bluuebunny/crossref_metadata_2025 huggingface dataset:
Peran Brand Image Situs Tripadvisor Memediasi Pengaruh Ewom terhadap Niat Beli Kamar di Kabupaten Badung
Authors: Citra Dewi Putu Putri , Utama I Putu , Widawati Ida Ayu Putri
Published: March 2024

EWOM given by other consumers in a sharing review platform or community can influence consumers' purchase intentions. TripAdvisor as an online review site that provides access for its customers to write a review. On the TripAdvisor site, people who want to share their experiences are required to become regular users and have their TripAdvisor account first and it is known that 65% of respondents see hotel reviews before making a booking. Thus, high ratings and good reviews from customers can create profits for hoteliers as EWOM can help hotels attract new customers. The purpose of this study was to determine the effect of EWOM on room purchase intention in Badung Regency and the role of Tripadvisor website brand image in mediating the relationship between EWOM and room purchase intention. This research method uses a quantitative approach and Partial Least Square Structural Equation Modeling (PLS-SEM) analysis. The population determined in this study is the Indonesian population with a sample of 180 respondents in accordance with the provisions of the sample calculation. The equation models analyzed are the outer model, the inner model and hypothesis testing. Based on the results of calculations using PLS-SEM software, the results show that there is no significant effect between the effect of EWOM on room purchase intentions, there is a significant effect of brand image on EWOM, the brand image of the Tripadvisor site has an effect on room purchase intention and there is a significant influence on brand image the Tripadvisor website as a media to mediate the influence of EWOM on room purchase intentions in Badung Regency. The implication of the results of this study shows that hotels around Badung Regency must maintain professionalism in improving the quality of services and facilities provided to tourists so that they can increase the value of reviews on the Tripadvisor site.
Aluminum Continues to Shine in Commercial Aircraft Applications
Authors: Sanders Robert , Marshall Graeme
Published: March 2024

During the 20th century, the use of aluminum alloys helped the Allied Powers win World War II and made modern global air travel possible. Continuous improvements in engine technology, alloys, and manufacturing methods enabled the development of practical and efficient aircraft with varying passenger capacity and range capability. Conventional wrought aluminum alloys make up 70-80% of the weight of single-aisle airliners. Aluminum sheet, plate, forgings, extrusions, and castings all continue to be utilized in modern aircraft construction. This article explores a brief history of the special alloys, tempers, and product forms required to meet the unique challenges of flight.
United States Advanced Ultra-Supercritical Component Test Facility with 760°C Superheater and Steam Turbine
Authors: Romanosky Robert , Cedro Vito , Purgert Robert , Phillips Jeffrey N. , Hack Horst , Weitzel Paul , Pschirer James , Claeys James
Published: March 2024

Following the successful completion of a 14-year effort to develop and test materials which would allow advanced ultra-supercritical (A-USC) coal-fired power plants to be operated at steam temperatures up to 760°C, a United States-based consortium has started on a project to build an A-USC component test facility, (A-USC ComTest). Among the goals of the facility are to validate that components made from the advanced alloys can perform under A-USC conditions, to accelerate the development of a U.S.-based supply chain for the full complement of A-USC components, and to decrease the uncertainty for cost estimates of future commercial-scale A-USC power plants. The A-USC ComTest facility will include a gas fired superheater, thick-walled cycling header, steam piping, steam turbine (11 MW nominal size) and valves. Current plans call for the components to be subjected to A-USC operating conditions for at least 8,000 hours by September 2020. The U.S. consortium, principally funded by the U.S. Department of Energy and the Ohio Coal Development Office with co-funding from Babcock & Wilcox, General Electric and the Electric Power Research Institute, is currently working on the Front-End Engineering Design phase of the A-USC ComTest project. This paper will outline the motivation for the project, explain the project’s structure and schedule, and provide details on the design of the facility.
Status of the Power Industry in China and Overall Progress for A-USC Technology
Authors: LIU Zhengdong
Published: March 2024

The Chinese power industry has experienced rapid development in the past decade. The newly built 600+°C ultra-super-critical (UCS) fossil fire power plants and pressed water reactor nuclear power plants in China are the world’s most advanced level technically and effectively. The available capacity of 600+°C UCS fossil fire power plant in China is more than 200 GW by the end of 2015, which has greatly contributed to the energy-saving and emission-reduction for China and the whole world. In China, the 610°C and 620°C advanced USC (A-USC) fossil fire power plants had been combined into the grid, 630°C A-USC fossil fire power plant is about to start to build, the feasibility of 650°C A-USC fossil fire power plant is under evaluation, 700°C AUSC fossil fire power plant has been included in the national energy development plan and the first Chinese 700°C A-USC testing rig had been put into operation in December 2015. The advanced heat resistant materials are the bottlenecking to develop A-USC fossil fire power plant worldwide. In this paper, the research and development of candidate heat resistant steels and alloys selected and/or used for 600+°C A-UCS fossil fire power plant in China is emphasized, including newly innovated G115 martensitic steel used for 630°C steam temperature, C-HRA-2 fully solid-solution strengthening nickel alloy used for 650°C steam temperature, C-HRA-3 solid-solution strengthening nickel alloy used for 680°C steam temperature, 984G iron-nickel alloy used for 680°C steam temperature, C-HRA-1 precipitation hardening nickel alloy and C700R1 solid-solution strengthening nickel alloy used for 700+°C steam temperature.
Materials Performance in the First U.S. Ultrasupercritical (USC) Power Plant
Authors: Crichton Michael , Shingledecker John
Published: March 2024

