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stress rupture test
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Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 259-269, October 15–18, 2024,
... and turbine rotor life, Sulzer has developed evaluation and rejuvenation processes that include microstructural assessment and stress rupture testing of specimens from service-exposed blades. While stress rupture testing presents certain limitations and challenges in evaluating material condition, Sulzer has...
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Gas turbine blades made from nickel-based superalloys, valued for their high temperature stability and creep resistance, undergo various forms of microstructural degradation during extended service at elevated temperatures that can ultimately lead to blade failure. To extend blade and turbine rotor life, Sulzer has developed evaluation and rejuvenation processes that include microstructural assessment and stress rupture testing of specimens from service-exposed blades. While stress rupture testing presents certain limitations and challenges in evaluating material condition, Sulzer has successfully rejuvenated hundreds of gas turbine blade sets across multiple superalloy types, including GTD 111, IN 738 LC, and U 500, demonstrating the effectiveness of heat treatment rejuvenation in improving microstructure and mechanical properties of service-degraded components.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 703-712, October 25–28, 2004,
.... For a 141MW unit main steam line, the remaining life calculated according to the German Boiler Code TRD 508 was found to be almost exhausted. It was recommended to remove a pipe sample with a circumference weld for laboratory examination. Stress rupture tests were performed on three types of specimens...
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Numerous factors, including actual chemical composition, heat treatment, microstructure, dimensions, and service conditions, determine the lifetime of creep-exposed components. This creates a wide gap between the real condition of a given steel pipe and its project specification. For a 141MW unit main steam line, the remaining life calculated according to the German Boiler Code TRD 508 was found to be almost exhausted. It was recommended to remove a pipe sample with a circumference weld for laboratory examination. Stress rupture tests were performed on three types of specimens: tangential, longitudinal, and longitudinal with a heat-affected zone in the middle of the gauge length using the isostress testing method. Metallographic examination of the broken specimens was conducted. Linear extrapolation of the rupture times to the service temperature yielded a residual service life of more than 100,000 hours.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1432-1440, October 22–25, 2013,
... Abstract The current study proposed a new method that utilizes digital image correlation (DIC) techniques to measure in-situ full field strain maps of creep resistant material welds. The stress-rupture test is performed in a Gleeble thermal mechanical simulator. This technique successfully...
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The current study proposed a new method that utilizes digital image correlation (DIC) techniques to measure in-situ full field strain maps of creep resistant material welds. The stress-rupture test is performed in a Gleeble thermal mechanical simulator. This technique successfully captured a significant difference in the local creep deformation between two Grade 91 steel welds with different pre-welding conditions (standard and non-standard). Strain contour plots exhibited inhomogeneous deformation in the weldments, especially at the heat-affected zone (HAZ). Standard heat-treated specimens had significant creep deformation in the HAZ. On the other hand, non-standard heat treated specimens showed HAZ local strains to be 4.5 times less than that of the standard condition, after a 90-hour creep test at 650°C and 70 MPa. The present study measured the full field strain evolution in the weldments during creep deformation for the first time. The proposed method demonstrated a potential advantage to evaluate local creep deformation in the weldments of any creep resistant material within relatively short periods of time.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 939-950, October 11–14, 2016,
... in respect to the alloy additions and microstructure. The mechanical properties of the weld metals at ambient temperature are examined. Creep properties of both undiluted weld metals and cross-weld joints are examined through stress rupture test and the data are evaluated and compared with those of the base...
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Despite the significant progress achieved in power generation technologies in the past two decades, finding effective solutions to further reduce emissions of harmful gases from thermal power plant still remains the major challenge for the power generation industry as well as alloy material developers. In the European material programmes COST 522 and COST 536, based on the existing 9-12%Cr creep resisting steels, an advanced 9%Cr-Mo martensitic alloy, C(F)B2 (GX13CrMoCoVNbNB9-2-1) alloy has been developed. By modification through alloying of boron and cobalt and together with other micro-adjustment of the composition, C(F)B2 alloys has showed very encouraging properties. The current paper summaries the development and evaluation of the matching filler metals for C(F)B2 grade. The design of the filler metal composition is discussed and comparison is made with the parent materials in respect to the alloy additions and microstructure. The mechanical properties of the weld metals at ambient temperature are examined. Creep properties of both undiluted weld metals and cross-weld joints are examined through stress rupture test and the data are evaluated and compared with those of the base alloy and other existing 9%Cr-Mo creep resisting steels.
