Search Results for fossil fuels

The INCONEL filler metals 72 and 72M have been utilized significantly for weld overlay protection of superheaters and reheaters, offering enhanced corrosion and erosion resistance in this service. Laboratory data conducted under simulated low-NOx combustion conditions, field exposure experience, and laboratory analysis (microstructure, chemical composition, overlay thickness measurements, micro-hardness) of field-exposed samples indicate that these overlay materials are also attractive options as protective overlays for water wall tubes in low-NOx boilers. Data and field observations will be compared for INCONEL filler metals 72, 72M, 625 and 622.

This work concerns a study into the design of creep resistant precipitation hardened austenitic steels for fossil fuel power plants using an integrated thermodynamics based model in combination with a genetic algorithm optimization routine. The key optimization parameter is the secondary stage creep strain at the intended service temperature and time, taking into account the coarsening rate of MX carbonitrides and its effect on the threshold stress for secondary creep. The creep stress to reach a maximal allowed creep strain (taken as 1%) at a given combination of service temperature and time is formulated and maximized. The model was found to predict the behavior of commercial austenitic creep resistant steels rather accurately. Using the alloy optimization scheme three new steel compositions are presented yielding optimal creep strength for various intended service times up to 105 hours. According to the evaluation parameter employed, the newly defined compositions will outperform existing precipitate strengthened austenitic creep resistant steels.

To address the escalating energy demands of the 21st century and meet environmental protection objectives, new fossil-fueled power plant concepts must be developed with enhanced efficiency and advanced technologies for CO 2 , sulfur oxide, and nitrogen reduction. As plant temperatures and pressures increase to improve overall efficiency, the property requirements for alloys used in critical components become increasingly demanding, particularly regarding creep rupture strength, high-temperature corrosion resistance, and other essential characteristics. Newer and existing nickel alloys emerge as promising candidates for these challenging applications, necessitating comprehensive development through detailed property investigations across multiple categories. These investigations encompass a holistic approach, including chemical composition analysis, physical and chemical properties, mechanical and technological properties (addressing short-term and long-term behaviors, aging effects, and thermal stability), creep and fatigue characteristics, fracture mechanics, fabrication process optimization, welding performance, and component property evaluations. The research spans critical areas such as materials development for membrane walls, headers, piping, reheater and superheater components, and various other high-temperature power plant elements. This paper provides a comprehensive overview of existing and newly developed nickel alloys employed in components of fossil-fueled, high-efficiency 700°C steam power plants, highlighting the intricate materials science challenges and innovative solutions driving next-generation power generation technologies.

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.

G115 is a novel ferritic heat resistant steel developed by CISRI in the past decade. It is an impressive candidate material to make tubes, pipes, and forgings for advanced ultra super critical (A-USC) fossil fired power plants used for the temperature scope from 600°C to 650°C. The successful development of G115 extends the upper application temperature limitation of martensitic steel from 600°C to about 650°C. This breakthrough is imperative for the design and construction of 610°C to 650°C A-USC fossil fired power plants, from the viewpoint of the material availability and economics of coal fired power plant designs. This paper introduces the development history and progress of G115 steel. The strengthening mechanism of the novel martensitic steel is briefly discussed, and the optimized chemical composition and mechanical properties of G115 steel are described. The details of industrial trials of G115 tube and pipe at BaoSteel in the past years are reviewed, with the emphasis on the microstructure evolution during aging and creep testing. These tests clearly show that the microstructure of G115 steel is very stable up to the temperature of 650°C. Correspondingly, the comprehensive mechanical properties of G115 steel are very good. The creep rupture time is longer than 17000 hours at the stress of 120MPa and at the temperature of 650°C and 25000+ hours at the stress of 100MPa and at the temperature of 650°C, which is about 1.5 times higher than that of P92 steel. At the same time, the oxidation resistance of G115 steel is a little bit better than that of P92 steel. If G115 steel is selected to replace P92 pipes at the temperature scope from 600°C to 650°C, the total weight of the pipe can be reduced by more than 50% and the wall thickness of the pipe can be reduced up to about 55%. In addition, the upper application temperature limitation of G115 steel is about 30°C higher than that of P92 steel. Thus, G115 steel is a strong candidate material for the manufacturing of 600+°C advanced ultra-super-critical (A-USC) fossil fuel power plants in China and elsewhere.