Early supercritical units such as American Electric Power (AEP) Philo U6, the world’s first supercritical power plant, and Eddystone U1 successfully operated at ultrasupercritical (USC) levels. However due to the unavailability of metals that could tolerate these extreme temperatures, operation at these levels could not be sustained and units were operated for many years at reduced steam (supercritical) conditions. Today, recently developed creep strength enhanced ferritic (CSEF) steels, advanced austenitic stainless steels, and nickel based alloys are used in the components of the steam generator, turbine and piping systems that are exposed to high temperature steam. These materials can perform under these prolonged high temperature operating conditions, rendering USC no longer a goal, but a practical design basis. This paper identifies the engineering challenges associated with designing, constructing and operating the first USC unit in the United States, AEP’s John W. Turk, Jr. Power Plant (AEP Turk), including fabrication and installation requirements of CSEF alloys, fabrication and operating requirements for stainless steels, and life management of high temperature components
Some Problems in Metal Material Service of Fossil Power Units in Mainland China
Authors: Jia Jianmin , Ma Hong , Cui Xionghua , Wang Junmin
Published: March 2024

Along with rapid development of thermal power industry in mainland China, problems in metal materials of fossil power units also change quickly. Through efforts, problems such as bursting due to steam side oxide scale exfoliation and blocking of boiler tubes, and finned tube weld cracking of low alloy steel water wall have been solved basically or greatly alleviated. However, with rapid promotion of capacity and parameters of fossil power units, some problems still occur occasionally or have not been properly solved, such as weld cracks of larger-dimension thick-wall components, and water wall high temperature corrosion after low-nitrogen combustion retrofitting.
Alloy 740H: Development of Fittings Capability for A-USC Applications
Authors: deBarbadillo John J. , Baker Brian A. , McCoy Stephen A.
Published: March 2024

INCONEL alloy 740H has been specified for tube and pipe for the boiler and heat exchanger sections of AUSC and sCO2 pilot plants currently designed or under construction. These systems also require fittings and complex formed components such as flanges, saddles, elbows, tees, wyes, reducers, valve parts, return bends, thin-wall cylinders and tube sheets. The initial evaluation of alloy 740H properties, leading to ASME Code Case 2702, was done on relatively small cross-section tube and plate. The production of fittings involves the use of a wide variety of hot or cold forming operations. These components may have complex geometric shapes and varying wall thickness. The utility industry supply chain for fittings is largely unfamiliar with the processing of age-hardened nickel-base alloys. Special Metals has begun to address this capability gap by conducting a series of trials in collaboration with selected fittings manufacturers. This paper describes recent experiences in first article manufacture of several components. The resulting microstructure and properties are compared to the published data for tubular products. It is concluded that it will be possible to manufacture most fittings with properties meeting ASME Code minima using commercial manufacturing equipment and methods providing process procedures appropriate for this class of alloy are followed. INCONEL and 740H are registered trademarks of Special Metals Corporation.
Influence of Data Scattering on Estimation of 100,000 Hours Creep Rupture Strength of Alloy 617 and Alloy 740 by Larson-Miller Method
Authors: Abe Fujio , Tabuchi Masaaki , Hayakawa Masao
Published: March 2024

The reasonable procedures for estimation of 100,000 h creep rupture strength have been investigated for Alloy 617 and Alloy 740 for A-USC power plants by Larson Miller method. The creep rupture data of longer duration than 500 h in the temperature range between 593 and 816 °C and between 600 and 850 °C were used for the analysis on Alloy 617 and Alloy 740, respectively. The data were obtained by Special Metals. In these temperature ranges, Ni3Al-γ’ can precipitate in Alloy 617 and Alloy 740 during creep. The maximum time to rupture was 40,126.7 and 24,066 h for Alloy 617 and Alloy 740, respectively. The rupture data for Alloy 617 exhibit large scattering, especially at 760 °C, showing a split into two groups. After eliminating the shorter time to rupture data at 760 °C, the regression analysis using the second order equation of Larson-Miller parameter gives us the Larson-Miller constant C of 12.70 and the 100,000 h creep rupture strength of 100 MPa at 700 °C. The regression analysis underestimates the constant C and corresponding 100,000 h creep rupture strength of Alloy 617, as shown by the regression curves locating below the rupture data at long times, while those locating above the rupture data at short times. The underestimation of constant C is caused by large data scattering. The linear extrapolation of log tr versus reciprocal temperature 1/T plot to 1/T = 0 at constant stresses gives us the constant C of 18.5, which is much larger than that by the regression analysis. Using an appropriate constant C of 18.45, the 100,000 h creep rupture strength of Alloy 617 is estimated to be 123 MPa at 700 °C. On the other hand, the rupture data for Alloy 740 exhibit only a little bit scattering. The regression analysis gives us C = 18.45, which agrees very well with that by the linear extrapolation of log tr versus 1/T plot to 1/T = 0. The 100,000 h creep rupture strength of Alloy 740 is estimated to be 214 and 109 MPa at 700 and 760 °C, respectively.
Correlation of Microstructure and Properties of Alloy 617B and Alloy C-263 for A-USC Power Plants
Authors: de Boer Nicole , Schraven Patrik
Published: March 2024

