Search Results for materials selection

Competitive pressures throughout the power generation market are forcing individual power plants to extend time between scheduled outages, and absolutely avoid costly forced outages. Coal fired power plant owners expect their engineering and maintenance teams to identify, predict and solve potential outage causing equipment failures and use the newest advanced technologies to resolve and evade these situations. In coal fired power plants, erosion not only leads to eventual failure, but during the life cycle of a component, affects the performance and efficiency due to the loss of engineered geometry. “Wear” is used very generally to describe a component wearing out; however, there are numerous “modes of wear.” Abrasion, erosion, and corrosion are a few of the instigators of critical component wear, loss of geometry, and eventual failure in coal fired plants. Identification of the wear derivation is critical to selecting the proper material to avoid costly down-times and extend outage to outage goals. This paper will focus on the proper selection of erosion resistant materials in the severe environment of a coal fired power plant by qualifying lab results with actual field experiences.

A study is being conducted on turbine materials for use in ultra-supercritical (USC) steam power plants, with the objective of ensuring no material-related impediments regarding maximum temperature capabilities and the ability to manufacture turbine components. A review of the state-of-the-art and material needs for bolting and casing applications in USC steam turbines was performed to define and prioritize requirements for the next-generation USC turbines. For bolting, several potentially viable nickel-base superalloys were identified for service at 760°C, with the major issues being final material selection and characterization. Factors limiting inner casing material capabilities include casting size/shape, ability to inspect for discontinuities, stress rupture strength, and weldability for fabrication and repairs. Given the need for precipitation-strengthened nickel-base alloys for the inner casing at 760°C, the material needs are two-fold: selection/fabrication-related and characterization. The paper provides background on turbine components and reviews the findings for bolting and casing materials.

The acceptance of materials for long-term, safety-critical power generation applications requires multiple testing stages and data generation. Initial screening involves short-term exposures under simplified, constant atmospheres and temperatures, which can eliminate unsuitable materials but fail to distinguish between those with broadly acceptable properties. Subsequent pilot plant testing, costing over £100K for month-long exposures, is typically required. An intermediate laboratory testing step that better replicates in-service conditions would offer a cost-effective approach to material selection and lifetime prediction. For steam oxidation degradation, key experimental parameters—such as water chemistry, pressure, steam delivery, and flow rate—must be tailored to produce oxide scale morphologies similar to those observed in actual plant conditions. This study examines the effects of these parameters through steam exposure tests on ferritic (P92), austenitic (Esshete 1250), and superalloy (IN740) materials. Results indicate that oxidation rates vary with dissolved oxygen levels in feed water, increasing for austenitic materials and decreasing for ferritic materials, while also influencing spallation tendencies. Additionally, steam pressure and delivery methods impact oxidation rates and scale morphology. A comparison with service-exposed materials revealed that traditional oxide scale morphologies were not adequately replicated, whereas cyclic oxidation tests provided a closer match to service-grown scales.

The U.S. Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) have recently initiated a project aimed at identifying, evaluating, and qualifying the materials needed for the construction of the critical components of coal-fired boilers capable of operating at much higher efficiencies than current generation of supercritical plants. This increased efficiency is expected to be achieved principally through the use of ultrasupercritical steam conditions (USC). The project goal initially was to assess/develop materials technology that will enable achieving turbine throttle steam conditions of 760°C (1400°F)/35 MPa (5000 psi), although this goal for the main steam temperature had to be revised down to 732°C(1350°F), based on a preliminary assessment of material capabilities. The project is intended to build further upon the alloy development and evaluation programs that have been carried out in Europe and Japan. Those programs have identified ferritic steels capable of meeting the strength requirements of USC plants up to approximately 620°C (1150°F) and nickel-based alloys suitable up to 700°C (1300°F). In this project, the maximum temperature capabilities of these and other available high- temperature alloys are being assessed to provide a basis for materials selection and application under a range of conditions prevailing in the boiler. This paper provides a status report on the progress to date achieved in this project.

