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Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 939-950, October 11–14, 2016,
... 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...
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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, 303-319, October 3–5, 2007,
... Abstract This paper presents comprehensive test results of thick-walled VM12 steel pipes containing 12% chromium, vanadium, and tungsten, with cobalt addition. The primary objective was to verify welding technologies for boiler superheater thick-walled components and characterize the strength...
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This paper presents comprehensive test results of thick-walled VM12 steel pipes containing 12% chromium, vanadium, and tungsten, with cobalt addition. The primary objective was to verify welding technologies for boiler superheater thick-walled components and characterize the strength, technological properties, and microstructure of welded joints produced at RAFAKO S.A. The extensive research program encompassed a broad range of tests on both parent material and welded joints, including mechanical property assessments at room temperature, creep resistance evaluations, low-cycle fatigue testing at room temperature and 600°C (1120°F), and detailed macro- and microstructural examinations. Furthermore, the investigation included a comprehensive microstructural stability assessment using light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), conducted after fatigue resistance testing at room and elevated temperatures, following additional annealing at 700°C (1,920°F), and after 1,000 hours of exposure for both parent material and welded joints. These investigations were conducted as part of the COST 536 Action, representing a collaborative effort to understand and characterize high-temperature creep-resistant steels like VM12 for advanced power generation applications.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 1066-1074, October 15–18, 2024,
... Abstract Nitridation is a high-temperature material degradation issue that can occur in air and in environments containing nitrogen, ammonia, etc., and in a variety of industrial processes. The nitridation behavior of several commercial nickel- and cobalt-based alloys is reviewed in this paper...
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Nitridation is a high-temperature material degradation issue that can occur in air and in environments containing nitrogen, ammonia, etc., and in a variety of industrial processes. The nitridation behavior of several commercial nickel- and cobalt-based alloys is reviewed in this paper. The alloys include Haynes 230, Haynes 188, Haynes 625, Haynes 617, Haynes 214, Hastelloy X, and Haynes 233. The environments discussed are high-purity nitrogen gas between 871°C and 1250°C, 100% ammonia gas at 982°C and 1092°C, and a simulated combustion atmosphere at 982°C. The results showed that nitridation occurred in all the environments containing nitrogen. The nitridation attack was strongly influenced by the alloy compositions and the type of oxide formed (i.e., chromia or alumina), as some degree of oxidation was expected in the environments in which residual oxygen was present. Thermal cycling is briefly discussed because the integrity of protective oxides is also an important factor in resisting high-temperature oxidation and nitridation attack.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 1280-1298, October 25–28, 2004,
... formation up to 1% content. While cobalt increased Laves phase fraction at 650°C, it did not improve long-term CRS and even caused a rapid decrease in short-term CRS. Copper, on the other hand, promoted the precipitation of fine Cu-rich particles that acted as nucleation sites for Laves phase and M 23 C 6...
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This study examines the influence of carbon and austenite stabilizing elements (Ni, Mn, Co, Cu) on Laves phase precipitation, Fe 2 W formation, and creep rupture strength (CRS) in 9-12% Cr steels at 600-700°C. Nickel and manganese had minimal impact on Laves phase and coarse carbide formation up to 1% content. While cobalt increased Laves phase fraction at 650°C, it did not improve long-term CRS and even caused a rapid decrease in short-term CRS. Copper, on the other hand, promoted the precipitation of fine Cu-rich particles that acted as nucleation sites for Laves phase and M 23 C 6 carbide. This resulted in a different needle-like Laves phase morphology compared to the globular type observed in nickel and cobalt alloys, leading to improved CRS in the copper alloy. Increasing carbon content from 0.1% to 0.2% effectively suppressed Laves phase formation, as confirmed by Thermo-Calc calculations. Notably, for cobalt alloys with higher tungsten content, higher carbon content (0.09% to 0.19%) improved CRS at 650°C, whereas the opposite effect was observed in nickel and nickel-manganese alloys. Copper alloys maintained improving CRS trends even with increased carbon, leading to the overall best CRS performance among the tested alloys with 0.2% carbon.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 909-923, October 15–18, 2024,
... compared to cobalt-based hardfacing materials, J513 demonstrates additional advantages in powder metallurgy applications due to its ability to achieve desired powder characteristics through atomization without requiring post-atomization annealing. Through experimental investigation based on fundamental...