Nickel-based Alloy 617B (DIN 2.4673) and Alloy C-263 (DIN 2.4650) with high creep strength and good fabricability are promising material candidates for the design of next generation coal-fired “Advanced Ultra-Super-Critical A-USC” power plants with advanced steam properties and thus higher requirements on the material properties. Microstructural studies of the precipitation hardened alloy C-263 were performed with Electron Microscopy (TEM) with respect to their strengthening precipitates like carbides and intermetallic gamma prime. Specimens were subjected to different ageing treatments at elevated temperatures for different times. The microstructural results of the investigated nickel alloy C-263 are presented and discussed with respect to their correlation with required properties for A-USC, e.g. the mechanical properties, the creep resistance and the high temperature stability and compared to Alloy 617B. The manufacturing procedure for the prematernal and forgings as well as for thin walled tube components for A-USC power plants is presented.
Effects of Trace Elements on Creep Properties of Nickel-Iron Base Superalloy
Authors: Hasebe Yusaku , Maeda Eiji , Takasawa Koichi
Published: March 2024

The aim of this work was to reveal the effects of trace elements on the creep properties of nickel-iron base superalloys, which are the candidate material for the large components of the advanced-ultrasupercritical (A-USC) power generation plants. High temperature tensile and creep properties of forged samples with seven different compositions were examined. No significant differences were observed in the creep rate versus time curves of the samples, of which contents of magnesium, zirconium, manganese and sulfur were varied. In contrast, the curves of phosphorus-added samples showed very small minimum creep rates compared to the other samples. The creep rupture lives of phosphorus-added samples were obviously longer than those of the other samples. Microstructure observation in the vicinity of grain boundaries of phosphorus-added samples after aging heat treatment revealed that there were fine precipitates consisting of phosphorus and niobium at the grain boundaries. The significant suppression of the creep deformation of phosphorus-added sample may be attributed to the grain boundary strengthening caused by the fine grain boundary precipitates.
A Newly Designed Nickel-Based Superalloy GH750 For 700°C Advanced Ultra-Supercritical Power Plants
Authors: Lin Fusheng , Zhao Shuangqun , Fu Rui , Wang Yanfeng , Xie Xishan , Chi Chengyu , Hu Yaohe , Zhang Maicang
Published: March 2024

A new nickel-based superalloy, designated as GH750, was developed to meet the requirements of high temperature creep strength and corrosion resistance for superheater/reheater tube application of A-USC power plants at temperatures above 750°C. This paper introduces the design of chemical composition, the process performance of tube fabrication, microstructure and the properties of alloy GH750, including thermodynamic calculation, room temperature and high temperature tensile properties, stress rupture strength and thermal stability. The manufacturing performance of alloy GH750 is excellent and it is easy to forge, hot extrusion and cold rolling. The results of the property evaluation show that alloy GH750 exhibits high tensile strength and tensile ductility at room and high temperatures. The 760°C/100,000h creep rupture strength of this alloy is larger than 100MPa clearly. Microstructure observation indicates that the precipitates of GH750 consist of the precipitation strengthening phase γ’, carbides MC and M23C6 and no harmful and brittle TCP phases were found in the specimens of GH750 after long term exposure at 700~850°C. It can be expected for this new nickel-based superalloy GH750 to be used as the candidate boiler tube materials of A-USC power plants in the future.
Design, Creep Performance and Deformation Behavior of an Eta-Phase Strengthened Nickel-Base Alloy for A-USC Power Plant Applications
Authors: Milligan W.W. , Sanders P.G. , White C.L. , Shingledecker J.P. , Purdy D.F.
Published: March 2024

By utilizing computational thermodynamics in a Design of Experiments approach, it was possible to design and manufacture nickel-base superalloys that are strengthened by the eta phase (Ni3Ti), and that contain no gamma prime (Ni3Al,Ti). The compositions are similar to NIMONIC 263, and should be cost-effective, and have more stable microstructures. By varying the aging temperature, the precipitates took on either cellular or Widmanstätten morphologies. The Widmanstätten-based microstructure is thermally stable at high temperatures, and was found to have superior ductility, so development efforts were focused on that microstructure. High temperature tensile test and creep test results indicated that the performance of the new alloys was competitive with NIMONIC 263. SEM and TEM microscopy were utilized to determine the deformation mechanisms during creep.
Creep and Creep Rupture Behavior of Nickel-Base Alloys for Superheaters After Cold Working
Authors: Mueller Falk , Oechsner Matthias
Published: March 2024

