Patent Grant
11313243
The present disclosure relates to generally relates to abradable coatings, and in particular, to non-continuous abradable coatings.
Components of high-performance systems, such as, for example, turbine or compressor components, operate in severe environments. For example, turbine blades, vanes, blade tracks, and blade shrouds exposed to hot gases in commercial aeronautical engines may experience metal surface temperatures of about 1000° C.
High-performance systems may include rotating components, such as blades, rotating adjacent a surrounding structure, for example, a shroud. Reducing the clearance between rotating components and a shroud may improve the power and the efficiency of the high-performance component. The clearance between the rotating component and the shroud may be reduced by coating the blade shroud with an abradable coating. Turbine engines may thus include abradable coatings at a sealing surface or shroud adjacent to rotating parts, for example, blade tips. A rotating part, for example, a turbine blade, can abrade a portion of a fixed abradable coating applied on an adjacent stationary part as the turbine blade rotates. Over many rotations, this may wear a groove in the abradable coating corresponding to the path of the turbine blade. The abradable coating may thus form an abradable seal that can reduce the clearance between rotating components and an inner wall of an opposed shroud, which can reduce leakage around a tip of the rotating part or guide leakage flow of a working fluid, such as steam or air, across the rotating component, and enhance power and efficiency of the high-performance component.
The disclosure describes components, systems, and techniques relating to non-continuous abradable coatings. In some examples, the abradable coating may include three or more portions, each portion including a plurality of coating blocks. For example, a first portion may include a first plurality of coating blocks, a second portion may include a second plurality of coating blocks, and a blade rub portion extending between the first and second portions may include a third plurality of coating blocks. At least one of the first or second plurality of coating blocks may be different than the third plurality of coating blocks in at least one coating block parameter, which may improve blade rub, reduce stress, increase erosion resistance, reduce leakage, require less coating material, or the like in comparison to some other coatings.
In one example, a component includes a substrate and a non-continuous abradable coating on the substrate. The abradable coating includes a first portion defining a first plurality of coating blocks, a second portion defining a second plurality of coating blocks, and a blade rub portion extending between the first portion and the second portion and defining a third plurality of coating blocks, where at least one of the first plurality of coating blocks or the second plurality of coating blocks is different than the third plurality of coating blocks in at least one coating block parameter.
In another example, a system includes a component including a substrate and a non-continuous abradable coating on the substrate and a rotating component configured to contact an abradable surface defined by the non-continuous abradable coating with a portion of the rotating component. The abradable coating includes a first portion defining a first plurality of coating blocks, a second portion defining a second plurality of coating blocks, and a blade rub portion extending between the first portion and the second portion and defining a third plurality of coating blocks, where at least one of the first plurality of coating blocks or the second plurality of coating blocks is different than the third plurality of coating blocks in at least one coating block parameter.
In yet another example, a method includes positioning one or more templates on a surface of a substrate and thermal spraying an abradable coating composition through the one or more templates to cause the abradable coating composition to deposit on the substrate as a non-continuous abradable coating. The one or more templates define a first portion defining a first plurality of coating block cells, a second portion defining a second plurality of coating block cells, and a blade rub portion extending between the first portion and the second portion and defining a third plurality of coating block cells. The abradable coating deposited on the substrate includes a first portion defining a first plurality of coating blocks, a second portion defining a second plurality of coating blocks, and a blade rub portion extending between the first portion and the second portion and defining a third plurality of coating blocks, where at least one of the first plurality of coating blocks or the second plurality of coating blocks is different than the third plurality of coating blocks in at least one coating block parameter.
The details of one or more examples of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.
The disclosure describes components, systems, and techniques relating to non-continuous abradable coatings. In some examples, the abradable coating may include at least three portions or regions, each portion or region including a plurality of coating blocks. For example, a first portion may include a first plurality of coating blocks, a second portion may include a second plurality of coating blocks, and a blade rub portion extending between the first and second portions may include a third plurality of coating blocks. At least one of the first or second plurality of coating blocks may be different than the third plurality of coating blocks in at least one coating block parameter. In some examples, the at least one coating block parameter may include one or more of average coating block size, average pitch between coating blocks, coating block shape, or coating block orientation. Such differences in the pluralities of coating blocks of the various portions of the non-continuous abradable coatings described herein may improve blade rub, reduce stress, increase erosion resistance, reduce leakage, require less coating material, or the like, in comparison to some other coatings not including at least one of a first or a second plurality of coating blocks different than a third plurality of coating blocks in at least one coating block parameter.
Some components of high temperature mechanical systems, such as components of gas turbine engines, may include continuous abradable coatings. In some such examples, the continuous abradable coatings may be subject to increased residual stress, as well as stress from thermal and/or mechanical conditions of the high temperature mechanical system. Continuous abradable coatings subject to increased stress may have reduced bond strength of the abradable coating to an underlying component or layer, may be more likely to spall or crack, may be less tolerant of thermal cycling of the component, or the like. In turn, the useful life of the coating may be reduced, which may result in premature replacement of the coating, reduced protection of the underlying component or layer, increased leakage, or the like. Moreover, continuous abradable coatings may require more coating material than non-continuous abradable coatings, may be more difficult to be abraded by a rotating component configured to contact the abradable coating, or the like.
