bluuebunny/crossref_metadata_2025_split huggingface dataset:
Creep Damage Assessment of 47Ni-23Cr-23Fe-7W Alloy
Authors: Shioda Yoshiki , Nakagawa Hirokatsu , Nomura Kyohei , Yamazaki Naoki , Kubushiro Keiji 
Published: March 2024

Abstract
In order to establish a creep damage assessment method for 47Ni-23Cr-23Fe-7W (HR6W), which is a candidate material of A-USC, microstructure observation of creep interrupted specimens and ruptured specimen was conducted, and the creep damage process was examined. Creep tests were conducted under conditions of 800°C, 70 MPa, 700°C, and 100 MPa. For creep damage assessment, an optical microscope was used for replicas sampled from the outer surface of specimens, and crack ratio at grain boundaries was assessed. The results indicated that creep voids and cracks were initiated at grain boundaries from about 0.35 of creep life ratio, and crack ratio increased drastically after creep life ratio of 0.65. This crack ratio was almost the same regardless of the specimen shape Therefore, the method to assess crack ratio using replicas is considered to be an effective method for creep damage assessment of HR6W. An increase in the crack ratio due to an increase in creep life ratio showed the same trend as the change in elongation of creep interrupted specimens. Microstructure observations were conducted with interrupted specimens using SEM-ECCI (Electron Channeling Contrast Imaging) in order to clarify the cause of acceleration creep. The results showed that sub-boundary developed significantly near grain boundaries, which indicates that sub-boundary development may cause acceleration.
Study on the Test Method of Oxide Scale Adhesion inside Superheater/Reheater Tubes Based on Image Recognition
Authors: Guo Junwen , Ma Jianmin , Qiao Yue , Li Zhigang , Niu Kun , Yan Aijun , Hao Le , Wen Wu , Yan Xiaojiang 
Published: March 2024

Abstract
The fall-off of oxide scale with poor adhesion inside superheater/reheater tubes in boilers for (ultra) supercritical power unit is the main cause of accidents such as superheater/reheater blockage, tube explosion and solid particle erosion in the steam turbine which cause serious economic losses. However, there is still no method for testing and assessing the adhesion of oxide scale inside the tube. A method for testing the adhesion of corrosion products in tubes by spiral lines is proposed in this paper, and the accuracy of adhesion evaluation is improved by adopting the image recognition method.
A Study of Sigma Phase Evolution in Long-Term Creep Tested Super 304H Samples
Authors: Lolla Tapasvi , Siefert John , West Geoff , Gagliano Mike 
Published: March 2024

Abstract
Due to their excellent high temperature oxidation resistance, utilities worldwide are adopting advanced austenitic stainless steels (A-ASS) for critical plant components, such as heat exchangers, as they aim to achieve higher operating conditions. However, challenges may be encountered in developing life assessment and life management strategies for such components. This is because conventional methods used for life assessment, such as measuring steam side oxide scale thickness in ferritic and conventional austenitic material to predict tube metal temperature, may not be successfully applied to A-ASS. In such instances, tracking the formation and evolution of microstructural features during service, may offer a possible method to predict the temperature of these steels. For such metallurgy based lifing strategy to be successful, it is essential to develop a good understanding of microstructure evolution in these steels. In this work one heat of Super 304H, that has been creep tested at 600°C, 650°C and 700°C, with applied stress ranging from 110 to 340 MPa, is characterized using a combination of advanced characterization tools and image analysis methods. The amount of sigma phase formed at the gauge and grip sections of the samples is quantified and the methodology used to quantify this phase is presented. From the results, a time-temperature-transformation diagram for sigma formation is developed.
Experimental Study of Extruded Powder Metallurgy γ-TiAl Based Alloys
Authors: Huvelin Z. , Perrut M. , Bachelier-Locq A. , Sallot P. 
Published: March 2024

