Pub Date : 2023-11-08DOI: 10.1080/09603409.2023.2276996
D. Baraldi, K.-F Nilsson, S. Holmström, I. Simonovski
A uniaxial creep model that describes creep over a wide stress range was developed for P91 steel using an artificial neural network (ANN). The training dataset was based on measurements from uniaxial creep tests and information derived from a combination of the logistic creep strain prediction and the Wilshire models. The ANN model reproduces the training dataset with high accuracy (R2 = 0.975; RMSE (Root Mean Square Error) = 0.19). The model can be easily implemented in finite element analysis (FEA) codes since it provides an analytical expression of the true creep rate as a function of temperature, true stress and true creep strain. In FEA simulations under the same conditions as the training dataset, the model provides times to rupture and minimum creep rates very close to those in the training dataset. The model can be adapted for heats with different properties from the average behaviour of the training dataset by means of a stress-scaling factor.
{"title":"Development of a P91 uniaxial creep model for a wide stress range with an artificial neural network","authors":"D. Baraldi, K.-F Nilsson, S. Holmström, I. Simonovski","doi":"10.1080/09603409.2023.2276996","DOIUrl":"https://doi.org/10.1080/09603409.2023.2276996","url":null,"abstract":"A uniaxial creep model that describes creep over a wide stress range was developed for P91 steel using an artificial neural network (ANN). The training dataset was based on measurements from uniaxial creep tests and information derived from a combination of the logistic creep strain prediction and the Wilshire models. The ANN model reproduces the training dataset with high accuracy (R2 = 0.975; RMSE (Root Mean Square Error) = 0.19). The model can be easily implemented in finite element analysis (FEA) codes since it provides an analytical expression of the true creep rate as a function of temperature, true stress and true creep strain. In FEA simulations under the same conditions as the training dataset, the model provides times to rupture and minimum creep rates very close to those in the training dataset. The model can be adapted for heats with different properties from the average behaviour of the training dataset by means of a stress-scaling factor.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"123 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135341879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We demonstrate a dislocation density-based crystal plasticity (CP) model approach for simulating mesoscale deformation and damage. The existing CP framework is extended to be compatible with the oxygen-free phosphorous copper microstructure that is the focus of this study. The key aim is to introduce relevant plastic deformation mechanisms and to develop a failure model capable of depicting creep damage in the material. The effect of local variations in material is evaluated, and the model response is compared with experiments and characterisation. The basis of this work is CP material modelling, including grain orientation and size, obtained using electron backscatter diffraction and experimental test data of real relaxation test specimens. This will yield a realistic description of texture and grain shape and, ultimately, accurate stress–strain response at the microstructural level for further evaluation of performance with respect to material creep(−fatigue) damage.
{"title":"Crystal plasticity model for creep and relaxation deformation of OFP copper","authors":"Tom. Andersson, Matti. Lindroos, Rami. Pohja, Abhishek. Biswas, Supriya. Nandy, Janne. Pakarinen, Juhani. Rantala","doi":"10.1080/09603409.2023.2278232","DOIUrl":"https://doi.org/10.1080/09603409.2023.2278232","url":null,"abstract":"We demonstrate a dislocation density-based crystal plasticity (CP) model approach for simulating mesoscale deformation and damage. The existing CP framework is extended to be compatible with the oxygen-free phosphorous copper microstructure that is the focus of this study. The key aim is to introduce relevant plastic deformation mechanisms and to develop a failure model capable of depicting creep damage in the material. The effect of local variations in material is evaluated, and the model response is compared with experiments and characterisation. The basis of this work is CP material modelling, including grain orientation and size, obtained using electron backscatter diffraction and experimental test data of real relaxation test specimens. This will yield a realistic description of texture and grain shape and, ultimately, accurate stress–strain response at the microstructural level for further evaluation of performance with respect to material creep(−fatigue) damage.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135634275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1080/09603409.2023.2276995
ARMAN Rabieifar, M. REZA Afshar, HAMIDREZA Najafi
ABSTRACTThe effect of oxide scale and microstructural changes during 10, 20, and 40 hot corrosion cycles on the high-temperature tensile properties of Rene-80 superalloy at 950 °C was investigated. Due to the formation of micro-cracks and micro-voids, compressive stresses produced from Cr2O3 and NiO growth, and tensile stresses stemming from NiMoO4 transformation and Al internal oxidation, the oxide scale spalled. By increasing the hot corrosion cycles, UTS (Ultimate Tensile Strength) and El.% (Elongation) first decreased and then increased due to the propagation of intergranular vertical cracks from the oxide scale to the Rene-80 after 20 cycles. During hot corrosion cycles, YS increased due to a rise in the density of near-surface intergranular cracks close to the Rene-80/oxide scale interface resulting from micro-void linkage and γ′-depleted zone. Due to the high area fraction and the small average size of secondary γ′, UTS and YS were the highest and lowest after ten cycles, respectively.KEYWORDS: Rene-80 superalloyhot corrosionoxide scaletensile propertiesfracture surfaceγ' precipitate Disclosure statementNo potential conflict of interest was reported by the author(s).