Some components of high temperature mechanical systems, such as components of gas turbine engines, may include relatively uniform non-continuous abradable coatings. A relatively uniform non-continuous abradable coating may be less abradable or provide reduced protection to the underlying component than the non-continuous abradable coatings described herein. For example, a relatively uniform non-continuous abradable coating configured to be easily abraded by a rotating component may have reduced erosion resistance, increased leakage, or the like, whereas a relatively uniform non-continuous abradable coating configured to provide increased erosion resistance and/or reduced leakage may be more difficult to be abraded by the rotating component. In other words, some non-continuous abradable coatings that are relatively uniform may exhibit some desired properties at the expense of some other properties.
In some examples, the non-continuous abradable coating described herein including at least one of a first plurality of coating blocks or a second plurality of coating blocks different than a third plurality of coating blocks in at least one coating block parameter may be more easily abraded by a rotating component configured to contact the non-continuous abradable coating, while still providing protection to an underlying component, in comparison to some other non-continuous abradable coatings. For example, the plurality of coating blocks of a blade rub portion of the non-continuous abradable coating different in at least one of average coating block size, average pitch between coating blocks, coating block shape, or coating block orientation from the first plurality of coating blocks, the second plurality of coating blocks, or both, may configure the blade rub portion to be more easily abraded in comparison to coatings in which a plurality of coating blocks of the blade rub portion are the same or substantially the same as a plurality of coating blocks of first or second portions flanked on either side of the blade rub portion (e.g., an abradable coating in which all of the plurality of coating blocks are all the same or substantially the same).
In the example of
In some examples, substrate 12 may include a ceramic or a ceramic matrix composite (CMC). Suitable ceramic materials may include, for example, a silicon-containing ceramic, such as silica (SiO2) and/or silicon carbide (SiC); silicon nitride (Si3N4); alumina (Al2O3); an aluminosilicate; a transition metal carbide (e.g., WC, Mo2C, TiC); a silicide (e.g., MoSi2, NbSi2, TiSi2); combinations thereof; or the like. In some examples in which substrate 12 includes a ceramic, the ceramic may be substantially homogeneous. In examples in which substrate 12 includes a CMC, substrate 12 may include a matrix material and a reinforcement material. The matrix material and reinforcement materials may include, for example, any of the ceramics described herein. The reinforcement material may be continuous or discontinuous. For example, the reinforcement material may include discontinuous whiskers, platelets, fibers, or particulates. Additionally, or alternatively, the reinforcement material may include a continuous monofilament or multifilament two-dimensional or three-dimensional weave, braid, fabric, or the like. In some examples, the CMC includes an SiC matrix material (alone or with residual Si metal) and an SiC reinforcement material.
Substrate 12 may define a leading edge 22 and a trailing edge 24. In some examples, leading edge 22 and trailing edge 24 may be substantially parallel to each other. In other examples, leading edge 22 and trailing edge 24 may not be substantially parallel to each other. In some cases, a first axis extending between leading edge 22 and trailing edge 24 may be in a substantially axial direction of a gas turbine engine including component 10 (e.g., parallel to the axis extending from the intake to the exhaust of the gas turbine engine). Thus, in some such cases, leading edge 22 and trailing edge 24 may be perpendicular or substantially perpendicular to the axial direction of the gas turbine engine including component 10.
Component 10 includes non-continuous abradable coating 14 on substrate 12. Non-continuous abradable coating 14 may extend from leading edge 32 to trailing edge 34 of substrate 12. In some examples, non-continuous abradable coating 14 may include a first portion 14a, a second portion 14b, and a blade rub portion 14c. Blade rub portion 14c may extend between first portion 14a and second portion 14b, and may be configured to be abraded, e.g., by blade 26 (or a tip of blade 26) of a gas turbine engine, in order to form a relatively tight seal between component 10 and blade 26. For example, blade 26 may be configured to rotate in the direction of arrow A shown in
As seen in
In the example of
At least one of the first plurality of coating blocks 16 or the second plurality of coating blocks 18 may be different from the third plurality of coating blocks 20 in at least one coating block parameter. In turn, at least one of first portion 14a or second portion 14b may have different properties than those of blade rub portion 14c. For example, the third plurality of coating blocks 20 of blade rub portion 14c may be configured to be more easily abraded than the first or second plurality of coating blocks 16, 18, and the first and/or second plurality of coating blocks 16, 18 of first and second portions 14a, 14b, respectively, may be configured to provide increased protection to the portions of non-continuous abradable coating 14 not configured to be contacted by blade 26. Thus, non-continuous abradable coating 14 including various portions 14a to 14c with pluralities of coating blocks 16, 18, and 20 that differ in at least one coating block parameter may enable non-continuous abradable coating 14 to be tailored to provide certain properties based on the portion of substrate 12 in which portions 14a to 14c of non-continuous abradable coating 14 are on. In other words, non-continuous abradable coating 14 that includes the third plurality of coating blocks 20 having at least one coating block parameter different from the first and/or second pluralities of coating blocks 16, 18 may improve blade rub, while also reducing stress, increasing erosion resistance, reducing leakage, or the like in comparison to some other coatings.
