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Metals
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Creep and Fatigue Behavior of Alloys
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Creep and Fatigue Behavior of Alloys

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Metal Failure Analysis".

Deadline for manuscript submissions: 15 May 2024 | Viewed by 6049

Special Issue Editor

Prof. Dr. A. Toshimitsu Yokobori, Jr.

E-Mail Website
Guest Editor
Advanced Comprehensive Research Organization, Teikyo University, Tokyo, Japan
Interests: corrosion; creep damage; fatigue behavior

Special Issue Information

Dear Colleagues,

Recently, to achieve the goal of reducing carbon dioxide emissions and using fossil fuel effectively, thermal power generation is strongly required to improve thermal efficiency by raising operating temperature and pressure using advanced heat-resistant materials. Under these circumstances, high-efficiency electric power plants with a higher steam temperature have been developed. Because the operating conditions of these power plants are exposed to more severe conditions than conventional systems, such as high temperature, high pressure, start–stop, and multi-axial stress, it is required to develop a highly accurate life prediction technique. Therefore, it is essential to standardize the testing and estimation methods of crack initiation and growth lives under high temperature creep-fatigue conditions accompanied with studies on the clarification of the deteriorated mechanism based on material science, which is useful to clarify the mechanism of damage formation under creep and fatigue conditions. The scope of this Special Issue includes research fields focusing on the clarification of the mechanism of damage formation and crack growth, the prediction of fracture life, and the establishment of testing methods under both stress- and strain-controlled creep and fatigue conditions.

Prof. Dr. A. Toshimitsu Yokobori, Jr.
Guest Editor

Manuscript Submission Information

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Keywords

  • creep-fatigue
  • strain-controlled
  • stress-controlled
  • prediction of fracture life
  • test method
  • heat-resistant materials

Published Papers (6 papers)

