This invention relates generally to the field of power generation, and more particularly to the hot gas path components of a combustion turbine engine, and specifically to ceramic insulating tiles applied over portions of a gas turbine component.
It is known to apply a ceramic insulating material over the surface of a component that is exposed to gas temperatures that exceed the safe operating temperature range of the component substrate material. Metallic combustion turbine (gas turbine) engine parts (e.g. nickel, cobalt, iron-based alloys) are routinely coated with a ceramic thermal barrier coating (TBC), for example as described in U.S. Pat. No. 6,365,281 issued to the present inventor, et al., and assigned to the present assignee. Such coatings are generally deposited by a vapor deposition or thermal spray process.
The firing temperatures developed in combustion turbine engines continue to be increased in order to improve the efficiency of the machines. Ceramic matrix composite (CMC) materials are now being considered for applications where the temperature may exceed the safe operating range for metal components. U.S. Pat. No. 6,197,424, assigned to the present assignee, describes a gas turbine component fabricated from CMC material and covered by a layer of a dimensionally stable, abradable, ceramic insulating material, commonly referred to as friable grade insulation (FGI). Hybrid FGI/CMC components offer great potential for use in the high temperature environment of a gas turbine engine, however, the full value of such hybrid components has not yet been realized due to their relatively recent introduction to the gas turbine industry.
Improved thermal insulation systems are needed for combustion turbine components, and improved hybrid FGI/CMC components for high temperature environments are desired.
An apparatus for use in a high temperature environment is described herein as including: a substrate comprising ceramic matrix composite material; a monolithic layer of ceramic insulating material disposed on a first portion of the substrate; and a plurality of individual tiles of ceramic insulating material disposed on a second portion of the substrate. The second portion of the substrate may be an area previously covered by the monolithic layer of ceramic insulating material and wherein a damaged portion of the monolithic ceramic insulating material has been removed and replaced with the plurality of individual tiles of ceramic insulating material. The plurality of individual tiles of ceramic insulating material may include a first layer of tiles disposed directly on the substrate and a second layer of tiles disposed on the first layer of tiles, wherein the first layer of tiles may be a material different than a material of the second layer of tiles. The pattern of gaps between adjacent tiles of the first layer of ceramic insulating tiles may be staggered in relation to a pattern of gaps between adjacent tiles of the second layer of ceramic insulating tiles.
A vane for a combustion turbine engine is described herein as including: an airfoil section; a platform section; a fillet along a joint between the airfoil section and the platform section; and a plurality of individual tiles of ceramic insulating material bonded to the fillet.
An apparatus for use in a high temperature environment is described herein as including: a substrate; a monolithic layer of ceramic insulating material disposed over a surface of the substrate; and a repaired region wherein a portion of the monolithic layer of ceramic insulating material has been removed and an individual tile of ceramic insulating material has been bonded. The entire thickness of the monolithic layer of ceramic insulating material may be removed in the repaired region with the individual tile being bonded to the substrate, or a partial thickness of the monolithic layer of ceramic insulating material may be removed in the repaired region to bond the individual tile to a remaining thickness of the monolithic layer of ceramic insulating material.
A component for use in a combustion gas stream environment is described herein as including: a ceramic matrix composite substrate material; and a layer of individual tiles of ceramic insulating material bonded to a portion of a surface of the substrate to isolate that portion of the substrate surface from the combustion gas stream.
These and other advantages of the invention will be more apparent from the following description in view of the drawings that show:
Components of a gas turbine engine are exposed to a corrosive, high temperature environment, and they must be able to withstand the erosion and impact effects of a high velocity combustion gas stream. A prior art gas turbine component 10 is shown in partial cross-section in
The insulating layer 14 may be exposed to impact by high-energy particles propelled by the combustion gas stream. An impact crater 16 is visible in the insulating layer 14. The major damage mechanisms that result from such surface impacts are a crush zone 18 directly under the site of the impact, thru-thickness cracking 20 caused by in-plane tensile stress in the area immediately surrounding the crush zone 18, and delamination 22 of the insulating material 14 from the substrate 12 caused by rebound stresses across the interface. The extent of such damage will depend not only upon the energy and size of the impacting particle, but also will depend upon the particular material composition and mechanical properties of the insulating material 14. Material properties of the insulating material 14 are often a compromise among conflicting parameters, and materials that are optimized for resisting erosion may be relatively brittle and more susceptible to impact damage.
An improved component 30 for a gas turbine engine or other high temperature application is illustrated in plan view in
Substrate 34 may be any appropriate structural material, for example an alloy material or composite material such as an oxide/oxide CMC material. Tiles 32 may be any appropriate insulating material, for example a friable grade insulation (FGI) as described in the above-cited '424 patent. Because the individual tiles 32 are separated from each other by gaps 38, any damage or cracking 20 associated with an impact crater 16 will not progress to any adjacent tile that is not actually struck by the impacting object. Because the gaps 38 function as a crack-tip limiter, the specific chemical and mechanical properties of the ceramic material used to form the tiles 32 may be optimized for erosion and/or another selected property with less concern needed for properties that affect impact damage containment. For example, the tiles 32 may be selected to be a ceramic insulating material that has purposefully increased strength and hardness when compared to alternatives, while the corresponding increase in brittleness and decreased impact resistance is of reduced concern since crack propagation and delamination are limited to individual tiles 32.
