Patent Application
20220049611
The disclosure relates to a coating and lubrication strategy for blade root interfaces, more particularly for blade root/disk interfaces of components of gas turbine engines.
Fretting wear at the disk/blade root interface, for example in fans, low pressure compressors, high pressure compressors and other portions of gas turbine engines is a major concern.
Fretting wear can result in high wear and cracking of components including the blade root and the disk in which the blade root is mounted.
Typical blade roots are made of titanium alloy, and a solid lubricant can be applied at both surfaces (i.e. to the blade root and also the disk), and/or a thermal spray coating can be applied on the blade root. However, this can realistically be done only once on both surfaces, prior to engine operation.
The applied solid lubricant wears out, and the underlying components have poor tribological behavior under the high contact stresses and the high vibratory energy in the system. Thus, known systems are not capable of effectively operating under the harsh conditions, resulting continuously in premature failure of the blade root due to wear issues.
Besides the need to constantly replace blades after wear or cracking of the blade root, this problem also frequently leads to further damage to more critical/expensive parts, such as the disk.
The present disclosure relates to a lubrication strategy of the blade root/disk interface which results in continuous self-lubrication at the interface, resulting in low friction and wear.
In one non-limiting configuration, a coating for a blade root/disk interface comprises a layer of soft metal matrix, and a solid lubricant distributed through the soft metal matrix.
In a further non-limiting configuration, the soft metal matrix is a composition of a first component selected from the group consisting of copper, nickel and mixtures thereof, and a second component different from the first component and selected from the group consisting of nickel, aluminum, indium and combinations thereof.
In a still further non-limiting configuration, the soft metal matrix is CuAl.
In another non-limiting configuration, the solid lubricant is selected from the group consisting of molybdenum disulfide, hexagonal boron nitride, graphite and combinations thereof.
In still another non-limiting configuration, the solid lubricant is molybdenum disulfide.
In a further non-limiting configuration, the layer has a thickness of between 0.001 and 0.005 inches.
In a still further non-limiting configuration, the layer contains between 10 and 20 weight percent of solid lubricant, and between 80 and 90 weight percent of soft metal matrix.
In another non-limiting configuration, the soft metal matrix comprises CuAl, and the layer contains between 2 and 8 weight percent of aluminum, and balance copper.
In still another non-limiting configuration, the coating, when exposed to wear, generates a solid lubricant-based tribofilm at a wear surface.
In one non-limiting configuration, a coated blade root/disk interface comprises a blade root mounted in a disk with contact surfaces defining at least one interface between the blade root and the disk; and a coating at the at least one interface, wherein the coating comprises a layer of soft metal matrix, and a solid lubricant distributed through the soft metal matrix.
In another non-limiting configuration, the at least one interface is defined by a blade root surface and an opposed disk surface, and the coating is on at least one of the blade root surface and the opposed disk surface.
In still another non-limiting configuration, the coating is on both of the blade root surface and the opposed disk surface.
In a further non-limiting configuration, the soft metal matrix is a composition of a first component selected from the group consisting of copper, nickel and mixtures thereof, and a second component, different from the first component and selected from the group consisting of nickel, aluminum, indium and combinations thereof.
In a still further non-limiting configuration, the soft metal matrix is CuAl.
In another non-limiting configuration, the solid lubricant is selected from the group consisting of molybdenum disulfide, hexagonal boron nitride, graphite and combinations thereof.
In still another non-limiting configuration, the solid lubricant is molybdenum disulfide.
In a further non-limiting configuration, the layer has a thickness of between 0.001 and 0.005 inches.
In a still further non-limiting configuration, the layer contains between 10 and 20 weight percent of solid lubricant, and between 80 and 90 weight percent of soft metal matrix.
In another non-limiting configuration, the soft metal matrix comprises CuAl, and the layer contains between 2 and 8 weight percent of aluminum, and balance copper.
In still another non-limiting configuration, the coating, when exposed to wear, generates a solid lubricant-based tribofilm at a wear surface.
The details of one or more embodiments 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.
A detailed description of preferred embodiments of the disclosure follows, with referenced to the attached drawings, wherein:
Like reference numbers and designations in the various drawings indicate like elements.
The present disclosure relates to a coating and coating strategy that is particularly useful in protecting the blade root and disk of fan and compressor components of turbomachinery such as gas turbine engines.