In some examples, the first plurality of coating blocks 16, the second plurality of coating blocks 18, or both, may be different than the third plurality of coating blocks 20 in at least one coating block parameter. In some such examples, the at least one coating block parameter may include an average coating block size, an average pitch between coating blocks, a coating block shape, or a coating block orientation. The average coating block size may be a population average of the largest diameters, or dimensions of major axis passing through geometric centers, of blocks of a respective portion. For example, in the case of circular blocks, the average coating block size may be determined in terms of population average of diameters of respective circular blocks. In the example of
In the example of
Non-continuous abradable coating 14 may include any suitable material. For example, non-continuous abradable coating 14 may be formed from materials that exhibit a hardness that is relatively lower than a hardness of blade 26 such that a blade tip of blade 26 can abrade blade rub portion 14c of non-continuous abradable coating 14 by contact. Thus, the hardness of non-continuous abradable coating 14, or at least blade rub portion 14c of non-continuous abradable coating 14, relative to the hardness of the blade tip may be indicative of the abradability of blade rub portion 14c. The composition of non-continuous abradable coating 14 will be described generally with respect to non-continuous abradable coating 14 (e.g., including first, second, and blade rub portions 14a to 14c). Thus, in some examples, first portion 14a, second portion 14b, and/or blade rub portion 14c may include the same or substantially the same composition. It should be understood that in other examples, however, at least one of first portion 14a, second portion 14b, or blade rub portion 14c may include a composition different than at least one other of first portion 14a, second portion 14b, or third portion 14c. For example, the abradability of non-continuous abradable coating 14 may depend on the respective composition (e.g., the physical and mechanical properties of the composition) of the coating, and therefore, in some cases, blade rub portion 14c may include a different composition than that of one or both of first portion 14a or second portion 14b.
In some examples, non-continuous abradable coating 14 may include a matrix composition. Such a matrix composition of non-continuous abradable coating 14 may include at least one of aluminum nitride, aluminum diboride, boron carbide, aluminum oxide, mullite, zirconium oxide, carbon, silicon carbide, silicon nitride, silicon metal, silicon alloy, a transition metal nitride, a transition metal boride, a rare earth oxide, a rare earth silicate, a stabilized zirconium oxide (for example, yttria-stabilized zirconia), a stabilized hafnium oxide (for example, yttria-stabilized hafnia), barium-strontium-aluminum silicate, or combinations thereof. In some examples, non-continuous abradable coating 14 includes at least one silicate, which may refer to a synthetic or naturally-occurring compound including silicon and oxygen. Suitable silicates include, but are not limited to, rare earth disilicates, rare earth monosilicates, barium strontium aluminum silicate, or combinations thereof.
In some cases, non-continuous abradable coating 14 may include a base oxide of zirconia or hafnia and at least one rare earth oxide, such as, for example, oxides of Lu, Yb, Tm, Er, Ho, Dy, Gd, Tb, Eu, Sm, Pm, Nd, Pr, Ce, La, Y, and Sc. For example, non-continuous abradable coating 14 may include predominately (e.g., the main component or a majority) the base oxide zirconia or hafnia mixed with a minority amounts of the at least one rare earth oxide. In some examples, non-continuous abradable coating 14 may include the base oxide and a first rare earth oxide including ytterbia, a second rare earth oxide including samaria, and a third rare earth oxide including at least one of lutetia, scandia, ceria, neodymia, europia, or gadolinia. In some examples, the third rare earth oxide may include gadolinia such that non-continuous abradable coating 14 may include zirconia, ytterbia, samaria, and gadolinia.
Non-continuous abradable coating 14 may optionally include other elements or compounds to modify a desired characteristic of the coating layer, such as, for example, phase stability, thermal conductivity, or the like. Example additive elements or compounds include, for example, rare earth oxides. The inclusion of one or more rare earth oxides, such as ytterbia, gadolinia, and samaria, within a layer of predominately zirconia may help decrease the thermal conductivity of non-continuous abradable coating 14, e.g., compared to a composition including zirconia and yttria.
In some examples, in addition to the coating block parameters and/or the composition of non-continuous abradable coating layer 14, the abradability of the non-continuous abradable coating 14 may also depend on a porosity of the coating blocks of the respective first, second, or third pluralities of coating blocks 16, 18, or 20. For example, a relatively porous composition of coating blocks 16, 18, 20 may exhibit a higher abradability compared to a relatively nonporous composition, and a composition with a relatively higher porosity may exhibit a higher abradability compared to a composition with a relatively lower porosity, everything else remaining the same. Moreover, relatively porous coating blocks of the plurality of coating blocks 16, 18, or 20 may have a decreased thermal conductivity in comparison to coating blocks with relatively lower porosities or dense microstructures.
