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Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1380-1388, October 21–24, 2019,
... DEFORMATION BEHAVIOR OF ADVANCED -TiAl BASED ALLOYS BY IN-SITU SEM OBSERVATION AND DIGITAL IMAGE CORRELATION TECHNIQUE Yotaro Okada, Ryosuke Yamagata, Hirotoyo Nakashima, Masao Takeyama Department of Materials Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology...
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Tensile deformation behavior of γ-TiAl based alloys consisting of α 2 -Ti 3 Al/γ lamellar colonies, β-Ti grains, and γ grains were investigated by in-situ scanning electron microscopy and digital image correlation technique, in order to identify the role of each microstructure constituents in deformation. The alloy with nearly lamellar microstructure, in which the volume fraction of β/γ duplex ( V DP ) is 10%, shows elongation of only 0.14%, whereas the alloy with nearly globular β/γ duplex microstructure with V DP of 94% shows elongation of 0.49%. In α 2 /γ lamellar microstructure, obvious strain localization occurs along lamellae and develops at specific regions with loading. In the case of β/γ duplex microstructure, strain localization is observed in γ grains and in β phase regions near the β/γ phase boundary, although no obvious deformation is observed in the β grains. β/γ phase boundaries enhances room temperature ductility of TiAl alloys by inducing multiple slip in γ phase and deformation of β phase.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 12-23, October 11–14, 2016,
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Since 2008, Japanese boiler, turbine and valve manufacturers, research institutes and utility companies have been working together to develop 700V A·USC technology, with support from the Japanese government. The key areas of discussion are technology development of high temperature materials such as nickel-based alloys and advanced 9Cr steels, and their application to actual power plants. At the EPRI conference in 2013, our report mainly focused on the development of fundamental material and manufacturing technology during the first five years of the project, and the preparation status of the boiler component test and turbine rotor test for the latter four years of the project. The boiler component test, using a commercially-operating boiler, began in May 2015 and is scheduled to be finished by the end of 2016. The turbine rotor test at 700°C with actual speed will be carried out from September 2016 to March 2017. At this year’s conference, we will: l) briefly summarize the development of fundamental material and manufacturing technology and 2) provide an update on the progress of the boiler component test and the turbine rotor test.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 931-938, October 11–14, 2016,
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Developed 9Cr-3W-3Co-Nd-B heat-resistant steel SAVE12AD (Recently designated as ASME Grade 93) pipes and tubes have higher creep strength in both base metal and welded joints than conventional high Cr ferritic steels such as ASME Grades 91, 92 and 122. The welded joints of SAVE12AD tubes with commercial filler wire for W62-10CMWV-Co (Gr. 92) or Ni base filler wire ERNiCr-3 (Alloy82) also have much better creep rupture strength than those of conventional steels because of suppression of refining in the Heat-Affected-Zone (HAZ). However, the creep rupture strength of weld metal of W62-10CMWV-Co was marginal. Additionally, the hot cracking susceptibility of weld metal using Ni base filler wire ERNiCr-3 was occasionally below the required level. Similar welding consumable for SAVE12AD has been developed to solve these problems. Optimization of nickel, neodymium and boron contents on similar welding consumable enables to obtain both the good long-term creep rupture strength and low enough hot cracking susceptibility of weld metal. Consequently, SAVE12AD welded joint is expected to be applied of piping and tubing above 600°C in USC power plants because of its good properties with similar welding consumable.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 513-522, October 21–24, 2019,
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Development of the advanced USC (A-USC) boiler technology has been promoted in recent years, which targets 700°C steam condition. HR6W (Ni-23Cr-7W-Ti-Nb-25Fe) and HR35 (Ni-30Cr-6W-Ti-15Fe) have been developed for A-USC boiler tubes and pipes. The former alloy is mainly strengthened by Fe 2 W type Laves phase. The latter one employs precipitation strengthening of α-Cr phase in addition to Laves phase. Characteristic alloy design of both alloys, which does not use precipitation strengthening of γ′ phase (Ni 3 Al), leads to superior ductility and resistance to stress-relaxation cracking. Stability of creep strength and microstructure has been confirmed by long-term creep rupture tests. The 100,000h average creep rupture strength of HR6W is 85MPa at 700C. That of HR35 is 126MPa at 700°C which is comparable with conventional Alloy617. Tubes of both alloys have been evaluated by the component test in Japanese national A-USC project with γ′ hardened Alloy617 and Alloy263. Detailed creep strength, deformation behavior and microstructural evolution of these alloys are described from the viewpoint of the difference in strengthening mechanisms. Capability of these alloys for A-USC boiler materials has been demonstrated by the component test in the commercial coal fired boiler as the part of the A-USC project.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 904-913, October 21–24, 2019,
... between the precipitate and matrix. In this article, the effect of various heat treatment schemes on the microstructure and hardness of the dual two-phase Ni3Al and Ni3V intermetallic alloys are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) measurement and hardness test...