The measurement of damage from high temperature solid particle erosion (HTSPE) can be a lengthy process within the laboratory with many lab-based systems requiring sequential heat and cooling of the test piece to enable mass and/or scar volume measurements to be made ex situ. Over the last few years a new lab-based system has been in development at the National Physical Laboratory which has the ability to measure the mass and volume change of eroded samples in situ without the need to cool the sample. Results have previously been shown demonstrating the in situ mass measurement, more recently the in situ volume measurement capability has been added and used to evaluate the erosion performance of additively manufactured materials. Selective laser melting (SLM) is an advanced manufacturing method which is growing in popularity and application. It offers the ability to manufacture low volume complex parts and has been used in rapid prototyping. As the technique has developed there is increasing interest to take advantage of the ability to manufacture complex parts in one piece, which in some case can be more cost and time effective than traditional manufacturing routes. For all the benefits of SLM there are some constraints on the process, these include porosity and defects in the materials such as ‘kissing bonds’, surface roughness, trapped powder and microstructural variation. These features of the processing route may have implications for component performance such as strength, fatigue resistance wear and erosion. To investigate this further SLM IN718 has been used to evaluate factors such as surface roughness, microstructure and morphology on the erosion performance as measured in situ and compared with conventional produced wrought IN718 material.

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.

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

As electricity markets become increasingly competitive, ultrasupercritical power plants must operate efficiently and flexibly. This necessitates attention to equipment design features and optimal material selection. Early studies by EPRI highlighted the need for boiler and steam turbine design improvements, as well as material advances, to enable the flexible operation of advanced supercritical units. Improvements such as turbine rotor cooling, cycling capability through improved control systems, enhanced blade tip sealing designs, turbine vibration control approaches, and erosion-resistant control stage designs were required. With ultrasupercritical plants moving towards even higher steam temperatures exceeding 700°C, these concerns need to be revisited from both metallurgical and design perspectives. Furthermore, features for efficiency improvements beyond advanced steam conditions should be considered, while minimizing environmental emissions like CO 2 . This paper reviews the needs for future ultrasupercritical plants with steam temperatures approaching or exceeding 700°C.

Coal ash corrosion testing was conducted on six solution-treated nickel-based alloy plates (Alloy 617, Alloy 263, Alloy 740, Alloy 141, HR6W [45Ni-23Cr-7W], and HR35 [50Ni-30Cr-4W-Ti]) intended for advanced-USC boilers, along with conventional ferritic and austenitic stainless tubes for comparison. Tests used synthetic coal ash (Na 2 SO 4 , K 2 SO 4 , Fe 2 O 3 ) with varying SO 2 concentrations (0.02-1.00 vol%). Results showed maximum metal loss at 700°C, with higher SO 2 levels causing increased corrosion. Materials with higher chromium content demonstrated better corrosion resistance, suggesting chromium content is a crucial factor in material selection for these applications.

India's current installed power generating capacity is about 225,000 MW, of which about 59% is coal based. It is projected that India would require an installed capacity of over 800,000 MW by 2032. Coal is likely to remain the predominant source of energy in India till the middle of the century. India is also committed to reducing the CO 2 emission intensity of its economy and has drawn up a National Action Plan for Climate Change, which, inter alia, lays emphasis on the deployment of clean coal technologies. With this backdrop, a National Mission for the Development of Advanced Ultra Supercritical Technology has been initiated. The Mission objectives include development of advanced high temperature materials, manufacturing technologies and design of equipment. A corrosion test loop in an existing plant is also proposed. Based on the technology developed, an 800 MW Demonstration A-USC plant will be established. Steam parameters of 310 kg/cm 2 , 710 °C / 720 °C have been selected. Work on selection of materials, manufacture of tubes, welding trials and design of components has been initiated. The paper gives details of India's A-USC program and the progress achieved.

The construction of highly efficient Ultra Supercritical (USC) boiler systems to operate with steam temperatures up to 760°C (1400°F) and with steam pressures up to 34.5 MPa (5000 psi) will require the use of advanced high temperature, high strength materials. As part of a 5-year project to qualify advanced boiler materials for USC power plants, a number of austenitic materials have been selected for further development and use in USC boiler systems, including alloys 230, 740, CCA 617, HR6W, and Super 304H. In one task of this project, boiler fabrication guidelines appropriate for the use of these alloys were investigated. Because it is recognized that cold formed and mechanically strained austenitic materials can degrade in material creep strength, a study to investigate the limits of strain and temperature exposure for the USC alloys was undertaken. An objective of this work was to determine for each USC alloy a relationship between the level of cold strain and the conditions of time and temperature that will cause recrystallization and significant microstructural change. The ultimate goal of this work was to determine limits of strain, due to cold forming, that can be tolerated before heat treatment is required, similar to those limits provided for the austenitic materials (e.g., 300-series stainless steels, alloy 800H) in Table PG-19 in Section I of the ASME Boiler and Pressure Vessel Code. This paper will describe the technical approach for 1) preparing specimens having discrete cold strains ranging from about 1 to 40 percent, 2) exposing these strained specimens for selected times at various elevated temperatures, 3) identifying the onset of recrystallization in the microstructures of the exposed specimens, and 4) establishing a useful engineering method to predict conditions for the onset of recrystallization in the USC alloys using the experimental results.