Proceedings Papers
AM-EPRI2007, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fifth International Conference, 940-967, October 3–5, 2007,
... of the filler material at operating temperatures, two types of high temperature tests were carried out, hot tensile tests (ASTM E21 (7)) and short-term stress rupture tests (aiming for failure in 100 hours). All of the high temperature testing was carried out at 1100°F (593°C). This is the same temperature...
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In the late 1980s, the domestic utility industry experienced failures in dissimilar metal welds (DMWs) between low-alloy ferritic tubing and austenitic tubing in superheaters and reheaters. Extensive research by EPRI identified that nickel-based filler metals significantly improved service life compared to 309 SS filler metals. Additionally, optimized joint geometries and increased weld metal reinforcement were found to further enhance durability. A new nickel-based filler metal was developed with thermal expansion properties similar to the low-alloy base metal, along with a low chromium content designed to minimize the carbon-denuded zone. However, this filler metal was never commercialized due to its tendency to microfissure, which resulted in a shorter-than-expected service life. This paper explores further investigations into the microfissuring of this filler metal and examines long-term testing to assess its suitability for high-temperature applications.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 933-948, August 31–September 3, 2010,
... strained tensile specimens was considered to be the most appropriate approach for this work. Test Programme and Validity of Creep Test Stress Levels The creep properties of the selected materials were evaluated by stress rupture testing for nominal test durations of 1000 hours and 3000 hours at a test...
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Cold working and bending during boiler manufacturing can induce strain hardening in austenitic stainless steel, potentially compromising creep ductility and leading to premature failures during operation. While design codes like ASME I, PG 19 provide guidelines for maximum strain levels before solution treating is required, industry concerns suggest these limits may be too high, prompting some boiler manufacturers to implement more conservative thresholds. This study examined the creep ductility of four austenitic stainless steels (TP310HCbN, XA704, TX304HB, and Sanicro 25) at prior strain levels of 12% and 15%, with Sanicro 25 demonstrating the highest ductility, followed by TX304HB, XA704, and TP310HCbN. Solution annealing successfully restored creep ductility to exceed 10% elongation in all materials, though this treatment may be necessary at strains of 12% and 15% for all materials except Sanicro 25 to ensure adequate creep ductility. The findings suggest that ASME I PG 19 guidelines for austenitic stainless steels containing Cb, V, and N should be reviewed, as lower strain limits could help reduce strain-induced precipitation hardening failures.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 556-567, October 11–14, 2016,
... on stress rupture testing of 2CrMoL weld metal, RWE realised that this type of P91 cold weld repair would have a limited life due to the weak 2CrMoL weld metal and could only be considered as a temporary repair for a maximum of 2 years. After this initial work on P91 cold weld repairs, it was decided...
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The application of cold weld repair techniques in the power industry has been well documented. This type of repair is only considered when a conventional repair (involving post-weld heat treatment) is impracticable or the penalties of time and cost for conventional repair are sufficiently high. A typical cold weld repair in the UK has involved low alloy ferritic steel (½Cr½Mo¼V, 2¼Cr1Mo) components welded with nickel based SMAW consumables or ferritic FCAW consumables. Modified 9Cr steel components have been used in UK power plant since the late 1980’s for a number of applications, such as superheater outlet headers, reheat drums and main steam pipework. The problems associated with this material have also been well documented, particularly premature type IV cracking of welds on creep weakened modified 9Cr steel. RWE Generation UK have developed modified 9Cr cold weld repairs on headers, pipework and tubes. These repairs have been underwritten with extensive testing. This paper will describe the work performed on developing T91 cold weld repairs and where they have been applied on power plant.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 190-201, October 11–14, 2016,
... Property The projected 100,000h stress rupture strength of alloy GH750 is more than 100MPa at 750°C. Extensive stress rupture tests were performed on tube and bar forms of the alloy to evaluate the stress rupture strength at 100,000 hours. The testing temperature range covered is from 700°C to 850°C...
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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 M 23 C 6 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.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1361-1372, October 21–24, 2019,
... for obtaining information about the material properties of steels and alloys when only a limited amount of test material is available that does not make it possible to perform conventional creep and/or stress rupture tests. SPCT testing can also be used for determination of the residual life of critical...
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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.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 98-119, October 22–25, 2013,
... phase in Super304H was analyzed by 3 dimensional atomic probe(3DAP) in detail. Mechanical properties of hardness, impact toughness and stress rupture lives were also tested in some investigated materials. RESULTS AND DISCUSSIONS Austenitic steels Austenitic heat-resistant steels TP347H, Super304H...
