Reinforced articles and methods of making the same

An article comprising a substrate; a bond layer disposed on the substrate, the bond layer comprising one or more bonding segments and at least one reinforcing segment; at least one protective layer disposed on the bond layer; and at least one cooling hole extending through the substrate, the at least one reinforcing segment and the at least one protective layer, wherein the at least one reinforcing segment reduces cracking and/or delamination at the interface between the substrate and the bond layer, and methods of making the same.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to reinforced articles, such as gas turbine engine components, and more particularly to reinforced articles which are resistant to cracking and/or delamination, and methods of making the same.

Gas turbine engines accelerate gases, forcing the gases into a combustion chamber where heat is added to increase the volume of the gases. The expanded gases are then directed toward a turbine to extract the energy generated by the expanded gases. In order to endure the high temperatures and extreme operating conditions in gas turbine engines, gas turbine engine components, such as turbine blades, are fabricated from metal, ceramic or ceramic matrix composite materials.

Thermal barrier coatings are applied to the surface of gas turbine engine components to provide added protection and to thermally insulate the gas turbine engine components during operation of the gas turbine engine at high temperatures. A thermal barrier coating has at least one protective layer and a bond layer. The at least one protective layer is applied to a substrate, such as a gas turbine engine component, via the bond layer. The protective layer is a ceramic material and can include multiple layers.

Cooling holes are incorporated into gas turbine engine components in order to allow for more efficient operation at higher operating temperatures. Cooling holes are drilled into the gas turbine engine component, for example, using laser drilling. In gas turbine engine components having a thermal barrier coating, the cooling holes extend through the at least one protective layer, the bond layer and the substrate of the gas turbine engine component.

During operation of the gas turbine engine, the areas surrounding these cooling holes undergo cracking and/or delamination. The process of drilling the cooling holes results in degradation at the interface between the bond layer and the substrate and/or the bond layer and the at least one protective layer. In addition, the hot gas environment in gas turbine engines results in oxidation of the bond layer and formation of a thermally grown oxide (TGO) layer. The TGO layer creeps into the at least one protective layer as a result of shear stress due to, for example, centrifugal load or mismatch of thermal expansion between adjacent layers or between a layer and the substrate. The formation and creep of the TGO layer causes cracking and/or delamination at the interface between the substrate and the bond layer and/or at the interface between the bond layer and the at least one protective layer, thereby increasing the frequency of repairs and/or reducing the overall lifetime of the component.

It is therefore desirable to provide reinforced articles having improved cracking and/or delamination resistance, and methods of making the same, which solve one or more of the aforementioned problems.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, an article comprises a substrate; a bond layer disposed on the substrate, the bond layer comprising one or more bonding segments and at least one reinforcing segment; at least one protective layer disposed on the bond layer; and a cooling hole extending through the substrate, the at least one reinforcing segment and the at least one protective layer, wherein the at least one reinforcing segment reduces cracking and/or delamination at the interface between the substrate and the bond layer.

According to another aspect of the invention, a method comprises providing a substrate, the substrate having a surface; forming one or more bonding segments on one or more portions of the surface of the substrate, forming at least one reinforcing segment on a portion of the surface of the substrate, the at least one reinforcing segment being formed on the surface of the substrate by electrospark deposition, wherein the one or more bonding segments and the at least one reinforcing segment form a bond layer; forming at least one protective layer on the bond layer, forming at least one cooling hole, the at least one cooling hole extending through the substrate, the at least one reinforcing segment and the at least one protective layer, wherein the at least one reinforcing segment reduces cracking and/or delamination at the interface between the substrate and the bond layer.

These and other advantages and features will become more apparent from the following description taken together in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments described herein generally relate to reinforced articles and methods of making the same. A reinforcing segment is provided for use in a bond layer, in conjunction with a substrate and a protective layer.

Referring toFIG. 1, an article10comprises a substrate20having a surface30. A bond layer40is disposed on the surface30of the substrate20. The bond layer40comprises at least one reinforcing segment50and one or more bonding segments60. At least one protective layer70is disposed on the bond layer40.

The substrate20is a metal, metal alloy, ceramic, or ceramic matrix composite (CMC) material. In one embodiment, the substrate20is a gas turbine engine component. In another embodiment, the substrate is a turbine blade, vane, shroud, liner, combustor, transition piece, rotor component, exhaust flap, seal or fuel nozzle. In yet another embodiment, the substrate20is a turbine blade formed using a CMC material.

In one embodiment, the substrate20is a new substrate which has not previously been in operation in an application. In another embodiment, the substrate20is a used substrate, which has previously been in operation in an application. The at least one reinforcing segment50is used to repair the used substrate20by replacing at least a portion of an existing coating on the used substrate.

The bond layer40assists in bonding the at least one protective layer70to the surface30of the substrate20. In one embodiment, the at least one reinforcing segment50and the one or more bonding segments60, cumulatively, constitute a continuous bond layer40.

