KR20090043155A - Mechanical seals and methods of making - Google Patents

Abstract

FIELD OF THE INVENTION The present invention relates to mechanical seals for use in seals, in particular rotating machinery, and methods of making the same. Such a mechanical seal comprises a pair of opposing seal faces 10, wherein the pair of opposing seal surfaces 10 comprises a multilayer coating 14 deposited on a substrate 12. Wherein the multilayer coating 14 comprises distinct layers that are periodically repeated, multiple composite layers, wherein two adjacent composite layers do not contain the same proportion of composite components at all; Both of these are included. The method of making a mechanical seal of the present invention includes depositing a multilayer coating 14 on a substrate 12 to form at least one side of a pair of opposing seal surfaces 10 of the mechanical seal. do.

Description

Mechanical seal and manufacturing method thereof {MECHANICAL SEALS AND METHODS OF MAKING}

The present invention relates to mechanical seals for use in seals, in particular for rotating machinery.

Mechanical seals are used in various rotating shaft devices such as blowers, compressors, vacuum pumps, expanders, hot gas passage assemblies and the like. Such a seal minimizes or suppresses fluid (gas or liquid) leakage from the workroom with a rotating shaft, for example by installing a barrier between the workroom and the external environment or between two successive stages of a compressor or turbine.

One such type of mechanical seal is a spiral groove seal in which a spiral-shaped groove region is provided on one side of a pair of opposing seal surfaces. When one side of the seal surface rotates with respect to the other side, due to hydrodynamic action, fluid flows through the grooves toward the ungrooved portion of the seal surface. At certain speeds, depending on the design of the seal, fluid pressure will separate the seal surface in precise amounts due to this pumping action. The grooveless portion of the seal surface acts as a seal dam that provides resistance to fluid discharge and also maintains a constant fluid pressure. One side of the pair of seal surfaces provides spring-loaded force to prevent separation of the two seal surfaces and to provide additional resistance to fluid discharge by minimizing the gap between the seal surfaces.

If the speed of rotation is too slow (for example, during starting and stopping the device with the helical groove seal), there is not enough pressure generated to separate the seal surface. As a result, even in simple cases, contact between the seal surfaces may be sufficient to cause microcrack, particle migration and / or particle collapse at the seal surface due to frictional heat and wear. The concentration of these defects can be increased due to repeated contact accidents that occur during normal operating conditions (ie rotational speeds) resulting in a lack of seals and ultimately a lack of seal housings and / or devices using the seals. And / or increase due to rim and centrifugal stress.

Conventional efforts to increase the life of seals have focused on increasing hardness, increasing crack resistance, reducing friction, or minimizing the number of contact accidents. Many seal surfaces are formed from high performance carbides (eg, various forms of tungsten carbide, silicon carbide, etc.) instead of oxides or metals in the roots. However, many such seals are limited in thickness and thus cannot maintain the wear conditions they are exposed to during their working life. Thus, despite improvements in the manufacturing environment, there remains a need in the art for improved mechanical seals.

The mechanical seal includes a pair of opposing seal surfaces, wherein at least one side of the pair of seal surfaces includes a multilayer coating disposed on a substrate, the multilayer coating comprising a separate layer that is periodically repeated. Include.

In another embodiment, the mechanical seal includes a pair of opposing seal surfaces, wherein at least one side of the pair of seal surfaces comprises a multilayer coating disposed on a substrate, the multilayer coating comprising a plurality of composites. Layers, and two adjacent composite layers do not contain composite components in the same proportion at all.

The method includes disposing a multilayer coating on a substrate to form at least one side of a pair of opposing seal surfaces of the non-contact mechanical seal.

Mechanical seals comprising the multilayer coating of the present invention provide a hard wear resistant seal surface with reduced friction and reduced wear associated with microcrack formation. The Vickers hardness (Hv) of the seal surface including the multilayered coating can be about 4000 to about 5000, which can significantly improve the life of such mechanical seals and devices using such seals.

The above described and other features are described in the following figures and detailed description.

The present invention discloses a mechanical seal and a method of manufacturing the same. In an exemplary embodiment, the mechanical seal is a non-contact mechanical seal. As used herein, the term "noncontacting" has a meaning conventionally known in the art (ie, the pressure-generating separation point between the opposing seal surfaces at some point in the operation of the device using the seal). It describes a seal (with pressure-generated separation). The speed of rotation at the point of separation between the opposing seal surfaces is also a function of the surface finish of the seal surface. When the seal surface deteriorates for more than the specified time, a higher rotational speed is required to separate it, resulting in increased heat generation and wear on the surface of the seal surface during their contact. Compared with the prior art, the seals disclosed herein and methods for making them are generally based on at least one seal surface comprising a multilayer coating. The use of multilayer coatings advantageously results in hard wear resistant seal surfaces that form microcracks associated with reduced friction and reduced wear. This feature ultimately increases the life of seals and devices.

