Patent Application
20130261034
NONE
The invention is directed to surface treatments for rotating turbomachinery. In particular, the invention is directed to surface treatments for gas turbine components that may exhibit stresses, and in further particularity, the invention is directed to surface treatments for gas turbine compressor blade components at their interface with compressor wheels, where they may exhibit stresses.
Previous gas turbine compressor blade component configuration may provide bare or non-treated compressor blades with an interface at the compressor wheel. For example, the compressor blade of the compressor may contact, or define an interface, against compressor wheels, such as but not limited to, CrMoV wheels. These areas of contact are at areas of high contact stresses between the elements. These stresses can lead to undesirable effects, such as but not limited to, fretting and galling. These undesirable effects, if left unaddressed, may lead to component failures and possible shutdown of related gas turbine units.
According to an aspect of the invention, a coating for turbomachinery comprises graphite-based sold film lubricant material.
In another aspect of the invention, a coating for turbomachinery is provided and comprises graphite-based sold film lubricant material; where the turbomachinery comprises at least a wheel comprising a slot and a bucket comprising a dovetail, the coating is applied to at least one of the slot and the dovetail; and coating comprises at least one of: graphite-based dry film lubricants, metal filled resin based systems, silicate binder with graphite; and high temperature lubricating additives.
Further, in yet another non-limiting aspect of the invention, A method for coating for turbomachinery to provide at least one of crevice corrosion resistance and fretting resistance, the method comprising providing a coating; and applying the coating to at least one of the slot and the dovetail; wherein the coating comprises graphite-based sold film lubricant material; the turbomachinery comprises at least a wheel comprising a slot and a bucket comprising a dovetail, the coating is applied to; and the coating comprises at least one of graphite-based dry film lubricants, metal filled resin based systems, silicate binder with graphite; and high temperature lubricating additives.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
Although the present invention may have general application to both turbomachinery, such as but not limited to, turbine wheels and compressor wheels, particularly for gas or steam turbines, the following embodiment is directed toward a compressor stage of a gas or steam turbine for concreteness of description. This description is not intended to limit the invention in any manner.
A compressor stage is conventionally fabricated with a wheel or disc affixed or integrally formed with an axial shaft. Female dovetail regions are machined into the surface of the wheel and male dovetail regions of compressor blades are fitted into the female dovetails.
Illustrated in
More specifically, and referring to both
Further, as embodied by the invention, the blade 18 of the turbomachinery may be formed of a superalloy, such as a precipitation hardenable, nickel-based alloy (Inconnel 718), or from stainless steel materials.
The wheel or disk 20 includes a plurality of axially disposed circumferentially spaced slots 42 in an outer perimeter 44 thereof which are complementary in shape to the blade dovetails 40, and which receive the dovetails 40 for attaching the blades 18 thereto. Air 46 is suitably channeled through the blades 18 and the vanes 14 and is compressed thereby.
Contact stresses between the compressor blade dovetail 40 and wheel 20 combined with the movement of the part in the wheel slot 42 when the turbine rotor and bladed disk assembly 12 rotates. These contact stresses can lead to high contact stress fretting and galling wear of the bladed disk assembly 12. To reduce the friction coefficient at the contact surface and lower the wear rate therebetween, a coating 50, as embodied by the invention, is applied to at least one of the bladed disk assembly 12 and the slot 42.
Preferably, the coating 50 is applied to the bladed disk assembly 12 surfaces in the slot 42, as embodied by the invention; however, the coating 50 can be the wheel slot 42. A coating 50 can be applied to either or both adjacent surfaces, of the bladed disk assembly 12 and/or the slot 42.
Applying coatings to the materials that form the bladed disk assembly 12 and the wheel 20, such as materials comprising duplex stainless steel materials, can be difficult due to geometry of these components. For example, and in no way limiting of the invention, some coatings can cause crevice corrosion issues on such materials. Accordingly, as embodied by the invention, coatings 50, as embodied by the invention, comprise a graphite-based sold film lubricant coating. Further, the coating 50 can comprise at least one of graphite based dry film lubricants or metal filled resin based systems that can be applied to at least one of the bladed disk assembly 12 and the wheel slot 42. These coating materials, as embodied by the invention, can be used to lower friction coefficients and reduce wear between the bladed disk assembly 12 and the wheel slot 42.
The coating 50, as embodied by the invention, provide at least one of anti-fretting resistance and resistance to crevice corrosion.
The coating 50 may comprise graphite materials, and it is within the scope of the invention that the coating comprises graphite grease. Moreover, the coating 50, as embodied by the invention, may comprise □ molybdenum grease, either alone or in combination with other graphite-based sold film lubricant coating materials.
For example, materials for the coating, as embodied by the invention, include limited to products, such as but not limited to, lubricants; dry lubricants; lubricants and bonding materials in a suitable solvent, an oil-soluble; sulfonate surfactant/wetting agent (for example SurfKote® LOB-1800-G from HOHMAN PLATING & MFG. INC.); titanium containing lubricants, such as but not limited to, Alumazite ZDA (from Tiodize Co., Inc.) and combinations thereof. In general, the coatings comprise a lubricating material, which can be combined with other components that provide desired material characteristics. For example, one non-limiting coating material can comprise silicate binder with graphite and other high temperature lubricating additives. Other additives can be desired dependent on the intended use of the blade, the environment of the blade and associated turbomachinery.
The coating 50, as embodied by the invention, are preferably applied to a compressor blade dovetail 40 of the blade 18 where it contacts the wheel slot 42. However, as embodied by the invention, the coating 50 can be applied to any pressure face surfaces of the dovetail 40 and/or the slot 42, if needed.
The coating 50, as embodied by the invention, is applied at a thickness in range from about 0.0005″ to about 0.002″. The coating 50 can be applied at a thickness, which can prevent galling, seizing and fretting of the dovetail base metal/substrate.
The coating 50, as embodied by the invention, can be applied by any appropriate coating process. Further, Exemplary coating processes, include, but are not limited to, painting; deposition, such as but not limited to, physical vapor deposition, plasma-enhanced chemical vapor deposition, and chemical vapor deposition; sputtering, such as etching and chemical sputtering; powder coating; air plasma spray, cold spraying, electroplating; and combinations thereof.
In conventional turbomachinery, bare compressor blades pressing against wheels, such as but not limited to, wheels formed of CrMoV, at high contact stresses may lead to excessive fretting and galling, among other undesired effects. This excessive fretting and galling, which left unaddressed, has shown to lead to component faults and possible shutdowns of turbomachinery and gas turbine units. The coating on the blade dovetail, as embodied by the invention, is effective in reducing a wear thereon to extend the turbomachinery component's lifetime. This improvement may also lead to improved gas turbine and/or compressor reliability. Also, the coating of the blade, as embodied by the invention, is simpler, less expensive and a more robust process than attempting to coat turbomachinery in the hard to reach areas, such as but not limited to, wheel slots of the turbine wheel into which blades slide.
The blades with the coating, as embodied by the invention, provide an anti fretting coating solution that will not cause crevice corrosion. The coating 50, as embodied by the invention, can be applied and coat superalloy substrates, such as a GTD450 blade, which can be difficult since coatings on GTD450 experience crevice corrosion issues. The blades with the coating, as embodied by the invention, can run as designed with high contact stresses, which may occur as a result of the operation of the turbomachinery. Further, as embodied by the invention, the coated component should not fail with the same fallout rate in the un-coated version.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