The rising global energy demand has led to a surge in the construction of high-efficiency power plants with advanced steam parameters. National and international projects indicate that fossil fuels will continue to be the primary source of power generation in the coming years, despite significant efforts and progress in utilizing alternative energy sources. Economic pressures and climate protection concerns necessitate more cost-efficient and environmentally sustainable energy production. Achieving this requires reducing specific fuel and heat consumption per kilowatt-hour, making it essential to improve the efficiency of new power plants beyond those commissioned in Germany between 1992 and 2002. While new construction and process innovations contribute to efficiency gains, the primary factors driving improvement are increased steam pressure and temperature. Current design parameters include steam temperatures of 605 °C (live steam) and 625 °C (hot reheat steam), along with pressures of 300 bar (live steam) and 80 bar (hot reheat steam), which have become critical for obtaining building and operating licenses in Germany. However, the European Creep Collaborative Committee’s (ECCC) 2005 reassessment of the creep strength of steel T/P92 (X10CrWMoVNb9-2) has placed limitations on further increasing steam temperatures beyond 625 °C.

To save fossil fuel resources and to reduce CO 2 emissions, considerable effort has been directed toward researching and developing heat-resistant materials that can help in improving the energy efficiency of thermal power plants by increasing their operational temperature and pressure conditions. Instead of conventional 9-12Cr ferritic heat-resistant steels with a tempered martensitic microstructure, we developed “Precipitation Strengthened 15Cr Ferritic Steel” based on a new material design concept: a solid-solution treated ferrite matrix strengthened by precipitates. Creep tests for 15Cr-1Mo-6W-3Co-V-Nb steels with ferrite matrix strengthened by a mainly Laves phase (Fe 2 W) showed that the creep strengths of 15Cr ferritic steel at temperatures ranging from 923 K to 1023 K were twice as high as those of conventional 9Cr ferric heat-resistant steel. 15Cr steels have higher steam oxidation resistance than that of conventional steel in the same temperature range as the creep tests. Thus, the new material design concept of heat-resistant steel pro- vides improved creep strength and steam oxidation resistance. We are attempting to determine the optimum compositions, especially that of carbon, in order to improve the high-temperature creep strength.

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.

Enhancement of the steam conditions is one of the most effective measures to achieve the goal of higher thermal efficiency. 700°C class A-USC (Advanced Ultra Super Critical Steam Conditions) power plant is one of the remarkable technologies to achieve the goal and reduce CO 2 emissions from fossil fuel power plants. Toshiba has been working on the A-USC development project with subsidy from METI (Ministry of Economy, Trade and Industry) and NEDO (New Energy and Industrial Technology Development Organization). In this project, A-USC power plants with steam parameters of 35MPa 700/720/720°C were considered. To date, various materials have been developed and tested to verify their characteristics for use in A-USC power plants. And some of these materials are being investigated as to their suitability for use in long term. Together with members of the project, we carried out the boiler component test using a commercially-operating boiler. We manufactured a small-scale turbine casing made of nickel-based alloy, and supplied it for the test. In addition, we manufactured a turbine rotor for turbine rotation tests, and carried out the test at 700°C and rotating speed of 3,600rpm conditions. In this paper, we show the results of the A-USC steam turbine development obtained by the project.

Alumina-forming austenitic stainless steels (AFAs) are potential materials for boiler/steam turbine applications in next generation fossil fuel power plants. They display a combination of good high temperature creep strength, excellent oxidation resistance and low cost. A recently-developed AFA alloy based on Fe-14Cr-32Ni-3Nb-3Al-2Ti (wt.%) shows better creep performance than a commercially-available Fe-based superalloy. In this paper we used scanning electron microscopy and transmission electron microscopy to study the fracture surfaces and cracking behavior in relation to the precipitates present in creep failure samples of this alloy tested at either 750°C/100 MPa or 700°C/170 MPa. It was found that most cracks are formed along the grain boundaries with precipitate-free zones beside the grain boundaries potentially providing the path for propagation of cracks.

