Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like
Reexamination Certificate
1999-03-03
2001-05-22
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Honeycomb-like
C029S888025, C415S208100, C416S224000, C416S22900R, C416S22900R, C428S593000
Reexamination Certificate
active
06235370
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to high temperature erosion resistant abradable composite coatings, and more particularly relates to the use of such coatings as thermal barriers in applications such as combustion turbine ring seal segments, vane segment shrouds, transitions and combustors.
BACKGROUND INFORMATION
Metal components of combustion turbines are operated at very high temperatures and often require the use of thermal barrier coatings (TBCs). Conventional TBCs typically comprise a thin layer of zirconia. In many applications, the coatings must be erosion resistant and must also be abradable. For example, turbine ring seal segments which fit with tight tolerances against the tips of turbine blades must withstand erosion and must preferentially wear or abrade in order to reduce damage to the turbine blades.
In order to provide sufficient adherence to the underlying metal substrate, conventional TBCs are provided as relatively thin layers, e.g., less than 0.5 mm. This thickness is limited by the thermal expansion mismatch between the coating and metallic substrate. However, such thin layers limit the heat transfer characteristics of the coatings, and do not provide optimal erosion resistance and abrasion properties.
The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.
SUMMARY OF THE INVENTION
The present invention provides a high temperature, thermally insulating and/or abradable composite coating system that may be used in gas turbine components such as ring seal segments and the like. The preferred composite material comprises a metal base layer or substrate, a metallic honeycomb structure, and a ceramic filler material. The ceramic filler material comprises hollow ceramic spheres within a phosphate matrix to provide high temperature capability and excellent thermal insulation. The resulting system is compliant and accommodates differential thermal strains between the ceramic and the metallic substrate material. The honeycomb/ceramic composite may optionally be overlaid with a ceramic layer to protect and insulate the metallic honeycomb.
In addition to improved thermal properties, the present composite may also display excellent abradable properties if tailored accordingly. The honeycomb structure provides good adhesion between the ceramic material and the underlying metallic substrate/component. By infiltrating the ceramic into the cells of the honeycomb during processing, the honeycomb provides additional mechanical anchoring to enhance ceramic to metal adhesion. The composite enables the use of relatively thick insulating coatings, e.g., on the order of 2 mm or more, to provide very high temperature protection to metallic hot section gas turbine parts.
The material system in addition to providing adequate abradability also possesses excellent erosion resistance. For example, the ceramic on a ring seal segment should wear preferentially to the metal of a blade in the case of ring seal segment/blade tip rubbing. This property provides the capability to restrict blade tip clearances and to improve engine efficiencies without incurring the damage to blade tips that conventional TBC coatings cause in similar situations.
The present invention provides a more durable, cost effective thermal barrier coating system for use with ring seal segments, transitions, combustors, vane platforms, and the like. The coating can be applied to greater thicknesses than conventional TBCs, thereby offering increased temperature protection for substrate metal components. By employing the metallic honeycomb structure to adhere the ceramic coating to the metal substrates, increased compliance between the base metal and the ceramic is achieved, minimizing local stresses and increasing component life. Because the coating system can be applied in simple steps such as brazing, back-filling and heat treating, fabrication of the system may be accomplished much more cost effectively than electron beam physical vapor deposition of conventional zirconia based TBC coatings and comparable to air plasma sprayed coatings.
An aspect of the present invention is to provide a composite thermal barrier coating comprising a metal substrate, a metal support structure secured to the substrate, and a ceramic filler material at least partially inside the metal support structure comprising hollow ceramic particles in a ceramic matrix.
Another aspect of the present invention is to provide a method of making a composite thermal barrier coating. The method includes the steps of securing a metal support structure to a metal substrate, at least partially filling voids of the metal support structure with a ceramic filler material comprising hollow ceramic particles and a binder material, and heating the ceramic filler material to form a ceramic matrix connecting the hollow ceramic particles.
These and other aspects of the present invention will be more apparent from the following description.
REFERENCES:
patent: 4177308 (1979-12-01), Beeler
patent: 4405284 (1983-09-01), Albrecht et al.
patent: 4639388 (1987-01-01), Ainsworth et al.
patent: 4664600 (1987-05-01), Perry
patent: 4802828 (1989-02-01), Rutz et al.
patent: 4867639 (1989-09-01), Strangman
patent: 4916022 (1990-04-01), Solfest et al.
patent: 5064727 (1991-11-01), Naik et al.
patent: 5180285 (1993-01-01), Lau
patent: 5310592 (1994-05-01), Baker et al.
patent: 5683825 (1997-11-01), Bruce et al.
patent: 5780146 (1998-07-01), Mason et al.
patent: 0 751 104 A2 (1997-01-01), None
patent: 1 556 274 (1979-11-01), None
patent: 2 130 244 (1984-05-01), None
Merrill Gary B.
Morrison Jay A.
Eckert Seamans Cherin & Mellott , LLC
Lorin Francis J.
Siemens Westinghouse Power Corporation
LandOfFree
High temperature erosion resistant, abradable thermal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High temperature erosion resistant, abradable thermal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High temperature erosion resistant, abradable thermal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2537831