Thus, in some examples, each coating block of the first, second, and/or third plurality of coating blocks 16, 18, 20 may include a plurality of pores. The plurality of pores may include at least one of interconnected voids, unconnected voids, partly connected voids, spheroidal voids, ellipsoidal voids, irregular voids, or voids having any predetermined geometry, or networks thereof. In some examples, each coating block of the first and second plurality of coating blocks 16, 18 may exhibit a lower porosity than each coating block of the third plurality of coating blocks 20. For example, each coating block of the first and second plurality of coating blocks 16, 18 may exhibit a porosity of less than about 10 vol. %, and each coating block of the third plurality of coating blocks 20 may exhibit a porosity between about 50 vol. % and about 80 vol. %, where porosity is measured as a percentage of pore volume divided by total volume of the respective coating block of the first, second, and/or third plurality of coating blocks 16, 18, 20. The porosity of the respective coating blocks may be measured using mercury porosimetry, optical microscopy, a method based on Archimedes' principle, e.g., a fluid saturation technique, or the like.
In some examples, at least one of the coating blocks of the first, second, and/or third plurality of coating blocks 16, 18, 20 may each have a porosity different than another of the coating blocks of the first, second, and/or third plurality of coating blocks 16, 18, 20. For instance, in some cases, each coating block of the third plurality of coating blocks 20 may have a higher porosity than one or both of the respective coating blocks of the first plurality of coating blocks 16 or the second plurality of coating blocks 18, which may enable blade rub portion 14c to be more easily abraded than first or second portion 14a, 14b. Moreover, the coating blocks of the first and/or second plurality of coating blocks 16, 18 with a relatively lower porosity than the coating blocks of the third plurality of coating blocks 20 may help prevent leakage, provide increased protection to substrate 12, increase erosion resistance, or combinations thereof.
In some examples, the porosity of the coating blocks may be created and/or controlled by plasma spraying the coating material using a co-spray process technique in which the coating material and a coating material additive are fed into a plasma stream with two or more radial powder feed injection ports. For example, a coating material additive that melts or burns at the use temperatures of component 10 may be incorporated into the coating material that forms the coating blocks of non-continuous abradable coating 14. The coating material additive may include, for example, graphite, hexagonal boron nitride, or a polymer such as a polyester, and may be incorporated into the coating material prior to deposition of the coating material on substrate 12 to form the coating blocks of non-continuous abradable coating 14. The coating material additive then may be melted or burned off in a post-formation heat treatment, or during operation of component 10 (e.g., operation of gas turbine engine 10), to form pores in the coating blocks. The post-deposition heat-treatment may be performed at up to about 1150° C. for a component having a substrate 12 that includes a superalloy, or at up to about 1500° C. for a component having a substrate 12 that includes a CMC or other ceramic.
In other examples, the porosity of the coating blocks of non-continuous abradable coating 14 may be created or controlled in a different manner, and/or the coating blocks of the plurality of coating blocks 16, 18, 20 may be deposited on substrate 12 using a different technique. For example, non-continuous abradable coating 14 may be deposited using a wide variety of coating techniques, including, for example, thermal spraying, e.g., air plasma spraying, HVOF spraying, low vapor plasma spraying, suspension plasma spraying; PVD, e.g., EB-PVD, DVD, or cathodic arc deposition; CVD; slurry process deposition; sol-gel process deposition; electrophoretic deposition; or the like.
As described above, non-continuous abradable coating 14 may extend between leading edge 22 and trailing edge 24 of substrate 12. For example, first portion 14a may extend from leading edge 22 to a center portion of substrate 12, second portion 14b may extend from trailing edge 24 to the center portion of substrate 12, and blade rub portion 14c may extend between first portion 14a and second portion 14b. In some examples, blade rub portion 14c may be wider than a width of blade 26 or a tip of blade 26. For instance, blade rub portion 14c may define a width measured along an axial axis extending from leading edge 22 to trailing edge 24 of substrate 12 that is greater than a width of blade 26 or a tip of blade 26 (and any potential axial travel of blade 26) measured along the axial axis. In this way, blade 26 may be able to form a blade path in blade rub portion 14c without contacting and/or abrading an underlying coating layer or substrate 12. In other examples, the width of blade rub portion 14c may be less than or equal to the width of blade 26 or a tip of blade 26 (and any potential axial travel of blade 26).
In some examples, non-continuous abradable coating 14 (or at least blade rub portion 14c of non-continuous abradable coating 14) may be thick enough such that the blade tip of blade 26 can abrade non-continuous abradable coating 14 to form a blade path in blade rub portion 14c without contacting and/or abrading an underlying coating layer or substrate 12. In some such examples, non-continuous abradable coating 14 may have a thickness of between about 0.025 mm (about 0.01 inches) and about 3 mm (about 0.12 inches). In other examples, non-continuous abradable coating 14 may have other thicknesses.
In some examples, in addition to, or as an alternative to, the third plurality of coating blocks 20 of blade rub portion 14c being different from at least one of the first plurality of coating blocks 16 or the second plurality of coating blocks 18 in average coating block size, the third plurality of coating blocks 20 of blade rub portion 14c may be different from at least one of the first plurality of coating blocks 16 or the second plurality of coating blocks 18 in a different coating block parameter. For example, the third plurality of coating blocks 20 of blade rub portion 14c may be different from at least one of the first plurality of coating blocks 16 or the second plurality of coating blocks 18 in an average pitch between coating blocks.
