|
Materials
For DE
PROJECTS
Monolithic
Ceramics and High Temperature Coatings
Silicon based ceramics including silicon nitride and silicon carbide have long been leading contenders for structural use in gas turbine engines due to their high temperature strength, creep resistance, and relative corrosion resistance. However, significant challenges have prevented their widespread use, and thus, the higher operating temperatures needed for higher efficiency engines has not been widely achieved. Technical barriers to reaching the high performance objectives have included low fracture toughness, vulnerability to impact resistance, and water vapor accelerated oxidation. Further, the cost of ceramic components has hindered more rapid commercialization. This has resulted in a dwindling supplier base for ceramic components, and has highlighted the need for improved materials or coatings to provide environmental protection.
Projects under this program are addressing these challenges. New sources of gas turbine grade ceramics are being explored, and environmental barrier coatings (EBCs) are being developed. Projects that are in progress, and that have been completed, include:
Active Projects
Saint-Gobain Hot-Section Materials Development
- Robert Licht
Environmental Protection Systems for Ceramics in Microturbines and Industrial Gas Turbine Applications
Part B: Slurry Coatings and Surface Alloying
- Beth Armstrong
Completed Projects
Kennametal’s
Hot-Section Material Development
- Russell Yeckley
High-Temperature Diffusion Barriers for Ni-Based Superalloys
- Dr. Bruce Pint
Accomplishments
Silicon Nitride-Based Turbine Components Improved Through New Forming Process (FY 05/06)
Slurry-Coated Materials Withstand Corrosive Turbine Engine Environment (FY 05/06)
ORNL Partners with Industry for Testing of Ceramics and EBCs (FY 04)
Software Evaluates Ceramic Materials for Turbine Efficiency (FY 04)
Posters
Environmental
Barrier Coating (PDF
5.2MB)
Conferences
2003 Environmental Barrier Coatings Workshop
2002 Environmental Barrier Coatings Workshop
Kennametal’s
Hot-Section Material Development
Contact:
Russell Yeckley
Kennametal Inc.
Ceramics Development
1600 Technology Way
Latrobe, PA 15650
(724) 539-4822
russ.yeckley@kennametal.com
Kennametal provides the aerospace and power generation manufacturers with advanced silicon nitride and SiAlON ceramics for useas cutting tools in high speed machining of superalloy materials. These same compositions exhibit some of the property characteristics required in microturbine applications, including high hardness, toughness and strength. The objective of this project was to determine whether a commercial SiAlON, or a compositional modification thereof, exhibits the strength, environmental stability, and manufacturability required for advanced microturbine applications. Key issues addressed are the dependence of mechanical properties (strength, strength distribution, toughness) at the appropriate temperature on the sialon phase assembly and microstructure.
Experimental results show that the strength and fatigue resistance of these silaons meets design requirements for microturbines operating at 1,050-1,250°C. Keiser rig testing of the materials shows corrosion resistance behavior similar to that of silicon nitride.
The latest and archived Quarterly Progress Reports are
available in the on-line material in the Reports section.
Recent Publications: Refer to the Bibliography section
for more publications
No
publications are available on this topic yet. Please refer to the
quarterly reports in the Reports section.