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Research

24 pages, 20879 KiB  
Article
Creep-Fatigue Life Evaluation for Grade 91 Steels with Various Origins and Service Histories
by Haruhisa Shigeyama, Yukio Takahashi, John Siefert and Jonathan Parker
Metals 2024, 14(2), 148; https://doi.org/10.3390/met14020148 - 25 Jan 2024
Viewed by 803
Abstract
Grade 91 steel is widely used in the boilers and piping of thermal power plants. There has been significant research interest in understanding the variations in creep characteristics among different heats of this steel for effective plant management. In recent years, thermal power [...] Read more.
Grade 91 steel is widely used in the boilers and piping of thermal power plants. There has been significant research interest in understanding the variations in creep characteristics among different heats of this steel for effective plant management. In recent years, thermal power plants have been subjected to frequent load changes and startup/shutdown to adjust power supply and demand and stabilize frequencies. These operational shifts have raised concerns regarding the potential for creep-fatigue damage in high-temperature components. Therefore, this research focuses on creep-fatigue properties of Grade 91 steel and their predictability. Tensile, creep, strain-controlled fatigue, and strain-controlled creep-fatigue tests were performed on six Grade 91 steels with different heats and/or histories, and the characteristics in each test were compared. As a result, the variations in creep-fatigue life among the materials were found to be correlated with the difference in creep characteristics and stress level during stress relaxation. Furthermore, the study involved a comparative assessment of the predictive performance of creep-fatigue life using five different approaches: time fraction, classical ductility exhaustion, modified ductility exhaustion, energy-based, and hybrid approaches. Among these approaches, the hybrid approach, based on inelastic strain energy density at fracture formulated as a function of inelastic strain rate, exhibited the most accurate predictive performance. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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14 pages, 5984 KiB  
Article
Creep–Fatigue Life Estimation of Gr.91 Steel and Its Welded Joints
by Isamu Nonaka
Metals 2023, 13(11), 1880; https://doi.org/10.3390/met13111880 - 13 Nov 2023
Viewed by 744
Abstract
A series of creep–fatigue tests of Gr.91 steel were performed at 600 °C. Fatigue life was reduced by tensile strain holding. The minimum life reduction factor was approximately 0.3. The creep–fatigue life could not be estimated properly via the conventional linear summation rule [...] Read more.
A series of creep–fatigue tests of Gr.91 steel were performed at 600 °C. Fatigue life was reduced by tensile strain holding. The minimum life reduction factor was approximately 0.3. The creep–fatigue life could not be estimated properly via the conventional linear summation rule of the fatigue damage and creep damage. Since this material is considered to have a large creep–fatigue interaction, it was proposed that the creep–fatigue life should be estimated using the improved linear summation rule of the fatigue damage, the creep damage and the creep–fatigue interaction damage. In the future, it will be necessary to clarify the creep–fatigue interaction mechanism and define its damage value. On the other hand, a series of creep–fatigue tests for Gr.91 steel welded joints were also performed in the strain range of 0.5% at 600 °C. Again, the fatigue life was shortened by the tensile strain holding. The minimum fatigue life reduction factor was approximately 0.2. All the test pieces fractured in the fine-grained HAZ of the welded joints. The creep–fatigue life could not be estimated properly using the linear summation rule of the fatigue damage and creep damage in the HAZ. One possible reason was thought to be the effects of the elastic follow-up phenomena peculiar to welded joints. The creep strain of the HAZ might increase due to the transfer of the elastic strain from both the base metal and the weld metal, according to the elastic follow-up phenomena during strain holding. In the future, it will be important to quantitatively estimate the effects of the elastic follow-up phenomena. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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18 pages, 7023 KiB  
Article
Studying a Repair Method of LY12 Aluminum Alloy Plate
by Cheng Lv, Fenghui Wang, Sen Yang and Xiang Zhao
Metals 2023, 13(10), 1758; https://doi.org/10.3390/met13101758 - 17 Oct 2023
Cited by 1 | Viewed by 1024
Abstract
The difference in the strengthening effect of different thickness reinforcement plates on an LY12 aluminum alloy central defect plate and the load distribution between the reinforcement plate and central defect plate in the reinforcement plate structure were studied. Through a method of equivalent [...] Read more.
The difference in the strengthening effect of different thickness reinforcement plates on an LY12 aluminum alloy central defect plate and the load distribution between the reinforcement plate and central defect plate in the reinforcement plate structure were studied. Through a method of equivalent transverse load in a small interval [a + Δa], the equivalent cyclic load of the central defect plate in the reinforced plate structure under different crack lengths was calculated, and then the distribution of the internal load of the reinforced plate structure with a different thickness with the crack propagation was solved. The secondary development program of the finite element software Abaqus was written in Python language, so that Abaqus software can solve the problem of high cycle fatigue. The finite element simulation of the different thickness-reinforced plate structure is carried out by this program. Through the output data, the equivalent cyclic load of the central defect plate in the reinforced plate structure under different crack lengths is calculated. Through three different fitting methods, the mathematical relationship between the equivalent cyclic load Δσ and the crack length a at both ends of the central defect plate in the reinforced plate structure is described. Based on the mathematical relationship and the finite element output data, the fatigue crack propagation life of the reinforced plate structures with different thicknesses is calculated. It is found that, under the same crack conditions, with the increase in the thickness of the reinforced plate, the bearing load of the cracked plate decreases and the life of the cracked plate increases. With the expansion of the crack, the bearing load ratio of the reinforced plate increases. The simulation method is compared with the experimental results to verify its effectiveness. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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16 pages, 3526 KiB  
Article
A Phenomenological Model for Creep and Creep-Fatigue Crack Growth Rate Behavior in Ferritic Steels
by Ashok Saxena
Metals 2023, 13(10), 1749; https://doi.org/10.3390/met13101749 - 15 Oct 2023
Viewed by 1076
Abstract
A model to rationalize the effects of test temperature and microstructural variables on the creep crack growth (CCG) and creep-fatigue crack growth (CFCG) rates in ferritic steels is described. The model predicts that as the average spacing between grain boundary particles that initiate [...] Read more.
A model to rationalize the effects of test temperature and microstructural variables on the creep crack growth (CCG) and creep-fatigue crack growth (CFCG) rates in ferritic steels is described. The model predicts that as the average spacing between grain boundary particles that initiate creep cavities decrease, the CCG and CFCG rates increase. Further, the CCG data at several temperatures collapse into a single trend when a temperature compensated CCG rate derived from the model is used. The CCG and CFCG behavior measured at different temperatures is used to assess the effects of variables such as the differences between the base metal (BM), weld metal (WM), and heat-affected zone (HAZ) regions. The model is demonstrated for Grade 22 and Grade 91 steels using data from literature. It is shown that differences between the CCG behavior of the Grade 22 steel in new and ex-service conditions are negligible in the BM and WM regions but not in the HAZ region. The CCG behavior of the Grade 91 steels can be separated into creep-ductile and creep-brittle regions. The creep-brittle tendency is linked to the presence of excess trace element concentrations in the material chemistry. Significant differences found in the CCG rates between the BM, WM, and HAZ regions of the Grade 91 steel are explained. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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Graphical abstract