In one embodiment, the at least one reinforcing segment50and/or the one or more bonding segments60of the bond layer40comprise silicon, cobalt, nickel, chromium, aluminum, yttrium or a combination comprising at least one of the foregoing. In another embodiment, the at least one reinforcing segment50is formed using a material which is also used to form the one or more bonding segments60. In yet another embodiment, the at least one reinforcing segment50and/or the one or more bonding segments60have the same or substantially the same coefficients of thermal expansion (CTE). In still another embodiment, the at least one reinforcing segment50is formed using a material which is different from a material used to form the one or more bonding segments60.

In one embodiment, the one or more bonding segments60are formed by first forming a continuous layer (not shown) on the surface30of the substrate20. The continuous layer is formed using thermal spraying, plasma spraying, atmospheric plasma spray (APS), chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), dip coating, spin coating, electro-phoretic deposition (EPD) or electrospark deposition (ESD). In a particular aspect of the embodiment, the continuous layer is formed using thermal spraying. At least one portion of the continuous layer is removed. The at least one portion of the continuous layer is removed using any suitable removal technique, including but not limited to, mechanical removal, chemical removal or burning off the at least one portion of the continuous layer using electrosparks. The remaining portion or portions of the continuous layer form the one or more bonding segments60of the bond layer40.

In another embodiment, the one or more bonding segments60are formed separately in a discontinuous layer wherein each of the one or more bonding segments60is formed on a different portion of the surface30of the substrate20. The one or more bonding segments60are formed using thermal spraying, plasma spraying, atmospheric plasma spray (APS), chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), dip coating, spin coating, electro-phoretic deposition (EPD) or electrospark deposition (ESD). In a particular aspect of the embodiment, the one or more bonding segments60is formed using thermal spraying.

The at least one reinforcing segment50is deposited onto a portion of the surface30of the substrate20using electrospark deposition (ESD). ESD is a pulse micro-welding method having an implied millisecond duration thermal cycle at temperatures between about 8,000° C. to about 25,000° C. Using ESD, the at least one reinforcing segment50is applied to a portion of a surface30of the substrate20via electric sparks. Both the deposition and the cooling, or self-quenching, of the at least one reinforcing segment50are rapid. Due to the short duration of the thermal pulses, the surface30of the substrate20is subjected to only low heat input during the ESD process. The microstructure of the surface30of the substrate20following deposition of the at least one reinforcing segment50using ESD is the same or substantially the same as the microstructure of the surface30of the substrate20before deposition of the at least one reinforcing segment50on the surface30of the substrate20.

Deposition of the at least one reinforcing segment50via ESD results in the formation of a metallurgical bond between the at least one reinforcing segment50and the substrate20. In one embodiment, electrosparks are used to remove at least a portion of an existing coating to form the one or more bonding segments60while simultaneously using electrosparks to deposit the at least one reinforcing segment50.

The at least one reinforcing segment50is built up to a desired thickness by repeatedly overlaying deposits of the at least one reinforcing segment50material. Each of the deposits which cumulatively form the at least one reinforcing segment50has a substantially uniform or uniform thickness. Each of the deposits which cumulatively form the at least one reinforcing segment50has an average thickness of about 1 μm to about 5 μm. The resulting at least one reinforcing segment50has an average thickness of about 1 μm to about 500 μm. In one embodiment, the average thickness of the at least one reinforcing segment50and/or the one or more bonding segments60is uniform or substantially uniform.

The at least one reinforcing segment50is formed on a portion of the surface30of the substrate20which is adjacent to the one or more bonding segments60. The at least reinforcing segment50and the one or more bonding segments60form a bond layer40which is continuous with the surface30of the substrate20. In one embodiment, the at least one reinforcing segment50is formed using ESD and the one or more bonding segments60are formed using thermal spraying. In another embodiment, the one or more bonding segments60and the at least one reinforcing segment50are formed using ESD.

The at least one protective layer70protects the substrate from the effects of environmental conditions to which the article10is subjected during operation such as hot gas, water vapor and/or oxygen. The at least one protective layer70is any material suitable to protect the substrate20from being contacted with hot gas, water vapor and/or oxygen when the article10is in operation. In one embodiment, the at least one protective layer70comprises a ceramic material. In another embodiment, the at least one protective layer70comprises silicon, zirconium, an oxide of one of the foregoing or a combination comprising at least one of the foregoing.

In one embodiment, the protective layer70comprises a single layer. In another embodiment, the bond layer40and the at least one protective layer70form a thermal barrier coating. In yet another embodiment, the at least one protective layer70comprises multiple layers of various materials. In still another embodiment, the article10further comprises an intermediate layer (not shown) disposed between the bond layer40and the at least one protective layer70, forming an environmental barrier coating (EBC).

The at least one protective layer70is disposed on the bond layer40using any suitable method, including but not limited to, atmospheric plasma spray (APS), chemical vapor deposition (CVD), plasma enhanced CVD (PECVD), dip coating, spin coating, electro-phoretic deposition (EPD) or electrospark deposition (ESD).

The at least one reinforcing segment50corresponds to a location in the article10where at least one cooling hole is to be formed. Referring toFIG. 2, at least one cooling hole80is formed in the article10. The at least one cooling hole80extends through the substrate20, the reinforcing segment50and the at least one protective layer70. The at least one cooling hole80is formed in the article10using any suitable method, including but not limited to, laser drilling or electric discharge machining (EDM).