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This overview paper contains a part of structure stability study on advanced austenitic heat-resisting steels (TP347H, Super304H and HR3C) and Ni-base superalloys (Nimonic80A, Waspaloy and Inconel740/740H) for 600-700°C A-USC fossil power plant application from a long-term joint project among companies, research institutes and university in China. The long time structure stability of these advanced austenitic steel TP347H, Super304H, HR3C in the temperature range of 650-700 °C and Ni-base superalloys Nimonic80A, Waspaloy and Inconel740/740H in the temperature range of 600-800°C till 10,000h have been detailed studied in this paper.
Proceedings Papers
AM-EPRI2007, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fifth International Conference, 220-230, October 3–5, 2007,
.... Mechanical property and oxidation resistance tests compared the modified alloys with the original Inconel alloy 740, yielding preliminary results that demonstrate minimal modifications can improve stress rupture strength while maintaining corrosion resistance. Microstructural examinations further confirmed...
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A new nickel-base superalloy, Inconel alloy 740, is being developed for ultra-supercritical (USC) boiler applications operating above 750°C, designed to meet critical requirements for long-term high-temperature stress rupture strength (100 MPa for 10 5 hours) and corrosion resistance (2 mm/2 × 10 5 hours). Experimental investigations revealed key structural changes at elevated temperatures, including γ coarsening, γ' to η transformation, and G phase formation. To enhance strengthening effects and structural stability, researchers conducted a systematic optimization process based on thermodynamic calculations, implementing small adjustments to several alloying elements and designing modified alloy compositions. Comprehensive testing examined the long-term structural stability of these modifications, with investigations conducted up to 5,000 hours at 750 and 800°C, and 1,000 hours at 850°C. Mechanical property and oxidation resistance tests compared the modified alloys with the original Inconel alloy 740, yielding preliminary results that demonstrate minimal modifications can improve stress rupture strength while maintaining corrosion resistance. Microstructural examinations further confirmed the enhanced thermal stability of the modified alloy, positioning Inconel alloy 740 as a promising candidate for USC boiler applications at 750°C or higher temperatures.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 161-168, October 11–14, 2016,
... for purpose of the transition joint by structural integrity assessment, additional mechanical test data, beyond the scope of ASME IX weld procedure qualification, was required. The range of mechanical testing included creep stress rupture testing (parent and cross weld), stress relaxation, cyclic stress...
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INCONEL 740H has been developed by Special Metals for use in Advanced Ultra Super Critical (A-USC) coal fired boilers. Its creep strength performance is currently amongst the ‘best in class’ of nickel based alloys, to meet the challenge of operating in typical A-USC steam temperatures of 700°C at 35 MPa pressure. Whilst the prime physical property of interest for INCONEL 740H has been creep strength, it exhibits other physical properties worthy of consideration in other applications. It has a thermal expansion co-efficient that lies between typical values for Creep Strength Enhanced Ferritic (CSEF) steels and austenitic stainless steels. This paper describes the validation work in support of the fabrication of a pipe transition joint that uses INCONEL 740H pipe, produced in accordance with ASME Boiler Code Case 2702, as a transition material to join P92 pipe to a 316H stainless steel header. The paper gives details of the material selection process, joint design and the verification process used for the joint.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 873-884, October 15–18, 2024,
... with uniaxial creep testing to quantify creep deformation rates, rupture time, some measure of creep ductility, and shape of the creep curve. Simple stress-rupture tests do not capture the essential data to properly assess heat-to-heat or material-to-material variability. Two heats of grade 91 steel...
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The time-dependent behavior of 9Cr creep strength enhanced ferritic (CSEF) steels has long fixated on the creep life recorded in uniaxial constant load creep tests. This focus is a consequence of the need to develop stress allowable values for use in the design by formulae approach of rules for new construction. The use of simple Design by Formula rules is justified in part by the assumption that the alloys used will invariably demonstrate high creep ductility. There appears to be little awareness regarding the implication(s) that creep ductility has on structural performance when mechanical or metallurgical notches (e.g., welds) are present in the component design or fabricated component. This reduced awareness regarding the role of ductility is largely because low alloy CrMo steels used for very many years typically were creep ductile. This paper focuses on the structural response from selected tests that have been commissioned or executed by EPRI over the last decade. The results of these tests demonstrate unambiguously the importance that creep ductility has on long-term, time-dependent behavior. The metallurgical findings from the selected tests are the focus of the Part II paper. The association of performance with notch geometry, weld strength, and other potential contributing factors will be highlighted with a primary objective of informing the reader of the variability, and heat-specific behavior that is observed among this class of alloys widely used in modern thermal fleet components and systems.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 861-872, October 15–18, 2024,
... condition. Mechanical and Environmental Testing Subsized samples for tensile and stress rupture tests were manufactured from blanks manufactured using identical conditions as for the processability samples, in the XY and Z directions. At least three tests per test condition were conducted to mitigate...