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So-called Ni base dual two-phase intermetallic alloys are composed of primary Ni 3 Al (L1 2 ) phase precipitates among eutectoid microstructures consisting of the Ni 3 Al and Ni 3 V (D0 22 ) phases. In this article, microstructural refinement of an alloy with a nominal composition of Ni 75 Al 10 V 15 (in at.%) was attempted by various heat treatment processes. When the alloy was continuously cooled down after solution treatment, fine and cuboidal Ni 3 Al precipitates were developed by rapid cooling while coarse, rounded and coalesced Ni 3 Al precipitates were developed by slow cooling. When the alloy was isothermally annealed at temperatures above the eutectoid temperature, the morphology of the Ni 3 Al 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 Ni 3 Al precipitates were grown keeping cuboidal morphology. The morphological change from the cuboidal to rounded Ni 3 Al 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 Ni 3 Al precipitates generally resulted in high hardness.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1487-1499, October 21–24, 2019,
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CO 2 emission reduction from coal power plants is still a serious issue to mitigate the impact of global warming and resulting climate change, though renewables are growing today. As one of the solutions, we developed A-USC (Advanced Ultra Super Critical steam condition) technology to raise the thermal efficiency of coal power plants by using high steam temperatures of up to 700℃ between 2008 and 2017 with the support of METI (Ministry of Economy, Trade and Industry) and NEDO (New Energy and Industrial Technology Development Organization). The temperature is 100℃ higher than that of the current USC technology. Materials and manufacturing technology for boilers, turbines and valves were developed. Boiler components, such as super heaters, a thick wall pipe, valves, and a turbine casing were successfully tested in a 700℃-boiler component test facility. Turbine rotors were tested successfully, as well, in a turbine rotating test facility under 700℃ and at actual speed. The tested components were removed from the facilities and inspected. In 2017, following the component tests, we started a new project to develop the maintenance technology of the A-USC power plants with the support of NEDO. A pressurized thick wall pipe is being tested in a 700℃ furnace to check the material degradation of an actual sized component.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 24-40, October 22–25, 2013,
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We have reported on the effort being done to develop the A-USC technology in Japan, which features the 700 deg-C steam condition, since the 2007 EPRI conference. Our 9 year project began in 2008. There have been some major changes in the electricity power market in the world recently. At first, the earthquake changed the power system violently in Japan. Almost all nuclear power plants have been shut down and natural gas, oil and coal power plants are working fully to satisfy the market's demands. In the USA, the so called ‘Shale gas revolution’ is going on. In Europe, they are working toward the target of reducing CO 2 emissions by the significant use of renewables with the backup of the fossil fuel power systems and enhancing power grids. A very rapid increase in power generation by coal is being observed in some countries. Despite some major changes in the electric sector in the world and the CO 2 problem, the global need for coal power generation is still high. We can reconfirm that the improvement of the thermal efficiency of coal power plants should be the most fundamental and important measure for the issues we are confronting today, and that continuous effort should be put towards it. Based on the study we showed at the 2007 conference, we developed 700 deg-C class technology mainly focusing on the material and manufacturing technology development and verification tests for key components such as boilers, turbines and valves. Fundamental technology developments have been done during the first half of the project term. Long term material tests such as creep rupture of base materials and welds will be conducted for 100,000hrs continuing after the end of the project with the joint effort of each participating company. Today, we are preparing the plan for the second half of the project, which is made up of boiler components test and the turbine rotating tests. Some boiler superheater panels, large diameter pipes and valves will be tested in a commercially operating boiler from 2015 to 2017. The turbine rotor materials which have the same diameter as commercial rotors will be tested at 700 deg-C and at actual speed.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 1229-1241, October 25–28, 2004,