Abstract
In the context of research of lighter and/or stronger high temperature materials in order to improve aeroengines, the present work shows an example of a powder metallurgy (PM) manufacturing route for TiAl alloys that could be used for low pressure turbine (LPT) blades processing. In this frame, two different alloys, Ti-47Al-1Fe-1Zr-1Mo-0.2Si (at. %) FZM and Ti- 43.5A1-4Nb-1Mo-0.1B (at.%) TNM-B1, were gas-atomized into powders, extruded, heat-treated and mechanically tested.
Effect of Heat Treatment on Microstructure and Mechanical Properties of Dual Two-Phase Ni3Al and Ni3V Intermetallic Alloys
Authors: Ioroi Kazushige , Kaneno Yasuyuki , TakasugiI Takayuki , Semboshi Satoshi 
Published: March 2024

Abstract
So-called Ni base dual two-phase intermetallic alloys are composed of primary Ni3Al (L12) phase precipitates among eutectoid microstructures consisting of the Ni3Al and Ni3V (D022) phases. In this article, microstructural refinement of an alloy with a nominal composition of Ni75Al10V15 (in at.%) was attempted by various heat treatment processes. When the alloy was continuously cooled down after solution treatment, fine and cuboidal Ni3Al precipitates were developed by rapid cooling while coarse, rounded and coalesced Ni3Al precipitates were developed by slow cooling. When the alloy was isothermally annealed at temperatures above the eutectoid temperature, the morphology of the Ni3Al precipitates changed from fine and cuboidal one to large and rounded one with increase in annealing time. When the alloy was annealed at temperatures below the eutectoid temperature, the Ni3Al precipitates were grown keeping cuboidal morphology. The morphological change from the cuboidal to rounded Ni3Al precipitates was induced by the transition from the growth driven by elastic interaction energy between the precipitate and matrix to that by the surface energy of the precipitate. Fine and cuboidal Ni3Al precipitates generally resulted in high hardness.
Effect of Dissolved Oxygen Level on Stress Corrosion Cracking Susceptibility of Structural Steels
Authors: Jun Jiheon , Raiman Stephen S. , De Las Casas Aranda Rogelio , Pint Bruce A. 
Published: March 2024

Abstract
Stress corrosion cracking (SCC) is a potential risk in structural steels used for steam boilers. To investigate the effect of dissolved oxygen (DO) on SCC susceptibility, three steels, T23, T24 and T91 were annealed at 1065°C and then quenched to create a susceptible microstructure and then exposed in a Jones test to stagnant and circulating water at 200°C with varying DO levels. The results indicated that among the tested steels, the SCC susceptibility was highest in T91 but lowest in T23 which did not exhibit crack initiation with 100 ppb DO. T24 showed no cracking with 50 ppb DO but cracked with 100 ppb DO under these conditions. Based on these results, the next planned step is to monitor crack growth in-situ and determine a critical DO content for each material.
Long-Term Performance of High Temperature Alloys in Oxidizing Environments and Supercritical CO2
Authors: Deodeshmukh V. P. , Pint B. A. 
Published: March 2024

Abstract
Long-term performance of high temperature alloys is critically linked to the oxidation behavior in power generation applications in wet air and steam. As power generation systems move towards higher efficiency operation, nextgeneration fossil, nuclear and concentrating solar power plants are considering supercritical CO2 cycle above 700°C. Wrought solid solution strengthened and precipitations strengthened alloys are leading candidates for both steam and Supercritical CO2 power cycles. This study evaluates the cyclic oxidation behavior of HAYNES 230, 282, and 625 alloys in wet air, flowing laboratory air, steam and in 1 and 300 bar Supercritical CO2 at ~750°C for duration of 1000 -10,000h. Test samples were thermally cycled for various times at temperature followed by cooling to room temperature. Alloy performances were assessed by analyzing the weight change behavior and extent of attack. The results clearly demonstrated the effects of alloy composition and environment on the long-term cyclic oxidation resistance. The extents of attack varied from alloy to alloy but none of the alloys underwent catastrophic corrosion and no significant internal carburization was observed in supercritical CO2. The performance of these alloys indicates that these materials are compatible not only in oxidizing environments, but also in Supercritical CO2 environments for extended service operation.
Research on On-line Detection Technology of Oxide Scale Based on Magnetic Sensitivity and Granularity Behavior
Authors: Aijun Yan , Zhigang Li , Hongnian Dong , Yue Qiao , Chen Hao , Shunsen Wang , Li Fang , Jingru Mao , Kang Chen , Jiacheng Wang , Jingyi Du 
Published: March 2024

