  
Author(s):  
Nobuhiko Saito ◽  
Nobuyoshi Komai
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Deformation Behavior ◽  
Minimum Creep Rate ◽  
Strengthening Mechanism ◽  
Creep Rupture ◽  
Microstructural Degradation ◽  
Solution Treated ◽  
Long Time ◽  
Strained Materials

The purpose of this study is to clarify the creep deformation behavior and microstructural degradation during creep of pre-strained 25Cr-20Ni-Nb-N steel (TP310HCbN), which has the highest creep strength among austenite stainless steels used for boiler tubes. The creep rupture strengths of the 20% pre-strained materials tested at 650°C under 210 MPa and 180 MPa were higher than those of solution-treated materials. However, the long time creep rupture strengths of the 20% pre-strained materials tested at 700°C and 750°C were lower than those of solution-treated materials. Thus, the creep strengths of the prestrained materials depend on test temperature and stress. Furthermore, the minimum creep rate of the 20% pre-strained materials and re-solution-treated materials tested at 650°C under 300MPa were 1.2 × 10−9 and 1.6 × 10−8 s−1, respectively. Thus, the minimum creep rate of the 20% pre-strained materials was lower than for re-solution-treated materials. The creep strengthening mechanism of the pre-strained materials at 650°C was considered to be that high-density dislocations were maintained until the late stage of creep. On the other hand, the creep rupture strengths of the 20% pre-strained materials were lower than those of solution-treated materials tested at over 700°C because of agglomeration and coarsening of precipitates and the recovery of dislocations.

The Creep Deformation and Elevated Temperature Microstructural Stability of a Two-Phase TiAl/Ti3Al Lamellar Alloy.

1994 ◽  
Vol 364 ◽  
Author(s):  
M. F. Bartholomeusz ◽  
J. A. Wert
Keyword(s):  
Elevated Temperature ◽  
Creep Rate ◽  
Microstructural Evolution ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Single Phase ◽  
Lamellar Microstructure ◽  
Microstructural Stability ◽  
Two Phase ◽  
The Individual

AbstractEnhanced work hardening of the phases in the lamellar microstructure has been cited as an explanation for the lower minimum creep rates of a two-phase TiAl/Ti3Al lamellar alloy compared with the minimum creep rates of the individual TiAl and Ti3Al single-phase alloys tested between 980 K and 1130 K. This proposition is confirmed by TEM observations. Thermal and thermomechanical exposure result in the microstructural evolution, which increases the minimum creep rate (εmin) of the lamellar alloy. The effect of microstructural evolution on εmin will be discussed in the present paper.

Interrelationship between Creep Deformation and Damage for Advanced Creep-Resistant Steels

2018 ◽  
Vol 774 ◽  
pp. 119-124
Author(s):  
Vàclav Sklenička ◽  
Květa Kuchařová ◽  
Marie Kvapilová ◽  
Luboš Kloc ◽  
Jiri Dvorak ◽  
...  
Keyword(s):  
Creep Deformation ◽  
Power Plants ◽  
Fracture Behaviour ◽  
Creep Data ◽  
Creep Life ◽  
Empirical Formulas ◽  
Deformation And Fracture ◽  
Creep Resistant Steels ◽  
Insight Into ◽  
Time Assessment

The components used in power plants generally operate at elevated and/or high temperature and are subjected to internal pressure. Under such conditions creep is of a great concern and there is an urgent demand for methods which can be used to predict the creep life. In this work, using our earlier published creep data for advanced creep-resistant T23 and P92 steels, the interrelationship between creep deformation and damage have been analysed by linking them to the identified acting mechanisms, in terms of empirical formulas for the fracture time assessment. The validity and the applicability of various formulas are examined with the objective to gain insight into the creep deformation and fracture behaviour of the steels under investigation.

Creep Life Prediction of Gr.91 Using Creep Parameters in Transient Region

2012 ◽  
Author(s):  
Fujio Abe
Keyword(s):  
Creep Rate ◽  
Minimum Creep Rate ◽  
Life Prediction ◽  
Test Duration ◽  
Creep Life ◽  
Average Value ◽  
Transient Region ◽  
Creep Life Prediction ◽  
Wide Range ◽  
Term Creep

The creep deformation behavior and its effect on creep life have been investigated for Gr.91 by analyzing creep strain data in the NIMS Creep Data Sheet. The creep life tr is mainly determined by the minimum creep rate ε̇min, indicating tr ∝ (ε̇min)−1. The ε̇min is mainly determined by the time to minimum creep rate tm, indicating ε̇min ∝ (tm)−1. Then the creep life is correlated with the tm as tr=3.7tm, where the constant 3.7 is as an average value for a wide range of temperature (450–725 °C), stress (40–450 MPa) and test duration (11–68,755 h). Using this equation, we can predict the creep life by carrying out a short-term creep test for up to the end of transient region, corresponding to about 30% of creep life. The (tm/tr), the ratio of duration of transient region to the creep life, slightly decreases with decreasing stress and is evaluated to be 0.22 at 100 MPa and above 550 °C, which gives us tr= 4.5 tm at 100 MPa. Taking the stress dependence of the (tm/tr) into account, the accuracy of creep life prediction is further improved.