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Tempered martensitic 9-12%Cr steels bearing tungsten, such as P92 and P122 showing higher creep rupture strength than the conventional steel P91, have been developed for thick section components in ultra-supercritical (USC) boilers. However, their creep strength is not sufficient for applying at the steam condition of 650°C/35MPa or above, which is a recent target condition in order to increase plant efficiency. The research and development project in NIMS on advanced high-Cr steels which can be applied at the steam condition of 650°C/35MPa as boiler components with large diameter and thick section has been carried out since 1997. In this project, it has been revealed that the addition of boron more than 0.01 mass% to the 0.08C-9Cr- 3W-3Co-V,Nb-<0.00ЗN steel remarkably improves creep strength. The boron enriched in M 23 C 6 carbides near prior-austenite grain boundaries suppresses coarsening of these carbides during creep deformation, leading to excellent microstructural stability and creep strength. Further improvement of creep strength is achieved by the addition of appropriate amount of nitrogen which enhances precipitation of fine MX. Excess addition of nitrogen to the high-B containing steel reduces creep rupture lives and ductility. The highest creep strength is obtained in the 0.08C-9Cr-3W-3Co-0.2V-0.05Nb-0.0139B-0.0079N (mass%) steel, resulting in excellent creep strength in comparison with that of P92 and P122. This steel shows good creep ductility even in the long term. It is, therefore, concluded that this high-B bearing 9Cr-3W-3Co-V,Nb steel with the addition of nitrogen in the order of 0.008 mass% is the promising candidate which shows superior creep strength without impairing creep ductility for thick section components in the 650°C-USC plant.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 72-85, August 31–September 3, 2010,
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Recent advances in materials technology for boilers materials in the advanced USC (A-USC) power plants have been reviewed based on the experiences from the strengthening and degradation of long term creep properties and the relevant microstructural evolution in the advanced high Cr ferritic steels. P122 and P92 type steels are considered to exhibit the long term creep strength degradation over 600°C, which is mainly due to the instability of the martensitic microstructure strengthened too much by MX carbonitrides. This can be modified by reducing the precipitation of VN nitride and by optimizing the Cr content of the steels. An Fe-Ni based alloy, HR6W strengthened by the Fe2W type Laves phase is found to be a marginal strength level material with good ductility at high temperatures over 700°C and to be used for a large diameter heavy wall thick piping such as main steam pipe and hot reheat pipe in A-USC plants, while Ni-Co based alloys such as Alloys 617 and 263 strengthened by a large amount of the y’ phase are found to be the high strength candidate materials for superheater and reheater tubes, although they are prone to relaxation cracking after welding and to grain boundary embrittlement during long term creep exposure. A new Ni based alloy, HR35 strengthened by a-Cr phase and other intermetallic phases has been proposed for piping application, which is specially designed for a good resistance to relaxation cracking as well as high strength and a good resistance to steam oxidation and fire-side corrosion at high temperatures over 700°C.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 778-789, October 11–14, 2016,
... steels (MARBN) - are discussed. In order to improve the creep behavior, MARBN steels with different heat treatments and microstructures were investigated using optical microscopy, SEM and EBSD. Furthermore, short term creep rupture tests at 650 degree Celsius were performed, followed by systematic...
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Sufficient energy availability in combination with lowest environmental pollution is a basic necessity for a high living standard in each country. To guarantee power supply for future generations, improved technologies to achieve higher efficiency combined with reduced environmental impact are needed. This challenge is not only aimed to the power station manufacturers, but also to the producers of special steel forgings, who have to handle with more and more advanced materials and complex processes. Bohler Special Steel is a premium supplier of forged high quality components for the power generation industry. This paper reports about experiences in the fabrication of forged components for steam turbines for ultra-supercritical application - from basic properties up to ultrasonic detectability results. The materials used so far are the highly creep-resistant martensitic 9-10% Cr steel class for operating temperatures up to 625°C developed in the frame of the European Cost research program. Additionally our research activities on the latest generation of high temperature resistant steels for operating temperatures up to 650 degree Celsius – the boron containing 9% Cr martensitic steels (MARBN) - are discussed. In order to improve the creep behavior, MARBN steels with different heat treatments and microstructures were investigated using optical microscopy, SEM and EBSD. Furthermore, short term creep rupture tests at 650 degree Celsius were performed, followed by systematic microstructural investigations. As a result it can be concluded, that advanced microstructures can increase the time to rupture of the selected MARBN steels by more than 10 percent.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1151-1162, October 22–25, 2013,
... Abstract An approach to phase analysis called multiphase separation technology (MPST) has been developed to determine phase chemistries of precipitated particles with sizes visible under SEM/EPMA observations based on the data from the conventional EDS measurements on bulk steel/alloy material...