{"title":"The effect of oxide scale and microstructural changes during cyclic hot corrosion on high-temperature tensile properties of Rene-80 superalloy","authors":"ARMAN Rabieifar, M. REZA Afshar, HAMIDREZA Najafi","doi":"10.1080/09603409.2023.2276995","DOIUrl":"https://doi.org/10.1080/09603409.2023.2276995","url":null,"abstract":"ABSTRACTThe effect of oxide scale and microstructural changes during 10, 20, and 40 hot corrosion cycles on the high-temperature tensile properties of Rene-80 superalloy at 950 °C was investigated. Due to the formation of micro-cracks and micro-voids, compressive stresses produced from Cr2O3 and NiO growth, and tensile stresses stemming from NiMoO4 transformation and Al internal oxidation, the oxide scale spalled. By increasing the hot corrosion cycles, UTS (Ultimate Tensile Strength) and El.% (Elongation) first decreased and then increased due to the propagation of intergranular vertical cracks from the oxide scale to the Rene-80 after 20 cycles. During hot corrosion cycles, YS increased due to a rise in the density of near-surface intergranular cracks close to the Rene-80/oxide scale interface resulting from micro-void linkage and γ′-depleted zone. Due to the high area fraction and the small average size of secondary γ′, UTS and YS were the highest and lowest after ten cycles, respectively.KEYWORDS: Rene-80 superalloyhot corrosionoxide scaletensile propertiesfracture surfaceγ' precipitate Disclosure statementNo potential conflict of interest was reported by the author(s).","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"74 7-8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135272430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-19DOI: 10.1080/09603409.2023.2261780
Daniel Osorio, Arianna Gotti, Florian Kauffmann, Andreas Klenk, Stefan Weihe
ABSTRACTThe aim of the paper is to investigate experimentally the fatigue and creep-fatigue material behaviour of improved materials and welded joints for the application in flexible future power plants. These materials promise a reduction in manufacturing costs as well as an increase in flexibility by providing enhanced creep strength thorugh a wall thickness reduction. At the temperature range between 500°C −550°C, the investigation focusses on the creep and low-cycle fatigue behaviour of dissimilar welded joints from conventional materials (bainitic and martensitic materials T24 and T92) to nickel-based alloys (A617B and HR6W) fabricated as tubes. At the temperature range between 700°C and 750°C, it focusses on the creep, low-cycle fatigue and creep-fatigue behaviour of similar and dissimilar welded joints from nickel-based alloys (A740H, A617B and A263) fabricated as tubes and as pipes. Metallographic investigations after testing provide support for understanding the influence of temperature, strain amplitude and dwell time on the microstructure change and the fatigue strength.KEYWORDS: Creepfatiguecreep-fatiguemartensitic/bainitic steelsnickel-based-alloyweld jointstubepipe Additional Notes to AuthorsDo you wish your paper to be submitted to Materials at High Temperatures … … … … … … Yes/NoThose papers accepted for inclusion in the MHT Journal will only appear in the conference proceedings as an abstract with reference to the full paper in the relevant edition of the Journal.An abstract book will be included within the delegate pack as below. You are invited to include a photo of the main author/presenter, to aid networking at the conference. If you prefer not to supply a photo we will happily include the abstract without a photo.Any questions relating to paper/presentation and submission to paper please contact the Chair of the Scientific Committee Dr Augusto Di Gianfrancesco, a.digianfrancesco@libero.it.Any questions relating to the organisation of the conference, registration or administration please contact the Chair of the Organising Committee Dr Peter Barnard, peter.barnard@mpiuk.comAcknowledgmentsThe results presented in this paper were generated within the European Research Project “Ni-based