Creep of Rheocast 7075 Aluminum Alloy at 300 °C

2013 ◽  
Vol 372 ◽  
pp. 288-291 ◽  
Author(s):  
Saravut Thongkam ◽  
Sirikul Wisutmethangoon ◽  
Jessada Wannasin ◽  
Suchart Chantaramanee ◽  
Thawatchai Plookphol
Keyword(s):  
Aluminum Alloy ◽  
Creep Rate ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
7075 Aluminum Alloy ◽  
Stress Range ◽  
Dislocation Glide ◽  
Semi Solid ◽  
Power Law Creep ◽  
Rupture Strain

Creep of rheocast 7075-T6 aluminum alloy produced by the Gas Induced Semi-Solid (GISS) process was investigated at temperature of 300 °C and stress range of 20-70 MPa and compared to that of wrought 7075-T651 aluminum alloy. The rheocast 7075-T6 alloy exhibited lower minimum creep rate and longer rupture time than the wrought 7075-T651 alloy. The total rupture strain of the rheocast alloy was shorter than that of the wrought one. According to the power law creep, the stress exponents, n of the rheocast 7075-T6 and the wrought 7075-T651 alloys were 5.9 and 7.9 respectively. Based on the determined n values, the creep deformation of both alloys was possibly controlled by the dislocation glide and climb-controlled mechanism.

scholarly journals Change in Microstructure at Grain Boundaries with Creep Deformation of Polycrystalline Nickel-Based Superalloy IN-100 at 1273K

2011 ◽  
Vol 278 ◽  
pp. 132-137
Author(s):  
N. Miura ◽  
Y. Kondo ◽  
Keiji Kubushiro ◽  
Satoshi Takahashi
Keyword(s):  
Plastic Deformation ◽  
Creep Rate ◽  
Grain Boundaries ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Stress Conditions ◽  
Stress Range ◽  
Polycrystalline Nickel ◽  
Nickel Based Superalloy ◽  
Heat Treated

The changes in the morphology of ’ precipitates and the dislocation substructures at the vicinity of grain boundaries with creep deformation were investigated on a polycrystalline nickel-based superalloy, IN-100. The experiments were done at 1273K in the stress range of 70-180MPa with one set of samples deformed until rupture and another interrupted after reaching the minimum creep rate. The cuboidal ’ precipitates were regularly arrayed at the vicinity of grain boundaries and eutectic ’ precipitates and carbides were observed at the grain boundaries on as-heat treated IN-100. However, on both the creep interrupted and ruptured samples at all stress conditions, plate - like shaped ’ precipitates covered the grain boundaries. The width of the plate - like shaped ’ precipitates increased with decreasing the stress and is wider in the creep ruptured than in the creep ruptured samples. There were few dislocations in the grains and in the plate - like shaped ’ precipitates, but a large number of the dislocations were observed around the interface of the plate - like shaped ’ precipitates. TEM observations on the specimen creep ruptured at 180MPa indicated that strong constant was observed at the vicinity of grain boundaries, but weak contrast in the grain interior. These results suggested that drastic plastic deformation occurred only at the vicinity of grain boundaries. Consequently, the plate - like shaped ’ precipitates at the grain boundaries inhibited the dislocations movement and acted as the creep strengthener.

scholarly journals Compression Creep Behavior of the 95.5Sn-(4.3, 3.9, 3.8)Ag-(0.2, 0.6, 0.7)Cu Solders

2006 ◽  
Vol 968 ◽  
Author(s):  
Paul Vianco ◽  
Jerome Rejent ◽  
Alice Kilgo ◽  
Joseph Martin
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Temperature Regime ◽  
Minimum Creep Rate ◽  
Short Circuit ◽  
Diffusion Mechanism ◽  
Aging Treatment ◽  
Fast Diffusion ◽  
Compression Creep ◽  
Rate Kinetics

ABSTRACTThe compression creep properties were evaluated for the Pb-free solders 95.5Sn-4.3Ag-0.2Cu (wt.%), 95.5Sn-3.9Ag-0.6Cu, and 95.5Sn-3.8Ag-0.7Cu to determine the effects of small composition differences on time-dependent deformation. The test temperatures were -25°C, 25°C, 75°C, 125°C, and 160°C. The nominal applied stresses were in the range of 2 – 45 MPa. Samples were tested in the as-fabricated condition as well as post-aged at 125°C for 24 hours. Negative creep was recorded for all three alloy compositions. However, the extent of this phenomenon was sensitive to alloy composition and the aging treatment. Creep deformation resulted in the formation of coarsened-particle boundaries within the eutectic regions of the microstructure. The boundaries were comprised of Cu6Sn5 and, to a lesser extent, Ag3Sn particles. The minimum creep rate kinetics were evaluated for these solders. The sinh term exponent, n, was 4 – 6 for the Sn-Ag-0.2Cu and Sn-Ag-0.6Cu solders and 1 – 2 for the Sn-Ag-0.7Cu alloy. The apparent activation energy (ΔH) values were in the range of 30 – 70 kJ/mol for all alloys, indicating that a short-circuit or fast-diffusion mechanism controlled creep deformation. The aging treatment did not consistently alter the rate kinetics parameters amongst the alloys. Separating the minimum creep rate data into the low and high temperature regimes, [-25°C, 75°C] and [75°C, 160°C], respectively, showed that bulk diffusion contributed to creep in the higher temperature regime. The ΔH values for the low temperature regime, which indicated that creep was dominated by a fast-diffusion mechanism, were sensitive to solder composition.

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