bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Large Sand Casting of Haynes 282 for A-USC Turbine
Authors: Thangirala (Mani) Subrahmanyam , Myers James 
Published: March 2024

Abstract
The United States Department of Energy Office of Fossil Energy and the Ohio Coal Development Office (OCDO) have led a U.S. consortium tasked with development of the materials technology necessary to build an advanced-ultra-Supercritical (A-USC) steam boiler and turbine with steam temperatures up to 760°C (1400°F). Part of this effort has focused on the need for higher temperature capable materials for steam turbine components, specifically cast nickel-base superalloys such as Haynes 282 alloy. As the size of the needed components is much larger than is capable of being produced by vacuum casting methods typically used for these alloys, an alternative casting process has been developed to produce the required component sizes in Haynes 282 alloy. The development effort has progressed from production of sub-scale sand castings to full size sand and centrifugal castings. The aim of this work was to characterize the microstructure and properties of a nickel alloy 282 casting with section size and casting weights consistent with a full sized component. A 2720 kg (6000 lbs.) nickel alloy 282 sand casting was produced and heat treated at MetalTek International. The casting was a half valve body configuration with a gating system simulated and optimized to be consistent with a full sized part. Following casting, heat treatment and NDE inspections, the half valve body was sectioned and tested. Tensile and high temperature creep was performed on material from different casting section thicknesses. Further analysis of the microstructure was carried out using light microscopy (LM), scanning electron microscopy (SEM), and X-ray spectroscopy (EDS). The paper also presents the mechanical properties obtained from the various sections of the large casting.
Analysis, Assessment and Processing of the Recirculation Pump Casing Damage in the Power Plant Staudinger Unit 5
Authors: Bader M. , Bagaviev A. , Kaufhold E. , Wolf H.-W. 
Published: March 2024

Abstract
A failure of the upper casing of the circulation pump led to a big damage in the PP Staudinger unit 5 on 12th of May 2014. According to the §18(2) BetrSichV an extensive root cause analysis (RCA) was started. From the beginning on different lines of activities were initiated to handle the situation with the required diligence. Decisions were made, taking into account safety regulations, possibility of repair and best practice engineering. Following the board decision to repair the unit 5, a lot of detailed work was done. All of the performed work packages were linked in different timelines and needed to meet in the key points. Consequently it was a challenge to achieve the agreed date of unit 5 restart on 15th of January 2015. The unit restart on the targeted date was a proof of the excellent collaboration between all involved parties. The presentation gives a summarizing overview about the damage, the main results of the RCA and the repair activities.
Corrosion of Nickel-Base Alloys by Supercritical CO2
Authors: Olivares R.I , Stein W. , Nguyen T.D. , Young D.J. 
Published: March 2024

Abstract
Nickel-base alloys were exposed to flowing supercritical CO2 (P = 20MPa) at temperatures of 700 to 1000°C for up to 1000 h. For comparison, 316L stainless steel was similarly exposed at 650°C. To simulate likely service conditions, tubular samples of each alloy were internally pressurised by flowing CO2, inducing hoop stresses up to 35 MPa in the tube walls. Materials tested were Haynes alloys 188, 230 and 282, plus HR120 and HR160. These alloys developed chromia scales and, to different extents, an internal oxidation zone. In addition, chromium-rich carbides precipitated within the alloys. Air aging experiments enabled a distinction between carburisation reactions and carbide precipitation as a result of alloy equilibration. The stainless steel was much less resistant to CO2 attack, rapidly entering breakaway corrosion, developing an external iron-rich oxide scale and internal carburisation. Results are discussed with reference to alloy chromium diffusion and carbon permeation of oxide scales.
Development of Matching Welding Consumables for Boron/Cobalt Alloyed 9%Cr-Mo Steels and the Weld Metal Properties
Authors: Zhang Zhuyao , Golding Mark , Bouillot Claude 
Published: March 2024