In addition, terms such as "first", "second", and the like are used to distinguish one element from another rather than to indicate any order, quantity, or importance; The terms “the”, “a” and “an”, etc., rather than the positive limit, indicate the presence of at least one reference item. The term “about”, used in reference to quantities, includes defined values and has the meanings mentioned in the sentence (eg, including the margin of error associated with a particular quantity of measurement). In addition, all ranges showing the same amount or physical property include the indicated end points and are independently combinable.

The seal generally comprises a pair of opposing seal surfaces comprising a multilayer coating having at least one seal surface disposed on a substrate. While driving the seal, one surface of the seal surface rotates with respect to the other surface. While either seal surface (or both seal surfaces) may comprise a multilayer coating, it is preferred that at least the rotating seal surface comprises a multilayer coating. In addition, although either seal surface (or both seal surfaces) may optionally comprise a spiral-shaped groove, it is preferred that at least the rotating seal surface comprises such a spiral-shaped groove.

The present invention will now be described with reference to the drawings. Referring to FIG. 1, a portion of the seal surface named 10 is shown. The seal surface 10 generally includes a substrate 12 and a multilayer coating 14 disposed thereon.

Substrate 12 on which multilayer coating 14 is disposed may be of a specific metal, metal alloy, or ceramic (eg, oxide, nitride, carbide, etc.) composition. In one exemplary embodiment, the substrate 12 is a carbide composition. Exemplary carbides include silicon carbide (eg, solid silicon carbide, silicon containing graphite, reactively bonded silicon carbide, self-sintered silicon carbide, or at least one of the foregoing Composite) and tungsten carbide (eg, tungsten carbide or metal-bonded tungsten carbide). It should be noted that the composition and microstructure of the substrate can adversely affect the performance of the seal surface.

In the multilayer coating 14, the composition of each layer is characterized by its properties including hardness, wear resistance, smoothness, thermal stress resistance, fracture toughness, adhesion, or at least one of the aforementioned properties. It may be chosen to provide the desired physical properties such as combination.

By way of example, where hardness, wear resistance and / or thermal stress are required, a ceramic material may be used as the composition for the layer of the multilayer coating 14. Suitable ceramic compositions include metal oxides such as Al ₂ O ₃ , Cr ₂ O ₃ , ZrO _2, and the like; Metal carbides such as Cr ₃ C ₂ , WC, TiC, ZrC, B ₄ C, and the like; Diamond, diamond-like carbon; Metal nitrides such as cubic BN, TiN, ZrN, H _f N, Si ₃ N ₄ , AlN, TiAlN, TiAlCrN, TiCrN, TiZrN, and the like; And combinations comprising at least one of the foregoing compositions. In other words, the composition for the layer of the multilayer coating 14 is a binder phase that is at least 51 vol% (vol%) of the above-mentioned suitable ceramic composition and a relatively soft low melting point composition, based on the total volume of the composite. ceramic composite containing a phase). Suitable ceramic binder phase compositions for ceramic composites include SiO ₂ , CeO ₂ , Y ₂ O ₃ , TiO ₂ , and combinations comprising at least one of the foregoing ceramic binder phase compositions. In another embodiment, the composition for the layer of multilayer coating 14 is a ceramic-metal composite (cermet). Suitable conductive alloys include WC / Co, WC / CoCr, WC / Ni, TiC / Ni, TiC / Fe, Ni (Cr) / Cr ₃ C ₂ , and combinations comprising at least one of the foregoing. There is this. Another composition for the layer of multilayer coating 14 includes a combination comprising at least one of a ceramic, a ceramic composite, or a ceramic alloy (eg, a metal or alloy matrix comprising one of the foregoing).

In another example, where smoothness is desired, the composition for the layer of multilayer coating 14 may be germanium, MoS ₂ , polyamide, fluoropolymers (eg polytetrafluoroethylene, fluorinated ethylenepoly). Propylene, etc.), graphite, transition metal borides, hexagonal boron nitride, and similar solid lubricants. Advantageously, such solid lubricants in addition to providing smoothness when in powder form will also facilitate the removal of heat from the contact surface of the seal.

In another example, where adhesion is required, the composition for the layer of multilayer coating 14 may be an MCrAl or MCrAlY alloy, where M represents iron, nickel, or cobalt; NiAl (Zr) composition and the like.

There is no specific upper limit to the number of individual layers that can form the multilayer coating 14, but it must be at least two layers or more. In the multilayer coating 14, thermal expansion between the individual layers including the substrate and thermal expansion between the individual layers should be considered. In addition, the layers must be able to withstand certain non-uniform strains.