In some examples, both the first plurality of coating blocks 34 and the second plurality of coating blocks 36 differ from the third plurality of coating blocks 38 in average pitch between coating blocks. The average pitch between coating blocks may be an average distance between adjacent coating blocks of the respective plurality of coating blocks 34, 36, 38 (e.g., an average size of the space between the respective adjacent coating blocks). For example, the first plurality of coating blocks 34 may define a first average pitch between coating blocks P1, the second plurality of coating blocks 36 may define a second average pitch between coating blocks P2, and the third plurality of coating blocks 38 may define a third average pitch between coating blocks P3. Although the first, second, and third average pitches P1, P2, P3 are illustrated in
In some examples, first average pitch between coating blocks P1 and/or second average pitch between coating blocks P2 may be different than third average pitch between coating blocks P3. For instance, at least one of first average pitch between coating blocks P1 or second average pitch between coating blocks P2 may be less than third average pitch between coating blocks P3. In other examples, at least one of first or second average pitch between coating blocks P1, P2 may be greater than third average pitch between coating blocks P3. In some examples, at least one of first average pitch between coating blocks P1 or second average pitch between coating blocks P2 being less than third average pitch between coating blocks P3 may enable the third plurality of coating blocks 38 to be more easily abraded in comparison to the first or second plurality of coating blocks 34, 36. For example, the relatively large third average pitch between coating blocks P3 may result in blade rub portion 32c of non-continuous abradable coating 32 being less dense than first and/or second portions 32a, 32b, which may facilitate abrasion of non-continuous abradable coating 32 in blade rub portion 32c by blade 26. In a similar manner, the relatively small first and/or second average coating pitches P1, P2 may result in first and/or second portions 32a, 32b of non-continuous abradable coating 32 being denser than blade rub portion 32c. In turn, first portion 32a and/or second portion 32b may reduce leakage, provide increased protection to substrate 12, increase erosion resistance, or the like. In turn, non-continuous abradable coating 32 with at least one of first or second plurality of coating blocks 34, 36 different than the third plurality of coating blocks 38 in average pitch between coating blocks may enable first and second portions 32a, 32b to have reduced leakage, increased protection, increased erosion resistance, or the like, while also enabling blade rub portion 32c to exhibit improved abradability.
In addition to, or as an alternative to, average coating block size or average pitch between coating blocks, at least one of first portion 32a or second portion 32b may differ from blade rub portion 32c in another coating block parameter. For example, the coating blocks of first and/or second portion 32a, 32b may differ from the coating blocks of blade rub portion 32c in at least one of a surface area, a perimeter length, a contour shape, or orientation of the coating blocks.
For example, each coating block of first plurality of coating blocks 44 may define a first shape, each coating block of second plurality of coating blocks 46 may define a second shape, and each coating block of third plurality of coating blocks 48 may define a third shape, and each coating block defining each of the first shape, second shape, or third shape may define a surface area, a perimeter length, and a contour shape. In some examples, at least one of the first or second shape may be different than the third shape in at least one of the respective surface area, perimeter length, or contour shape. In some examples, the respective coating blocks of at least one of first plurality of coating blocks 44, second plurality of coating blocks 46, or third plurality of coating blocks 48 may define more than one shape. For example, as illustrated in
In some examples, the respective coating blocks of the first, second, or third plurality of coating blocks 44, 46, 48 may be aligned along a predetermined orientation. For example, in some cases, the coating blocks of the third plurality of coating blocks 48 may be oriented to substantially align with blade 26. In the example illustrated in
As described herein, at least one of the first plurality of coating blocks 44 or the second plurality of coating blocks 46 may be different than the third plurality of coating blocks 48 in at least one coating block parameter, such as, for example, average coating block size, average pitch between coating blocks, coating block shape, or coating block orientation. In this way, different portions 42a-42c of non-continuous abradable coating 42 can exhibit different properties. In some examples, it may be desirable for first and second portions 42a, 42b to have reduced leakage, increased protection, increased erosion resistance, or the like, and for blade rub portion 42c to have improved abradability. Therefore, the at least one coating parameter of first and/or second plurality of coating blocks 44, 46 different from the third plurality of coating blocks 48 may contribute to the different properties exhibited by the respective portions 42a-42c. For example, coating block parameters configured to increase the tortuosity, increase an overall density, decrease a size of spacings between coating blocks, or the like of first and/or second portions 42a, 42b may contribute to reduced leakage, increased protection, and/or increased erosion resistance of first and/or second portions 42a, 42b. On the other hand, coating block parameters configured to decrease an overall density, increase an average coating block size, reduce stress on blade 26, increase a size of spacings between coating blocks, align with blade 26, improve the pushability of the respective coating blocks, or the like of first and/or second portions 42a, 42b may contribute to improved abradability of blade rub portion 42c. Thus, any combination of coating block parameters in accordance with the disclosure may be used to form non-continuous abradable coating 42.
