skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Materials for Advanced Ultrasupercritical Steam Turbines Task 3: Materials for Non-Welded Rotors, Buckets, and BoltingMaterials for Advanced Ultrasupercritical Steam Turbines

Abstract

The primary objective of the task was to characterize the materials suitable for mechanically coupled rotor, buckets and bolting operating with an inlet temperature of 760°C (1400°F). A previous study DOE-FC26-05NT42442, identified alloys such as Haynes®282®, Nimonic 105, Inconel 740, Waspaloy, Nimonic 263, and Inconel 617 as potential alloys that met the requirements for the necessary operating conditions. Of all the identified materials, Waspaloy has been widely utilized in the aviation industry in the form of disk and other smaller forgings, and sufficient material properties and vendor experience exist, for the design and manufacture of large components. The European program characterizing materials for A-USC conditions are evaluating Nimonic 263 and Inconel 617 for large components. Inconel 740 has been studied extensively as a part of the boiler consortium and is code approved. Therefore, the consortium focused efforts in the development of material properties for Haynes®282® and Nimonic 105 to avoid replicative efforts and provide material choices/trade off during the detailed design of large components. Commercially available Nimonic 105 and Haynes®282® were evaluated for microstructural stability by long term thermal exposure studies. Material properties requisite for design such as tensile, creep / rupture, low cycle fatigue, high cycle fatigue, fatigue crackmore » growth rate, hold-time fatigue, fracture toughness, and stress relaxation are documented in this report. A key requisite for the success of the program was a need demonstrate the successful scale up of the down-selected alloys, to large components. All property evaluations in the past were performed on commercially available bar/billet forms. Components in power plant equipment such as rotors and castings are several orders in magnitude larger and there is a real need to resolve the scalability issue. Nimonic 105 contains high volume fraction y’ [>50%], and hence the alloy is best suited for smaller forging and valve internals, bolts, smaller blades. Larger Nimonic 105 forgings, would precipitate y’ during the surface cooling during forging, leading to surface cracks. The associate costs in forging Nimonic 105 to larger sizes [hotter dies, press requirements], were beyond the scope of this task and not investigated further. Haynes®282® has 20 - 25% volume fraction y’ was a choice for large components, albeit untested. A larger ingot diameter is pre-requisite for a larger diameter forging and achieves the “typically” accepted working ratio of 2.5-3:1. However, Haynes®282® is manufactured via a double melt process [VIM-ESR] limited by size [<18-16” diameter], which limited the maximum size of the final forging. The report documents the development of a 24” diameter triple melt ingot, surpassing the current available technology. A second triple melt ingot was manufactured and successfully forged into a 44” diameter disk. The successful developments in triple melting process and the large diameter forging of Haynes®282® resolved the scalability issues and involved the first of its kind attempt in the world for this alloy. The complete characterization of Haynes®282® forging was performed and documented in this report. The dataset from the commercially available Haynes®282® [grain size ASTM 3-4] and the finer grain size disk forging [ASTM 8-9] offer an additional design tradeoff to balance creep and fatigue during the future design process.« less

Authors:
Publication Date:
Research Org.:
Energy Industries Of Ohio Incorporated
Sponsoring Org.:
USDOE
OSTI Identifier:
1223685
DOE Contract Number:
FE0000234
Resource Type:
Other
Country of Publication:
United States
Language:
English

Citation Formats

Saha, Deepak. Materials for Advanced Ultrasupercritical Steam Turbines Task 3: Materials for Non-Welded Rotors, Buckets, and BoltingMaterials for Advanced Ultrasupercritical Steam Turbines. United States: N. p., 2015. Web.
Saha, Deepak. Materials for Advanced Ultrasupercritical Steam Turbines Task 3: Materials for Non-Welded Rotors, Buckets, and BoltingMaterials for Advanced Ultrasupercritical Steam Turbines. United States.
Saha, Deepak. Tue . "Materials for Advanced Ultrasupercritical Steam Turbines Task 3: Materials for Non-Welded Rotors, Buckets, and BoltingMaterials for Advanced Ultrasupercritical Steam Turbines". United States. doi:. https://www.osti.gov/servlets/purl/1223685.