Moreover, within the multilayer coating 14, each layer may have a different thickness and / or each layer may have a homogeneous thickness. The average thickness of each layer can be independently from about 5 nanometers (nm) to about 25 micrometers (μm). Within this range, the average thickness of each layer can independently be at least about 10 nm, specifically at least about 20 nm. Also within this range, the average thickness of each layer can independently be about 10 nm or less, specifically about 5 nm or less. The average thickness of the entire multilayer coating 14 may be between about 2 μm and about 500 μm. Within this range, the average thickness of the entire multilayer coating 14 may be at least about 5 μm, specifically at least about 8 μm. Also within this range, the average thickness of the entire multilayer coating 14 may be about 200 μm or less, specifically about 50 μm or less.

In one embodiment, at least a portion of the multilayer coating 14 may be a separate layer that is periodically repeated. For example, two different compositions can be stacked alternately to form three or more layers. In addition, three different compositions may be laminated by being substituted a specific number of times in the order of 1-2-3-1-2-3-, 1-2-3-2-1-, and the like, but are not limited thereto. It is not. When these alternating layers are sufficiently thin (eg, about 100 nm or less), heterostructures or superlattices are formed that can have significantly improved hardness and crack resistance than thicker individual layers. do.

In other embodiments, the multilayer coating 14 may include one or more separate layers of the composite such that each layer has components of the same component but different amounts and ratios. For example, a composite comprising nanoparticles dispersed in a matrix can be used in each layer of the multilayer coating 14 while increasing (or decreasing) the amount of nanoparticles in the next adjacent layer such that the slope of the physical property is present. . As used herein, with reference to the layers of a multilayer coating, the term "adjacent" refers to physical contact (ie, no interference layer disposed between two layers, referred to as layers adjacent to each other). Refers to two layers in.

Each layer of the multilayer coating 14 is, for example, electron beam physical vapor deposition (EB-PVD), radiofrequency sputtering, ion beam sputtering, plasma assisted vapor deposition, cathode arc deposition, and cathode arc plasma. Physical vapor deposition (PVD), including deposition; Chemical vapor deposition (CVD); It may be independently deposited or otherwise formed on the substrate 12 by a variety of specific techniques such as and the like. Those skilled in the art can form individual layers of the multilayer coating 14 using each of these techniques in light of the present disclosure without inappropriate experimentation. Depending on the technique used, the atomic structure of each layer can be made independently crystalline or amorphous as may be required for a particular sealing application. In addition, when crystalline, the particle shape can also be made as required for certain sealing applications.

Referring again to FIG. 1, an exemplary rotating seal surface 10 of a mechanical seal may be formed on a Ni-bonded WC conductive alloy substrate 12. The average longest dimension of the WC particles is at least about 3 μm. Specifically, the particle size distribution has two modes, wherein about 60% of the particles have an average longest dimension of about 3 μm or more and the rest of the particles have an average longest dimension of less than about 2 μm. The amount of nickel present in the ceramic alloy is about 6 to about 15 weight percent (wt%) based on the total weight of the ceramic alloy. Within this range, it may be desirable for at least about 9 wt% nickel to be present in the conductive alloy. In this way, certain cracks occurring in the WC may be inhibited from growth due to the presence of increased amounts of nickel.

Multilayer coating 14 is formed by depositing alternating layers of TiN 18, 22 and 26 and ZrN 20 and 24. For reference, only five shifts (ie, 18, 20, 22, 24 and 26) were created, but it should be noted that this is for illustrative purposes only. Those skilled in the art will appreciate that a certain number of shifts may be used. In addition, although the first alternating layer 18 (ie, the layer closest to the substrate) in this embodiment is referred to as a TiN layer, ZrN may be used as the first alternating layer.

Alternating layers 18, 20, 22, 24, and 26 are deposited by PVD techniques, and on any substrate 12 or any adhesive layer, which may adhere better to substrate 12 than first alternating layer 18. It can be deposited directly on (16). Any adhesive layer 16 may be deposited using CVD techniques to better control particle growth on the substrate. It is desirable for any adhesive layer 16 to have the same composition as the first alternating layer 18 to provide the greatest compatibility between them. The alternating layers 18, 20, 22, 24, and 26 generally have a thickness of about 20 nm to about 100 nm, respectively, to form a heterostructure. In one embodiment, the overall thickness of all of the alternating layers 18, 20, 22, 24, and 26 is between about 3 μm and about 8 μm. The optional adhesive layer 16 may have a thickness of about 1 μm to about 25 μm.

Optionally, a low friction layer 28 may be deposited on the last (ie outermost from substrate) alternating layer 26. Any low friction layer 28 may be, for example, a diamond-like carbon layer. Certain low friction layers 28 may be deposited using any of the techniques described above.