In some examples, non-continuous abradable coating 54 may be a first abradable coating, and component 52 may include a second abradable coating 62. For example, component 52 may include second abradable coating 62 on substrate 12. In some such examples, second abradable coating 62 may be between adjacent coating blocks of at least one of the first plurality of coating blocks 56, the second plurality of coating blocks 58, or the third plurality of coating blocks 60 of non-continuous abradable coating 54. In the example of
Second abradable coating 62 may include any suitable material. For example, second abradable coating 62 may include may material described above with respect to non-continuous abradable coating 14. Thus, in some cases, second abradable coating 62 may have the same or substantially the same composition as non-continuous abradable coating 54. In other examples, second abradable coating 62 may have a different composition than non-continuous abradable coating 54.
As described above with respect to non-continuous abradable coating 14, second abradable coating 62 may include a plurality of pores, such as, for example, at least one of interconnected voids, unconnected voids, partly connected voids, spheroidal voids, ellipsoidal voids, irregular voids, or voids having any predetermined geometry, or networks thereof. In some examples, such as examples in which second abradable coating 62 is between adjacent coating blocks of the first plurality of coating blocks 56, the second plurality of coating blocks 58, and/or the third plurality of coating blocks 60 and not on non-continuous abradable coating 54 (e.g., such that second abradable coating 62 is also substantially non-continuous), the porosity of second abradable coating 62 may be measured as a percentage of pore volume divided by total volume of the respective non-continuous block between the respective coating blocks of non-continuous abradable coating 54. In other examples, such as examples in which second abradable coating 62 is relatively continuous, the porosity of second abradable coating 62 may be measured as a percentage of pore volume divided by total volume of second abradable coating 62.
In some examples, second abradable coating 62 may have a relatively higher porosity (e.g., may be less dense) than the respective coating blocks of non-continuous abradable coating 54. Second abradable coating 62 having a relatively high porosity may result in component 52 having improved erosion resistance, improved protection, and/or reduced leakage, while maintaining improved thermal cycling resistance and decreased stress. For example, the relatively high porosity of second abradable coating 62 between adjacent coating blocks of non-continuous abradable coating 54 may be able to still accommodate thermal expansion of the respective coating blocks, which may reduce thermal stress in comparison to a continuous abradable coating or a second abradable coating with a relatively low porosity.
In some cases, component 52 may have one or more additional coating layers on substrate. For example, component 52 may include a bond coat 64 and/or an intermediate coating 66 on substrate 12. In some such examples, non-continuous abradable coating 54, second abradable coating 62, or both may be on one or both of bond coat 54 or intermediate coating 66 such that bond coat 64 and/or intermediate coating 66 are between substrate 12 and the abradable coatings 54, 62. As described herein, spacings between adjacent coating blocks of the respective first, second, and third plurality of coating blocks 56, 58, 60 may extend though an entire thickness of non-continuous abradable coating 54. In such examples, the spacings between each respective coating block of the first, second, and third plurality of coating blocks 56, 58, 60 and respective adjacent coating blocks may not extend through any part of a layer underlying non-continuous abradable coating 54, such as intermediate coating 66 or bond coat 64. In some such examples, substrate 12 may be better protected by intermediate coating 66 or bond coat 64 in comparison to components in which the spacings extend from non-continuous abradable coating 54 to substrate 12 through intermediate coating 66 and/or bond coat 64.
Component 52 including bond coat 64 may improve adhesion between substrate 12 and an overlying layer, such as intermediate coating 66. The bond coat may include any suitable material configured to improve adhesion between substrate 12 and the overlaying layer. In some examples, component 52 may not include intermediate coating 66 such that non-continuous abradable coating 54 and/or second abradable coating 62 is on bond coat 64. In such examples, the composition of bond coat 64 may be selected to increase adhesion between substrate 12 and non-continuous abradable coating 54 and/or second abradable coating 62.
In examples in which substrate 12 includes a superalloy, bond coat 64 may include an alloy, such as an MCrAlY alloy (where M is Ni, Co, or NiCo), a β-NiAl nickel aluminide alloy (either unmodified or modified by Pt, Cr, Hf, Zr, Y, Si, or combinations thereof), a γ-Ni+γ′-Ni3Al nickel aluminide alloy (either unmodified or modified by Pt, Cr, Hf, Zr, Y, Si, or combinations thereof), or the like. In examples in which substrate 12 includes a ceramic or CMC, bond coat 64 may include a ceramic or another material that is compatible with the material from which substrate 12 is formed. For example, bond coat 64 may include mullite (aluminum silicate, Al6Si2O13), silicon metal or alloy, silica, a silicide, or the like. Bond coat 64 may further include other elements, such as a rare earth silicate including a silicate of lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium (Er), holmium (Ho), dysprosium (Dy), gadolinium (Gd), terbium (Tb), europium (Eu), samarium (Sm), promethium (Pm), neodymium (Nd), praseodymium (Pr), cerium (Ce), lanthanum (La), yttrium (Y), and/or scandium (Sc).
