bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creep Behaviors of Alloy 718 Type Ni-Based Superalloys
Authors: Kobayashi Satoru , Tsuya Takumi 
Published: October 2024

Abstract
Alloy 718 is an important class of Nb-bearing Ni-based superalloys for high-temperature applications, such as compressor disks/blades and turbine disks in gas turbine systems. The service temperature of this alloy is, however, limited below 650 °C probably due to the degradation of its strengthening phase γ"-Ni3Nb. Aiming at understanding and improving creep properties of 718-type alloys, we investigated creep behaviors of alloy 718 and alloy Ta-718 where different types of γ" phases, Ni3Nb and Ni3Ta, were precipitated, respectively. Creep tests were conducted at 700 °C under stress conditions of 400 and 500 MPa for the two alloys in aged conditions. It was found that while the minimum creep rates were comparable in the two alloys, the creep rate acceleration was lower in alloy Ta-718 than in alloy 718 under the creep conditions studied. Microstructural observations on the specimens before and after the creep tests suggested that the γ" precipitates were distinguishably finer in alloy Ta-718 than in alloy 718 throughout the creep tests. The formation of planar defects and shearing of γ" precipitates occurred frequently in the alloy 718 specimen. The observed creep deformations were discussed in terms of the critical resolved shear stress due to shearing of γ" particles by strongly paired dislocations.
Creep Rupture Strength and Ductility of Grade 92 Steel
Authors: Komai Nobuyoshi , Arisue Ko , Hashimoto Keita , Saito Nobuhiko , Tominaga Kimihiko 
Published: October 2024

Abstract
This study aims to elucidate the chemical compositions and microstructural factors that affect longterm creep rupture strength and creep rupture ductility using multiple heats of Gr.92 steel. Evaluating the reduction behavior in long-term creep rupture strength, we propose a relative creep rupture strength value, which is expressed as the logarithmic ratio of the estimated creep strength for each rupture time exceeding 10,000 hours, with 10,000 hours as the reference. Higher initial hardness correlates with greater pronounced strength reduction in the long-term regime. While smaller prior austenite grain sizes lead to greater reductions in creep rupture strength, this effect diminishes above 30 μm. However, no clear correlation was observed between Cr content and creep strength reduction in this study. Brittle creep ruptures with smooth test specimens were observed just below the extensometer ridge in the parallel section of test specimen, indicating notch weakening. Even in heats with excellent creep ductility, the amount of inclusions tended to be higher than in heats with lower creep ductility. Factors other than inclusions also seem to influence long-term creep ductility.
Study on Creep Rupture Properties of Inconel 617B and 10%Cr Steel Dissimilar Metal Weld
Authors: Li Songlin , Huo Xin , Li Kejian , Cai Zhipeng 
Published: October 2024

Abstract
In this paper, the dissimilar metal welds (DMWs) between 617B nickel-based alloy and 10%Cr martensitic heat-resistant steel filled by 617 filler metal was studied, focused on the high temperature creep rupture properties. The high temperature creep rupture properties of welded joints with different welding processes were tested, and the microstructure of welded joints before and after the creep rupture test was observed by OM and SEM. The results showed that, there were three failure modes: base metal failure, type W failure and interface failure, among which interface failure caused the most serious life reduction. The welded joints using ER NiCr-3 filler metal reduced the strain concentration at the interface, so the fracture location shifted from the interface to HAZ of 10%Cr martensitic heat-resistant steel under high temperature and low stress conditions, and creep rupture life was improved. Similarly, weld cap shifted the creep crack propagation path by changing the groove form, so as to altered the stress state of joint and prolong the creep rupture life.
Understanding the Kinetics of Sigma Phase Evolution in Super 304H using Lab Creep Tested Heats and Long-term Service Aged Components
Authors: Lolla T. , Siefert J. , Lee H. , Kim J. , Hashimoto K. , Komai N. , Tominaga K. 
Published: October 2024