Abstract
Despite the significant progress achieved in power generation technologies in the past two decades, finding effective solutions to further reduce emissions of harmful gases from thermal power plant still remains the major challenge for the power generation industry as well as alloy material developers. In the European material programmes COST 522 and COST 536, based on the existing 9-12%Cr creep resisting steels, an advanced 9%Cr-Mo martensitic alloy, C(F)B2 (GX13CrMoCoVNbNB9-2-1) alloy has been developed. By modification through alloying of boron and cobalt and together with other micro-adjustment of the composition, C(F)B2 alloys has showed very encouraging properties. The current paper summaries the development and evaluation of the matching filler metals for C(F)B2 grade. The design of the filler metal composition is discussed and comparison is made with the parent materials in respect to the alloy additions and microstructure. The mechanical properties of the weld metals at ambient temperature are examined. Creep properties of both undiluted weld metals and cross-weld joints are examined through stress rupture test and the data are evaluated and compared with those of the base alloy and other existing 9%Cr-Mo creep resisting steels.
Microstructural Characterisation of Creep Tested 9Cr Welds for MarBN Steel
Authors: Guo J. , Jepson M. A. E. , Thomson R. C. 
Published: March 2024

Abstract
Creep properties of 9Cr heat resistant steels can be improved by the addition of boron and nitrogen to produce martensitic boron-nitrogen strengthened steels (MarBN). The joining of this material is a crucial consideration in the material design since welds can introduce relatively weak points in the structural material. In the present study, creep tests of a number of MarBN weld filler metals have been carried out to determine the effect of chemistry on the creep life of weld metal. The creep life of the weld metals was analysed, and the evolution of creep damage was investigated. Significant differences in the rupture life during creep have been observed as a function of boron, nitrogen and molybdenum concentrations in the weld consumable composition. Although the creep lives differed, the particle size and number in the failed creep tested specimens were similar, which indicates that there is a possible critical point for MarBN weld filler metal creep failure.
The Evolutionary Behavior of Laves Phase in Virgin FB2 Steel During Welding and Its Effect on Weld Joints
Authors: Li Kejian , Cai Zhipeng , Pan Jiluan 
Published: March 2024

Abstract
In 9~12% Cr containing martensitic stainless steels, Laves phase usually occurs after long term high temperature exposure, while in the present work, some sparse relatively large particles of (Fe,Cr)2Mo type Laves phase were observed in virgin FB2 steel. It is speculated that the large Laves phase particles formed in casting process due to dendritic segregation. Then the evolutionary behavior of Laves phase during welding thermal cycle was studied and constitutional liquation of Laves phase was found, suggesting a liquation crack tendency in FB2 steel. At last, the hot ductility tests showed that the area where constitutional liquation occurred would act as crack initiation site, and the tested specimen fractured without any obvious plastic deformation. This work provided some guidance for the practical production of welded turbine rotors made of FB2 steel.
Effect of Aging on Creep Strength of Grade 91 Steel Weld Metal
Authors: Nakahashi Sosuke , Yaguchi Masatsugu , Tamura Koji , Minami Yusuke 
Published: March 2024

Abstract
Type IV damage is observed in creep-strength-enhanced ferritic (CSEF) steel used in USC plants and the research on the evaluation of such damage has been carried out in the world. Type I failure is recently reported in welded joint of Gr.91 so that the importance of the evaluation of the creep strength of the weld metal is increasing. In this study, the change in hardness with aging and creep strength before and after aging were evaluated to determine the creep strength of the weld metal of Gr.91. The hardness of the weld metal subjected to aging significantly decreased compared with that of the base metal and the heat-affected zone (HAZ). The creep strength of the weld metal was also decreased by aging. From these results, it is suggested that the failure morphology of Gr.91 steel welded joint used for a long term may change from type IV to type I.
Assessment and Quantification of Damage in the Grade 91 Steel Partially Transformed Zone
Authors: Siefert John A. , Parker Jonathan D. , MacLachlan Ryan , Yan Sabrina , Thomson Rachel 
Published: March 2024