Abstract
The oxide exfoliation is one of the main problems that cause the explosion of superheater or reheater, which threaten the safety of power plant units, but there is no direct test method of the particle concentration of the scales in high temperature steam. Based on the study of ferromagnetic and optical characteristics of scales, the technology and equipment were developed for on-line measurement based on magnetic sensitivity and granularity behavior. Through numerical simulation and dynamic simulation experiments of scale movement under high temperature and high pressure steam, calculating method of the particle concertation of scales in the main steam or reheated steam pipeline was retrieved by local sampling concentration.
Approaches to Modeling Fireside Corrosion of Superheater/Reheater Tubes in Coal and Biomass Fired Combustion Power Plants
Authors: Simms N J , Ekpe B , Riccio C , Mori S , Sumner J , Oakey J E 
Published: March 2024

Abstract
The combustion of coal and biomass fuels in power plants generates deposits on the surfaces of superheater / reheater tubes that can lead to fireside corrosion. This type of materials degradation can limit the lives of such tubes in the long term, and better methods are needed to produce predictive models for such damage. This paper reports on four different approaches that are being investigated to tackle the challenge of modelling fireside corrosion damage on superheaters / reheaters: (a) CFD models to predict deposition onto tube surfaces; (b) generation of a database of available fireside corrosion data; (c) development of mechanistic and statistically based models of fireside corrosion from laboratory exposures and dimensional metrology; (d) statistical analysis of plant derived fireside corrosion datasets using multi-variable statistical techniques, such as Partial Least Squares Regression (PLSR). An improved understanding of the factors that influence fireside corrosion is resulting from the use of a combination of these different approaches to develop a suite of models for fireside corrosion damage.
Investigating the Electrical Resistance Technique for Structural Alloy Corrosion Monitoring within Supercritical CO2 Power Cycles
Authors: Walker Matthew , Chames Jeff , Cebrian Javier , Vega Heidy 
Published: March 2024

Abstract
Structural alloy corrosion is a major concern for the design and operation of supercritical carbon dioxide (sCO2) power cycles. Looking towards the future of sCO2 system development, the ability to measure real-time alloy corrosion would be invaluable to informing operation and maintenance of these systems. Sandia has recently explored methods available for in-situ alloy corrosion monitoring. Electrical resistance (ER) was chosen for initial tests due the operational simplicity and commercial availability. A series of long duration (&gt;1000 hours) experiments have recently been completed at a range of temperatures (400-700°C) using ER probes made from four important structural alloys (C1010 Carbon Steel, 410ss, 304L, 316L) being considered for sCO2 systems. Results from these tests are presented, including correlations between the probe measured corrosion rate to that for witness coupons of the same alloys.
Status of Large Scale Manufacture of Nickel Alloy Turbine Rotor Forgings for A-USC Steam Power Plants
Authors: Donth B. , Blaes N. , Diwo A. , Böttcher D. 
Published: March 2024

Abstract
The need to reduce carbon dioxide emissions of new fossil power plants is one of the biggest challenges of mankind in the next decades. In this context increasing net efficiency is the most important aspect which has led to the development of not only new steels for potential plant operation up to 650°C, but also to forged nickel alloys for 700°C and maybe 750°C. For steam temperatures of 700°C Alloy 617 and variants like TOS1x have been already intensively investigated, and manufacturability of large rotor parts was demonstrated. For operation temperatures of 750°C, only the use of γ‘ age-hardenable nickel base alloys is possible. Alloy 263 is one of the most promising alloys for manufacturing large forged components. For this material grade Saarschmiede has produced successfully a large rotor forging for the first time. Considering the complexity in manufacturing large nickel base alloy forgings, the implementation of simulation tools for calculation and optimization of production parameters becomes especially important. Numerical simulation methods are essential to predict material behavior and to optimize material quality-related manufacturing steps. In reference to mechanical properties, microstructure, uniformity of chemical composition FEM computer simulations for the key manufacturing processes re-melting, forging and heat treatment are in application. This paper will present the current status of production of very large prototype nickel base alloy rotor forgings for 700°C and 750°C A-USC power plants. Test results of an Alloy 617 large full scale turbine rotor component recently with improved properties produced will be highlighted. Experiences and results in applying numeric simulation models to ingot manufacturing and forging will also be reported.
Analysis of Steam Valve Jam of Turbine Served for 8541 Hours at 600 °C
Authors: Fan Z.D. , Ma J.M. , Ke Y.J. , Zhang Z.B. , Liu L.C. , Ma Y.C. , Yan A.J. 
Published: March 2024