@article{osti_1223685,
title = {Materials for Advanced Ultrasupercritical Steam Turbines Task 3: Materials for Non-Welded Rotors, Buckets, and BoltingMaterials for Advanced Ultrasupercritical Steam Turbines},
author = {Saha, Deepak},
abstractNote = {The primary objective of the task was to characterize the materials suitable for mechanically coupled rotor, buckets and bolting operating with an inlet temperature of 760°C (1400°F). A previous study DOE-FC26-05NT42442, identified alloys such as Haynes®282®, Nimonic 105, Inconel 740, Waspaloy, Nimonic 263, and Inconel 617 as potential alloys that met the requirements for the necessary operating conditions. Of all the identified materials, Waspaloy has been widely utilized in the aviation industry in the form of disk and other smaller forgings, and sufficient material properties and vendor experience exist, for the design and manufacture of large components. The European program characterizing materials for A-USC conditions are evaluating Nimonic 263 and Inconel 617 for large components. Inconel 740 has been studied extensively as a part of the boiler consortium and is code approved. Therefore, the consortium focused efforts in the development of material properties for Haynes®282® and Nimonic 105 to avoid replicative efforts and provide material choices/trade off during the detailed design of large components. Commercially available Nimonic 105 and Haynes®282® were evaluated for microstructural stability by long term thermal exposure studies. Material properties requisite for design such as tensile, creep / rupture, low cycle fatigue, high cycle fatigue, fatigue crack growth rate, hold-time fatigue, fracture toughness, and stress relaxation are documented in this report. A key requisite for the success of the program was a need demonstrate the successful scale up of the down-selected alloys, to large components. All property evaluations in the past were performed on commercially available bar/billet forms. Components in power plant equipment such as rotors and castings are several orders in magnitude larger and there is a real need to resolve the scalability issue. Nimonic 105 contains high volume fraction y’ [>50%], and hence the alloy is best suited for smaller forging and valve internals, bolts, smaller blades. Larger Nimonic 105 forgings, would precipitate y’ during the surface cooling during forging, leading to surface cracks. The associate costs in forging Nimonic 105 to larger sizes [hotter dies, press requirements], were beyond the scope of this task and not investigated further. Haynes®282® has 20 - 25% volume fraction y’ was a choice for large components, albeit untested. A larger ingot diameter is pre-requisite for a larger diameter forging and achieves the “typically” accepted working ratio of 2.5-3:1. However, Haynes®282® is manufactured via a double melt process [VIM-ESR] limited by size [<18-16” diameter], which limited the maximum size of the final forging. The report documents the development of a 24” diameter triple melt ingot, surpassing the current available technology. A second triple melt ingot was manufactured and successfully forged into a 44” diameter disk. The successful developments in triple melting process and the large diameter forging of Haynes®282® resolved the scalability issues and involved the first of its kind attempt in the world for this alloy. The complete characterization of Haynes®282® forging was performed and documented in this report. The dataset from the commercially available Haynes®282® [grain size ASTM 3-4] and the finer grain size disk forging [ASTM 8-9] offer an additional design tradeoff to balance creep and fatigue during the future design process.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Sep 15 00:00:00 EDT 2015},
month = {Tue Sep 15 00:00:00 EDT 2015}
}
  • The Steam Turbine critical stationary structural components are high integrity Large Shell and Valve Casing heavy section Castings, containing high temperature steam under high pressures. Hence to support the development of advanced materials technology for use in an AUSC steam turbine capable of operating with steam conditions of 760°C (1400°F) and 35 Mpa (5000 psia), Casting alloy selection and evaluation of mechanical, metallurgical properties and castability with robust manufacturing methods are mandated. Alloy down select from Phase 1 based on producability criteria and creep rupture properties tested by NETL-Albany and ORNL directed the consortium to investigate cast properties of Haynesmore » 282 and Haynes 263. The goals of Task 4 in Phase 2 are to understand a broader range of mechanical properties, the impact of manufacturing variables on those properties. Scale up the size of heats to production levels to facilitate the understanding of the impact of heat and component weight, on metallurgical and mechanical behavior. GE Power & Water Materials and Processes Engineering for the Phase 2, Task 4.0 Castings work, systematically designed and executed casting material property evaluation, multiple test programs. Starting from 15 lbs. cylinder castings to world’s first 17,000 lbs. poured weight, heavy section large steam turbine partial valve Haynes 282 super alloy casting. This has demonstrated scalability of the material for steam Turbine applications. Activities under Task 4.0, Investigated and characterized various mechanical properties of Cast Haynes 282 and Cast Nimonic 263. The development stages involved were: 1) Small Cast Evaluation: 4 inch diam. Haynes 282 and Nimonic 263 Cylinders. This provided effects of liquidus super heat range and first baseline mechanical data on cast versions of conventional vacuum re-melted and forged Ni based super alloys. 