Abstract
Super 304H is a new generation of advanced austenitic stainless steels that is increasingly being used in superheater/ reheater (SH/RH) sections of thermal ultra-supercritical steam power plants due to its high creep strength combined with good oxidation resistance and microstructure stability. However, recent studies have shown significant microstructural changes and associated degradation in creep performance during long-term service exposure in this alloy. Microstructure evolution during service and its effect on the long-term creep performance has not been comprehensively assessed. In this work, variations in the microstructure of long-term service exposed Super 304H RH tubes (~99,600 hours at 596°C steam temperature) are documented. The results for the ex-service material are compared to well-documented laboratory studies to provide perspective on improved life management practices for this mainstay advanced stainless steel.
Creep Deformation Mechanisms in IN738LC Manufactured With Laser Powder Bed Fusion
Authors: Megahed Sandra , Krämer Karl Michael , Kontermann Christian , Heinze Christoph , Udoh Annett , Weihe Stefan , Oechsner Matthias 
Published: October 2024

Abstract
This study investigates the influence of build orientation on the high-temperature mechanical properties of IN738LC manufactured via metal laser powder bed fusion (PBF-LB/M). Since the PBF-LB/M layer-wise manufacturing process significantly affects grain morphology and orientation—ranging from equiaxed to textured grains—mechanical properties typically exhibit anisotropic behavior. Samples were manufactured in three build orientations (0°, 45°, and 90°) and subjected to hot tensile and creep testing at 850°C following DIN EN ISO 6892-2 and DIN EN ISO 204 standards. While tensile properties of the 45° orientation predictably fell between those of 0° and 90° orientations, creep behavior over 100-10,000 hours revealed unexpected results: the 45° orientation demonstrated significantly shorter rupture times and faster creep rates compared to other orientations. Microstructural analysis revealed distinct creep deformation mechanisms active within different build orientations, with the accelerated creep rate in 45° specimens attributed to multiple phenomena, particularly η-phase formation and twinning. These findings provide crucial insights into the orientation-dependent creep behavior of PBF-LB/M-manufactured IN738LC components.
Influence of Solution Annealing on Creep Behavior of Additively Manufactured 316H SS Using Microstructurally Graded Specimen
Authors: Snitzer John , Lou Xiaoyuan , Wei Bingqiang , Wang Jian 
Published: October 2024

Abstract
Laser additive manufacturing (AM) is being considered by the nuclear industry to manufacture net- shape components for advanced reactors and micro reactors. Part-to-part and vendor-to-vendor variations in part quality, microstructure, and mechanical properties are common for additively manufactured components, attributing to the different processing conditions. This work demonstrates the use of microstructurally graded specimen as a high throughput means to establish the relationship between process-microstructure-creep properties. Through graded specimen manufacturing, multiple microstructures, correlated to the processing conditions, can be produced in a single specimen. The effects of a solution annealing heat treatment on the microstructure and creep properties of AM 316H are investigated in this work. Using digital image correlation (DIC), the creep strain can be calculated in these graded regions, allowing for multiple microstructures to be probed in a single creep test. The solution annealing heat treatment was not sufficient in recrystallization of the large, elongated grains in the AM material; however, it was sufficient in removing the cellular structure commonly found in AM processed alloys creating a network of subgrains in their place. The resulting changes in microstructure and mechanical properties are presented. The heat treatment was found to generally increase the minimum creep rate, reduce the minimum creep rate, and reduce the ductility. Significant amounts of grain boundary carbides and cavitation were observed.
Nitridation Resistance of Several Modern High-Temperature Nickel- and Cobalt-Based Alloys
Authors: Tossey Brett , Li Bingtao 
Published: October 2024

Abstract
Nitridation is a high-temperature material degradation issue that can occur in air and in environments containing nitrogen, ammonia, etc., and in a variety of industrial processes. The nitridation behavior of several commercial nickel- and cobalt-based alloys is reviewed in this paper. The alloys include Haynes 230, Haynes 188, Haynes 625, Haynes 617, Haynes 214, Hastelloy X, and Haynes 233. The environments discussed are high-purity nitrogen gas between 871°C and 1250°C, 100% ammonia gas at 982°C and 1092°C, and a simulated combustion atmosphere at 982°C. The results showed that nitridation occurred in all the environments containing nitrogen. The nitridation attack was strongly influenced by the alloy compositions and the type of oxide formed (i.e., chromia or alumina), as some degree of oxidation was expected in the environments in which residual oxygen was present. Thermal cycling is briefly discussed because the integrity of protective oxides is also an important factor in resisting high-temperature oxidation and nitridation attack.
Cracking of Grade 91 Steel Welds in Longer-Term Service - Case Studies
Authors: Totemeier Terry , Weiss Wendy , Studer Tony , Gressler Steven 
Published: October 2024