In order to enable a compact design for boiler superheaters in modern thermal power plants, cold-worked tube bending is an economical option. For service metal temperatures of 700 °C and above, nickel-based alloys are typically employed. To ensure a safe operation of such cold-worked alloys, their long-term mechanical behavior has to be investigated. In general, superheater tube materials in a cold-worked state are prone to a degradation of their long-term creep behavior. To predict this degradation, sensitive experiments have to be conducted. In this publication, the effects of cold working on the long-term creep behavior of three currently used nickel-based alloys are examined. Creep and creep rupture experiments have been conducted at typical service temperature levels on nickel-based alloys, which have been cold worked to various degrees. As a result, Alloy 263 exhibits no significant influence of cold working on the creep rupture strength. For Alloy 617, an increase of creep strength due to cold working was measured. In contrast, Alloy 740 showed a severe degradation of the creep strength due to cold working. The mechanism causing the sensitivity to cold working is not yet fully understood. Various formations of carbide precipitates at the grain boundaries are believed to have a major influence. Nevertheless, the experimentally observed sensitivity should always be considered in material selection for boiler tube design.
Design, Operation, Numerical Simulation and Damage Assessment of a Header in the HWT Test Loop
Authors: Speicher Magdalena , Klenk Andreas , Steck Tobias , Helmrich Andreas , Kluger Frank
Published: March 2024

In the test loop HWT II (High Temperature Materials Test Loop) installed in the fossil power plant Grosskraftwerk (GKM) Mannheim in Germany, thick-walled components made of nickel base alloys were operated up to temperature of 725 °C. The operation mode chosen (creep-fatigue) was to simulate a large number of start-ups and shutdowns with high gradients as expected for future high efficient and flexible power plants and to investigate the damage due to thermal fatigue of the used nickel base alloys. In this paper the damage evolution of a header made of the nickel base alloys Alloy 617 B and Alloy C263, which was a part of HWT II test rig, were investigated using nondestructive and destructive techniques. Furthermore, the damage has been considered and evaluated by using numerical methods. In addition, different lifetime assessment methods of standards and recommendations with focus on creep-fatigue damage were used and evaluated. The different lifetime models are applied to the header and the results were compared to the results of metallographic investigations and damage observations.
Creep Failure Analysis of Superheater Tubes in a Supercritical Boiler
Authors: Che Chang , Qian Gong , Qian Linfeng , Chen Xinzhong
Published: March 2024

Up to now, the amount of supercritical boilers in China has ranked number one in the world. Many supercritical boilers have run for more than 100,000 hours. Creep becomes one of the main reasons for supercritical boiler tubes failure. In this article, the failure of superheater tubes in a supercritical boiler was analyzed, the microstructural evolution of austenitic stainless steel tubes were studied, a full investigation into the failure cause was carried out involving in visual examination, optical microscope, SEM, TEM and XRD. The results show, sigma phase precipitates in this austenitic steel with the extension of service time, sigma precipitates form at grain boundaries by continuous chain. Sigma precipitates are hard and brittle, weaken grain boundaries and cause microscopic damage, eventually lead to boiler tubes failure.
Microstructure Impacts on Mechanical Properties in a High Temperature Austenitic Stainless Steel
Authors: Purdy D. , Maziasz P.J. , Wharry J. , Dolph C.
Published: March 2024

Austenitic and super-austenitic stainless steels are a critical component of the spectrum of high temperature materials. With respect to power generation, alloys such as Super 304H and NF709 span a gap of capability between ferritic and martensitic high chromium steels and nickel-based alloys in boiler tube applications for both conventionally fired boilers and heat-recovery steam generators (HRSG). This research explores a wrought version of a cast austenitic stainless steel, CF8C-Plus or HG10MNN, which offers promise in creep strength at relatively low cost. Various manufacturing techniques have been employed to explore the impact of wrought processing on nano-scale microstructure and ultimately performance, especially in high temperature creep. Transmission electron microscopy has been used to quantify and characterize the creep-strengthening particles examining the relationship between traditional melting and extrusion as compared to powder metallurgy.
Thermal Fatigue Properties of Dissimilar Welded Part of SUPER304H Boiler Steel Tube
Authors: Noguchi Yasutaka , Hirata Hiroyuki , Yoshizawa Mitsuru , Tanaka Katsuki
Published: March 2024

Austenitic stainless steels have been used for boiler tubes in power plants. Since austenitic stainless steels are superior to ferritic steels in high temperature strength and steam oxidation resistance, austenitic stainless steel tubes are used in high temperature parts in boilers. Dissimilar welded joints of austenitic steel and ferritic steel are found in the transition regions between high and low temperature parts. In dissimilar welded parts, there is a large difference in the coefficient of thermal expansion between austenitic and ferritic steel, and thus, thermal stress and strain will occur when the temperature changes. Therefore, the dissimilar welded parts require high durability against the repetition of the thermal stresses. SUPER304H (18Cr-9Ni-3Cu-Nb-N) is an austenitic stainless steel that recently has been used for boiler tubes in power plants. In this study, thermal fatigue properties of a dissimilar welded part of SUPER304H were investigated by conducting thermal fatigue tests and finite element analyses. The test sample was a dissimilar welded tube of SUPER304H and T91 (9Cr-1Mo-V-Nb), which is a typical ferritic heat resistant boiler steel.
Creep Behavior and Microstructure Evolution in AISI 316LN + 0.1 Wt.% Nb Steel at 600 and 625°C
Authors: Vodärek Vlastimil , Řehořek Jakub
Published: March 2024