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This study explores the expanded applications of Alloy J513, a high-performance material traditionally used in cast engine valvetrain components, for powder metallurgy and surface cladding applications. While already recognized for its superior heat and wear resistance at a lower cost compared to cobalt-based hardfacing materials, J513 demonstrates additional advantages in powder metallurgy applications due to its ability to achieve desired powder characteristics through atomization without requiring post-atomization annealing. Through experimental investigation based on fundamental metallurgical principles and cladding engineering processes, the presented research demonstrates J513’s exceptional weldability and favorable weldment structure compared to conventional cobalt-based alloys. The study establishes crucial relationships between weldment behavior and unit energy input, providing valuable insights for advanced cladding techniques while highlighting J513’s potential as a sustainable alternative to traditional nickel- and cobalt-based alloys in various manufacturing processes, including surface overlay and additive manufacturing.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 460-469, October 21–24, 2019,
... to protect them from wear and to reduce friction. Stellite 6 (Cobalt-based alloy) is the benchmark hardfacing owing to its anti-galling properties. However, the latest results tend to indicate that it is not suitable for high pressure application above 700°C. An alternative hardfacing will be required...
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Materials are the key to develop advanced ultra-supercritical (A-USC) steam generators. Operating at temperature up to 760°C and sustained pressure up to 4500 psi. Pressure vessel and piping materials may fail due to creep, oxidation, and erosion. Valves are particularly subjected to loss of function and leakage due to impermeant of the sealing surfaces. New materials, less susceptible to the above damage modes are needed for A-USC technology. Two Ni-based superalloys have been identified as prime candidates for valves based materials. Hardfacing is applied to sealing surfaces to protect them from wear and to reduce friction. Stellite 6 (Cobalt-based alloy) is the benchmark hardfacing owing to its anti-galling properties. However, the latest results tend to indicate that it is not suitable for high pressure application above 700°C. An alternative hardfacing will be required for A-USC. New Ni- and Co- based alloys are being developed for applications where extreme wear is combined with high temperatures and corrosive media. Their chemistry accounts for the excellent dry-running properties of these alloys and makes them very suitable for use in adhesive (metal-to- metal) wear. These new alloys have better wear, erosion, and corrosion resistance than Stellite 6 in the temperature range 800°C ~ 1000°C. As such, they have the potential to operate in A-USC. Velan recently developed an instrumented high temperature tribometer in collaboration with Polytechnique Montreal to characterize new alloys including static and dynamic coefficients of friction up to 800°C. We present herein the methodology that has been devolved to explore the effects of elevated temperature on the tribological behavior of those advanced material systems, with the goal of capturing the basis for the specification, design, fabrication, operation, and maintenance of valves for A-USC steam power plants.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 1256-1269, October 25–28, 2004,
... (dislocation pinning) is used for sustained strengthening. Different MX-forming elements (V, Ta, Ti) are investigated to identify the optimal combination for high quantities of finely distributed strengthening particles. Additionally, cobalt and copper are employed to promote a fully martensitic microstructure...
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This study explores methods to enhance the creep strength of 12%Cr martensitic/ferritic steels. The approach focuses on utilizing various precipitates to hinder microstructure coarsening and dislocation movement. A combination of Laves phase (slow precipitation) and MX carbonitrides (dislocation pinning) is used for sustained strengthening. Different MX-forming elements (V, Ta, Ti) are investigated to identify the optimal combination for high quantities of finely distributed strengthening particles. Additionally, cobalt and copper are employed to promote a fully martensitic microstructure and potentially slow down diffusion or provide nucleation sites for Laves phase precipitation. Long-term creep tests confirm the effectiveness of Laves phase precipitation, particularly with tungsten present. Tantalum's influence on both MX precipitation and the Laves phase is also observed. Combining multiple MX-forming elements (V/Ta, V/Ti, Ta/Ti) further improves creep strength, supported by predictions of high MX carbonitride formation from Thermo-Calc calculations. Partially replacing cobalt with copper (1%) also demonstrates positive effects on creep properties.
Proceedings Papers
AM-EPRI2007, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fifth International Conference, 377-390, October 3–5, 2007,
... a molybdenum-containing superalloy to achieve low thermal expansion. They systematically investigated the effects of molybdenum and cobalt content, gamma prime phase amount, and aluminum/titanium ratio on thermal expansion, tensile properties, and creep-rupture properties. These investigations were conducted...