Abstract
This paper presents three recent example cases of cracking in Grade 91 steel welds in longer-term service in high temperature steam piping systems: two girth butt welds and one trunnion attachment weld. All the cases were in larger diameter hot reheat piping, with the service exposure of the welds ranging from approximately 85,000 to 150,000 hours. Cracking in all cases occurred by creep damage (cavitation and microcracking) in the partially transformed heat-affected zone (PTZ, aka Type IV zone) in the base metal adjacent to the welds. The location and morphology of the cracking are presented for each case along with operating conditions and potential contributors to the cracking, such as system loading, base metal chemical composition, and base metal microstructure.
Fatigue and Creep-Fatigue Evaluation of Alloy 709 at 760 and 816°C
Authors: Wang Yanli , Sham Ting-Leung 
Published: October 2024

Abstract
A significant research and development effort is underway to support the qualification of Alloy 709 as a Class A construction material in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section III, Division 5, High Temperature Reactors. This initiative includes a comprehensive Alloy 709 code qualification plan aimed at generating extensive material testing data crucial for compiling the code case data package. The data package is essential in establishing material-specific design parameters for Alloy 709 to be used as Section III, Division 5 Class A construction material for fast reactors, molten salt reactors and gas-cooled reactors. An ASME Section III, Division 5 material code case requires the evaluation of mechanical properties from a minimum of three commercial heats, covering anticipated compositional ranges. A key part of the data package involves fatigue and creep-fatigue testing at elevated temperatures, needed for developing the fatigue design curves and the damage envelope of the creep-fatigue interaction diagram (D-diagram). This paper summarizes the strain-controlled fatigue testing on three commercial heats of Alloy 709 at 760 and 816°C with strain ranges between 0.25% and 3%. The fatigue failure data are used to generate a preliminary fatigue design curve. Additionally, the creep-fatigue testing results at 816°C with tensile hold times of 10, 30, and 60 minutes are presented in support of developing the D-diagram for Alloy 709.
Estimation of Creep Strength of ASME Grade 91 Type Steel in Actual Service Conditions
Authors: Yaguchi Masatsugu , Hamaguchi Tomoaki , Yuga Masao , Nomura Kyohei , Komai Nobuyoshi 
Published: October 2024

Abstract
The creep strength of the base metals and welded joints of ASME Grade 91 type steel under actual service conditions was investigated using long-term used materials in this study. Creep tests were conducted on the materials used for hot reheat or main steam piping at power plants. The remaining creep life of each material under actual service conditions was evaluated using the Larson-Miller parameter for the test result. Then, the creep life of each material under the service condition was estimated as a summation of the service time at the plants and the remaining creep life. The estimation results were useful for examining the validity of the life evaluation formula in the long-term region because it is extremely difficult to obtain creep rupture data under such conditions owing to the long test duration. The estimated creep lives were compared with creep life evaluation curves, which were regulated for Grade 91 type steel in Japan. Regarding the base metals, the estimation results suggest that Grade 91 pipe-type steel tends to exhibit a shorter life than the 99% confidence lower limit of the evaluation curve of the material. This finding indicated that the life evaluation formula for the Grade 91 type steel base metals should be reviewed. On the other hand, the estimation results suggest that the welded joints of Grade 91 type steel generally exhibit a longer life than the 99% confidence lower limit of the evaluation curve of the material, indicating that there is no need to review the life evaluation formula for the Grade 91 type steel welded joints.
Characterization of Precipitation-Strengthening Heat-Resistant Austenitic Stainless Steels for Life-Prediction Modeling
Authors: Yamamoto Yukinori , Ren Qing-Qiang , Pillai Rishi , Hoelzer David , Brady Michael , Zhao Yajie , Poplawsky Jonathan , Lala-Curzio Edgar , Mariyappan Arul Kumar , Lebensohn Ricardo , Capolungo Laurent , Glazoff Michael , Gao Michael , Detrois Martin , Jablonski Paul , Hawk Jeffery , Alman David 
Published: October 2024