Abstract
Both of high pressure main throttle valves and one governing valves were jammed during the cold start of steam turbine served for 8541 hours at 600 °C in an ultra supercritical power plant. Other potential failure mechanisms were ruled out through a process of elimination, such as low oil pressure of digital electro-hydraulic control system, jam of orifice in the hydraulic servo-motor, and the severe bending of valve stem. The root cause was found to be oxide scales plugged in clearances between the valve disc and its bushing. These oxide scales are about 100~200 μm in thickness while the valve clearances are about 210~460 μm at room temperature. These oxide scales are mainly composed of Fe3O4 and Fe2O3 with other tiny phases. Both of valve disc and its bushing were treated with surface nitriding in order to improve its fatigue resistance, which unexpectedly reduces the steam oxidation resistance. On the other hand, significant fluctuation of valve inner wall temperature during operation accelerated the exfoliation of oxide scales, and the absence of full stroke test induced the gradual accumulation of scales in valve clearances. In light of the steam valve jam mechanism in the present case, treatments in aspects of operation and resistance to steam oxidation are recommended.
Development of High Creep Resistant 9%Cr MarBN Steels for Forgings in Advanced Steam Turbines up to 650 °C
Authors: Zeiler Guenter , Plesiutschnig Ernst 
Published: March 2024

Abstract
Approximately 75% of the worldwide energy supply is based on fossil energy but the discussions on CO2 emission require improvements of the conventional power technologies and also an increase of renewable energy resources. Over the past 40 years, enormous efforts, especially in the development of new materials, were made to establish the technology for the ultra-supercritical power plants, which are the standard of today’s power generation. For decades voestalpine Boehler Special Steel has been a full package supplier of customized high quality special steels and forgings with close relationships to plant manufacturers to provide products ahead of their time. This paper reports on improvements and research activities of the currently best available martensitic 9% Cr steel FB2 and the latest generation, the so-called MarBN steels, raising the operating temperatures of the 9% Cr steel class from 620 °C to 650 °C. Increasing the operating temperature requires adaptations in processes and manufacturing methods to adjust optimized microstructures with improved toughness properties and increased creep rupture strength at the same time. The microstructure of two Boron containing 9% Cr steels, FB2-2 and NPM1, developed within the framework of COST / KMM-VIN, have been investigated comparatively after different heat treatments and discussed after creep rupture tests at 650°C. The results show a dependency of the creep rupture strength on the stability of precipitates and the creep rupture time of both steels was increased by more than 30 % without negatively affecting the creep rupture strain and impact values.
Changes in Electrochemical Polarization Characteristics of High Chromium Steels by Thermal Aging Treatment
Authors: Watanabe Yasuaki , Yamashita Mitsuo , Izumi Sakae , Wang Zihao , Shoji Tetsuo 
Published: March 2024

Abstract
The nucleation and growth of precipitates such as Laves phases, carbides and nitrides reduce fracture toughness and high-temperature strength of high chromium steels used in thermal power plants. For this reason, to ensure a long-term plant reliability, it is important to estimate material deterioration by aging. The study presented in this paper involves micro structural evolution by thermal aging of COST-E, F, and FB2 steels, all turbine materials. The results indicate that the Laves phases and other precipitates can be separately detected and quantified by the electrochemical technique. The results also clarify the correlation between the amount of Laves phases precipitated and electrochemical polarization parameters.
Low Cycle Fatigue Properties and Impact Toughness of Advanced 10% Cr Steel with High Boron and Low Nitrogen Contents
Authors: Mishnev Roman , Dudova Nadezhda , Kaibyshev Rustam 
Published: March 2024