2) Step block castings of 300 lbs. and 600 lbs. Haynes 282 from 2 foundry heats were evaluated which demonstrated the importance of proper heat treat cycles for Homogenization, and Solutionizing parameters selection and implementation. 3) Step blocks casting of Nimonic 263: Carried out casting solidification simulation analysis, NDT inspection methods evaluation, detailed test matrix for Chemical, Tensile, LCF, stress rupture, CVN impact, hardness and J1C Fracture toughness section sensitivity data and were reported. 4) Centrifugal Casting of Haynes 282, weighing 1400 lbs. with hybrid mold (half Graphite and half Chromite sand) mold assembly was cast using compressor casing production tooling. This test provided Mold cooling rates influence on centrifugally cast microstructure and mechanical properties. Graphite mold section out performs sand mold across all temperatures for 0.2% YS; %Elongation, %RA, UTS at 1400°F. Both Stress-LMP and conditional Fracture toughness plots data were in the scatter band of the wrought alloy. 5) Fundamental Studies on Cooling rates and SDAS test program. Evaluated the influence of 6 mold materials Silica, Chromite, Alumina, Silica with Indirect Chills, Zircon and Graphite on casting solidification cooling rates. Actual Casting cooling rates through Liquidus to Solidus phase transition were measured with 3 different locations based thermocouples placed in each mold. Compared with solidification simulation cooling rates and measurement of SDAS, microstructure features were reported. The test results provided engineered casting potential methods, applicable for heavy section Haynes 282 castings for optimal properties, with foundry process methods and tools. 6) Large casting of Haynes 282 Drawings and Engineering FEM models and supplemental requirements with applicable specifications were provided to suppliers for the steam turbine proto type feature valve casing casting. Molding, melting and casting pouring completed per approved Manufacturing Process Plan during 2014 Q4. The partial valve casing was successfully cast after casting methods were validated with solidification simulation analysis and the casting met NDT inspection and acceptance criteria. Heat treated and sectioned to extract trepan samples at different locations comparing with cast on coupons test data. Material properties requisite for design, such as tensile, creep/rupture, LCF, Fracture Toughness, Charpy V-notch chemical analysis testing were carried out. The test results will be presented in the final report. The typical Haynes 282 large size Steam Turbine production casting from Order to Delivery foundry schedule with the activity break up is shown in Figures 107 and 108. • From Purchase Order placement to Casting pouring ~ 26 weeks. 1. Sales and commercial review 3 2. Engineering Drawings/models review 4 3. Pattern and core box manufacturing 6 4. Casting process engineering review 4 5. FEM and solidification simulation analysis 4 6. Gating & Feeder Attachments, Ceramic tiling 2 7. Molding and coremaking production scheduling 6 8. Melting planning and schedule 3 9. Pouring, cooling and shake out 2 • From Pouring to casting Delivery ~ 29 weeks 10. Shot blast and riser cutting, gates removal 3 11. Homogenizing , solutionizing HT furnace prep 4 12. Grinding, Fettling 2 13. Aging HT Cycle, cooling 2 14. VT and LPT NDT inspections 2 15. Radiographic inspection 4 16. Mechanical testing, Chemical analysis test certs 4 17. Casting weld repair upgrades and Aging PWHT 4 18. NDT after weld repairs and casting upgrades 3 19. Casting Final Inspection and test certifications 3 20. Package and delivery 2 Hence the Total Lead time from P.O to Casting delivery is approximately 55 weeks. The Task 4.2 and Task 4.3 activities and reporting completed.« less
  • The U.S. Department of Energy (DOE) and the Ohio Coal Development Office (OCDO) have sponsored a project aimed at identifying, evaluating, and qualifying the materials needed for the construction of the critical components of coal-fired power plants capable of operating at much higher efficiencies than the current generation of supercritical plants. This increased efficiency is expected to be achieved principally through the use of advanced ultrasupercritical (A-USC) steam conditions. A limiting factor in this can be the materials of construction for boilers and for steam turbines. The overall project goal is to assess/develop materials technology that will enable achieving turbinemore » throttle steam conditions of 760°C (1400°F)/35MPa (5000 psi). This final technical report covers the research completed by the General Electric Company (GE) and Electric Power