In some examples, intermediate coating 66 may include at least one of an environmental barrier coating (EBC) layer or a thermal barrier coating (TBC) layer. In some examples, a single intermediate coating 66 may perform two or more of these functions. For example, an EBC layer may provide environmental protection, thermal protection, and calcia-magnesia-alumina-silicate (CMAS)-resistance to substrate 12. In some examples, instead of including a single intermediate coating 66, component 52 may include a plurality of intermediate coatings, such as at least one bond coat 64, at least one EBC layer, at least one TBC layer, or combinations thereof.
In examples in which intermediate coating 66 includes an EBC layer, the EBC layer may include at least one of a rare-earth oxide, a rare-earth silicate, an aluminosilicate, or an alkaline earth aluminosilicate. For example, an EBC layer may include mullite, barium strontium aluminosilicate (BSAS), barium aluminosilicate (BAS), strontium aluminosilicate (SAS), at least one rare-earth oxide, at least one rare-earth monosilicate (RE2SiO5, where RE is a rare-earth element), at least one rare-earth disilicate (RE2Si2O7, where RE is a rare-earth element), or combinations thereof. The rare-earth element in the at least one rare-earth oxide, the at least one rare-earth monosilicate, or the at least one rare-earth disilicate may include at least one of Lu, Yb, Tm, Er, Ho, Dy, Tb, Gd, Eu, Sm, Pm, Nd, Pr, Ce, La, Y, or Sc.
In some examples, an EBC layer may include at least one rare-earth oxide and alumina, at least one rare-earth oxide and silica, or at least one rare-earth oxide, silica, and alumina. In some examples, an EBC layer may include an additive in addition to the primary constituents of the EBC layer. For example, the additive may include at least one of TiO2, Ta2O5, HfSiO4, an alkali metal oxide, or an alkali earth metal oxide. The additive may be added to the EBC layer to modify one or more desired properties of the EBC layer. For example, the additive components may increase or decrease the reaction rate of the EBC layer with CMAS, may modify the viscosity of the reaction product from the reaction of CMAS and the EBC layer, may increase adhesion of the EBC layer to substrate 12 and/or another coating layer, may increase or decrease the chemical stability of the EBC layer, or the like.
In some examples, the EBC layer may be substantially free (e.g., free or nearly free) of hafnia and/or zirconia. Zirconia and hafnia may be susceptible to chemical attack by CMAS, so an EBC layer substantially free of hafnia and/or zirconia may be more resistant to CMAS attack than an EBC layer that includes zirconia and/or hafnia. An EBC layer may be a substantially dense layer, e.g., may include a porosity of less than about 10 vol. %, measured as a fraction of open space compared to the total volume of the EBC layer using, for example, mercury porosimetry, optical microscopy, a method based on Archimedes' principle, e.g., a fluid saturation technique, or the like. The EBC layer may also provide resistance to CMAS.
Additionally, or alternatively, intermediate coating 66 may include a TBC layer. The TBC layer may have a low thermal conductivity (e.g., both an intrinsic thermal conductivity of the material(s) that forms the TBC layer and an effective thermal conductivity of the TBC layer as constructed) to provide thermal insulation to substrate 12 and/or another coating layer of intermediate coating 66. In some examples, a TBC layer may include a zirconia- or hafnia-based material, which may be stabilized or partially stabilized with one or more oxides. In some examples, the inclusion of rare-earth oxides such as ytterbia, samaria, lutetia, scandia, ceria, gadolinia, neodymia, europia, yttria-stabilized zirconia (YSZ), zirconia stabilized by a single or multiple rare-earth oxides, hafnia stabilized by a single or multiple rare-earth oxides, zirconia-rare-earth oxide compounds, such as RE2Zr2O7 (where RE is a rare-earth element), hafnia-rare-earth oxide compounds, such as RE2Hf2O7 (where RE is a rare-earth element), and the like may help decrease the thermal conductivity of the TBC layer. In some examples, a TBC layer may include a base oxide including zirconia or hafnia, a first rare earth oxide including ytterbia, a second rare earth oxide including samaria, and a third rare earth oxide including at least one of lutetia, scandia, ceria, neodymia, europia, or gadolinia. A TBC layer may include porosity, such as a columnar or microporous microstructure, which may contribute to relatively low thermal conductivity of the TBC layer.
Bond coat 64 and/or intermediate coating 66 may be formed on substrate 12 using, for example, thermal spraying, e.g., air plasma spraying, high velocity oxy-fuel (HVOF) spraying, low vapor plasma spraying, suspension plasma spraying; physical vapor deposition (PVD), e.g., electron beam physical vapor deposition (EB-PVD), directed vapor deposition (DVD), cathodic arc deposition; chemical vapor deposition (CVD); slurry process deposition; sol-gel process deposition; electrophoretic deposition; or the like.