The paper deals with microstructural evolution in the AISI 316LN + 0.1 wt.% Nb steel during long-term creep exposure at 600 and 625°C. The following minor phases formed: Z-phase (NbCrN), M23C6, M6X (Cr3Ni2SiX type), η-Laves (Fe2Mo type) and σ-phase. M6X gradually replaced M23C6 carbides. Primary Z-phase particles were present in the matrix after solution annealing, while secondary Z-phase particles formed during creep. Precipitation of Z-phase was more intensive at 625°C. The dimensional stability of Z-phase particles was excellent and these particles had a positive effect on the minimum creep rate. However, niobium also accelerated the formation and coarsening of σ-phase, η-Laves and M6X. Coarse particles, especially of σ-phase, facilitated the development of creep damage, which resulted in poor long-term creep ductility.
Influence of Holding Time During Tempering on the Long-Term Creep Rupture Strength of MOD.9Cr-1Mo Steel
Authors: Komai Nobuyoshi , Arisue Ko , Tominaga Kimihiko , Fujita Masaaki
Published: March 2024

The influence of holding time during tempering on the long-term creep rupture strength of mod.9Cr-1Mo steel was investigated in this study, so as to elucidate proper heat treatment for boiler applications. Tempering was conducted at 770°C for 0.5h, 1h, 3h, 10h and 100h for the test materials, after re-normalization at 1050°C for 1h in all cases. Creep rupture tests were conducted at 600°C, and ruptured specimens were investigated to better understand the microstructural changes, including changes in the number density of precipitates, in order to observe and discuss their creep strength. All creep rupture test results for materials tempered within 10h exceeded the average creep strength of T91. Shorter tempering times such as 0.5h and 1h were clearly correlated with longer time to rupture at 600°C under 80MPa to 100MPa stress conditions. Reduction of area in creep-ruptured specimens decreased principally with lowered creep stress. Materials tempered for 0.5h and 100h showed the lowest reduction of area at 90MPa and 100MPa respectively, and their reduction of area recovered at lower than those stress levels. These stresses, showing minimum reduction of area, met inflection stress in the creep rupture strength curve.
Effect of Stress and Strain on Microstructural Changes During Long-Term Creep in T91 Steel
Authors: Sawada Kota , Hara Toru , Kushima Hideaki , Kimura Kazuhiro , Tabuchi Masaaki
Published: March 2024

In order to clarify the effect of stress and strain on microstructural changes during creep for T91 steel, creep interrupted tests were performed at 600°C for 10000h, 20000h, 30000h, 50000h and 70000h. The steel studied was T91 steel with high Ni content (0.28mass%) in the range of specification. Changes of dislocation structure and precipitates distributions were observed for the grip and gauge portions of creep interrupted samples. The subgrain size gradually increased with increasing creep time up to 50000h in both the grip and gauge portions. However, the subgrain size abruptly increased after 50000h in the gauge portion as compared with the grip portion. Decrease in dislocation density inside subgrain was promoted in the gauge portion as compared with the grip portion. The size of M23C6 gradually increased with increasing creep time up to 50000h in both the grip and gauge portions. The increase in M23C6 size was accelerated after 50000h in the gauge portion as compared with the grip portion. The Z phase formation was promoted in the gauge portion as compared with the grip portion. The number density of all kinds of particles gradually decreased with increasing creep time in the gauge and grip potions. After 50000h, the number density rapidly decreased in the gauge portion as compared with the grip portion.
Evaluation of Long Term Creep Strength of Mod. 9Cr Heat Resistant Ferritic Steel with the Aid of System Free Energy Concept
Authors: Murata Yoshinori , Watanabe Naoya , Nagae Yuji
Published: March 2024

In order to evaluate long term creep strength of modified 9Cr ferritic steels, the system free energy of creep ruptured specimens at both 650 and 700 °C is evaluated as the sum of chemical free energy, strain energy and surface energy, which are obtained by a series of experiments, i.e., chemical analysis using extracted residues, X-ray diffraction, and scanning transmission electron microscopy. Change ratio of the system free energy and creep stress showed the relationship with one master curve irrespective of creep conditions, indicating that the steel ruptures when the applied stress exceeds a limited stress depending on the microstructural state expressed by the change ratio of system free energy. Furthermore, it was found that dominant factor of the change ratio was the chemical free energy change. On the basis of these results, long term creep strength of the steel was evaluated at 700 °C, for example, 19MPa at 700 °C after 105 h. It is concluded that long term creep strength of modified 9Cr ferritic steels can be predicted by the system free energy concept using the ruptured specimens with various creep conditions.
Small Scale Impression Creep Testing of an Ex-Service Mis-Heat Treated Seam Welded Grade 91 Hot Reheat Bend
Authors: Brett S J , Lant T , Clark A
Published: March 2024