alloys for Operation of 725°C Power Plants, acronym NIBALO725“. This project has received funding from the Research Fund for Coal and Steel under grant agreement No. 709976. The authors thank the project consortium for the fruitful discussion during the project meetings, especially Special Metals for providing the A740H material (tube and pipe) and GE Power GmbH (former GE Boiler Deutschland GmbH) for the fabrication of the pipe and tube weldments.Disclosure statementNo potential conflict of interest was reported by the authors.Additional informationFundingThis work was supported by the Research Fund for Coal and Steel [709976].
摘要本文的目的是对未来柔性电站中应用的改进材料和焊接接头的疲劳和蠕变疲劳材料性能进行实验研究。这些材料有望降低制造成本，并通过减少壁厚提供增强的蠕变强度来增加灵活性。在500°C - 550°C的温度范围内，研究了从传统材料(贝氏体和马氏体材料T24和T92)到管状镍基合金(A617B和HR6W)的不同焊接接头的蠕变和低周疲劳行为。在700°C至750°C的温度范围内，重点研究了由镍基合金(A740H、A617B和A263)制成的管和管的相似和不同焊接接头的蠕变、低周疲劳和蠕变疲劳行为。试验后的金相研究为了解温度、应变幅值和停留时间对组织变化和疲劳强度的影响提供了支持。关键词:蠕变疲劳蠕变疲劳马氏体/贝氏体钢-镍基合金焊接接头作者补充说明您是否希望将您的论文提交给高温材料... ... ... ... ... ...是/否那些被纳入MHT期刊的论文将仅作为参考期刊相关版本全文的摘要出现在会议论文集中。一个摘要书将包括在委托包如下。我们邀请您附上主要作者/演讲者的照片，以帮助在会议上建立网络。如果您不愿意提供照片，我们将很高兴地包括没有照片的摘要。任何关于论文/演示和提交论文的问题请联系科学委员会主席auguto Di Gianfrancesco博士，a.digianfrancesco@libero.it.Any关于会议组织，注册或管理的问题请联系组织委员会主席Peter Barnard博士，peter.barnard@mpiuk.comAcknowledgmentsThe本文中提出的结果是在欧洲研究项目“用于725°C发电厂运行的镍基合金，缩写为NIBALO725”中产生的。本项目已获得煤炭和钢铁研究基金资助，资助协议号为709976。作者感谢项目联合体在项目会议期间进行的富有成果的讨论，特别是特种金属公司提供的A740H材料(管和管)和GE Power GmbH(原GE Boiler Deutschland GmbH)制造的管和管焊接件。披露声明作者未报告潜在的利益冲突。本研究得到了煤炭和钢铁研究基金[709976]的支持。
{"title":"Creep, fatigue and creep-fatigue behaviour of martensitic/bainitic steels and nickel-based alloys and their welded joints at the temperature range 500°C–750°C","authors":"Daniel Osorio, Arianna Gotti, Florian Kauffmann, Andreas Klenk, Stefan Weihe","doi":"10.1080/09603409.2023.2261780","DOIUrl":"https://doi.org/10.1080/09603409.2023.2261780","url":null,"abstract":"ABSTRACTThe aim of the paper is to investigate experimentally the fatigue and creep-fatigue material behaviour of improved materials and welded joints for the application in flexible future power plants. These materials promise a reduction in manufacturing costs as well as an increase in flexibility by providing enhanced creep strength thorugh a wall thickness reduction. At the temperature range between 500°C −550°C, the investigation focusses on the creep and low-cycle fatigue behaviour of dissimilar welded joints from conventional materials (bainitic and martensitic materials T24 and T92) to nickel-based alloys (A617B and HR6W) fabricated as tubes. At the temperature range between 700°C and 750°C, it focusses on the creep, low-cycle fatigue and creep-fatigue behaviour of similar and dissimilar welded joints from nickel-based alloys (A740H, A617B and A263) fabricated as tubes and as pipes. Metallographic investigations after testing provide support for understanding the influence of temperature, strain amplitude and dwell time on the microstructure change and the fatigue strength.KEYWORDS: Creepfatiguecreep-fatiguemartensitic/bainitic steelsnickel-based-alloyweld jointstubepipe Additional Notes to AuthorsDo you wish your paper to be submitted to Materials at High Temperatures … … … … … … Yes/NoThose papers accepted for inclusion in the MHT Journal will only appear in the conference proceedings as an abstract with reference to the full paper in the relevant edition of the Journal.An abstract book will be included within the delegate pack as below. You are invited to include a photo of the main author/presenter, to aid networking at the conference. If you prefer not to supply a photo we will happily include the abstract without a photo.Any questions relating to paper/presentation and submission to paper please contact the Chair of the Scientific Committee Dr Augusto Di Gianfrancesco, a.digianfrancesco@libero.it.Any questions relating to the organisation of the conference, registration or administration please contact the Chair of the Organising Committee Dr Peter Barnard, peter.barnard@mpiuk.comAcknowledgmentsThe results presented in this