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An approach to phase analysis called multiphase separation technology (MPST) has been developed to determine phase chemistries of precipitated particles with sizes visible under SEM/EPMA observations based on the data from the conventional EDS measurements on bulk steel/alloy material samples. Quite accurate results from its applications have successfully been demonstrated by comparisons of SEM/EPMA - EDS + MPST with some other currently available means, for instance, chemical extractions (CA), TEM-EDS, AP-FIM and Thermo-Calc. etc. Applied examples regarding the relations of change in phase parameters including type, composition, volume fraction, size and distribution of the precipitated particles with material qualities, creep rupture lives, property stabilities, property recovery and boiler tube failures for some advanced heat resistant steels (P92, Super304H, HR3C, TP347HFG (H)) are given through the use of the SEM/EPMA - EDS + MPST in this contribution. Examples on phase quantifications of some nickel base superalloys (Nimonic263, Inconel 740 and Rhenium-containing alloys) are also shown to reveal the feasibility of its use in determining phase chemistries of precipitated particles under different measurement conditions. Practical applications of this combined technology to the material quality control and assessments, processing parameter improvements, as well as fracture/failure analyses of high temperature components have shown that this technology is quite convenient and effective when used for microstructural analysis purposes during R&D, manufacturing and operating processes.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 156-161, October 21–24, 2019,
... Abstract Microstructure change during creep at 650°C has been examined for a high-B 9%Cr steel by FIB-SEM serial sectioning 3D observation, Nano-SIMS, SEM, EBSD and TEM. The precipitates formed in the steel were M 23 C 6 , Laves phase, and a quite small amount of MX. For as-tempered steel...
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Microstructure change during creep at 650°C has been examined for a high-B 9%Cr steel by FIB-SEM serial sectioning 3D observation, Nano-SIMS, SEM, EBSD and TEM. The precipitates formed in the steel were M 23 C 6 , Laves phase, and a quite small amount of MX. For as-tempered steel, precipitation of M 23 C 6 on the prior austenite grain boundaries was clearly found, while precipitation of the Laves phase was not confirmed during tempering. The volume fraction of the Laves phase gradually increased with elapsed time, while M 23 C 6 appeared to increase once and decrease afterward, based on the comparison between the 2,754 h ruptured sample and the 15,426 h ruptured sample. Nano-SIMS measurements have revealed that B segregates on the prior austenite grain boundaries during normalizing, and it dissolves into M 23 C 6 .
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 235-245, October 21–24, 2019,
... increase in the number per unit area of Laves phase particles in high compared with low Mo content areas. To study the effect of MX particles on segregation a methodology combining SEM and TEM was employed. This involved chemically mapping the larger V containing particles using EDS in the SEM...
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Modified 9Cr-1Mo steel (ASTM Gr.91) is widely used in components of fossil fueled power plants around the world today. This grade of steel has however been shown to exhibit significant variations in creep life and creep ductility, which has led to premature in-service failures. The aim of this work is to define potential metallurgical risk factors that lead to this variation in performance. To achieve this, a set of creep test samples that represent a wide range in this variation of creep behavior in this steel grade have been studied in detail. As a first stage in this characterization the macro-scale chemical homogeneity of the materials were mapped using micro-XRF. Understanding the segregation behavior also allows quantification of microstructural parameters in both segregated and non-segregated areas enabling the variations to be determined. For example this showed a significant increase in the number per unit area of Laves phase particles in high compared with low Mo content areas. To study the effect of MX particles on segregation a methodology combining SEM and TEM was employed. This involved chemically mapping the larger V containing particles using EDS in the SEM in segregated and unsegregated areas and then comparing the results to site-specific TEM analysis. This analysis showed that although the average size of the V containing samples is in the expected 0-50 nm size range, these particles in some samples had a wide size distribution range, which significantly overlaps with the M 23 C 6 size distribution range. This together with the segregation characteristics has important implications for determining meaningful quantitative microstructural data from these microstructurally complex materials.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1093-1103, October 22–25, 2013,
... in the temperature range between 525°C and 700°C. Selected crept specimens have been investigated using light optical microscopy, SEM with EDX and TEM. In this study, the oxidation behavior of a number of typical martensitic 9-12%Cr steels was compared with the newly developed 12% Cr steel VM12-SHC. The compositions...
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The recently developed 12%Cr steel VM12-SHC is characterized by very good creep properties at temperatures up to 620°C. This new material development exhibits an excellent oxidation resistance in steam atmospheres at the typical application temperature but also at temperatures up to 650°C. In comparison to the existing 9% Cr grades T/P91 and T/P92, VM12-SHC steel opens due to its excellent oxidation behavior, new possibilities for its application as a heat exchanger boiler component. It was found that outside its application temperature range VM12-SHC also shows, as all 9-12%Cr steels, the appearance of the so called Z-phase. This effect was investigated to understand its influence on creep properties of this class of ferritic/martensitic steels aiming at controlling the microstructure stabilities for future grade developments. Creep testing has been carried out in the temperature range between 525°C and 700°C. Selected crept specimens have been investigated using light optical microscopy, SEM with EDX and TEM. In this study, the oxidation behavior of a number of typical martensitic 9-12%Cr steels was compared with the newly developed 12% Cr steel VM12-SHC. The compositions and morphologies of oxide scales formed after 5000 h exposure steels in simulated steam environments as function of temperature were characterized by light optical metallography and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX).