Abstract
In this study, the role of minor alloying additions in 347H stainless steels (UNS34709, ASTM A240/240M) on creep-rupture properties at 650-750°C and microstructure evolution during isothermal exposure at 750°C has been investigated, aiming to provide the experimental dataset as boundary conditions of physics-based modeling for material/component life prediction. Four different 347H heats containing various amounts of boron and nitrogen additions were prepared and evaluated. The combined additions of B and N are found to stabilize the strengthening secondary M23C6 carbides and retarding the transition from M23C6 to sigma phase precipitates during thermal exposure. The observed kinetics of microstructure evolution reasonably explains the improvement of creep-rupture properties of 347H stainless steels with the B and N additions.
Interactions Between U-Bearing Fluoride Fuel Salts and Graphite
Authors: Park Jaewoo , Leong Amanda , Zhang Jinsuo 
Published: October 2024

Abstract
A thorough understanding of interactions between graphite and fluoride fuel salts is crucial, as graphite is a promising candidate for the moderator of molten salt reactors. This study investigates the infiltration of fluoride fuel salts into graphite and the fluorination of graphite by these salts under various pressures and temperatures. A high-pressure salt infiltration test apparatus was developed to examine the infiltration of NaF-KF-UF4 and NaF-BeF2-UF4-ZrF4 fuel salts into two types of graphite at high temperatures. For tests using NaF-BeF2-UF4-ZrF4, two different temperatures were selected to assess the impact of temperature on threshold pressure. The study observed salt infiltration into graphite at pressures exceeding its threshold pressure, and the threshold pressure for infiltration was lower at the higher temperature. In addition, the formation of carbon fluorides on the surface of post-test graphite specimens was identified.
Design and Application Prototype of soft starting Three-Phase AC Motor by Using Analog Electronics Control for Teaching Aids of Power Electronics Practice
Authors: Effendi Effendi , Zakwansyah Zakwansyah 
Published: October 2024

In general, palm oil processing factories, from fresh fruit bunches to Crude Palm Oil, require three-phase electric motors to drive or rotate it. The problems that often arise when using three-phase electric motors simultaneously in large numbers will result in very large surges in the electric current, which can affect the performance of electronic devices. To overcome this problem, a prototype of a three-phase AC voltage regulator circuit was made by adjusting the SCR triggering delay angle using an analog electronics equipment control that can be used for three-phase motor soft start applications in a palm oil factory. This prototype will be used as a learning tool for the practical for Aceh Polytechnic students for power electronics courses. This system is built with a method where the three-phase source is first lowered using a transformer arranged in a star on the primary and secondary sides, then each voltage is compared to the ground using an IC LM324, which aims to produce pulses wave. This pulse then connected to a triangular wave generator circuit, this triangular wave is then compared with the DC source voltage from the potentiometer, which aims to regulate the SCR triggering angle of SCR via MOC3063 driver, where the load used is resistive and connected in a star. The measurement using an oscilloscope and observing the change of triggering angle for several variations of each phase, the different Vrms voltage between measurements compared to mathematical analysis influenced by several factors, including, the transformer is made of three transformers that not identically, the electronic components used are not in ideal condition, and observations on the oscilloscope are carried out visually using the eye and manually adjusting the potentiometer rotation so that the level of measurement accuracy between one person and another will produce different values.
Díez Oronoz, A. y Narbarte Hernández, J. PORTUARRAK. Una mirada histórica a la comunidad marítima de Hondarribia
Authors: Fernández Olivera Mariana , Sánchez Lorena Marina 
Published: October 2024

Reseña del libro PORTUARRAK. Una mirada histórica a la comunidad marítima de Hondarribia, de Diaz Oronoz, A. y Narbarte Hernández, J. (2024).
Perspektif Mahasiswa Pendidikan Matematika di Kota Langsa Terhadap Masalah Pembelajaran Matematika Pada Masa Pandemi Covid-19
Authors: Ihsan Iden Rainal , Priyanda Roni , Amalia Rizki 
Published: October 2024