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The operating temperature of ultrasupercritical (USC) power plants is increasing, with planned temperatures reaching up to 700°C. Austenitic superalloys are promising alternatives to ferritic heat-resistant steels due to their potential for high strength at temperatures around 650-700°C. While austenitic nickel-base superalloys generally exhibit higher creep rupture strength than ferritic heat-resistant steels, they also have drawbacks, including higher thermal expansion, lower creep rupture ductility, and increased costs. Initially, the researchers focused on developing a molybdenum-containing superalloy to achieve low thermal expansion. They systematically investigated the effects of molybdenum and cobalt content, gamma prime phase amount, and aluminum/titanium ratio on thermal expansion, tensile properties, and creep-rupture properties. These investigations were conducted using the conventional molybdenum-containing Alloy 252 as a reference. The developed superalloy, notably free of cobalt and combined with a modified heat treatment, demonstrated significantly improved creep rupture elongation compared to Alloy 252, while maintaining low thermal expansion and high creep rupture strength similar to the reference alloy. Additionally, the research evaluated creep-rupture properties at 700°C for up to approximately 20,000 hours to assess long-term applications. The study also examined the weldability and mechanical properties of weld joints at 750°C, focusing on potential boiler tube applications.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 768-777, October 11–14, 2016,
... Abstract 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...
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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.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 482-490, October 22–25, 2013,
... Abstract Hardfacing alloys are commonly used for wear- and galling-resistant surfaces for mechanical parts under high loads, such as valve seats. Cobalt-based Stellite, as well as, stainless-steel-based Norem02 and Tristelle 5183 alloys show similar microstructural features that correlate...
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Hardfacing alloys are commonly used for wear- and galling-resistant surfaces for mechanical parts under high loads, such as valve seats. Cobalt-based Stellite, as well as, stainless-steel-based Norem02 and Tristelle 5183 alloys show similar microstructural features that correlate with good galling resistance. These microstructures contain hard carbides surrounded by a metastable austenite (fcc) phase that transform displacively to martensite (hcp or bcc or bct) under deformation. As a result, the transformed wear surface forms a hard layer that resists transition to a galling wear mechanism. However, at elevated temperature (350°C), the stainless steel hardfacing alloys do not show acceptable galling behavior, unlike Stellite. This effect is consistent with the loss of fcc to bcc/bct phase transformation and the increase in depth of the heavily deformed surface layer. Retention of high hardness and low depth of plastic strain in the surface tribolayer is critical for retaining galling resistance at high temperature.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 35-46, October 11–14, 2016,
... with chemical concentration of Cobalt and tungsten higher than that of CB2 (GX-13CrMoCoVNbNB9) typically, 2% to 3 Co, 3%W, with controlled B and N additions. The paper will discuss the work undertaken on prototype MarBN steel castings produced in UK funded research projects, and summarise the results achieved...
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The necessity to reduce carbon dioxide emissions of new fossil plant, while increasing net efficiency has lead to the development of not only new steels for potential plant operation of 650°C, but also cast nickel alloys for potential plant operation of up to 700°C and maybe 750°C. This paper discusses the production of prototype MarBN steel castings for potential plant operation up to 650°C, and gamma prime strengthened nickel alloys for advanced super critical plant (A-USC) operation up to 750°C. MarBN steel is a modified 9% Cr steel with chemical concentration of Cobalt and tungsten higher than that of CB2 (GX-13CrMoCoVNbNB9) typically, 2% to 3 Co, 3%W, with controlled B and N additions. The paper will discuss the work undertaken on prototype MarBN steel castings produced in UK funded research projects, and summarise the results achieved. Additionally, within European projects a castable nickel based super alloy has successfully been developed. This innovative alloy is suitable for 700°C+ operation and offers a solution to many of the issues associated with casting precipitation hardened nickel alloys.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1237-1249, October 21–24, 2019,
... 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...
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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.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 304-320, October 22–25, 2013,
..., SdF produced a prototype FB2 rotor using a conventional process. FB2, a 10% Cr steel containing cobalt and boron but lacking tungsten, emerged from the COST 522 program as the best candidate for scaling up from a laboratory experiment to a full-sized industrial component. Notably, the addition...