paper were generated within the European Research Project “Ni-based alloys for Operation of 725°C Power Plants, acronym NIBALO725“. This project has received funding from the Research Fund for Coal and Steel under grant agreement No. 709976. The authors thank the project consortium for the fruitful discussion during the project meetings, especially Special Metals for providing the A740H material (tube and pipe) and GE Power GmbH (former GE Boiler Deutschland GmbH) for the fabrication of the pipe and tube weldments.Disclosure statementNo potential conflict of interest was reported by the authors.Additional informationFundingThis work was supported by the Research Fund for Coal and Steel [709976].","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135729732","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-16DOI: 10.1080/09603409.2023.2268332
Mark Evans
A reliable means of assessing the accuracy of a creep model’s predictions is fundamental to safe power plant operation. This paper introduces a method of decomposing the mean absolute prediction error for such a purpose to overcome the limitations that are inherent in the traditional approach of squaring prediction errors to prevent over and underestimates of life offsetting each other. When this method is applied to 2.25Cr-1Mo steel and 316 H stainless steel, it was found that squared errors leads to overestimates of the average prediction error associated with a particular creep model, and it also dramatically underestimates the proportion of this error that is systematic in nature. These differences were more noticeable for 316 H stainless steel.
{"title":"Assessing the predictive performance of creep models using absolute rather than squared prediction errors: an application to 2.25Cr-1Mo steel and 316H stainless steel","authors":"Mark Evans","doi":"10.1080/09603409.2023.2268332","DOIUrl":"https://doi.org/10.1080/09603409.2023.2268332","url":null,"abstract":"A reliable means of assessing the accuracy of a creep model’s predictions is fundamental to safe power plant operation. This paper introduces a method of decomposing the mean absolute prediction error for such a purpose to overcome the limitations that are inherent in the traditional approach of squaring prediction errors to prevent over and underestimates of life offsetting each other. When this method is applied to 2.25Cr-1Mo steel and 316 H stainless steel, it was found that squared errors leads to overestimates of the average prediction error associated with a particular creep model, and it also dramatically underestimates the proportion of this error that is systematic in nature. These differences were more noticeable for 316 H stainless steel.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136142363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-12DOI: 10.1080/09603409.2023.2264061
A. Tonti, A. Alvino, A. Antonini, C. Delle Site, D. Lega, S. Matera, O. Tassa
ABSTRACTP91 and P92 steels are widely used in power plants and petrochemical industry for long-term service components. Due to high resistance to creep, fatigue and corrosion, the use of grade 91 and grade 92 steels allows ultrasupercritical conditions (600 °C, 300 bar). To achieve this goal the alloy design was based on the following metallurgical concepts: stable tempered martensitic microstructure, precipitation strengthening through M23C6 (Cr, Fe, Mo or W carbides) and fine MX (V, Nb carbides), solution hardening through elements as Mo or Mo/W and high Cr content. This study is focused on the microstructure evolution of grade 91 and grade 92 steels under aging and creep conditions. Three sets of laboratory-aged specimens heated in oven at 550°C, 600°C and 650°C were examined. Furthermore, the influence of stress on the microstructure was evaluated. The microstructures were characterized by several means of investigations and the results were compared to literature.KEYWORDS: MXM23C6Laves phaseZ phasecreep cavityinclusions Disclosure statementNo potential conflict of interest was reported by the authors.