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The advancement of additive manufacturing (AM) technology has heightened interest in producing components from nickel-based superalloys for high-temperature applications; however, developing high gamma prime (γ’) strengthened alloys suitable for AM at temperatures of 1000°C or higher poses significant challenges due to their “non-weldable” nature. Traditional compositions intended for casting or wrought processes are often unsuitable for AM due to their rapid heating and cooling cycles, leading to performance compromises. This study introduces ABD-1000AM, a novel high gamma prime Ni-based superalloy designed using the Alloys-by-Design computational approach to excel in AM applications at elevated temperatures. Tailored for AM, particularly powder bed fusion, ABD-1000AM demonstrates exceptional processing capability and high-temperature mechanical and environmental performance at 1000°C. The study discusses the alloy design approach, highlighting the optimization of key performance parameters, composition, and process-microstructure-performance relationships to achieve ABD-1000AM’s unique combination of processability and creep resistance. Insights from ABD-1000AM’s development inform future directions for superalloy development in complex AM components.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 429-439, October 11–14, 2016,
... 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...
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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.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 693-704, August 31–September 3, 2010,
... and headers. This paper investigated microstructural evolution of P92 and 10Cr9MoW2VNbBN steel during creep and its influence on mechanical behaviors to reveal the degradation mechanism of P92 and 10Cr9MoW2VNbBN based on high temperature stress-rupture test. 1. Materials and experiment P92 steel ( 457×70mm...
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In this paper, the microstructural evolution of P92 steel were studied in the viewpoint of degradation mechanism based on the creep rupture experiment results obtained at elevated temperature by means of macroscopic, metallographic, electronic microscope, energy spectrum, XRD and TEM examination. The results show that the decrease of mechanical properties of P92 steel is mainly due to the change of microstructure and the transformation of carbides, and there is definite relationship between microstructure evolution, mechanical properties and life loss of P92 steel. The results are beneficial to the further study of mechanism of high temperature creep rupture strength and microstructural evolution of heat-resistant steel. It also has important instructive significance to quantitative identification of scientific selection of materials.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 1194-1198, October 11–14, 2016,
... and 2.5mm/s respectively. A 9Cr-1Mo filler wire with 1.6mm in diameter was used. The welded plates were post-weld heat treated (PWHT) in a furnace at 760°C for 2 hours, followed by air-cooling to room temperature. The treated plates were sectioned and machined for creep tests. Stress-Rupture Test...
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Fossil fuels continue to be the primary source of energy in the U.S and worldwide. In order to improve the efficiency of fossil power plants, advanced structural materials need to be developed and deployed to meet the need of high temperature creep resistance and corrosion resistance. Examples include creep strength enhanced ferritic (CSEF) steels, austenitic stainless steels, nickel-based superalloys, and oxide dispersion strengthened alloys. Welding is extensively used in construction of fossil power plants. The performance of the weld region can be critical to the safe and economical operation of fossil power plants. Degradations in performance such as reduced creep strength and premature failure in the weld region (e.g. Type IV failure in ferritic steels) are examples of longstanding welding and weldability problems for boiler and other components. In the past, extensive studies have been carried out to characterize the different microstructures in different regions of a weld, and to a certain extent, to establish the correlations between the microstructure and the creep strength. However, the metallurgical or microstructural induced local stress/strain variations have been seldom quantified. In addition, it has been long recognized that, due to the sharp microstructure and property gradients in the weld and HAZ, the standard creep testing procedure for the base metal can produce erroneous results when used for weld testing.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 283-294, October 11–14, 2016,
... of SP2215 Figure 17: Grain size and inclusion evaluation of SP2215 Figure 18: Tubing component qualification performance for flare and flattening tests MECHANICAL PROPERTIES Tensile properties and stress-rupture tests results at different temperatures are shown in Fig.19 and Fig.20 (Larson-Miller Plot). 291...