This paper reports the results of a collaborative small scale creep testing exercise carried out by the UK generating companies Centrica, SSE, Engie and RWE as part of an investigation of an ex-service grade 91 bend.
Impression Creep Testing and Its Role in Power Plant Component Integrity Management
Authors: Dyson C. , Sun W. , Brett S. J. , Hyde T. H. , Hyde C. J. , Shingledecker J. , Purdy D.
Published: March 2024

The impression creep test method using a rectangular indenter has been well established and the applicability of the technique has been supported by the test data for a number of metallic materials at different temperatures and stresses. The technique has proved to be particularly useful in providing material data for on-site creep strength assessments of power plant components operating in the creep regime. Due to these reasons, “standard” assessment procedures using the impression testing method are needed in order for the technique to be more widely used. This paper will first address some key issues related to the use of the impression creep test method, involving the data conversion method, typical test types and validity of the test technique etc. Then some recommendations on a number of practical aspects, such as the basic requirements of test rigs, “standard” specimen geometry, indenter dimensions, sampling procedures for scoop samples, specimen preparation, temperature and loading control, and displacement measurement, are briefly addressed. Finally, applications of the test data to assist with the risk management and life assessment programme of power plant components, particularly those with service-exposed materials, using data obtained from scoop samples, are described. Proposals for future exploitation and for improvement of the technique are addressed.
The Effect of Pre-Service Treatments on the Long Term Properties of 9Cr Steels Strengthened by Boron and Nitrogen
Authors: Sammarco A. , Thomson R. C. , Vanstone R.
Published: March 2024

Martensitic 9Cr steels have been developed which are strengthened by boron in order to stabilize the microstructure and improve their long-term creep strength. Boron plays a key role in these steels by stabilising the martensitic laths by decreasing the coarsening rate of M23C6 carbides, which act as pinning points in the microstructure. In this work two modified FB2 steel forgings are compared. Both forgings have similar compositions but one underwent an additional remelting process during manufacture. Creep tests showed that this additional processing step resulted in a significant increase in time to failure. In order to investigate the effect of the processing route on microstructural evolution during aging and creep, a range of advanced electron microscopy techniques have been used including ion beam induced secondary electron imaging and High Angle Annular Dark Field (HAADF) imaging in the Scanning Transmission Electron Microscope. These techniques have enabled the particle population characteristics of all the second phase particles (M23C6, Laves phase, BN and MX) to be quantified for materials from both forging processes. These quantitative data have enabled a better understanding of how the processing route affects the microstructural evolution of FB2 steels.
Research on Test and Evaluation of High Depth-To-Width Ratio Longitudinal Defects of Boiler Tube Inner Wall
Authors: Zhang Lei , Ma Hong , Cui Jinwen , Shi Zhigang , Cui Xionghua
Published: March 2024

To solve crack problems at the tube elbow induced by high depth-to-width ratio longitudinal defects on the inner wall of boiler tube, a number of testing experiments and testing methods have been applied to analysis on the sensitivity and correspondence of such defects, and it has been found that the flattening test has an outstanding advantage to detect such defects. However, according to relevant standards, the judgment is controversy. It can be noted from the research that if a steel tube with a ratio of wall thickness to outer diameter larger than 0.1 is turned prior to the flattening test, to reduce such ratio to be less than or equal to 0.1, the shortcomings in detection and evaluation of such defects specified in the current relevant standards of many countries can be effectively overcome. The method has been proposed and adopted preliminarily in the relevant Chinese standard.
Analysis on Effect of Piping Stress and Supports and Hangers on Cracking of Tee Welds
Authors: Zhao Bo , Ma Hong , Dong Lei , Wang Junmin , Wang Bining , Deng Linghui , Cheng Yongming
Published: March 2024

The piping stress and thermal displacement corresponding to different types of riser rigid support and hanger devices in different installation directions have been calculated by means of finite element analysis, to further analyze the impact on cracking of adjacent steam tee welds exerted by the constraint effect of riser rigid hangers on angular displacement. It can be seen from the analysis that a riser rigid hanger has a constraint effect on angular displacement, and such a constraint effect, however, is weak and limited on the piping stress and thermal displacement, so the piping stress and supports and hangers are not the main reasons for the cracking of tee welds. In addition, the calculation results alert that for an axial limiting hanger of riser with a dynamic axial pipe clamp and rigid struts, its constraint effect on angular displacement has a significant impact on the piping stress and thermal displacement.
The Influence of Prior Austenite Grain Size on Fatigue Crack Growth Threshold of welds in Cr-Mo-V Steel Components
Authors: Huo Xin , Wang Peng , Hu Mengjia , Cai Zhipeng , Pan Jiluan
Published: March 2024