Abstract
Damage in the grade 91 steel partially transformed zone of weld heat affected zones has historically been associated with many different types of microstructural features. Features described as being responsible for the nucleation of creep damage include particles such as laves phase, coarse M23C6, inclusions, nitrides, or interactions between creep strong and creep week grains, grain boundaries and potentially other sources. Few studies have attempted to link the observations of damage on scales of increasing detail from macro, to micro, to nano. Similarly, assessments are not made on a statistically relevant basis using 2D or 3D microscopy techniques. In the present paper, 2D assessment using scanning electron microscopy (SEM) and quantification techniques such as energy dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) are utilized in combination with 3D serial sectioning of large volumes using plasma focused ion beam milling (P-FIB) and simultaneous EDS to evaluate an interrupted cross-weld creep test. Moreover, the sample selected for examination was from a feature cross-weld creep test made using a parent material susceptible to the evolution of creep damage. The test conditions were selected to give creep brittle behaviour and the sample was from a test interrupted at an estimated life fraction of 60%. The findings from these evaluations provide perspective on the features in the microstructure responsible for the nucleation and subsequent growth of the observed damage.
Microstructural Evaluation in Heat-Affected Zone of 9Cr-3W-3Co-Nd-B Heat-Resistant Steel
Authors: Hamaguchi Tomoaki , Kurihara Shinnosuke , Hirata Hiroyuki , Okada Hirokazu 
Published: March 2024

Abstract
A newly developed ferritic heat-resistant steel; 9Cr-3W-3Co-Nd-B steel has higher creep rupture strength both in the base metal and welded joints than the conventional high-Cr ferritic heat-resistant steels. The creep rupture strengths of 9Cr-3W-3Co-Nd-B steel welded joints were below the lower limit of the base metal in long-term creep stage more than 20,000 hours. The creep rupture position was heat-affected zone (HAZ) from 1.0 to 1.5 mm apart from the fusion line on the welded joint specimen ruptured at 34,966 hours. The equiaxed subgrains and coarsened precipitates were observed in HAZ of the ruptured specimen. In order to clarify the creep fracture mechanism of the welded joints, the microstructures of HAZ were simulated by heat cycle of weld, then observed by EBSD analysis. Fine austenite grains formed along the prior austenite grain boundaries in the material heated just above AC3 transformation temperature, however there were no fine grains such as conventional steel welded joints. The prior austenite grain boundaries were unclear in the material heated at 1050 °C. The creep rupture life of the material heated at just above AC3 transformation temperature exceeded the lower limit of base metal and there was no remarkable degradation, although it was shorter than the other simulated materials. It is, therefore, concluded that the creep fracture of 9Cr-3W-3Co-Nd-B steel welded joint in long-term stage occurred at HAZ heated at from just above AC3 transformation temperature to 1050 °C. It is speculated that the fine austenite grains formed along the prior austenite grain boundaries and inhomogeneous microstructures cause the coarsening precipitates and recovery of lath structure during long-term creep deformation.
Relationship of Long-Term Creep Rupture Strength between Base Metal and Weldment in Mod.9Cr-1Mo Steels
Authors: Arisue Ko , Komai Nobuyoshi , Tominaga Kimihiko , Fujita Masaaki 
Published: March 2024

Abstract
Long-term creep rupture tests up to 105 hours at 600℃ and 650℃ were carried out on mod.9Cr- 1Mo steel base metal and weldments from five different materials, consisting of various chemical compositions and heat treatments as well as welding conditions. As a result, positive correlations of creep rupture strength were clarified between the base metal and weldments from the same materials. Microstructural observations and thermokinetic calculations revealed that the strength correlations were attributed to the precipitation strengthening behavior of finely dispersed M23C6 carbides and V-type MX carbonitrides, where their precipitation distribution characteristic in the fine-grained HAZ microstructures partially or almost entirely took over those in base metal. This finding implies that the long-term creep rupture strength of mod.9Cr-1Mo steel weldment might be able to be evaluated as long as the corresponding base metal strength is obtained.
Martensitic Steel CPJ7 for Improved High-Temperature Creep Capabilities in Power Plants
Authors: Detrois Martin , Jablonski Paul D. , Hawk Jeffrey A. 
Published: March 2024