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For raising thermal efficiency and decreasing CO 2 emission, China had constructed the first 600°C ultra-supercritical(USC) fossil power plant in 2006. Now more than a hundred 600°C, 1000MW USC electric power units have been put in service. Recently, China has also developed 620°C USC power units and some of them have been put in service already. Meanwhile, more than fifty 620°C USC boilers will be produced by various China boiler companies. The austenitic steels TP347H, Super304H and HR3C are routinely used for 600°C USC boilers. Among these steels, a big amount of Super304H has been used for boiler superheater/reheater components application. However, Super304H is characterized by good stress-rupture strength but poor corrosion/oxidation resistance. On the other side, HR3C is characterized by very good corrosion/oxidation resistance but lower stress-rupture strength than Super304H. Now, the China 620°C USC project needs a new austenitic heat resisting steel with high stress-rupture strength and good corrosion/oxidation resistance to fulfill the superheater/reheater tube components application requirement. A new austenitic heat resisting steel SP2215 is based on 22Cr-15Ni with certain amount of Cu and also Nb and N for multiphase precipitation (MX, Cu-rich phase, NbCrN) strengthening in Fe-Cr-Ni austenitic matrix and M 23 C 6 carbide precipitation at grain boundaries. This SP2215 new austenitic steel is characterized by high stress-rupture strength (650°C, 105h>130MPa) and good corrosion/oxidation resistance. SP2215 austenitic steel has been commercially produced in tube product form. This SP2215 new austenitic heat-resisting steel is recommended to be used as superheater/reheater components for 620°C USC boiler application.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1047-1058, October 22–25, 2013,
... impact test. To select the annealing conditions for stress relief, stress relaxation tests and hardness tests were conducted on the weld joints after various heat treatments. The microstructure was also evaluated by SEM and TEM. Creep rupture tests are being performed for the weld joints with and without...
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Welding processes and fabrication techniques have been studied in the development of Advanced USC boilers. Advanced 9Cr steels, Fe-Ni alloy (HR6W) and Nickel base alloys (HR35, Alloy 617, Alloy 263, Alloy 740 and Alloy 740H) have been selected as candidate materials for the boiler. The weld joints of these alloys were prepared from plates, small diameter tubes and large pipes, and welding procedure tests were performed. In this study, TIG and SMAW were applied. Both welding process produced good weld joints, and they showed good results in bending tests, tensile tests and the Charpy impact test. To select the annealing conditions for stress relief, stress relaxation tests and hardness tests were conducted on the weld joints after various heat treatments. The microstructure was also evaluated by SEM and TEM. Creep rupture tests are being performed for the weld joints with and without heat treatment. The maximum creep rupture tests are expected to take over 100,000 hours. In the study of fabrication techniques, hot bending tests by high frequency induction heating for large pipes and cold/hot bending tests for small diameter tubes were established. After the bending tests, mechanical property tests such as tensile tests, impact tests and creep rupture tests were conducted. The effect of pre-strain on creep strength was studied to take the creep test results after bending into consideration. The creep rupture test will be continued for specimens from weld joints and bending pipes to show their long term reliability.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1237-1249, October 21–24, 2019,
... of an alloy 625 to IBN-1 transverse stress rupture specimen - test temperature 650°C. (Photograph courtesy of TWI) 1241 5 IBN-1 (Transverse Weld) CB2 Castings 100 IBN-1 Castings (MPaS)tress 10 Larson Miller_ (no value for comparative purpose only) Fig.6 IBN-1 Cross weld mean stress rupture curve (hatched red...
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To meet worldwide emission targets many Government policies either avoid the use of coal burning plant for future energy production, or restrict emissions per kilogram of coal consumed beyond the capability of most conventional plant. As a result this has accelerated current worldwide developments of steel and nickel alloys for coal-fired plant to operate at temperatures in excess of 625°C. Within the UK a modified 9%Cr steel has been developed which is based on the MarBN steel first proposed by Professor Fujio Abe of NIMS Japan, and has been designated IBN-1. The steel is modified by additions of, typically, 3% cobalt and tungsten with controlled additions of boron and nitrogen. While development of 9%Cr steels has continued since the last EPRI high temperature material conference in 2016 (Portugal), parallel developments in nickel alloy castings for even higher temperature and pressure applications have also continued. This paper summarises the latest developments in both of these material types.
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