Recent Presentations: Refer to the Bibliography section for more presentations
Yeckley R., Hellman, J., Fox, K., “Sialon Hot-Section Components: Phase I Wrap-up,” presented at the Environmental Barrier Coatings Workshop, Nashville TN, November 17-18, 2004. (PDF 8,177KB)
Yeckley R., Hellman, J., Fox, K., “Sialon Materials Development,” presented at the Environmental Barrier Coatings Workshop, Nashville TN, November 18-19, 2003. (PDF 1,061KB)
Yeckley,
R., “SiAlON Materials Development at Kennametal,” presented
at the Environmental Barrier coatings Workshop, Nashville
TN, November 6, 2002. (EBC Workshop PDF)
Saint-Gobain
Hot Section Materials Development
Contact:
Robert Licht
Saint-Gobain Ceramics & Plastics
9 Goddard Rd
Northboro, MA 01532-1545
(508) 351-78-5
robert.h.licht@saint-gobain.com
Saint-Gobain Ceramics & Plastics, Inc. started their Phase I subcontract under the Microturbine Program in August 2002, to re-establish and optimize a silicon nitride composition for microturbine applications. The microturbine grade NT154 silicon nitride processing and properties have been re-established. The closed loop processed NT154 samples have been tested at room and high temperature (1200°C) both at Norton Research and Development Center (NRDC) and ORNL to demonstrate the baseline bulk and as-processed (AP) properties suitable for microturbine applications. In addition, successful net shape forming of several radial integral bladed microturbine rotors was accomplished. Excellent average part-to-part variation, concentricity, and average surface roughness were achieved for rotors. Biaxial flexure AP strengths of samples taken from the blade and hub region were high and consistent with tile data. This series of tests suggest that the mechanical property data generated from test bars have been reproduced in net-shape components. |
 |
The development of a more stable composition, suitable surface modification, or a compatible environmental barrier coating (EBC) that will insure long-term environmental stability (>20,000 hr) is underway. An internal recession test rig to screen potential candidate materials and coatings has been developed at NRDC. Internal work focused on the evaluation of different EBC and surface modification strategies. A novel EBC composition has been defined based upon thermodynamic computations and coefficient of thermal expansion (CTE) simulations to match with the NT154 substrate. The EBC composition was tested in the NRDC recession rig showing at least a factor of three improvements over the bare NT154 substrate. The composition has also shown excellent stability in the high pressure Keiser Rig at ORNL after 500 hours of testing. Because of its excellent CTE match with the substrate, this composite system will be utilized as a bond coat for a rare earth di- silicate based top coat that was already proven to be a recession resistant composition.
The current effort will focus on three major areas:
- Supply NT154 specimens and components to ORNL and ORNL subcontractors.
- Improve slow crack growth (SCG) resistance of NT154.
- Recession resistant surface improvements.
The latest and archived Quarterly Progress Reports are available in the on-line material in the Reports section.
Recent Publications: Refer to the Bibliography section for more publications
No publications are available on this topic yet. Please refer to the quarterly reports in the Reports section.
Recent Presentations: Refer to the Bibliography section for more presentations
Pujari, V. K. ,A.M. Vartabedian, W. Collins, R.H. Licht, "Optimization of High Temperature Silicon Nitride for Microturbine Applications", ACERS 29th International Conference on Advanced Ceramics and Composites, Cocoa Beach Conference, January 25, 2005. (PDF 2,694KB)
Licht, R. H., "Hot Section Silicon Nitride Materials Development for Advanced Microturbine Component Applications," Presented at the 28th Annual Conference on Composites, Materials, and Structures, January 29, 2004, Cocoa Beach, FL. (PDF 1,202KB)
Licht, R. H., “Hot Section Silicon Nitride Materials Development for Advanced Microturbine Component Applications,” Presented at the 27th Annual Conference on Composites, Materials, and Structures, January 29, 2003, Cocoa Beach, FL. (PPT 3.18MB)
Environmental Protection Systems for Ceramics in Microturbines and Industrial Gas Turbine Applications
Part B: Slurry Coatings and Suface Alloying
Contact: Ms. Beth Armstrong
Oak Ridge National Laboratory
Bethel Valley Road
P.O. Box 2008
Oak Ridge, TN 37831-6063
(865) 241-5862
armstrongbl@ornl.gov
Monolithic silicon nitride (Si3N4) ceramics are the primary ceramic material currently used in combustion engine environments. These ceramics are also under consideration for use as hot-section structural materials in microturbines and other advanced combustion systems. However, Si3N4 typically forms a surface oxidation layer (silicate) in oxidizing conditions. The silicate layer rapidly degrades in the corrosive and erosive turbine engine environment, severely limiting life of the ceramic. Long-term use of Si3N4 material in advanced combustion engine applications will require the development of environmental barrier coatings (EBC) that can withstand high temperature, high pressure, high gas velocity, and the presence of water vapor.
The slurry (dip) coating process is a promising, low-cost approach for the production of EBCs. Slurry coating is a non-line-of-sight process, which coats all surfaces of the part. Components with complex shapes can be dipped into a slurry (ceramic particles suspended in a solvent medium), and subsequently dried and heat treated at elevated temperatures to promote densification. Successful EBCs for Si3N4 materials have been developed through the formulation of crack-free and adhesive slurry compounds. Because no unique equipment is required to establish coating capability, and this flexible process allows a variety of ceramic powders to be applied to various substrate compositions, this technology can be easily transitioned to industrial production.