The fatigue crack propagation thresholds of SAW weld metal of 25Cr2Ni2MoV simulating product of fossil and nuclear power low pressure turbine rotor at different stress ratios are tested. There is a big dispersity of the test results, even at the same stress ratio. The double logarithm curves of the fatigue crack growth rate and stress intensity factor range are researched. The difference of critical points between stable propagation region and near-threshold region in different specimens is found to be an important cause to the dispersity. Their locations in the specimens can be determined by the method of backward inference. After the observation of the microstructures around the critical points, a good correspondence between the size of prior austenite grain and the maximum size of monotonic plastic zone on the crack tip is confirmed. The difference of the critical points at the same stress ratio is caused by the inhomogeneous microstructures. So the inhomogeneous microstructures in the multi-pass and multi-layer weld metal contribute to the dispersity of the experimental threshold values.
Alternate Analytical Methodology to ASME Section I Design for Membrane Walls with Bimetallic Tube for High Temperature Sections of Advanced Ultrasupercritical (AUSC) Boilers
Authors: Ganta Reddy
Published: March 2024

High temperature regions in the upper sections of the advanced ultrasupercritical (AUSC) boilers are exposed to temperatures higher than traditional supercritical (SC) boilers and require high strength materials. Use of modified 9-12% Cr materials such as T91 and T92, while meeting the strength requirements, are still under research stage for large-scale fabrication of the membrane walls for several reasons, such as required post weld heat treatment PWHT (ASME Code) or hardness limits on as-welded structures (European codes). The main objective of this paper is to explore alternate tubing materials that do not require a PWHT in the high temperature sections of the AUSC boiler membrane walls. Composite bimetallic tubing with high strength cladding, applied by weld overlay or co-extrusion that may meet the requirement of high operating temperature and high overall strength, is addressed through an alternate design criterion. Bimetallic tubes can replace the single metal tubes made from 9-12% Cr materials. The bimetallic tube is assumed to be fabricated from Grade 23 steel (base tubes) with Alloy 617 overlaid. The alternate design method is based on an iterative analytical solution for the through-wall heat transfer and stresses in a composite tube with temperatures and strength variations of both the materials considered in detail. A number of different analyses were performed using the proposed analytical approach, methodology verified through benchmark solutions and then applied to the membrane wall configurations.
Qualification of UNS N07028 for Forged Steam Turbine Rotors
Authors: Saha Deepak , Coryell Stephen , deBarbadillo John , Dempster Ian , Barber Lee
Published: March 2024

The US Advanced Ultra-Supercritical (A-USC) Consortium conducted an extensive program to evaluate available superalloys for use in rotors for steam turbines operating at a nominal temperature of 760 °C (1400 °F). Alloys such as 282, Waspaloy, 740H, 720Li, and 105 were tested in the form of bar supplied from the alloy producers. Ultimately, alloy 282 was down-selected for the turbine rotor based on its combination of creep strength, phase stability, ductility, and fatigue resistance. The next step in development was to produce a full-size rotor forging for testing. A team was established consisting of GE Power (project management and testing), Wyman-Gordon (forging and testing) and Special Metals (melting and billetizing) to pursue the work. A research license to melt the alloy was obtained from Haynes International. The first step of the development was to devise a triple melt (VIM-ESR-VAR) practice to produce 610 mm (24 inch) diameter ingot. Two ingots were made, the first to define the VAR remelting parameters and the second to make the test ingot utilizing optimum conditions. Careful attention was paid to ingot structure to ensure that no solidification segregation occurred. A unique homogenization practice for the alloy was developed by the US Department of Energy (DOE) and National Energy Technology Laboratory (NETL). Billetization was performed on an open die press with three upset and draw stages. This procedure produced an average grain size of ASTM 3. A closed die forging practice was developed based on compressive flow stress data developed by Wyman Gordon Houston for the consortium project. Multiple 18 kg forgings were produced to define the forging parameters that yielded the desired microstructure. The project culminated with a 2.19 metric ton (4830 lb), 1.22 m (48 inch) diameter crack-free pancake forging produced on Wyman Gordon’s 50,000 ton press in Grafton, MA. The forging process produced a disk with an average grain size of ASTM 8 or finer. Forging cut-up, microstructural characterization, and mechanical property testing was performed by GE Power. Fatigue and fracture toughness values of the disk forging exceeded those previously reported for commercially available rolled bar.
New Material and Manufacturing Developments for USC and A-USC Steam Turbine Rotor Forgings
Authors: Donth B. , Blaes N. , Diwo A. , Bokelmann D.
Published: March 2024