Abstract
9-12%Cr martensitic steels can be applied to the next highest temperature components such as boiler tracts, steam pipelines and turbines of advanced ultra-supercritical power plants with steam temperatures of 650°C. New 10%Cr martensitic steels with high B and low N contents can be a worthy candidate for use in production because it has superior creep resistance. At the same time, resistance to cyclic and dynamic loads is very important. In this work, we studied the low cycle fatigue (LCF) properties at room and elevated (500-650°C) temperatures and Charpy impact toughness at temperatures ranging from -196…100°C of advanced 10% Cr martensitic steel with high B and low N contents. The effect of new alloying scheme and corresponding peculiarities of M23C6 carbides on the low cycle fatigue resistance and impact toughness of the 10%Cr martensitic steel is analyzed. It is revealed that fine and densely distributed carbides has no effect on the fatigue resistance except for the slight improvement of fatigue life at small strain amplitudes and shift the ductile-brittle transition temperature (DBTT) to higher but satisfactory value of +10°C as compared to other high-chromium martensitic steels.
Comparison of Conventional, Accelerated, and Small Punch Creep Test Results in Dissimilar Weld Joints of FB2 and F Steels
Authors: Kasl Josef , Jandová Dagmar , Mandziej Stan T. , Kuboň Zdeněk 
Published: March 2024

Abstract
A trial weld joint of COST F and COST FB2 steels was produced using the GTAW HOT-WIRE method in conditions used in industry for production of welding steam turbine rotors. Conventional long-term creep tests (CCT) to the rupture of this weldment and the base materials were carried out at temperatures ranging from 550 °C to 650 °C in the stress range from 70 to 220 MPa (the longest time to rupture was above 52,000 hours). Creep rupture strength was evaluated using Larson-Miller parameter model. Assessment of microstructure was correlated with the creep strength. Precipitation of Laves phase and structure recovery during creep exposures were the main reasons for the failure which occurred in the heat affected zone of steel COST F. The recently developed simulative accelerated creep testing (ACT) on thermal-mechanical simulator allows the microstructural transformation of creep-resisting materials in a relatively short time to a state resembling that of multiyear application under creep conditions. ACT of samples machined from various positions in the weldment was performed at 600 °C under 100 MPa. Changes in the hardness and the microstructures of the samples, which underwent both types of creep tests, were compared. Small sample creep test (SPCT), another alternative method how to obtain information about the creep properties of materials when only a limited amount of test material is at disposal, were performed. It was shown that the same stress-temperature dependence and relationships are valid in the SPCT as in the CCT. Using a simple load-based conversion factor between the SPCT test and the CCT test with the same time to rupture, the results of both test types can be unified.
Heat-Resistant Fe-Al-Ni Based Alloys with NiAl Precipitates
Authors: Yasuda Hiroyuki Y. , Cho Ken , Edahiro Taisuke , Ikeda Kenshi 
Published: March 2024

Abstract
NiAl precipitates with the B2 structure are known to be effective in increasing the strength of ferritic heat-resistant steels. The strengthening mechanism by the NiAl precipitates was examined using Fe-21Al-2Ni and Fe-23Al-6Ni (at%) single crystals. As a result, the difference in primary slip system between the bcc matrix and the NiAl precipitates is responsible for strong hardening. The B2-NiAl phase was precipitated in the bcc matrix satisfying the cube-on-cube orientation relationship with small misfit strain. The primary slip direction of the bcc matrix and the NiAl precipitates are &lt;111&gt; and &lt;001&gt;, respectively. However, in the ferritic alloys, the NiAl precipitates were cut by paired 1/2&lt;111&gt; dislocations in the bcc matrix, resulting in the hardening. The size and volume fraction of the NiAl precipitates strongly influenced the strength. The stress increase by the NiAl precipitates was also discussed quantitatively based on the precipitation hardening theory. Based on the experimental results obtained by the single crystal study, we developed Fe-Al-Ni-Cr-Mo ferritic heat-resistant alloy containing the NiAl precipitates. The alloy exhibited excellent creep properties at 923 K.