22 pages, 18307 KiB  
Article
Microstructural Evolution of a Re-Containing 10% Cr-3Co-3W Steel during Creep at Elevated Temperature
by Alexandra Fedoseeva, Ivan Brazhnikov, Svetlana Degtyareva, Ivan Nikitin and Rustam Kaibyshev
Metals 2023, 13(10), 1683; https://doi.org/10.3390/met13101683 - 01 Oct 2023
Viewed by 769
Abstract
Ten percent Cr steels are considered to be prospective materials for the production of pipes, tubes, and blades in coal-fired power plants, which are able to operate within ultra-supercritical steam parameters. The microstructural evolution of a Re-containing 10% Cr-3Co-3W steel with low N [...] Read more.
Ten percent Cr steels are considered to be prospective materials for the production of pipes, tubes, and blades in coal-fired power plants, which are able to operate within ultra-supercritical steam parameters. The microstructural evolution of a Re-containing 10% Cr-3Co-3W steel with low N and high B content during creep was investigated at different strains at 923 K and under an applied stress of 120 MPa using TEM and EBSD analyses. The studied steel had been previously normalized at 1323 K and tempered at 1043 K for 3 h. In the initial state, the tempered martensite lath structure with high dislocation density was stabilized by M23C6 carbides, NbX carbonitrides, and M6C carbides. At the end of the primary creep stage, the main microstructural change was found to be the precipitation of the fine Laves phase particles along the boundaries of the prior austenite grains, packets, blocks, and martensitic laths. The remarkable microstructural degradation processes, such as the significant growth of martensitic laths, the reduction in dislocation density within the lath interiors, and the growth of the grain boundary Laves phase particles, occurred during the steady-state and tertiary creep stages. Moreover, during the steady-state creep stage, the precipitation of the V-rich phase was revealed. Softening was in accordance with the dramatic reduction in hardness during the transition from the primary creep stage to the steady-state creep stage. The reasons for the softening were considered to be due to the change in the strengthening mechanisms and the interactions of the grain boundary M23C6 carbides and Laves phase with the low-angle boundaries of the martensitic laths and free dislocations. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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20 pages, 6056 KiB  
Article
Modeling of Creep Deformation Behavior of DZ411 and Finite Element Simulation of Turbine Blade
by Yihui Liu, Yanrong Wang, Dasheng Wei, Xianghua Jiang and Qiannan Tao
Metals 2023, 13(8), 1389; https://doi.org/10.3390/met13081389 - 02 Aug 2023
Cited by 2 | Viewed by 1030
Abstract
Creep tests were conducted on DZ411 material at 930 °C and 850 °C, and creep curves were recorded and employed in normalization creep model building. A yield function suitable for directional solidification nickel-based materials was proposed in an ascending-order approach. Combined with the [...] Read more.
Creep tests were conducted on DZ411 material at 930 °C and 850 °C, and creep curves were recorded and employed in normalization creep model building. A yield function suitable for directional solidification nickel-based materials was proposed in an ascending-order approach. Combined with the normalized creep model and the proposed function, a creep subroutine was compiled to simulate the creep deformation behavior of a turbine blade. The typical boundary conditions of the blade were determined and used for finite element analysis. According to the analysis results, the assessment positions for the actual application of a turbine blade were determined and checked for endurance intensity. The phenomenon of deviation angle between crystal axis and blade height direction in actual casting was further analyzed. Multiple angles and directional deviation angles were simulated for 10,000 h creep deformation. Considering the difficulties and challenges of the complex geometric structures of blades, it is necessary to conduct creep tests of DZ411 material and a simulation analysis of a real blade. Based on the above analysis and discussion, the present work sheds light on finite element analysis and has great potential for structural analyses in the engineering applications of complex high-temperature structures. Full article
(This article belongs to the Special Issue Creep and Fatigue Behavior of Alloys)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: A PHENOMENOLOGICAL MODEL FOR CREEP AND CREEP-FATIGUE CRACK GROWTH RATE BEHAVIOR IN FERRITIC STEELS
Authors: Ashok Saxena
Affiliation: Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR, USA
Abstract: A micro-mechanics model is described that rationalizes the effects of test temperature and microstructural variables such as grain boundary particles on the creep crack growth rate (CCGR) behavior of ferritic steels. The model predicts that as the average spacing between particles that initiate creep cavities on grain boundaries decreases, the CCG rates are expected to increase. CCGR data at several temperatures can be collapsed into a single trend using the proposed temperature compensated creep crack growth rate. The applicability of the model is demonstrated for Grade 22 and Grade 91 steels using extensive amounts of data available in the literature on new and service degraded conditions and their weldments. It is shown that differences between the CCGR behavior of Grade 22 steel in new and ex-service conditions are negligible in the base metal region but not in welds and along the heat-affected-zone (HAZ). Significant differences were observed between new and ex-service materials in the CCGR behavior of Grade 91 materials even in the base metal region and also in the weld and HAZ regions.