摘要p91和P92钢广泛用于电厂和石化行业的长期服务部件。由于具有较高的抗蠕变、抗疲劳和抗腐蚀性能，使用91级和92级钢可以在超超临界条件下(600°C, 300 bar)使用。为了实现这一目标，合金设计基于以下冶金理念:稳定的回火马氏体组织，通过M23C6 (Cr、Fe、Mo或W碳化物)和细小的MX (V、Nb碳化物)进行沉淀强化，通过Mo或Mo/W元素和高Cr含量进行固溶硬化。研究了91级和92级钢在时效和蠕变条件下的组织演变。分别在550°C、600°C和650°C的烤箱中加热三组实验室老化试样。进一步评价了应力对微观组织的影响。通过多种研究手段对其微观结构进行了表征，并与文献进行了比较。关键词:MXM23C6Laves phase ez phase蠕形空洞内含物披露声明作者未报告潜在利益冲突。
{"title":"Steel grades 91 and 92 microstructure and precipitate evolution atlas and life assessment tool","authors":"A. Tonti, A. Alvino, A. Antonini, C. Delle Site, D. Lega, S. Matera, O. Tassa","doi":"10.1080/09603409.2023.2264061","DOIUrl":"https://doi.org/10.1080/09603409.2023.2264061","url":null,"abstract":"ABSTRACTP91 and P92 steels are widely used in power plants and petrochemical industry for long-term service components. Due to high resistance to creep, fatigue and corrosion, the use of grade 91 and grade 92 steels allows ultrasupercritical conditions (600 °C, 300 bar). To achieve this goal the alloy design was based on the following metallurgical concepts: stable tempered martensitic microstructure, precipitation strengthening through M23C6 (Cr, Fe, Mo or W carbides) and fine MX (V, Nb carbides), solution hardening through elements as Mo or Mo/W and high Cr content. This study is focused on the microstructure evolution of grade 91 and grade 92 steels under aging and creep conditions. Three sets of laboratory-aged specimens heated in oven at 550°C, 600°C and 650°C were examined. Furthermore, the influence of stress on the microstructure was evaluated. The microstructures were characterized by several means of investigations and the results were compared to literature.KEYWORDS: MXM23C6Laves phaseZ phasecreep cavityinclusions Disclosure statementNo potential conflict of interest was reported by the authors.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"248 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135967763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-09DOI: 10.1080/09603409.2023.2261783
C. Kontermann, A. Erbe, V. Knauthe, M. von Buelow, T.-U. Kern, M. Oechsner
ABSTRACTThe ductility of a material represents a very important value for both the classification and application of high-temperature alloys in real components. Commonly, different values have been defined and can be used to characterise the ductility of the material. Within this work, a 3D-scanning system has been developed which allow a highly precise digital reconstruction of fractured creep specimens. The digital reconstruction is used to compare and refine conventions for determining one of the ductility candidate values, the uniform elongation, in a consistent, robust and objective way. By utilizing this system, a large amount of long-term creep specimens were re-evaluated including P92 samples with challenging, since macroscopically low ductility values. The results will be discussed in by providing uniform elongation trends and by the use of the Ductility Evaluation of Creep Specimens (DECS) diagram.KEYWORDS: Uniform elongation3D-Scannercreep ductility AcknowledgmentsThe underlying research project (FVV project no. 1371) was performed by the Institute of Materials Technology of the Technical University Darmstadt, by the Interactive Graphics Systems Group and by the Materials Testing Institute at the University of Stuttgart. The research project was funded by the AVIF (Research Association for the Iron and Metal Processing Industry eV, AVIF No. A314). The authors gratefully acknowledge the support received from the funding organisation, from the FVV eV and from all scientific and industry experts involved in this project.Disclosure statementNo potential conflict of interest was reported by the author(s).