Non-continuous abradable coatings 14, 32, 42, 54 may be applied to substrate 12 using a thermal spraying technique, such as plasma spraying. Non-continuous abradable coatings 14, 32, 42, 54 may define a relatively large thickness, such as up to about 2 millimeters (mm) or more. As such, abradable coatings may be applied using multiple passes of the thermal spraying device. For each pass, the thermal spraying device deposits a layer of material on the substrate (or an underlying layer). This deposited layer then begins to cool, and an additional layer is deposited on the cooling layer. This results in residual stress in the abradable coating. This residual stress reduces bond strength of the abradable coating to an underlying layer and may result in spallation or cracking of the non-continuous abradable coating upon being used in a high temperature environment. This issue with residual stress may be exacerbated in examples in which non-continuous abradable coating 14, 32, 42, 54 is applied to a continuous blade track or shroud. However, spacings between adjacent coating blocks in the non-continuous abradable coating 14, 32, 42, 54 may reduce strain within the non-continuous abradable coating 14, 32, 42, 54 at an interface between the non-continuous abradable coating 14, 32, 42, 54 and an underlying layer (e.g., intermediate coating 66, bond coat 64, or substrate 12), thus increasing bond strength and reducing a likelihood of cracking, spallation, or both.
In some examples, the spacings between adjacent coating blocks of non-continuous abradable coating 14, 32, 42, 54 may be formed in non-continuous abradable coating 14, 32, 42, 54 by mechanical removal of portions of abradable coating material after deposition of the abradable coating material on substrate 12. However, in some examples, this may not efficiently reduce residual stress in non-continuous abradable coating 14, 32, 42, 54. Hence, in some examples, the spacings between adjacent coating blocks may be defined in non-continuous abradable coating 14, 32, 42, 54 as part of forming non-continuous abradable coating 14, 32, 42, 54.
In some examples, the technique of
The example technique of
In the example of
Template 80 may be formed of any suitable material, e.g., any material that substantially maintains its shape at temperatures experienced by template 80 during thermal spraying of non-continuous abradable coating 14. For example, the material from which template 80 is formed may be capable of withstanding a temperature of about 250° C. Example materials for template 80 may include a silicone rubber, a polyimide, a polyamide, a fluoropolymer, a metal, or the like. In some examples, template 80 may be formed using a molding process, in which template 80 is initially formed using a negative mold. The negative mold may define voids corresponding to the shape of template 80. In some examples, the mold additionally may define one or more features for positioning template 80 relative to substrate 12, restraining template 80 relative to substrate 12, or both. For example, the mold may define one or more straps, bands, hooks, or the like to facilitate positioning template 80 relative to substrate 12, restraining template 80 relative to substrate 12, or both. In some examples, the mold may be formed by 3D printing (or additive manufacturing) a suitable mold material.
In some examples, rather than forming template 80 using molding, template 80 may be 3D printed (or additively manufactured) using a suitable high-temperature material, such as a silicone rubber, a polyimide, a polyamide, a fluoropolymer, a metal, or the like.
In some implementations, template 80 may be adhered to the surface of substrate 12 (or bond coat 64 or intermediate coating 66) using a high temperature adhesive. In other implementations, adhesion between template 80 and the surface of substrate 12 (or bond coat 64 or intermediate coating 66) may be sufficiently high that the adhesive may be omitted.
Once template 80 has been positioned on substrate 12 (70), the technique of
One or more of the spray duration, spray flow rate, or number of passes at a given location may determine the thickness of the respective coating blocks of the first, second, and third pluralities of coating blocks 16, 18, 20 deposited by thermal spraying. For example, an increase in the duration, in the flow rate, or the number of passes may increase the thickness of the respective coating blocks of the first, second, and third pluralities of coating blocks 16, 18, 20, while a reduction in the duration, flow rate, or number of passes may maintain the thickness of the respective coating blocks of the first, second, and third pluralities of coating blocks 16, 18, 20 below or at a predetermined thickness.
In some examples, the at least one precursor composition may be suspended or dispersed in a carrier medium, for example, a liquid or a gas. The precursor composition may also include an additive as described herein configured to define pores in the respective coating blocks in response to thermal treatment. In some examples, the additive may be sacrificially removed in response to heat subjected by the thermal spraying, or by a separate heat treatment. For example, the technique of
The heat treating may result in removal or disintegration of the additive to leave pores in the respective coating blocks of the first, second, and third pluralities of coating blocks 16, 18, 20. The heat treatment may be at a temperature of between about 600° C. and about 700° C. In other examples, the technique of
In some examples, the heat treating additionally may cause removal of template 80, e.g., via burning off, melting, or the like. In other examples, template 80 may be removed from substrate 12 in another manner 12. For instance, template 80 may burn off or otherwise be removed upon use of substrate 12 at high temperature. As another example, template 80 may be mechanically removed from substrate 12. In any case, the removal of template 80 from substrate 12 leaves non-continuous abradable coating 14 including first portion 14a defining first plurality of coating blocks 16, second portion 14b defining second plurality of coating blocks 18, and blade rub portion 14c extending between first portion 14a and second portion 14c and defining third plurality of coating blocks 20, as shown in
Example systems and techniques according to the disclosure may be used to prepare example non-continuous abradable coatings.
Various examples have been described. These and other examples are within the scope of the following claims.
This application claims the benefit of U.S. Provisional Patent Application No. 62/697,076 filed Jul. 12, 2018, which is incorporated herein by reference in its entirety.
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| Number | Date | Country | |
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