The material selected for the first layer of tiles 56 may be different than that selected for the second layer of tiles 58. For example, the first layer 56 may be formed from a ceramic insulating material that optimizes its thermal insulating characteristics, while the second layer 58 may be formed from a ceramic insulating material that optimizes its erosion resistance properties. An inner layer 56 may be formed with aluminum phosphate, aluminosilicate or other low modulus matrix material that is compatible with the substrate 54 but that is somewhat prone to erosion and environmental attack, such as from water vapor in a combustion gas. An outer layer 58 that is more erosion resistant, e.g. alumina, stabilized zirconia, stabilized hafnia, but is more prone to impact damage would benefit from having the inner tile layer 56 act as a compliant layer. Additional layers of insulating tiles may be used, or a single layer of insulating tiles may be placed over a monolithic layer of insulating material deposited directly onto the substrate. A layer of tiles may be used over a monolithic layer of ceramic insulating material in order to provide thermal shock and/or impact resistance on an outer surface over an environmentally resistant under layer.
A filler material or grout 64 may be deposited in the gaps 60, 62 of either or both layers 56, 58. Grout 64 functions as a barrier to the direct passage of the hot combustion gas and it smoothes the airflow across the top surface 66 of the component 50. Grout 64 may be selected to have mechanical properties that are different than those of the tiles of layers 56, 58. For example, grout 64 may be a ceramic insulating material having a low elastic modulus and a high damage tolerance, i.e. likely to micro crack instead of macro crack, such as mullite or submicron blends of multiple phase-stable ceramics such as alumina-zirconia, alumina-hafnia, alumina ceria.
The insulating tiles 32, 56, 58 of the present invention may be manufactured by net shape casting or by machining from a larger slab of ceramic material. Individual tiles may have a rectangular or square or other shape along their exposed surface and they may be shaped to fit complex substrate surface shapes. A typical tile may be square with sides of 6–50 mm. In one embodiment, a tile is 25 mm by 25 mm by 2 mm in thickness. The tiles may be bonded individually to the substrate 12, 34, 54 or to an underlying layer of tiles 56 by applying adhesive 36 to the back of the tile, to the surface of the substrate, or to both. The individual tiles are then pressed onto the surface of the substrate and a permanent bond is achieved by drying and firing at an elevated temperature, typically 1,000–1,200° C. The tiles can be bonded to the substrate after they have been partially or fully fired to selectively reduce the amount of shrinkage that is experienced by the tiles once they are affixed onto the substrate. Multiple tiles may be attached to a supportive, flexible scrim such as a woven ceramic cloth 68. An entire sheet containing multiple tiles may thus be applied with adhesive as described above to expedite the application process.
Additional ceramic insulating tiles 84 are shown as applied to a portion of a leading edge 86 of the airfoil section 72. These tiles 84 have been installed in an area of the vane 70 that was previously damaged, such as during a manufacturing operation or during in-service use in a combustion turbine engine. A damaged area of the monolithic insulating material 80 has been removed either to a portion of the depth of the monolithic material or completely to the surface of the underlying material which may be a ceramic matrix composite structural ceramic material. At least one tile 84 has been installed in place of the damaged material, with the tile 84 being bonded to the substrate material or to the remaining thickness of the monolithic insulating material. The damaged material may be removed from the surface of the airfoil section 72 by a mechanical operation such as grinding. Additional processes such as milling, grit blasting using dry ice, alumina, silica, quartz, ice, etc. may be used to prepare the surface for bonding. The tiles 84 are then applied with an adhesive and a grout may be applied to fill in any gaps adjacent to the tiles 84. The part is then heated to fully cure the adhesive and grout, as necessary, and the vane 70 is returned to service.
While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
4124732 | Leger | Nov 1978 | A |
4308309 | Frosch et al. | Dec 1981 | A |
4928575 | Smirlock et al. | May 1990 | A |
5170690 | Smirlock et al. | Dec 1992 | A |
5191166 | Smirlock et al. | Mar 1993 | A |
5331816 | Able et al. | Jul 1994 | A |
5404793 | Myers | Apr 1995 | A |
5636508 | Shaffer et al. | Jun 1997 | A |
5639531 | Chen et al. | Jun 1997 | A |
5972819 | Cohen | Oct 1999 | A |
6174565 | Daws et al. | Jan 2001 | B1 |
6197424 | Morrison et al. | Mar 2001 | B1 |
6287511 | Merrill et al. | Sep 2001 | B1 |
6322322 | Rhodes et al. | Nov 2001 | B1 |
6332390 | Lyons | Dec 2001 | B1 |
6365281 | Subramanian et al. | Apr 2002 | B1 |
20020178900 | Ghiorse et al. | Dec 2002 | A1 |
Number | Date | Country | |
---|---|---|---|
20060216547 A1 | Sep 2006 | US |