{"title":"Uniform elongation measurements on creep specimens by a novel 3D-scanning system","authors":"C. Kontermann, A. Erbe, V. Knauthe, M. von Buelow, T.-U. Kern, M. Oechsner","doi":"10.1080/09603409.2023.2261783","DOIUrl":"https://doi.org/10.1080/09603409.2023.2261783","url":null,"abstract":"ABSTRACTThe ductility of a material represents a very important value for both the classification and application of high-temperature alloys in real components. Commonly, different values have been defined and can be used to characterise the ductility of the material. Within this work, a 3D-scanning system has been developed which allow a highly precise digital reconstruction of fractured creep specimens. The digital reconstruction is used to compare and refine conventions for determining one of the ductility candidate values, the uniform elongation, in a consistent, robust and objective way. By utilizing this system, a large amount of long-term creep specimens were re-evaluated including P92 samples with challenging, since macroscopically low ductility values. The results will be discussed in by providing uniform elongation trends and by the use of the Ductility Evaluation of Creep Specimens (DECS) diagram.KEYWORDS: Uniform elongation3D-Scannercreep ductility AcknowledgmentsThe underlying research project (FVV project no. 1371) was performed by the Institute of Materials Technology of the Technical University Darmstadt, by the Interactive Graphics Systems Group and by the Materials Testing Institute at the University of Stuttgart. The research project was funded by the AVIF (Research Association for the Iron and Metal Processing Industry eV, AVIF No. A314). The authors gratefully acknowledge the support received from the funding organisation, from the FVV eV and from all scientific and industry experts involved in this project.Disclosure statementNo potential conflict of interest was reported by the author(s).","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135095099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-10-03DOI: 10.1080/09603409.2023.2265261
Z. Guo, J. Hu, N. Saunders, J.Ph. Schillé
ABSTRACTThe creep resistance of martensitic power plant steels depends strongly on the dispersion of various types of precipitates in the microstructure. Reliable prediction of rupture strength of such alloys thus demands accurate description of the microstructure evolution during service. A material model that calculates the simultaneous precipitation kinetics and hardening in these steels has been reported previously. The creep rupture model reported here is a natural extension of the previous research. This model has been validated against experimental creep rupture data of wide-used 9–12% Cr steels. It allows the effect of variation in alloy conditions, such as composition and heat treatments, on rupture strength to be quantitatively evaluated for a given alloy grade. Results show that such variations can lead to significant differences in the calculated rupture strength, which are believed to be largely responsible for the wide scatter in the experimental data.KEYWORDS: Rupture strengthrupture lifeprecipitationpower plant steelsmaterials modelling Disclosure statementNo potential conflict of interest was reported by the authors.