Steel castings of creep-resistant steels are critical components in the high and intermediate pressure turbine sections of fossil fuel-fired power plants. As plant efficiencies improve and emission standards tighten, steam parameters become more stringent, necessitating constant enhancement of material creep resistance. Steel foundries alone cannot conduct necessary material development at an appropriate scale, so all power plant component suppliers cooperate to define optimal chemical compositions, perform test melts, creep tests, microstructure investigations, and test pilot components, such as through the COST program developing new 9-12%Cr cast steel grades. This paper illustrates a steel foundry's role in COST, describing the transfer of these new cast steel grades from research into commercial production of heavy cast components, outlining incurred problems, process development cycles, comparisons with low-alloy steels, welding tests, base material/weld investigations, heat treatment optimization, and casting of pilot components/weldability test plates to verify castability of larger parts and make necessary adjustments. Parallel to ongoing COST creep tests, the steel grades were introduced into commercial large component production, involving solutions to process-related issues, with over 180 components successfully manufactured to date, while further COST program developments present ongoing challenges.

This paper discusses the development of matching filler metals for new creep-resistant steels (P911 and P92) that enable higher operating temperatures (600-625 °C) in fossil fuel power plants, improving efficiency. The filler metals were evaluated with long-term testing (up to 30,000 hours) confirming their suitability for welded components in power stations. This development benefits not only power plant operators by reducing maintenance costs and downtime, but also builders, suppliers, and inspection bodies by providing a reliable solution for high-temperature applications. Additionally, matching filler metals developed for VM12 (12% Cr) martensitic steel are discussed.

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.

A global movement is pushing for improved efficiency in power plants to reduce fossil fuel consumption and CO 2 emissions. While raising operating temperatures and pressures can enhance thermal efficiency, it necessitates materials with exceptional high-temperature performance. Currently, steels used in power plants operating up to 600°C achieve efficiencies of 38-40%. Advanced Ultra Supercritical (A-USC) designs aim for a significant leap, targeting steam temperatures of 700°C and pressures of 35 MPa with a lifespan exceeding 100,000 hours. Ni-based superalloys are leading candidates for these extreme conditions due to their superior strength and creep resistance. Haynes 282, a gamma prime (γ′) precipitation-strengthened alloy, is a promising candidate for A-USC turbine engines, exhibiting excellent creep properties and thermal stability. This research investigates the microstructural evolution in large, sand-cast components of Haynes 282. Microstructure, referring to the arrangement of grains and phases within the material, significantly impacts its properties. The research examines the alloy in its as-cast condition and after various pre-service heat treatments, aiming to fully identify and quantify the microstructural changes. These findings are then compared with predictions from thermodynamic equilibrium calculations using a dedicated Ni alloy database. The research reveals that variations in heat treatment conditions can significantly affect the microstructure development in Haynes 282, potentially impacting its mechanical properties.

This paper briefly introduces the state-of-the-art of the research and development of candidate heat resistant materials used for the manufacturing of 700°C advanced ultra-super-critical (AUSC) fossil fuel power plants (PP) in China, especially, focus on the impressive progress in the past three years. The detailed advancements (technical exploration and industrial investigation) of candidate materials spectra for the boiler system of A-USC PP will be presented in the current paper, including novel ferritic heat resistant steels, advanced austenitic heat resistant steels, Fe- Ni-based alloys and Ni-based alloys, which serve and cover the steam temperature scope from 600°C to 720°C. Some newly available data associated with above materials will be released.

Sufficient available energy in combination with lowest environmental pollution is a basic necessity for a high standard of living in every country. In order to guarantee power supply for future generations it is necessary to use fossil fuels as efficient as possible. This fact calls for the need of power plants with improved technologies to achieve higher efficiency combined with reduced environmental impact. In order to realize this goal it is not only a challenge for power station manufacturers, but also for manufacturers of special steels and forgings, who have to produce improved components with more advanced materials and more complex manufacturing processes. This paper reports about experiences in the fabrication of forged components for gas and steam turbines followed by achievable mechanical properties and ultrasonic detectability results. The materials are the creep resistant martensitic Cr steels developed in the frame of the European Cost research programme. Whereas Boron containing 10% Cr steels are suitable for steam temperatures of 625°C and slightly higher, Ni-based alloys shall be used for temperatures of 700°C and above. One pilot rotor forging, representing a HP-rotor for welded construction, has been manufactured out of alloy Inconel 625 within the frame of the European Thermie project AD700.