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Driven by the need to reduce CO 2 emissions through increased steam temperature and pressure in new power plants, research in Europe led to the development of enhanced high-chromium steels with improved creep resistance and service temperature stability. After years of development, Rotor E, a steel composition created during the COST programs (501, 522, and 536), has become a commercially available product. While traditionally forged and remelted using electroslag remelting (ESR), this paper demonstrates the successful production of large rotor components using a conventional process without ESR, achieved through tailored process control. This paper details Società delle Fucine's (SdF) current production of Rotor E using a conventional route based on ladle furnace and vacuum degassing, as well as the mechanical and creep behaviors of the resulting forged products. Additionally, SdF produced a prototype FB2 rotor using a conventional process. FB2, a 10% Cr steel containing cobalt and boron but lacking tungsten, emerged from the COST 522 program as the best candidate for scaling up from a laboratory experiment to a full-sized industrial component. Notably, the addition of boron effectively improved the microstructure's stability and consequently enhanced the creep resistance of these new, advanced martensitic steels. Finally, the paper will present updates on the long-term characterization program for the FB2 steel trial rotor.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 321-332, October 22–25, 2013,
... Abstract A 9% Cr steel containing cobalt and boron, X13CrMoCoVNbNB9-2-1, has been manufactured by electroslag remelting (ESR) to evaluate its performance and to compare its creep strength and microstructure to a forging made from electroslag hot-topping ingot. The evaluation results confirm...
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A 9% Cr steel containing cobalt and boron, X13CrMoCoVNbNB9-2-1, has been manufactured by electroslag remelting (ESR) to evaluate its performance and to compare its creep strength and microstructure to a forging made from electroslag hot-topping ingot. The evaluation results confirm that it is possible to produce rotor forgings with homogeneous composition and good properties by the ESR process. The results of creep rupture tests up to 5000 h indicate that the creep strength of the forging made from ESR ingot is similar to that of the forging produced by the electroslag hot-topping process. Martensitic lath microstructures with high density dislocations and the precipitations of M 23 C 6 , VX, NbX and M2X are observed after the quality heat treatments at the center portion of both forgings. There is no large difference in the martensitic lath widths, distributions, and sizes of those particles between both trial forgings.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 191-201, October 25–28, 2004,
... prior austenite grain boundaries, as excess dislocations inside the grain are difficult to rearrange. This paper presents a new approach using carbon-free martensitic alloys strengthened by intermetallic compounds. An iron-nickel-cobalt martensite matrix with Laves phase as the precipitate is selected...
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Achieving long-term stability of the tempered martensite is considered crucial for increasing the creep resistance of steels at elevated temperatures above 700°C. It is noted that at low stress levels, the creep deformation of the tempered martensite proceeds heterogeneously around prior austenite grain boundaries, as excess dislocations inside the grain are difficult to rearrange. This paper presents a new approach using carbon-free martensitic alloys strengthened by intermetallic compounds. An iron-nickel-cobalt martensite matrix with Laves phase as the precipitate is selected. The creep characteristics are discussed across a wide range of testing conditions, and the thermal cycle test behavior is examined to evaluate the potential of these alloys for future ultrasupercritical power plants operating in severe environments.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 506-519, October 25–28, 2004,
... of this COST grade E steel. Secondly, it reports on the manufacturing of a trial melt of a later 9%Cr steel containing cobalt and boron from COST development, describing its long-term creep behavior, microstructural features responsible for superior creep resistance, and test results including short-term...
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Within the pursuit of improved economic electricity production with reduced environmental pollution, the European research activities COST 501/522 aimed to develop advanced 9-12%Cr steels for highly stressed turbine components by increasing thermal efficiency through higher steam temperatures up to 600/625°C. One such modified Cr steel, a tungsten-alloyed 10%Cr steel, has been in industrial production for several years in steam and gas turbine applications. This paper firstly discusses experiences in manufacturing, non-destructive testing, and mechanical properties achieved in forgings of this COST grade E steel. Secondly, it reports on the manufacturing of a trial melt of a later 9%Cr steel containing cobalt and boron from COST development, describing its long-term creep behavior, microstructural features responsible for superior creep resistance, and test results including short-term properties, detectable flaw size, and initial creep results for a full-size trial rotor forging.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 552-558, October 25–28, 2004,
... producing nickel and cobalt-base alloy forgings for applications like aircraft engines, aerospace, land-based gas turbines, and offshore. This paper reports on the manufacturing and testing of large-section forgings made from candidate nickel-base alloys like 617 and 625 for high-pressure/intermediate...
