Effect of Plasma Nitriding on Creep Behavior at 550 °C of a Maraging Steel (300 Grade) Solution Annealed

2014 ◽  
Vol 802 ◽  
pp. 452-456 ◽  
Author(s):  
Adriano Gonçalves dos Reis ◽  
Danieli Aparecida Pereira Reis ◽  
Antônio Jorge Abdalla ◽  
Jorge Otubo
Keyword(s):  
Comparative Analysis ◽  
Creep Rate ◽  
Stress Exponent ◽  
Maraging Steel ◽  
Creep Behavior ◽  
Plasma Nitriding ◽  
Strong Impact ◽  
Stress Range ◽  
Creep Tests ◽  
Before And After

The objective of this work is to evaluate creep behavior of a maraging steel (300 grade) solution annealed before and after superficial treatment of plasma nitriding. Creep tests were conducted on a standard creep machine at stress range of 200 to 500 MPa at 550°C. Samples with a gage length of 18.5 mm and a diameter of 3.0 mm were used for all tests. Creep parameters are determined and a comparative analysis is established with the results gotten from the alloy with and without plasma nitriding. Maraging 300 steel plasma nitrided has showed a similar creep behavior compared with the same alloy without superficial treatment, with creep rate and stress exponent results very close to the material only solution annealed. This result can be associated with the strong impact of reversion of martensite to austenite and overaging at this temperature and time of exposure that minimizes the benefits of a superficial treatment.

Microstructures and Creep of AM50-Sb-Gd Alloys

2005 ◽  
Vol 488-489 ◽  
pp. 749-752 ◽  
Author(s):  
Su Gui Tian ◽  
Keun Yong Sohn ◽  
Hyun Gap Cho ◽  
Kyung Hyun Kim
Keyword(s):  
Activation Energy ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Deformation Mechanism ◽  
Creep Resistance ◽  
Fine Particles ◽  
Dislocation Climb ◽  
The Matrix

Creep behavior of AM50-0.4% Sb-0.9%Gd alloy has been studied at temperatures ranging from 150 to 200°C and at stresses ranging from 40 to 90 MPa. Results show that the creep rate of AM50-0.4%Sb-0.9%Gd alloy was mainly controlled by dislocation climb at low stresses under 50 MPa. The activation energy for the creep was 131.2 ± 10 kJ/mol and the stress exponent was in the range from 4 to 9 depending on the applied stress. More than one deformation-mechanism were involved during the creep of this alloy. Microstructures of the alloy consist of a–Mg matrix and fine particles, distinguished as Mg17Al12, Sb2Mg3, and Mg2Gd or Al7GdMn5 that were homogeneously distributed in the matrix of the alloy, which effectively reduced the movement of dislocations, enhancing the creep resistance. Many dislocations were identified to be present on non-basal planes after creep deformation.

Creep Behavior and Microstructural Stability of Lamellar γ-T1AI (Cr, Mo, Si, B) with Extremely Fine Lamellar Spacing

2000 ◽  
Vol 646 ◽  
Author(s):  
Wolfram Schillinger ◽  
Dezhi Zhang ◽  
Gerhard Dehm ◽  
Arno Bartels ◽  
Helmut Clemens
Keyword(s):  
Creep Rate ◽  
Creep Behavior ◽  
Lamellar Microstructure ◽  
Lamellar Spacing ◽  
Primary Creep ◽  
Vacuum Arc ◽  
Internal Stresses ◽  
Microstructural Stability ◽  
Thermodynamical Equilibrium ◽  
Creep Tests

ABSTRACTγ-T1AI (Cr, Mo, Si, B) specimens with two different fine lamellar microstructures were produced by vacuum arc melting followed by a two-stage heat treatment. The average lamellar spacing was determined to be 200 nm and 25–50 nm, respectively. Creep tests at 700°C showed a very strong primary creep for both samples. After annealing for 24 hours at 1000 °C the primary creep for both materials is significantly decreased. The steady-state creep for the specimens with the wider lamellar spacing appears to be similar to the creep behavior prior to annealing while the creep rate of the material with the previously smaller lamellar spacing is significantly higher. Optical microscopy and TEM-studies show that the microstructure of the specimens with the wider lamellar specing is nearly unchanged, whereas the previously finer material was completely recrystallized to a globular microstructure with a low creep resistance. The dissolution of the fine lamellar microstructure was also observed during creep tests at 800 °C as manifested in an acceleration of the creep rate. It is concluded that extremely fine lamellar microstructures come along with a very high dislocation density and internal stresses which causes the observed high primary creep. The microstructure has a composition far away from the thermodynamical equilibrium which leads to a dissolution of the structure even at relatively low temperatures close to the intended operating temperature of γ-T1AI structural parts. As a consequence this limits the benefit of fine lamellar microstructures on the creep behavior.