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

As the demand for worldwide electricity generation grows, pulverized coal steam generator technology is expected to be a key element in meeting the needs of the utility power generation market. The reduction of greenhouse gas emissions, especially CO 2 emissions, is vital to the continued success of coal-fired power generation in a marketplace that is expected to demand near-zero emissions in the near future. Oxycombustion is a technology option that uses pure oxygen, and recycled flue gas, to fire the coal. As a result, this system eliminates the introduction of nitrogen, which enters the combustion process in the air, and produces a highly-concentrated stream of CO 2 that can readily be captured and sequestered at a lower cost than competing post-combustion capture technologies. Oxycombustion can be applied to a variety of coal-fired technologies, including supercritical and ultra-supercritical pulverized coal boilers. The incorporation of oxycombustion technology in these systems raises some new technical challenges, especially in the area of advanced boiler materials. Local microclimates generated near and at the metal interface will influence and ultimately govern corrosion. In addition, the fireside corrosion rates of the boiler tube materials may be increased under high concentration oxygen firing, due to hotter burning coal particles and higher concentrations of SO 2 , H 2 S, HCl and ash alkali, etc. There is also potential to experience new fouling characteristics in the superheater and heat recovery sections of the steam generator. The continuous recirculation of the flue gases in the boiler, may lead to increasing concentrations of deleterious elements such as sulfur, chlorine, and moisture. This paper identifies the materials considerations of oxycombustion supercritical and ultrasupercritical pulverized coal plants that must be addressed for an oxycombustion power plant design.

This paper presents an overview of China’s electric power development and the National 700°C Ultra-Supercritical (USC) Coal-Fired Power Generation Technology Innovation Consortium. Besides, the R&D plan and latest progress of China 700°C USC coal-fired power generation technology is also introduced in this paper.

The construction of highly efficient, coal-burning Ultra Supercritical (USC) boiler systems to operate with steam temperatures up to 760°C (1400°F) and with steam pressures up to 35 MPa (5000 psi) will require the use of advanced high temperature, high strength materials. As part of a 5-year project to develop boiler materials for advanced USC power plants, principally funded by the Department of Energy (U.S. DOE No. DE-FG26-01NT41175) and the Ohio Coal Development Office (OCDO No. D-00-20), six alloys have been selected for development and implementation in USC boiler systems. The selected alloys are Haynes 230 (produced by Haynes International), Inconel 740 (produced by Special Metals Corp.), CCA 617 (produced by Krupp VDM GMBH), HR6W, Super 304H, and SAVE 12 (all three produced by Sumitomo Metal Industries). In this project, one of the goals has been to establish boiler fabrication guidelines for the use of these alloys. The principal objectives have been 1) to understand the behavior of these materials when subjected to conventional boiler fabrication processes, 2) to determine the thermomechanical treatments or other actions necessary to restore material properties which might degrade due to fabrication operations, and 3) to investigate prototypical manufacturing operations for producing both thick wall components (such as headers) and thin wall components (such as superheaters) from the USC alloys. This paper discusses some of the characteristics of these alloys, describes the technical approach used to assess their fabricability, and presents some of the results that have thus far been generated in this task effort.

To improve efficiency and flexibility and reduce CO 2 emissions, advanced ultra super critical (AUSC) power plants are under development, worldwide. Material development and its selection are critical to the success of these efforts. In several research and development programs / projects the selection of materials is based on stress rupture, oxidation and corrosion tests. Without doubt, these criteria are important. To improve the operational flexibility of modern power plants the fatigue properties are of increased importance. Furthermore, for a safe operation and integrity issues the knowledge about the crack behavior is essential. Crack initiation and crack growth may be caused by natural flaws or cracks induced by component operation. In order to develop new materials, properties like tensile strength and creep strength are an important part of qualification and subsequent approval by notified bodies. Consequently short term properties as well as time-temperature dependent properties are generated and taken into considerations. In the case of high strength γ'-strengthening nickel-base alloys investigating the creep crack behavior is also strongly recommended. This article shows results of currently investigated nickel-based alloys for newly developed headers, pipes and other high temperature boiler applications and their critical creep crack propagation behavior.