Pandemi Covid-19 membawa tuntutan perubahan dan penyesuaian dalam pelaksanaan kegiatan belajar di sekolah yang beralih menjadi kegiatan pembelajaran secara daring. Hal ini tentu mendatangkan permasalahan. Pada artikel ini disajikan hasil survei yang dilakukan kepada 27 mahasiswa pendidikan matematika yang mengikuti program magang, Pengenalan Lapangan Persekolahan, terkait permasalahan pembelajaran matematika di sekolah. Survei dilakukan dua kali, pre-survey dan post-survey, yang untuk selanjutnya dilakukan komparasi terkait kedua hasil yang diperoleh. Dikaji juga perspektif mahasiswa dalam hal permasalahan pembelajaran matematika yang relevan untuk dikaji pada masa pandemi Covid-19. Hasil survei pertama terhadap perspektif mahasiswa menunjukan permasalahan pembelajaran matematika sekolah terbesar adalah masalah kompetensi kognitif peserta didik yang masih rendah, kemudan hasil survei kedua setelah mahasiswa mengikuti kegiatan pengenalan lapangan persekolahan masalah yang sering muncul adalah rendahnya minat peserta didik dalam belajar, secara lebih teperinci terdapat 5 topik teratas menurut perspektif mahasiswa, yakni kesulitan belajar, minat, media, desain, dan prestasi (dalam hal ini kompetensi kognitif). Kata Kunci: pembelajaran daring, pembelajaran matematika, perspektif.
Peningkatan Kemampuan Pemahaman Konsep Matematika Siswa SMP melalui Model Pembelajaran Pair Check
Authors: Rahmadani Risma , Jusniani Nia , Muhammad Guntur Maulana 
Published: October 2024

Penelitian ini bertujuan untuk mengetahui peningkatan kemampuan pemahaman konsep matematika, dan sikap siswa terhadap pembelajaran matematika dengan menggunakan model pembelajaran Pair Check. Metode yang digunakan dalam penelitian ini adalah quasi experiment dengan desain nonequivalent pretest-posttest control group. Instrumen yang digunakan adalah soal tes uraian dan instrumen non tes berupa skala sikap. Data yang diperoleh dari hasil penelitian ini diolah menggunakan bantuan program software SPSS versi 24 dengan criteria uji normalitas, uji homogenitas, dan uji perbedaan dua rata-rata. Hasil penelitian menunjukkan bahwa peningkatan kemampuan pemahaman konsep matematika siswa dengan menggunakan model pembelajaran Pair Check lebih baik dari pada peningkatan kemampuan pemahaman konsep matematika siswa dengan menggunakan pembelajaran biasa. Selain itu hasil skala sikap menunjukkan bahwa pada umumnya siswa bersikap positif terhadap model pembelajaran PairCheck.Kata Kunci : Pemahaman Konsep Matematika, Model Pembelajaran Pair Check.
Meta Analisis Penggunaan Model PBL Guna Meningkatkan Kemampuan Literasi Matematika Siswa
Authors: Dinata Oto Iskandar 
Published: October 2024

Mendiagnosa kesulitan siswa merupakan langkah utama daripada merancang dan mengelola kegiatan belajar di kelas. Penelitian ini bertujuan menganalisis penemuan mengenai peningkatan literasi matematika pada siswa sekolah dasar menggunakan PBL. PBL adalah model yang bertaut siswa turut aktif dengan memberikan suatu masalah pada siswa. Sehingga, siswa akan terlibat langsung dalam pembelajaran. Secara harfiah, literasi berarti kecakapan matika guna pengembangan pendidikan matematika. Penelitian ini menggunakan metode penelitian meta analisis. metode penelitian yang digunakan adalah meta analisis. metode meta analisis yaitu metode dengan cara mencari, merangkum, kemudian melakukan analisis dari artikel ilmiah sebelumnya. Pengumpulan data dilakukan dengan mencari 30 artikel terakreditasi nasional dan 20 artikel terakreditasi internasional yang membahas penggunaan model PBL guna meningkatkan kemampuan literasi matematika siswa. Dari total artikel, peneliti memperoleh 5 artikel terindeks Sinta, 1 artikel terindeks Garuda, 1 artikel terindeks Google Scholar yang memeuhi kriteria. Penelitian ini bertujuan menganalisis penemuan atau penelitian sebelumnya tentang penggunaan model PBL terhadap kemampuan literasi matematika. Hasil meta analisis membuktikan bahwa penerapan model PBL dalam proses pembelajaran mampu meningkatkan kemampuan literasi matematika yang semula terendah 7,65% sampai tertinggi 48,27% sehingga terjadi peningkatan sangat signifikan yaitu 29,0138%.