Title: Heat-to-heat variations in creep-fatigue properties of Grade 91 steel
Authors: Haruhisa Shigeyama
Affiliation: Central research institute of electric power industry

Title: Creep/Fatigue Multiaxial Response in 3D Pabricated Ti Alloys
Authors: Jiangjing Xi; Yun Hu; Jun Jian; Kamran Nikbin
Affiliation: School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
Abstract: Combined creep-fatigue failure mode are frequent sources of failure in high temperature components. In this paper a combined multiaxial multisite inter/transgranular crack growth model at the meso-scale level is proposed in order to conveniently deal with the various failure scenarios that may exist in plant components. The modelling process was tested out on multiaxial notched bar and Fracture Mechanics specimen using material properties for 3D printed Ti Alloy. An idealized microstructure with random grains and finite thickness grain boundaries was generated which could allow multiple damage and crack initiation sites either along grain boundaries or inside grains. It is shown that the simulated crack under the combination of time dependent creep mainly propagates along grain boundaries initiating from the surface, exhibiting crack branching whereas under fatigue the crack grows in a transgranular manner. Furthermore, the role of creep, fatigue and oxidation on the failure life is shown to be dependent on the applied duration period at peak loads. For an overall validation of the model the predicted rupture times for notched bars are shown to compare well with the experimental data. It is also shown that the failure modes due to different damage mechanisms and loading conditions corresponds with those observed in engineering alloys.

Title: The fracture life of circular notched specimens under load and displacement controlled creep-fatigue conditions for P92 steel
Authors: A.T. Yokobori,Jr1), G.Ozeki1), K.Jinno2), T.Nakagawa2), R.Sugiura3), I.Nonaka4), M.Tabuchi5) and K.Nikbin 6)
Affiliation: 1) Teikyo University, 2) Student of Graduate School of Tohoku University, 3)Nihon University,4)Tohoku University,5)NIMS,6) Imperial College
Abstract: Previously, we have proposed the prediction method of creep-fatigue crack initiation and growth life for P92 steel using a circular notched round bar specimen under displacement controlled creep-fatigue conditions. The validity of using the stress range ,that is the stress amplitude, was shown to define the life of crack initiation and failure. In this paper, we have conducted more detailed experiments and clarified the following results. 1) Estimating crack growth life by the frequency characteristics law of crack growth life, the linear cumulative damage law and Manson-Coffin law, crack growth life of a sharp notched specimens for W added 9Cr steel (P92 steel ) is found to be dominated by fatigue damage under displacement controlled condition and by creep-fatigue damage under load controlled condition. 2) By deriving activation energy of crack growth life under creep –fatigue conditions based on Q* concept, activation energy is found to be less sensitive to the holding time under displacement controlled condition and to take almost equal value to that under fatigue condition. On the other hand, activation energy under load controlled condition, it is found to increase with increase in load holding time and saturate to that under creep condition.

Title: Creep crack initiation life characteristics of solidification-controlled Ni-based superalloy notched specimens analyzed by misorientation analysis.
Authors: Daisuke Kobayashi
Affiliation: Chubu Electric Power Co.
Abstract: Gas turbines require proper operation and maintenance, and predicting the creep crack initiation life of turbine blades made of a solidification-controlled Ni-based superalloy is crucial. A unified life assessment method was developed to assess creep crack initiation life at various stress-concentrated regions, using a misorientation parameter which is equivalent to the relative notch opening displacement. This parameter can predict creep crack initiation life using crystal orientation distribution measured by the EBSD method. In this study, the influence of the specimen plate thickness was investigated, and it was confirmed that there is no issues with practical applicability.

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