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.

Grain Size Effect on the Creep Behavior of Monolithic MoSi2

1994 ◽  
Vol 364 ◽  
Author(s):  
C.R. Feng ◽  
K. Sadananda
Keyword(s):  
Grain Size ◽  
Size Effect ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Molybdenum Disilicide ◽  
Grain Size Effect ◽  
Stress Range ◽  
Creep Stress ◽  
Creep Stress Exponent

AbstractThe grain size effect on the creep behavior of hot-pressed monolithic molybdenum disilicide was investigated at 1200°C in a 19–255 MPa stress range. The creep-stress exponent, n, increased from 1 at low stresses to 4 at high stresses. The grain size exponent, p, varied from 0, to 3.5 and to 8 depending on the grain size, the creep-stress exponent, and creep history.

scholarly journals Nanoindentation Studies of Plasticity and Dislocation Creep in Halite

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 79 ◽  
Author(s):  
Christopher Thom ◽  
David Goldsby
Keyword(s):  
Strain Rate ◽  
Stress Exponent ◽  
Creep Behavior ◽  
Constant Load ◽  
Dislocation Creep ◽  
Indentation Creep ◽  
Creep Tests ◽  
Creep Flow ◽  
A Value ◽  
Flow Laws

Previous deformation experiments on halite have collectively explored different creep mechanisms, including dislocation creep and pressure solution. Here, we use an alternative to conventional uniaxial or triaxial deformation experiments—nanoindentation tests—to measure the hardness and creep behavior of single crystals of halite at room temperature. The hardness tests reveal two key phenomena: (1) strain rate-dependent hardness characterized by a value of the stress exponent of ~25, and (2) an indentation size effect, whereby hardness decreases with increasing size of the indents. Indentation creep tests were performed for hold times ranging from 3600 to 106 s, with a constant load of 100 mN. For hold times longer than 3 × 104 s, a transition from plasticity to power-law creep is observed as the stress decreases during the hold, with the latter characterized by a value of the stress exponent of 4.87 ± 0.91. An existing theoretical analysis allows us to directly compare our indentation creep data with dislocation creep flow laws for halite derived from triaxial experiments on polycrystalline samples. Using this analysis, we show an excellent agreement between our data and the flow laws, with the strain rate at a given stress varying by less than 5% for a commonly used flow law. Our results underscore the utility of using nanoindentation as an alternative to more conventional methods to measure the creep behavior of geological materials.

Creep Behaviors of Stress-Relieved and Annealed Zr-1Nb-0.7Sn-0.1Fe Nuclear Cladding Tubes at Intermediate Temperatures

2012 ◽  
Vol 248 ◽  
pp. 343-348
Author(s):  
Jong Min Lee ◽  
Sun Ig Hong
Keyword(s):  
Grain Size ◽  
Creep Rate ◽  
Stress Exponent ◽  
Creep Resistance ◽  
Size Control ◽  
Dislocation Climb ◽  
Creep Life ◽  
Creep Tests ◽  
Grain Size Control ◽  
Zr Alloys

In order to explore the possibility of enhanced creep resistance by grain size control, creep tests of stress-relieved and annealed Zr-1Nb-0.7Sn-0.1Fe cladding tubes were carried out at intermediate temperatures. The creep rate decreased significantly with increase of grain size from ~1.2 μm to 4 μm with annealing. The stress exponent was observed to be in the range of 5.0~6.5 for both stress-relieved and annealed Zr-1Nb-0.7Sn- 0.1Fe, suggesting that the dislocation climb is the rate controlling creep mechanism. It was shown that not only the creep rate decreased but also creep life increased in the annealed Zr-1Nb-0.7Sn-0.1Fe, suggesting the grain size control may provide an effective way to enhance the creep resistance in Zr alloys for nuclear application.