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Improving power plant efficiency through supercritical steam pressures and very high steam temperatures up to 700°C and beyond is an effective approach to reducing fuel consumption and CO2 emissions. However, these extreme steam temperatures necessitate the use of nickel-base alloys in the high-pressure/intermediate-pressure turbine sections requiring very large component sections that cannot be met by steels. Saarschmiede, involved in manufacturing large components for the power generation industry and research programs on advanced 9-12% chromium steels, has extensive experience producing nickel and cobalt-base alloy forgings for applications like aircraft engines, aerospace, land-based gas turbines, and offshore. This paper reports on the manufacturing and testing of large-section forgings made from candidate nickel-base alloys like 617 and 625 for high-pressure/intermediate-pressure turbine components in power stations operating at 700°C and higher steam temperatures.
Proceedings Papers
AM-EPRI2004, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fourth International Conference, 919-929, October 25–28, 2004,
... such as cobalt, tungsten, and boron to meet a range of requirements, including extending fatigue life. The steel is designed to have the same creep strength as T/P92 but with better oxidation resistance due to the higher chromium content. It has about a 0.2% increase in mechanical properties compared to T/P92...
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A new 12%Cr steel, VM12, has been developed with the combined strength and oxidation resistance characteristics desired for high-temperature applications. The steel increases chromium content by around 0.2% to improve oxidation properties while alloying with other elements such as cobalt, tungsten, and boron to meet a range of requirements, including extending fatigue life. The steel is designed to have the same creep strength as T/P92 but with better oxidation resistance due to the higher chromium content. It has about a 0.2% increase in mechanical properties compared to T/P92 steel. Results are presented for tubes and pipes cast with a variety of surface conditions. In addition, detailed results are provided on the effects of alloying elements on creep and oxidation resistance.
Proceedings Papers
AM-EPRI2007, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fifth International Conference, 208-219, October 3–5, 2007,
.... This new steel, with a chromium content of 12% and with other additional elements such as cobalt, tungsten and boron, is named VM12. Manufacturing of this grade has been successfully demonstrated by production of several laboratory and industrial heats and rolling of tubes and pipes in several sizes using...
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The T/P91 and T/P92 steel grades were developed as a result of a demand of high creep strength for advanced power plants. Nevertheless, their operating temperature range is limited by their oxidation performance which is lower compared with usual 12%Cr steels or austenitic steels. Moreover, the new designed power plants require higher pressure and temperature in order to improve efficiency and reduce harmful emissions. For these reasons, Vallourec and Mannesmann have recently developed a new 12%Cr steel which combines good creep resistance and high steam-side oxidation resistance. This new steel, with a chromium content of 12% and with other additional elements such as cobalt, tungsten and boron, is named VM12. Manufacturing of this grade has been successfully demonstrated by production of several laboratory and industrial heats and rolling of tubes and pipes in several sizes using different rolling processes. This paper summarizes the results of the investigations on base material, including creep tests and high temperature oxidation behavior, but also presents mechanical properties after welding, cold bending and hot induction bending.
Proceedings Papers
AM-EPRI2007, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Fifth International Conference, 366-376, October 3–5, 2007,
... ultimately selecting the most promising candidate, FB2, a 10% Cr steel containing cobalt and boron additions, notably without tungsten. Società delle Fucine (SdF) successfully produced an FB2 prototype rotor using a conventional manufacturing process involving ladle furnace and vacuum degassing techniques...
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The development of new ferritic-martensitic steels for rotor applications was a primary focus of the joint research projects COST 501 and COST 522. During COST 501, multiple trial compositions of 9-10% chromium steels underwent comprehensive testing, with the COST 522 project ultimately selecting the most promising candidate, FB2, a 10% Cr steel containing cobalt and boron additions, notably without tungsten. Società delle Fucine (SdF) successfully produced an FB2 prototype rotor using a conventional manufacturing process involving ladle furnace and vacuum degassing techniques. A comprehensive creep test program was initiated to characterize the full-size component's properties, with results demonstrating consistency with laboratory material performance in both creep resistance and ductility. The extensive testing, which exceeded 30,000 hours, aimed to achieve a 15-20 MPa improvement over Grade 92, targeting 100,000 creep hours at 600°C. Complementing the mechanical testing, a parallel microstructural investigation program was launched to evaluate structural evolution and gain deeper insights into boron's role as a creep-strengthening element in advanced ferritic-martensitic steels.
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