Abstract
A creep resistant martensitic steel, CPJ7, was developed with an operating temperature approaching 650°C. The design originated from computational modeling for phase stability and precipitate strengthening using fifteen constituent elements. Approximately twenty heats of CPJ7, each weighing ~7 kg, were vacuum induction melted. A computationally optimized heat treatment schedule was developed to homogenize the ingots prior to hot forging and rolling. Overall, wrought and cast versions of CPJ7 present superior creep properties when compared to wrought and cast versions of COST alloys for turbines and wrought and cast versions of P91/92 for boiler applications. For instance, the Larson Miller Parameter curve for CPJ7 at 650°C almost coincides with that of COST E at 620°C. The prolonged creep life was attributed to slowing down the process of the destabilization of the MX and M23C6 precipitates at 650°C. The cast version of CPJ7 also revealed superior mechanical performance, well above commercially available cast 9% Cr martensitic steel or derivatives. The casting process employed slow cooling to simulate the conditions of a thick wall full-size steam turbine casing but utilized a separate homogenization step prior to final normalization and tempering. To advance the development of CPJ7 for commercial applications, a process was used to scale up the production of the alloy using vacuum induction melting (VIM) and electroslag remelting (ESR), and underlined the importance of melt processing control of minor and trace elements in these advanced alloys.
Degradation Mechanism of Long-Term Creep Rupture Strength in Gr.23 (2.25Cr-1.6W) Steel
Authors: Komai Nobuyoshi , Imazato Toshiyuki , Tominaga Kimihiko , Fujita Masaaki 
Published: March 2024

Abstract
Creep strength degradation behavior of normalized and tempered 2.25Cr-1.6W-V-Nb(Gr.23) steel was investigated by conducting extra long-term creep rupture tests. Creep strength drop was observed in long-term creep range at 600°C and above, while signs of a creep strength drop were not identified at 550°C and 575°C. Creep strength drop of around 110 MPa at 600°C was caused not by the effect of oxidation but rather by a change of the deformation mechanism or the weakening of deformation resistance by the microstructural change during creep. The effect of oxidation was significant for causing a further creep strength drop in the range which exceeded 20,000 h in rupture time at 600°C. As a result, the creep strength at 60 MPa and 600°C was almost the same regardless of long tempered or aged steel.
Grain Boundary Design Using Precipitation of Delta-Ni3Nb Phase for Ni-Based Wrought Alloys
Authors: Kobayashi Satoru , Otsuka Tomoki , Takeyama Masao , Aoki Chuya , Ueno Tomonori 
Published: March 2024

Abstract
Effects of alloying additions of Ti or Mo to a simplified chemical composition of the γ′′-Ni3Nb strengthened type Ni-based alloy 718 on the precipitation mode of δ-Ni3Nb phase were investigated to aim at designing grain boundaries using the δ phase for raising temperature capability of the γ′′ strengthened Ni-based wrought alloys. In the base alloy of Ni-22Cr-16Fe-3.5Nb, the δ phase precipitated at the grain boundaries of the matrix phase in a platelet form by continuous precipitation mode at temperatures above 1273K (1000°C) but in a lamellar morphology by discontinuous precipitation mode below that temperature. The boundary temperature where the continuous/discontinuous precipitation mode changes was raised by addition of 1 % Ti and lowered by addition of 5% Mo. The increase in the boundary temperature by Ti addition can be considered to have occurred by an increase in the solvus temperature of γ′′ phase. The decrease in the boundary temperature by Mo addition can be interpreted by the reduction of the strain energy caused by the coherent γ′′ precipitates and/or the volume change by the formation of δ phase from the γ/γ′′ phases, which may promote the continuous precipitation with respect to the discontinuous precipitation.
Desulfurization Mechanism of Molten Ni-Base Superalloy Containing Al Using CaO Rod
Authors: Kishimoto Yuki , Iguchi Taketo , Kono Takaaki , Yokokawa Tadaharu , Osawa Makoto , Kawagishi Kyoko , Suzuki Shinsuke , Harada Hiroshi 
Published: March 2024