To improve the efficiency of fossil fuel power plants the operating temperatures and pressures need to be increased. However, at high temperatures the steam side oxidation resistance becomes a critical issue for the steels used especially at the final stages of superheaters and reheaters. Apart from the chemical composition of the material, surface condition is a major factor affecting the oxidation resistance in steam and supercritical water. In this paper, stainless boiler steels (UNS S34710, S31035, S31042, and S30942) are investigated for oxidation resistance in flowing supercritical water. Tests were conducted in an autoclave environment (250 bar, with 125 ppb dissolved oxygen and a pH of 7) at 625°C, 650°C and 675°C for up to 1000 h. Materials were tested with as-delivered, shot peened, milled or spark eroded and ground surface finish. The results show a strong influence of surface finish at the early stages of oxidation. Oxides formed on cold worked surfaces were more adherent and much thinner than on a spark eroded and ground surface. This effect was stronger than the influence of temperature or alloy composition within the tested ranges.

Driven mainly by the environmental and economic concerns, there is an urgent need for increasing the thermal efficiency of fossil fuel power generation plants, which still languishes at around 32% under current practices. Several programs have been undertaken worldwide to address this issue. One of the immediate options is to increase the steam temperature and pressure (to the supercritical range). However, the current power plant materials appear to have inadequate creep resistance under these demanding conditions along with corrosion/oxidation problems. Hence, to meet these challenges a variety of new steels and stainless steels have been developed in the United States, Japan, and Europe. Alloy design and microstructural design approaches in developing these alloys (ferritic/martensitic, austenitic and oxide-dispersion- strengthened steels) will be briefly reviewed. Further, this paper presents creep data of these steels found in the literature in terms of Larson-Miller parameters (LMP). A detailed account of plausible creep micromechanisms in these advanced steels is also be summarized.

Reducing emissions and increasing economic competitiveness require more efficient steam power plants that utilize fossil fuels. One of the major challenges in designing these plants is the availability of materials that can stand the supercritical and ultra-supercritical steam conditions at a competitive cost. There are several programs around the world developing new ferritic and austenitic steels for superheater and reheater tubes exposed to the advanced steam conditions. The new steels must possess properties better than current steels in terms of creep strength, steamside oxidation resistance, fireside corrosion resistance, and thermal fatigue resistance. This paper introduces a series of experimental 9%Cr steels containing Cu, Co, and Ti. Stability of the phases in the new steels is discussed and compared to the phases in the commercially available materials. The steels were tested under both the dry and moist conditions at 650°C for their cyclical oxidation resistance. Results of oxidation tests are presented. Under the moist conditions, the experimental steels exhibited significantly less mass gain compared to the commercial P91 steel. Microstructural characterization of the scale revealed different oxide compositions.

The increasing steam parameters in modern high-efficiency fossil fuel power plants demand advanced materials with enhanced creep strength for operation under extreme temperature and pressure conditions. Tenaris has focused on developing ferritic-martensitic and austenitic grades for tube and pipe applications. At TenarisDalmine, efforts on ferritic-martensitic steels include ASTM Grade 23, a low-alloyed alternative to Grade 22 with 1.5% W, offering good weldability, creep resistance up to 580°C, and cost competitiveness. Additionally, ASTM Grade 92, an improved version of Grade 91, provides high creep strength and long-term stability for components like superheaters and headers operating up to 620°C. At TenarisNKKT R&D, austenitic steel development includes TEMPALOY AA-1, an improved 18Cr-8NiNbTi alloy with 3% Cu for enhanced creep and corrosion resistance, and TEMPALOY A-3, a 20Cr-15Ni-Nb-N alloy with superior creep and corrosion properties due to its higher chromium content. This paper details the Tenaris product lineup, manufacturing processes, and key material properties, including the impact of shot blasting on the steam oxidation resistance of austenitic grades. It also covers ongoing R&D efforts in alloy design, creep testing, data assessment, microstructural analysis, and damage modeling, conducted in collaboration with Centro Sviluppo Materiali.