Creep-resistant austenitic stainless steels are known to be the potential candidate materials for use as super- and re-heater tubes in ultra-super critical (USC) power plants. Among them, ASTM A213/A213M S30432, a novel 18-8 stainless steel (18Cr- 9Ni-3Cu-Nb-N), has attracted considerable attention from electric industry due to its combined lower cost and more excellent performance in contrast to traditional TP347H steel. More than 10 years of service in Japan laid a solid foundation for the steel being selectable USC boiler materials. Steels of S30432 have been recently developed in China during the past few years. This paper presents the evaluation results of S30432 tubes manufactured by four steel plants in China as well as Sumitomo super304H tubes for comparison. A detailed microstructural analysis of the tubes has been performed by using optical and electron microscope, and mechanical properties of the tubes have been evaluated using hardness testing as well as tensile testing up to 700°C. It was found that the impurity elements, nonmetallic inclusions and grain size of the S30432 tubes were well controlled. TEM observation revealed the microstructural changes for a selected batch of S30432 specimens in condition of hot rolled material, as-extruded tube, solution treated tube and 650°C/1000h aged tube. Most attention was paid to the morphology and distribution of precipitates in the microstructure which should be responsible for the enhanced performance of the steel. Although the hardness of all the evaluated tubes was measured to be similar, they showed more or less differences in tensile properties between each other. Creep rupture testing is still in progress, and the steel might exhibit excellent long-term creep rupture strength at 650°C as was predicted from the currently available testing results.

In downstream oil industry applications, high-temperature sulfidation corrosion is generally caused by sulfur species coming from the crude; additionally, naphthenic acids or hydrogen can considerably worsen the corrosivity of the environment. During plant operations, several events may occur that boost the severity of corrosion: high feedstock turnover, with increasing “active” sulfur species; skin temperature rise due to the increasing insulation effect of the scale, generating an over-tempering of the material and possible degeneration into creep conditions. Thor115 is a ferritic steel with 11% chromium content to resist sulfidation. It has excellent creep properties for high temperature environments: higher allowable stresses than grade 91, keeping the same manufacturing and welding procedures. At the same time, it has the characteristics of ferritic steel, ensuring enhanced thermal conductivity and lower thermal expansion compared to austenitic steels. Comparative corrosion tests between Thor115 and other ferritic steels typically used in this industry (e.g., grade T/P5 and grade T/P9) have been carried out to simulate different corrosive conditions, confirming the superior properties of Thor115 relative to other ferritic grades. For these reasons, Thor 115 is a suitable replacement material for piping components that need an upgrade from grade T/P9 or lower, in order to reduce corrosion rate or frequency of maintenance operations.

This paper reports the performance of HR6W iron-nickel based alloy and 617B nickel based alloy which are the candidate material for high temperature reheater outlet header of advanced secondary reheat ultra-supercritical unit boiler with reheat steam 653 °C, and analysis the applicable temperature range of the material. As a result, HR6W is the appropriate material to manufacture high temperature reheater outlet header of A-USC boiler with parameters 620°C /653°C/653°C.

In response to the need to reduce carbon dioxide gas emissions, Japan has been actively researching 700°C-class thermal power plants with a focus on improving overall plant efficiency. This technological advancement is fundamentally grounded in advanced materials development, encompassing the creation of high-strength alloys, fireside corrosion-resistant materials, and steamside oxidation-resistant alloys. A significant challenge emerged as some of the developed materials fell outside the scope of existing domestic technical standards. Moreover, the potential failure modes for advanced ultra-supercritical (A-USC) components operating at 700°C were anticipated to differ substantially from those observed in traditional ultra-supercritical (USC) components at 600°C. Consequently, researchers systematically examined and analyzed the potential failure modes specific to 700°C A-USC components, using these insights to establish comprehensive performance requirements. The research initiative, which commenced in June 2006, was strategically planned to develop a draft technical interpretation by March 2011. This paper provides a detailed overview of the investigative process, encompassing the comprehensive analysis of failure modes, the derivation of performance requirements, and the progression toward developing a new technical interpretation framework for high-temperature power plant components.