Abstract
It is required to reduce the lifetime cost of turbine blades. To achieve the cost reduction, a refining and recycling method of scrapped turbine blades is proposed. For the establishment of the method, desulfurization mechanism of Ni-base superalloy by solid CaO was studied. 500 g of superalloy containing sulfur was heated in a vacuum induction furnace and kept at 1600 °C. A CaO rod was inserted into the molten alloy and held for 600 s. After the experiment, sulfur content in the alloy decreased from 200 ppm to 54 ppm. On the surface of the CaO rod after the experiment, only Ca, O, Al, and S were found by EPMA analysis. Especially, Al and S were distributed at the surface and grain boundaries of the rod. By powder XRD analysis, CaO, CaS and 3CaO･Al2O3 were identified as constituent phases on the rod. The desulfurization mechanism of superalloy at 1600 °C is supposed to be three steps: (1) Al and S in the alloy react with CaO to generate CaS and Al2O3, respectively. (2) Al2O3 melts with CaO as liquid slag. (3) CaS is captured by the slag, therefore, sulfur is removed from the alloy.
Generation Behavior of Abnormally Large Grain in Superalloy 718
Authors: Aoki Chuya , Date Masayoshi , Ueno Tomonori , Ohno Takehiro , Oikawa Katsunari 
Published: March 2024

Abstract
The behavior of strain-induced abnormal grain growth (AGG) in superalloy 718 has been investigated using compression testing and subsequent heat treatment below the d-phase solvus temperature of 980 °C. The nuclei of AGG grains were slightly newly recrystallized grains by a nucleation because small grains without dislocation was observed in the as- deformed microstructure. AGG was caused by the difference in intragranular misorientation (related to the stored strain energy in a grain) between dynamic recrystallized grains and deformed matrix. The initiation of AGG was retarded with decreasing plastic strain and produced microstructures consisted of larger grains having more complex morphology. It was observed that grain boundary migrated locally in the direction perpendicular to, or mainly in the direction parallel to the S3 {111} twin boundaries along with the formation of high-order twins. As a result of multiple twinning, AGG grains seemed to evolve with the growing directions changed.
An Economical 1-Step Aging Treatment for Haynes 282 Superalloy—Effects on Microstructure and High-Temperature Properties
Authors: Terner Mathieu , Shin Kyeong-Yong , Kim Jin-Hyeok , Hong Hyun-Uk , Kong Byeong-Ook 
Published: March 2024

Abstract
Haynes 282 is a great candidate to meet advanced ultra-super-critical (A-USC) steam conditions in modern coal-fired power plants. The standard 2-step aging treatment has been designed for optimizing microstructure therefore providing excellent mechanical properties. We studied an alternative, more economical, 1-step aging treatment and compared microstructure, tensile properties at 750˚C and deformation behavior. Moreover, three cooling rates from the solution temperature were studied to simulate large-scale components conditions. We found that as much as about 20% of fine spherical intragranular γ' particles were successfully precipitated in all cases. Their average size increased as the cooling rate decreased. All four heat-treated alloys exhibited good mechanical properties at 750˚C with a yield strength well over 620MPa. As expected, the yield strength increased and the ductility decreased as the average γ' size decreased. The alloys exhibited a mixed mode of deformation, though the dominant deformation mechanism depended on the different γ' characteristics. The major operative deformation mechanism could be well predicted by strength increment calculations based on the precipitation strengthening model. Our results suggest that wrought Haynes 282 produced by a more economical 1-step aging treatment may be a reliable candidate for high temperature applications under A-USC conditions.
Characterization of Ni-Based Alloys for Advanced Ultra-Supercritical Power Plants
Authors: Chen Xiang , Tortorelli Peter , Shyam Amit , Santella Michael , Dryepondt Sebastien , Unocic Kinga A. , Lara-Curzio Edgar , Maziasz Philip 
Published: March 2024

Abstract
The harsh operating conditions of Advanced Ultra-Supercritical (A-USC) power plants, i.e., steam operation conditions up to 760°C (1400°F)/35 MPa (5000 psi), require the use of Ni-based alloys with high temperature performance. Currently, the U.S. Department of Energy Fossil Energy program together with Electric Power Research Institute (EPRI) and Energy Industries of Ohio (EIO) is pursuing a Component Test (Comets) project to address material- and manufacturing-related issues for A-USC applications. Oak Ridge National Laboratory (ORNL) is supporting this project in the areas of mechanical and microstructure characterization, weld evaluation, environmental effect studies, etc. In this work, we present results from these activities on two promising Ni-based alloys and their weldments for A-USC applications, i.e., Haynes 282 and Inconel 740H. Detailed results include microhardness, tensile, air and environmental creep, low cycle fatigue, creep-fatigue, environmental high cycle fatigue, and supporting microstructural characterization.