During FY05, coatings of doped alumino- and rare-earth silicates were tested for use on silicon nitride substrates in simulated microturbine environments. A cationic poly-electrolyte, poly-ethylenimine (PEI), was used to tailor the rheological behavior of mullite, doped aluminosilicate, and rare-earth silicate suspensions. Latex emulsions were used to promote improved wetting, drying, and green strength of the ceramic layers. Uniform, crack-free layers were demonstrated on a wide variety of substrates.
The latest and archived Quarterly Progress Reports are available in the on-line material in the Reports section.
Recent Publications: Refer to the Bibliography section for more publications
Kirby, G., Cooley, K. M., Lin H.T. and Armstrong, B. L., “Deposition of Environmental Protection Systems from Collodal Suspension,” Presented at the Industrial Gas Turbine Institute ASME Turbo Expo, Power for Lands, Sea, and Air, June 6, 2005. (PDF 4,531KB)
M. P. Brady, B. L. Armstrong, H. T. Lin HT, M. J. Lance, K. L. More, L.R. Walker, F. Huang, and M. L. Weaver., “Feasibility Assessment of Self-Grading Metallic Bond Coat Alloys for EBCs/TBCs to Protect Si-Based Ceramics,” SCRIPTA MATERIALIA 52 (5): 393-397, March 2005. (PDF 411KB)
M. P. Brady, P. F. Tortorelli, K. L. More, E. A. Payzant, B. L. Armstrong, H. T. Lin, M. J. Lance, F. Huang, and M. L. Weaver, "Coatings and near-surface Modification Design Strategies for Protective and Functional Surfaces," Metals and Corrosion 56(11) 748-755. (PDF 363KB)
Recent Presentations: Refer to the Bibliography section for more presentations
Armstrong, B. L., Cooley, K. M., Hayes, J. A., Lin, H. T., Surry Based Environmental Barrier Coating (EBC) Concepts,"presented at the Environmental Barrier Coatings Workshop, Nashville TN, November 6, 2002. (EBC Workshop PDF)
Armstrong, B. L., “Slurry Deposition of Environmental Protection Systems,” presented at the Environmental Barrier Coatings Workshop, Nashville TN, November 16, 2005. (PDF 12,951KB)
Armstrong, B. L. and G. Kirby, “Slurry-based Environmental Protection Systems,” presented at the Environmental Barrier Coatings Workshop, Nashville, TN, November 16, 2005. (PDF 2,780KB)
High-Temperature
Diffusion Barriers for Ni-Base Superalloys
Contact
Dr. Bruce Pint
Oak Ridge National Laboratory
Bethel Valley Rd
PO Box 2008
Oak Ridge, TN 37831-6156
(865) 576-2897
pintba@ornl.gov
Aluminide coatings have been developed to protect Ni-based superalloys from high-temperature oxidation. Unfortunately, the oxidation resistance of these coatings deteriorates as Al is lost from the coating. The Al content of the coating decreases with time for two reasons: 1) Al is consumed due to the formation of the protective aluminum oxide scale, and 2) large quantities of Al are lost due to the diffusion into the Ni-base superalloy substrate. The goal of this project was to fabricate and assess potential compounds for use as high-temperature diffusion barriers between the coating and the substrate. Ideally, the barrier would act to reduce the inward diffusion of Al as well as reduce the outward diffusion of substrates elements (Cr, Re, Ta, and W) which also degrade the oxidation resistance of the coating.
This work has shown that fabrication of Engle-Brewer compounds as thin films is possible. A Hf-Pt layer was formed with low Al and Ni content. However, during subsequent Chemical Vapor Deposition aluminizing, the layer dissolved. Other similar compounds may be more successful, or a different processing method may be necessary.
The latest and archived Quarterly Progress Reports are available in the on-line material in the Reports section.
Recent
Publications: Refer to the Bibliography section for more publications
Haynes, J. A., Y. Zhang, K. M. Cooley, L. Walker, K. S. Reeves, and B. A. Pint, “High-temperature diffusion barriers for protective coatings”, Surface and Coatings Technology, v. 188-189, 2004, p. 153-157. (PDF 1,351KB)
Recent Presentations: Refer to the Bibliography section for more presentations
Haynes, J. A., Y. Zhang, K. M. Cooley, L. Walker, K. S. Reeves, and B. A. Pint, “High-temperature Diffusion Barriers For Protective Coatings”, Poster presented at the International Conference on Metallurgical Coatings and Thin Films, San Diego, CA, April, 2004. (PDF 1,876KB)
|