Tensile and Compressive Creep Behavior of Coarse-Grained Mg-Al-Sr Castings

2007 ◽  
Vol 546-549 ◽  
pp. 171-174 ◽  
Author(s):  
Peng Zhao ◽  
Qu Dong Wang ◽  
Chun Quan Zhai ◽  
Wen Jiang Ding
Keyword(s):  
Creep Rate ◽  
Coarse Grained ◽  
Stress Range ◽  
Creep Tests ◽  
Gravity Casting ◽  
Creep Properties ◽  
Compressive Creep ◽  
Creep Mechanisms ◽  
Asymmetric Behavior ◽  
Tension And Compression

Tensile and compressive creep properties of Mg-5wt.%Al-1wt.%Sr alloy produced by gravity casting were investigated in this paper. Creep tests were carried out in the temperature range from 125 °C to 200 °C and stress range from 35 to 85MPa. The second creep rate in tension is significant different from that in compression, indicating that coarse-grained Mg-Al-Sr alloy exhibits tension/compression asymmetric behavior. Moreover, the activation energies and stress exponent in tension and compression are not the same, which suggest that creep mechanisms in tension and compression are different.

Creep Behavior and Deformation Mechanism Map of Sn-Pb Eutectic Solder Alloy

2002 ◽  
Vol 125 (1) ◽  
pp. 81-88 ◽  
Author(s):  
X. Q. Shi ◽  
Z. P. Wang ◽  
Q. J. Yang ◽  
H. L. J. Pang
Keyword(s):  
Solder Alloy ◽  
Creep Behavior ◽  
Deformation Mechanism ◽  
Constitutive Models ◽  
Stress Range ◽  
Creep Tests ◽  
Eutectic Solder ◽  
Diffusion Controlled ◽  
Miniature Specimens ◽  
And Diffusion

In this study, a large number of creep tests were carried out using miniature specimens in order to investigate the creep behavior of 63Sn/37Pb eutectic solder alloy over a wide temperature range from −40 to 150°C and stress range from 0.75 to 70 MPa. Based on dislocation and diffusion theories, two unified constitutive models were developed to describe the dislocation-controlled and diffusion-controlled creep behaviors observed. It was found that the two models accurately predict the experimental data. A deformation mechanism map was established for this eutectic solder alloy in order to interpret the creep mechanism under different temperature and loading conditions.

Evaluation of Short-term Creep Behavior of PE-HD after Aging in Oil Derivatives

2018 ◽  
Vol 26 (3) ◽  
pp. 243-250 ◽  
Author(s):  
Ayrton Alef Castanheira Pereira ◽  
José Roberto Moraes d'Almeida ◽  
Thiago Motta Linhares Castro
Keyword(s):  
Creep Behavior ◽  
Diesel Oil ◽  
Aging Effects ◽  
Short Term ◽  
Creep Tests ◽  
Before And After ◽  
Oil Derivatives ◽  
Term Creep ◽  
Effects Of Aging ◽  
Short Term Creep

The creep behavior of a high density polyethylene (PE-HD) was evaluated before and after aging in contact with gasoline and diesel oil. Four viscoelastic models were used to assess changes in creep properties of the material: three parameters model, four parameters model, stretched Burgers model and Findley Law. Viscoelastic properties, stationary creep rate and compliance were used to analyze and compare the behavior between samples. A strain increase could be seen in aged samples in comparison with as-received ones, caused by plasticization due to aging effects. An increase in flexibility and decrease in stiffness in aged samples was also noted. This work also shows that the effects of aging on the creep response of a polymeric material can be analyzed using short term creep tests.

CREEP ANALYSIS FOR A WIDE STRESS RANGE BASED ON STRESS RELAXATION EXPERIMENTS

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5413-5418 ◽  
Author(s):  
HOLM ALTENBACH ◽  
KONSTANTIN NAUMENKO ◽  
YEVGEN GORASH
Keyword(s):  
Experimental Data ◽  
Creep Rate ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Power Law ◽  
Creep Behavior ◽  
Minimum Creep Rate ◽  
High Stress ◽  
Stress Range ◽  
Power Law Creep

Many materials exhibit a stress range dependent creep behavior. The power-law creep observed for a certain stress range changes to the viscous type creep if the stress value decreases. Recently published experimental data for advanced heat resistant steels indicates that the high creep exponent (in the range 5-12 for the power-law behavior) may decrease to the low value of approximately 1 within the stress range relevant for engineering structures. The aim of this paper is to confirm the stress range dependence of creep behavior based on the experimental data of stress relaxation. An extended constitutive model for the minimum creep rate is introduced to consider both the linear and the power law creep ranges. To take into account the primary creep behavior a strain hardening function is introduced. The material constants are identified for published experimental data of creep and relaxation tests for a 12% Cr steel bolting material at 500°C. The data for the minimum creep rate are well-defined only for moderate and high stress levels. To reconstruct creep rates for the low stress range the data of the stress relaxation test are applied. The results show a gradual decrease of the creep exponent with the decreasing stress level. Furthermore, they illustrate that the proposed constitutive model well describes the creep rates for a wide stress range.

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