COST FB2 steel alloyed with boron is currently the best available martensitic 9% Cr steel for turbine shafts subjected to steam temperatures up to 620°C and meanwhile introduced into production for application in commercial power plants. Currently several development programs are running to develop materials for further increase of application temperature up to 650°C. For realization of a 650ºC power plant not only creep strength, but also resistance against steam oxidation must be improved by increase of Cr content up to 11-12%. In the past all attempts to develop stable creep resistant martensitic 11-12% Cr steels for 650°C failed due to breakdown in long-term creep strength. Therefore new alloy concepts have been developed by replacing the fine nitride strengthening particles by controlled and accelerated precipitation of the more stable Z phase. Therefore the European project “Z-Ultra” was launched for further development and manufacture of this new alloy type. Saarschmiede participates in this project and contributed by manufacturing trial melts, boiler tubes and a large scale turbine rotor forging. Production experience and test results are presented. In order to exceed the temperature limit of 650°C, only nickel base alloys can be used. One of the most promising candidate alloys for rotor forgings subjected to steam temperatures of 700°C is Alloy 617, which was already intensively investigated. For still higher temperatures in the range of 750°C only γ‘-precipitation hardened nickel base alloys, such as Alloy 263, can be applied. Therefore the “NextGenPower” project was launched and aimed at manufacture and demonstration of parts from Ni-based alloys for application in steam power plants at 750°C. One of the main goals was to develop turbine rotor materials and to demonstrate manufacturability of forgings for full scale turbine rotor parts. Contributing to this project, Saarschmiede has produced for the first time a large rotor forging in the Ni base Alloy 263. Numeric simulations of ingot manufacture, forging and heat treatment have been performed and a large trial rotor forging in Alloy 263 with a diameter of 1000 mm was successfully produced from a triple melt ingot. Experiences in manufacture and test results are presented.
Creep Crack Behavior in Alloy C-263 Used for Thick-Walled Components
Authors: Mueller Falk , Oechsner Matthias , de Boer Nicole , Knezevic Vida
Published: March 2024

For safe operation of thick-walled components for Advanced Ultra Super Critical (A-USC) power plants, detailed knowledge of the creep crack initiation and growth behavior is essential. The high loading and high temperature conditions in an A-USC power plant require, in many cases, the employment of nickel base super alloys. Unfortunately, both manufacturing and nondestructive evaluation (NDE) of thick-walled components (> 50 mm) made of nickel base super alloys are quite challenging. In this paper, one candidate material for such applications, Alloy C-263, was tested for creep and creep crack behavior at 700 °C. Objective of the study was to determine a critical flaw size. In order to establish this size, the duration to achieve the 1%-strain limit at a given load is compared with the time to grow the initial flaw for Δa = 0.5 mm when the component was loaded with the same given load. It will be shown that manufacturing parameters, e. g. heat treatment procedures, have a significant influence on the creep crack initiation and growth behavior and thus on component life. Decoration of grain boundaries with precipitates, for instance caused by the manufacturing process, can reduce the creep crack resistance and thus increase the risk for premature component failure.
Microstructural Changes in GX12CRMOWVNBN10-1-1 Steel During Creep at 893 K
Authors: Dudko V. , Borisova J. , Kaibyshev R. , Skorobogatykh V. , Schenkova I.
Published: March 2024

Microstructure in the gage sections of ruptured GX12CrMoWVNbN10-1-1 cast steel specimens was examined after creep tests under applied stresses ranging from 120 to 160 MPa at T=893 K. The microstructure after tempering consisted of laths with an average thickness of 332 nm. The tempered martensite lath structure was characterized by M23C6-type carbide particles with an average size of about 105 nm, and MX carbonitrides with an average size of about 45 nm. Precipitation of Laves phase occurred during creep test. The structural changes in the gauge section of the samples were characterized by the evolution of relatively large subgrains with remarkably lowered density of interior dislocations within former martensite laths. MX carbonitrides and M23C6-type carbide particles increase in size slightly under long-term creep. Microstructural degradation mechanisms during creep in GX12CrMoWVNbN10-1-1 cast steel are discussed.
Mechanical Analysis of a Boiler Water Circulation Pump
Authors: Haßlöcher Marcus
Published: March 2024

In previous investigations on life with flexible driving were highly stressed components predominantly in hot continuous pressurized part of power plants in the foreground. However cases of damage and subsequent studies on peripheral components such as the boiler circulation system (boiler circulating pump) showed that a potential failure as well as a high hazard potential respectively great consequential damage can occur when such components are operated under different conditions. To avoid damages and losses resulting from damage to peripheral components, these components have to be subjected to further analysis. Here especially the pump housing is in the focus.
Robust Quantification of Phase Formation Potential Over a Wide Chemistry Space
Authors: Purdy D.
Published: March 2024

Due to a high degree of mixing between substrate and weld deposit, fusion welding of dissimilar metal joints functionally produce new, uncharacterized alloys. In the power generation industry, such mixing during the application of cobalt-based hardfacing has led to a disconcerting number of failures characterized by the hard overlay welds disbonding. Investigations into this failure mechanism point to the unknown alloy beneath the surface of the hardfacing layer transforming, hardening, and becoming brittle during service. This research describes a methodology for exploring a chemical space to identify alloy combinations that are expected to be safe from deleterious phase formation. Using thermodynamic modeling software and a stepped approach to potential chemistries, the entire phase stability space over the full extent of possible mixing between substrate and weld material can be studied. In this way diffusion effects – long term stability – can also be accounted for even in the case where mixing during application is controlled to a low level. Validation of predictions specific to the hardfacing system in the form of aged weld coupons is also included in this paper. Though the application of this methodology to the hardfacing problem is the focus of this paper, the method could be used in other weld- or diffusion- combinations that are expected to operate in a high temperature regime.