{"title":"Rupture strength prediction of martensitic power plant steels","authors":"Z. Guo, J. Hu, N. Saunders, J.Ph. Schillé","doi":"10.1080/09603409.2023.2265261","DOIUrl":"https://doi.org/10.1080/09603409.2023.2265261","url":null,"abstract":"ABSTRACTThe creep resistance of martensitic power plant steels depends strongly on the dispersion of various types of precipitates in the microstructure. Reliable prediction of rupture strength of such alloys thus demands accurate description of the microstructure evolution during service. A material model that calculates the simultaneous precipitation kinetics and hardening in these steels has been reported previously. The creep rupture model reported here is a natural extension of the previous research. This model has been validated against experimental creep rupture data of wide-used 9–12% Cr steels. It allows the effect of variation in alloy conditions, such as composition and heat treatments, on rupture strength to be quantitatively evaluated for a given alloy grade. Results show that such variations can lead to significant differences in the calculated rupture strength, which are believed to be largely responsible for the wide scatter in the experimental data.KEYWORDS: Rupture strengthrupture lifeprecipitationpower plant steelsmaterials modelling Disclosure statementNo potential conflict of interest was reported by the authors.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135738806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-27DOI: 10.1080/09603409.2023.2263719
O. Öhlin, R. Siriki, G. Chai
ABSTRACTFor heat resistant alloys, long-term structural stability at high temperatures is a critical issue for alloy design and applications. In this paper, the long-term creep behaviours and structural stabilities of six heat resistant high Ni alloys and austenitic stainless steels have been studied. The longest creep rupture life is up to 359 283 hours. High Ni and Cr alloys show a good combination of high creep and oxidation resistances. Precipitation of nano MX particles with a very low growth rate improves long-term creep resistance at high temperatures. Long-term stable multiple nanoprecipitates of MX, Cu-rich, Laves and M23C6 phases can greatly contribute to the creep strength. Low Ni austenitic stainless steels show comparatively low oxidation and creep resistances. It was first found that at 800°C, Cr2N could form in the low Ni steel with a long-term crept by the absorption of nitrogen from the air into the matrix.KEYWORDS: Creepaustenitic stainless steelNi based alloystructural stabilitymicrostructure AcknowledgmentsThis paper is published by permission of Alleima EMEA AB. The supports of Dr Tom Eriksson and Mr Martin Östlund are greatly acknowledged.Disclosure statementNo potential conflict of interest was reported by the author(s).
{"title":"Long-term creep behaviours and structural stabilities of austenitic heat-resistant stainless steels","authors":"O. Öhlin, R. Siriki, G. Chai","doi":"10.1080/09603409.2023.2263719","DOIUrl":"https://doi.org/10.1080/09603409.2023.2263719","url":null,"abstract":"ABSTRACTFor heat resistant alloys, long-term structural stability at high temperatures is a critical issue for alloy design and applications. In this paper, the long-term creep behaviours and structural stabilities of six heat resistant high Ni alloys and austenitic stainless steels have been studied. The longest creep rupture life is up to 359 283 hours. High Ni and Cr alloys show a good combination of high creep and oxidation resistances. Precipitation of nano MX particles with a very low growth rate improves long-term creep resistance at high temperatures. Long-term stable multiple nanoprecipitates of MX, Cu-rich, Laves and M23C6 phases can greatly contribute to the creep strength. Low Ni austenitic stainless steels show comparatively low oxidation and creep resistances. It was first found that at 800°C, Cr2N could form in the low Ni steel with a long-term crept by the absorption of nitrogen from the air into the matrix.KEYWORDS: Creepaustenitic stainless steelNi based alloystructural stabilitymicrostructure AcknowledgmentsThis paper is published by permission of Alleima EMEA AB. The supports of Dr Tom Eriksson and Mr Martin Östlund are greatly acknowledged.Disclosure statementNo potential conflict of interest was reported by the author(s).","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135537085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-09-25DOI: 10.1080/09603409.2023.2261665
Sandra Megahed, Karl Michael Krämer, Christoph Heinze, Christian Kontermann, Annett Udoh, Stefan Weihe, Matthias Oechsner