Research Institute (EPRI), with support from Oak Ridge National Laboratory (ORNL) and the National Energy Technology Laboratory (NETL) – Albany Research Center, to develop the A-USC steam turbine materials technology to meet the overall project goals. Specifically, this report summarizes the industrial scale-up and materials property database development for non-welded rotors (disc forgings), buckets (blades), bolting, castings (needed for casing and valve bodies), casting weld repair, and casting to pipe welding. Additionally, the report provides an engineering and economic assessment of an A-USC power plant without and with partial carbon capture and storage. This research project successfully demonstrated the materials technology at a sufficient scale and with corresponding materials property data to enable the design of an A-USC steam turbine. The key accomplishments included the development of a triple-melt and forged Haynes 282 disc for bolted rotor construction, long-term property development for Nimonic 105 for blading and bolting, successful scale-up of Haynes 282 and Nimonic 263 castings using traditional sand foundry practices, and a techno-economic study of an A-USC plant including cost estimates for an A-USC turbine which showed A-USC to be economically attractive for partial carbon and capture compared to today’s USC technology. Based on this successful materials research and a review with U.S. utility stakeholders, a new project to develop a component test facility (ComTest) including the world’s first A-USC turbine has been proposed to continue the technology development.« less
  • Recently, the Gas Turbine capacity has been increased step by step to improve initial cost of the Gas turbine and plant efficiency as well as to improve cycle conditions that is, temperature, pressure and cycle. In accordance with this improvement, the steam turbine capacity has been increased gradually in combined-cycle plants. In this application, the steam turbine became larger and the steam turbine is generally equipped with multiple rotors. When the rotor forging with a good combination of creep rupture strength in the HP section and toughness in the LP section is available, the steam turbine can be designed asmore » a single rotor, instead of multiple rotors, which makes the steam turbine to be compact and to be simple. The authors have already developed an HLP rotor forging (first generation), which has been applied to turbine rotors of units having capacities up to around 100 MW with a last stage blade (LSB) of a maximum 26 inch (660 mm) class. Recently, the advanced HLP rotor forging has been developed, which can be applied to longer LSBs of 42 inch (1070 mm) for 50 Hz machines, and 40 inch (1016 mm) for 60 Hz machines. As a result of the development, the steam turbines of 100 to 250 MW capacity in thermal power plants and advanced combined-cycle plants can be made more compact through this single-cylinder design. This paper describes development and application of the steam turbine with the advanced HLP rotor for advanced combined-cycle plants as well as for conventional thermal plants.« less
  • The U.S. Department of Energy's goals include power generation from coal at 60% efficiency, which requires steam conditions of up to 760 {sup o}C and 340 atm, so-called ultrasupercritical conditions. Evaporation of protective chromia scales is a primary corrosion mechanism. A methodology to calculate Cr evaporation rates from chromia scales was developed and combined with Cr diffusion calculations within the alloy (with a constant flux of Cr leaving the alloy from evaporation) to predict Cr concentration profiles and to predict the time until breakaway oxidation. At the highest temperatures and pressures, the time until breakaway oxidation was quite short formore » the turbine blade, and of concern within the steam pipe and the higher temperature portions of the superheater tube. Alloy additions such as Ti may allow for a reduction in evaporation rate with time, mitigating the deleterious effects of chromia evaporation.« less
  • The ''High Efficiency Steam Turbines with Ultra Long Buckets'' program developed and analytically validated the conceptual designs for full-speed 54 inch steel-hybrid and 62 inch titanium-hybrid last stage buckets (LSBs). It identified, tested (both environmentally and operationally), and selected candidate lightweight filler materials suitable for steel and titanium LSBs, with extensibility to upstream bucket stages. To mitigate risk and accelerate the introduction of this technology, the project designed and built a full-scale demonstrator 33.5 inch steel-hybrid LSB, with an advanced 3-dimensional aerodynamic shape that may serve as the basis for the first introduction into service. The project included subscale testingmore » of a stage of 33.5 inch buckets in the GE Energy Low Pressure Development Turbine (LPDT) facility. Preliminary investigation into high temperature materials was studied to broaden applicability of this technology. Finally, the program assessed the benefits of hybrid bucket technology including bucket/system dynamic tuning, damping and mid-span damping devices.« less