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1163-1172, October 22–25, 2013,
... and thermal ageing has been investigated. The investigations were carried out by Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). Besides, equilibrium and Scheil calculations were carried out using...
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25Cr-20Ni-Nb-N (Tp310HCbN) steel is a promising austenitic steel for applications in superheater tubes in coal fired thermal power plants due to the high creep strength and oxidation resistance. In this work, the microstructural evolution of this material during heat treatment and thermal ageing has been investigated. The investigations were carried out by Light Optical Microscopy (LOM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Energy Dispersive Spectroscopy (EDS). Besides, equilibrium and Scheil calculations were carried out using the thermodynamic software MatCalc to analyse the stable phases and the solidification process, respectively. Precipitation calculations during solution annealing and subsequent ageing at 650 and 750°C were performed to predict the phase fraction and precipitates radius up to 10.000h ageing time. SEM and TEM investigations of aged specimens revealed the presence of six different precipitates: M 23 C 6 , Cr 2 N, sigma, Z-phase, eta-phase (Cr 3 Ni 2 Si(C,N)) and Nb(C,N). These precipitates were predicted and confirmed by MatCalc simulations. The calculated phase fraction and mean radius show good agreement with experimental data. Finally, simulations of different Cr-, C- and N-content in Tp310HCbN were performed.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 202-212, October 11–14, 2016,
... 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. advanced ultra...
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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.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 347-355, October 11–14, 2016,
... 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...
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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.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 388-399, October 11–14, 2016,
... the magnetism difference after high-temperature service, and XRD, SEM, TEM, SAED and EDS has been adopted to observe and analyze their microstructure, phase structure and composition. The research results show that compared with the delivery state, the lath α´-Martensite and sometimes the lamellar ε-Martensite...
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The delivery state of austenitic heat resistant steel boiler tubes is paramagnetic, such as TP304H, TP347H and S30432, the material state, however, appears obviously magnetic after long-time high-temperature service. Vibrating Sample Magnetometer (VSM) has been employed to test the magnetism difference after high-temperature service, and XRD, SEM, TEM, SAED and EDS has been adopted to observe and analyze their microstructure, phase structure and composition. The research results show that compared with the delivery state, the lath α´-Martensite and sometimes the lamellar ε-Martensite will occur in areas adjacent to grain boundaries due to martensite transformation in the microstructure of austenitic heat resistant steel boiler tube after high temperature service. There are high density dislocations tangled together in the substructure of α´-Martensite, and lamellar stacking faults arrayed orderly by a large number of dislocations in the substructure of ε-Martensite. The magnetism of α´-Martensite, its internal stress and carbides is the reason why the austenitic heat resistant steel boiler tubes appear obviously magnetic after high temperature service, and the α´-Martensite plays a major role.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 446-457, October 11–14, 2016,
... Abstract ASME Grade 91 steel seam-welded elbow pipe, which has been used in a USC plant (A-Plant) for about 6 × 10 4 h, was investigated to clarify the microstructure and remaining creep life of the material at long-term region. SEM and TEM observations were conducted on specimens cut from...
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ASME Grade 91 steel seam-welded elbow pipe, which has been used in a USC plant (A-Plant) for about 6 × 10 4 h, was investigated to clarify the microstructure and remaining creep life of the material at long-term region. SEM and TEM observations were conducted on specimens cut from the welded portions of the intrados and extrados of the elbow, and the number density of creep voids in fine-grained HAZ was measured in the wall-thickness direction. Then, creep rupture tests were performed to examine the remaining life of each portion of the base metal and welded joint. On the basis of the results, it was suggested that the microstructural changes were small and that the cumulative creep damage was also small for the elbow pipe during its use at the USC plant for about 6 × 10 4 h. The present result was compared with the result of an investigation on Grade 91 steel elbow used in another USC plant (B-Plant) for about 5 × 10 4 h. The A-Plant material had a creep life about ten times longer than that of the B-Plant material for not only the base metals but also the welded joint. Through the comparison of the investigation results, it was suggested that the difference in the creep deformation property between the base metals of the elbows was the main reason for the difference in their creep lives.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 690-701, October 11–14, 2016,
... 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. advanced ultra-supercritical steam...
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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.
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