ABSTRACTThe microstructural anisotropy caused by the highly oriented solidification of the metal Laser Powder Bed Fusion (PBF-LB/M) process affects mechanical short- and long-term properties. Component build orientation influences grain morphology and orientation, and thus, mechanical properties. While the creep behaviour of samples manufactured parallel and perpendicular to the build direction are studied intensively, the 45° build orientation remains uncharacterised. In this study, IN738LC creep samples are manufactured via PBF-LB/M in three build orientations (0°, 45° and 90°). While the results of 90° and 0° are as expected, where 90° achieves the longest time to rupture and largest rupture strain, the 45° specimen shows the least fracture time. Differences in microstructure and twinning behaviour are identified as one of the root causes for this unexpected behaviour. This study discusses the correlation between microstructure, twinning and build orientation and their effect on creep behaviour, with special focus on the 45° build orientation.KEYWORDS: Laser powder bed fusionIN738LCbuild orientationcreepmicrostructuretwinning Disclosure statementNo potential conflict of interest was reported by the author(s).PatentsThere are no patents resulting from the work reported in this manuscript.Notes1. Hausner ratio, h = .Tapped Powder DensityBulk Powder Density2. Volume energy density,EV = Laser PowerScan Speed×Hatch Distance×Layer ThicknessAdditional informationFundingThe research project (FVV project no.1401) was performed by the Institute of Materials Technology of the Technical University Darmstadt under the guidance of Prof. Dr.-Ing. Matthias Oechsner and by the Materials Testing Institute at the University of Stuttgart under the guidance of Prof. Dr.-Ing. Stefan Weihe. Based on a decision taken by the German Bundestag, it was supported by the Federal Ministry for Economic Affairs and Climate Action (BMWK) and the AIF (German Federation of Industrial Research Associations eV) within the framework of the industrial collective research (IGF) programme (IGF No. 21220 N/1) The authors gratefully acknowledge the support received from the funding organisations, from the FVV eV and from all those involved in the project.
{"title":"Creep of IN738LC manufactured with laser powder bed fusion: effect of build orientation and twinning","authors":"Sandra Megahed, Karl Michael Krämer, Christoph Heinze, Christian Kontermann, Annett Udoh, Stefan Weihe, Matthias Oechsner","doi":"10.1080/09603409.2023.2261665","DOIUrl":"https://doi.org/10.1080/09603409.2023.2261665","url":null,"abstract":"ABSTRACTThe microstructural anisotropy caused by the highly oriented solidification of the metal Laser Powder Bed Fusion (PBF-LB/M) process affects mechanical short- and long-term properties. Component build orientation influences grain morphology and orientation, and thus, mechanical properties. While the creep behaviour of samples manufactured parallel and perpendicular to the build direction are studied intensively, the 45° build orientation remains uncharacterised. In this study, IN738LC creep samples are manufactured via PBF-LB/M in three build orientations (0°, 45° and 90°). While the results of 90° and 0° are as expected, where 90° achieves the longest time to rupture and largest rupture strain, the 45° specimen shows the least fracture time. Differences in microstructure and twinning behaviour are identified as one of the root causes for this unexpected behaviour. This study discusses the correlation between microstructure, twinning and build orientation and their effect on creep behaviour, with special focus on the 45° build orientation.KEYWORDS: Laser powder bed fusionIN738LCbuild orientationcreepmicrostructuretwinning Disclosure statementNo potential conflict of interest was reported by the author(s).PatentsThere are no patents resulting from the work reported in this manuscript.Notes1. Hausner ratio, h = .Tapped Powder DensityBulk Powder Density2. Volume energy density,EV = Laser PowerScan Speed×Hatch Distance×Layer ThicknessAdditional informationFundingThe research project (FVV project no.1401) was performed by the Institute of Materials Technology of the Technical University Darmstadt under the guidance of Prof. Dr.-Ing. Matthias Oechsner and by the Materials Testing Institute at the University of Stuttgart under the guidance of Prof. Dr.-Ing. Stefan Weihe. Based on a decision taken by the German Bundestag, it was supported by the Federal Ministry for Economic Affairs and Climate Action (BMWK) and the AIF (German Federation of Industrial Research Associations eV) within the framework of the industrial collective research (IGF) programme (IGF No. 21220 N/1) The authors gratefully acknowledge the support received from the funding organisations, from the FVV eV and from all those involved in the project.","PeriodicalId":49877,"journal":{"name":"Materials at High Temperatures","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135816259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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