The at least one cooling hole80is drilled through the article10at any desired angle. In one embodiment, the at least one cooling hole80is perpendicular or substantially perpendicular to the surface30of the substrate20. In another embodiment, the at least one cooling hole80is at angle of inclination which is not perpendicular or substantially perpendicular to the surface30of the substrate20. In yet another embodiment, the at least one cooling hole80is at an angle of inclination which is equal to or less than about 60° relative to the surface30of the substrate20. In still another embodiment, the at least one cooling hole80is at an angle of inclination which is equal to or less than about 45° relative to the surface30of the substrate20. In yet another embodiment, the at least one cooling hole80is at an angle of inclination which is equal to or less than about 30° relative to the surface30of the substrate20.

In one embodiment, the bond layer40comprises a plurality of reinforcing segments50, a plurality of cooling holes80and a plurality of bonding segments60(not shown). The number of cooling holes80may be selected based on the desired application and/or cooling properties.

The at least one reinforcing segment50reinforces the bond layer40during the drilling process to form the cooling hole80. In one embodiment, the reinforcing segment50reduces degradation of the interface between the bond layer40and the substrate20and/or the interface between the bond layer40and the at least one protective layer70during the drilling process.

In one embodiment, the at least one reinforcing segment50reduces or inhibits the formation of thermally grown oxide generated at the bond layer40. During the operation of the article10at high temperatures, exposure to hot gases, water vapor and/or oxygen results in oxidation of the bond layer40. Upon melting and oxidation, the bond layer40forms a viscous fluid layer (not shown), such as a viscous glass layer between the bond layer40and the at least one protective layer70. The viscous fluid layer comprises thermally grown oxide (TGO). The viscous fluid layer moves, or slides, under shear stress caused by centrifugal load applied to the article10during operation and/or a mismatch of the coefficients of thermal expansion (CTE) with the bond layer40, the substrate20and/or the at least one protective layer70. This phenomenon is referred to as “creep”.

In another embodiment, the at least one reinforcing segment50reduces or inhibits cracking and/or delamination in the article10. The formation of the TGO layer and/or creep results in cracking and/or delamination of the interface between the bond layer40and the surface30of the substrate20and/or the interface between the bond layer40and the at least one protective layer70, reducing the overall lifetime of the article10and/or increasing the frequency of repairs. The at least one reinforcing segment50forms a metallurgical bond with the surface30of the substrate20upon deposition of the reinforcing segment50using electrospark deposition. The metallurgical bond between the at least one reinforcing segment50and the substrate20increases the bonding strength of the bond layer40to the substrate20. The metallurgic bond formed by the reinforcing segment50reinforces the bond layer40locally where the at least one cooling hole80is drilled.

During the operation of the article10, contact between hot gas flowing through the at least one cooling hole80and the at least one reinforcing segment50of the bond layer40is reduced or inhibited, increasing the oxidation resistance of the bond layer40and reducing or inhibiting the amount of thermally grown oxide generated at the bond layer40. The at least one reinforcing segment50therefore reduces or inhibits cracking and/or delamination at the interface between the bond layer40and the substrate20or at the interface between the bond layer40and the at least one protective layer70. The reinforcing segment50also assists in bonding, or adhering, the bond layer40to the surface30of the substrate20. In one embodiment, the interface between the at least one reinforcing segment50and the substrate20and/or the interface between the reinforcing segment50and the at least one protective layer70is crack-free.

In addition, when the at least one cooling hole80is drilled at angle of inclination which is not perpendicular or substantially perpendicular to the surface30of the substrate20, the at least one cooling hole80undercuts the interface between the bond layer40and the substrate20and the bond layer40and the at least one protective layer70. This undercutting promotes the growth rate of the TGO layer and cracking at the interface between the bond layer40and the at least one protective layer70. The at least one reinforcing segment50reduces cracking and/or delamination at the interface between the bond layer40and the substrate20and/or the interface between the bond layer40and the at least one protective layer70wherein the at least one cooling hole80is drilled perpendicular or substantially perpendicular to the surface30of the substrate20or at an angle of inclination which is not perpendicular or substantially perpendicular to the surface30of the substrate20.

The at least one reinforcing segment50provides improved crack resistance, delamination resistance, oxidation resistance, creep resistance and/or temperature resistance, thereby improving the performance and overall lifetime of the article10and/or increasing the time interval between repairs.

In one embodiment, a method comprises providing a substrate20, the substrate having a surface30; forming one or more bonding segments60on a portion of the surface30of the substrate20, forming at least one reinforcing segment50on a portion of the surface30of the substrate20, the at least one reinforcing segment50being formed on the surface30of the substrate20by electrospark deposition, wherein the one or more bonding segments60and the at least one reinforcing segment50form a bond layer40; forming at least one protective layer70on the bond layer40, forming at least one cooling hole80, the at least one cooling hole80extending through the substrate20, the at least one reinforcing segment50and the at least one protective layer70, wherein the at least one reinforcing segment50reduces cracking and/or delamination at the interface between the substrate20and the bond layer40.