Gas turbine engines typically have a number of fans and compressors which each comprise a plurality of blades that are mounted to disks through blade roots that are received in sockets of the disk. During operation, the blade roots and sockets are subject to fretting wear that can lead to failure of the blade root, as well as damage to the disk.
During operation of a gas turbine engine containing a blade 10 and disk 14 assembly as shown, forces and stresses are applied to both blade 10 and disk 14, and socket 12, for example where shown at arrows T, V and W. This leads to a fretting wear between contacting surfaces of blade root 16 and socket 12 of disk 14, and one area of fretting wear is identified at 18 in
Blade roots 16 and the surfaces of sockets 12 of disks 14 are typically manufactured from a titanium alloy. One example of titanium alloy that can be utilized is Ti-64, although other titanium alloys are also useful. While titanium alloys have excellent properties in terms of strength, toughness and weight, when they are in contact with each other under load with relative motion, they create an interface that forms a mechanical mixed layer, leading to high friction and significant wear.
One strategy for protecting the titanium alloy components, shown in
Another strategy, shown in
Finally, in
MoS2 is effective at reducing the friction and wear, but it is difficult or impossible to keep this lubricant in place because it is hard to apply this coating after an engine has been manufactured. Thus, engines having interfaces that have been coated with a MoS2 lubricant at the interface operate with good properties until such time as the lubricant wears out. This is as is illustrated in
The coating of the present disclosure can be provided from various combinations of soft metal matrix and solid lubricant. The soft metal matrix can for example be metal compositions of a first component selected from the group consisting of copper, nickel or the like with a second component, different from the first component, and selected from the group consisting of nickel, aluminum and/or indium or the like. Specific non-limiting examples of soft metal matrix compositions include CuAl, CuIn, NiIn, CuNi, CuNiIn and combinations thereof.
The solid lubricant can be any composition having desirable lubricious properties. One particular non-limiting example of a solid lubricant that is useful in this disclosure is MoS2. Additional useful solid lubricants include hexagonal boron nitride (hBN), graphite and the like, and combinations thereof. These and other solid lubricants will have different desirable properties under different conditions. As a lubricant, hBN is not as lubricious as MoS2. However, hBN has a higher temperature capability and environmental stability. This can lead to hBN to be advantageous in application methods that use high temperature, or in environments of use where the temperature will be particularly high. When this is not the case, MoS2 has particularly desirable lubricating properties.
The coating as disclosed herein can have a composition by weight percentage of components of between 10 and 20 weight percent solid lubricant, between 2 and 8 weight % of matrix material such as aluminum, and the balance soft metal such as copper. Within these ranges, one non-limiting example of a specific coating composition is 5.0 weight % aluminum, 15 weight % MoS2 and the balance (80 weight %) copper.
The coating as disclosed herein can be applied at a thickness of between 0.001 and 0.005 inches, and one particular non-limiting example is a coating that has a thickness of 0.003 inches.
The coating as disclosed herein can be applied in any manner that results in the solid lubricant material being somewhat uniformly distributed through the matrix material. This can be accomplished by co-depositing the materials, for example utilizing high velocity oxygen fuel (HVOF) application. This leads to desirable distribution of the solid lubricant material through the matrix. Alternatively, the coating could be applied utilizing air plasma spray, flame spray, cold spray, low pressure plasma spray (LPPS) or the like.
When MoS2 is the solid lubricant, it is useful to apply with a process that keeps temperature below about 1100° F. as at this temperature and above, the MoS2 can oxidize and lose the desired lubricity. Further, above 1300° F. the Mo can evaporate. If these high temperatures are needed for other reasons, then an alternate solid lubricant such as hBN can be selected.
In another non-limiting configuration, the solid lubricant can be distributed through the matrix in particles of solid lubricant that have a particle size distribution of −177+10 micro meters (μm).
Turning to
The present disclosure is made in terms of a coating strategy at the blade root/disk interface, but this strategy could be utilized at other interfaces that are subjected to similar fretting and high friction forces, for example at other locations in a gas turbine engine, particularly in areas where combined conditions of high temperature and significant vibratory motion are experienced.
One or more embodiments of the present disclosure have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. For example, different materials and coating configurations could be utilized, and coatings can be applied utilizing other application methods. Accordingly, other embodiments are within the scope of the following claims.