Alternatively, or in addition to any low friction layer 28, a seal surface 10 that rotates by depositing any solid lubricant layer 30 on the last alternating layer 26 (or any low friction layer 28). ) May provide increased smoothness to the rotating seal surface 10 when in contact with an opposing seal surface (not shown). Any solid lubricant layer 30 may be deposited on the last alternating layer 26 (or any low friction layer 28) using a shiny or binder phase.

As soon as the top layer of the multilayer coating 14 is deposited on the substrate 12, the spiral-shaped groove 32 as shown in FIG. 2 may be etched into the surface of the top layer or processed using a machine. The substrate 12 may also be processed or etched using a machine and then the multilayer coating 14 may be deposited, while retaining the spiral-shaped grooves after deposition. Exemplary techniques for depositing the multilayer coating 14 on substrates 12 that have already been processed or etched using a machine include EB-PVD, cathodic arc deposition techniques, and the like.

In another embodiment, instead of alternating layers of TiN (18, 22, and 26) and ZrN (20 and 24), each layer in the plurality of layers may be composed of Al ₂ O ₃ nanoparticles that are different from certain immediately adjacent layers. Multiple layers of a composite are used that include Al ₂ O ₃ nanoparticles dispersed in a nanostructured NiCrAl or CoCrAl alloy matrix to have a concentration (eg, volume fraction). For example, one layer may be rich in ceramic, while the next adjacent layer may be rich in alloy. Within the composite, Al ₂ O ₃ nanoparticles have an average longest dimension of about 10 nm to about 200 nm. Also in the accumulated complex, the total Al ₂ O ₃ volume fraction is high enough to give the composite an increased hardness (eg, about 70 to about 80%).

Multiple composite layers 18, 20, 22, 24, and 26 are deposited using PVD techniques, and similarly, are better on substrate 12 or on substrate 12 than on first composite layer 18. It can be deposited directly on any adhesive layer 16 that can be bonded. The overall thickness of the plurality of composite layers 18, 20, 22, 24, and 26 is about 50 μm to about 300 μm.

In another exemplary embodiment, the multilayer coating 14 includes a combination of multiple composite layers and heterostructures to provide increased hardness. Preferably, a plurality of composite layers are deposited on the substrate such that the heterostructures are deposited on the plurality of composite layers on the surface opposite the substrate and then the layer comprising the heterostructures is deposited.

Those skilled in the art should appreciate that the mechanical seals disclosed herein and methods for making them provide a hard wear resistant seal surface with reduced friction and reduced wear associated with microcrack formation. For example, the Vickers hardness (Hv) of the seal surface including the multilayered coating may be about 4000 to about 5000. As a result, the mechanical seal and the life of the device using such a seal can be significantly improved.

In addition, mechanical seals and devices using such seals may be provided with springs, shafts (for spring-loading on at least one of a pair of spring faces, which are generally static faces), It should also be noted that mechanical seals such as rotors, stators, secondary O-ring seals, and the like, and other components known to be used with devices using such mechanical seals, may be included.

While the present disclosure has been described with reference to exemplary embodiments so far, those skilled in the art know that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention. There will be. In addition, many modifications may be made to a particular situation or event to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.

The following figures are illustrative embodiments in which like elements are denoted by like numerals.

1 is a longitudinal cross-sectional view of a portion of a non-contact mechanical seal surface;

2 is a schematic representation of a non-contact mechanical seal surface with a spiral groove.

Brief description of the main parts of the drawing

10 Seal face 12 Base

14 Multilayer Coating 16 Adhesive Layer

18, 20, 22, 24, 26 Coating Layer 28 Low Friction Layer

30 solid lubricant layers 32 helix-shaped groove

Claims (10)

A pair of opposing seal faces 10 (here, a pair of opposing seal faces 10 includes a multilayer coating 14 deposited on a substrate 12 and a multilayer coating 14 ) Includes distinct layers that repeat periodically), multiple composite layers (where two adjacent composite layers do not contain the same proportion of composite components at all), or both Mechanical seal. The method of claim 1, And wherein said separate layer forms a heterostructure. The method according to claim 1 or 2, The mechanical seal of the multilayer coating (14) further comprises an adhesive layer (16), a low friction layer (28), a lubricant layer (30) or a combination thereof. The method according to any one of claims 1 to 3, At least one of the pair of seal surfaces (10) comprising a multilayer coating (14) deposited on the substrate (12) rotates while the non-contact mechanical seal is in operation. The method according to any one of claims 1 to 4, At least one of the pair of seal surfaces (10) comprising a multilayer coating (14) deposited on the substrate (12) comprises a spiral-shaped groove (32). The method according to any one of claims 1 to 5, Mechanical seal, a non-contact mechanical seal. A method of making a mechanical seal comprising disposing a multilayer coating (14) on a substrate (12) to form at least one surface of a pair of opposing seal surfaces (10) of the mechanical seal. The method of claim 7, wherein A method in which the multilayer coating (14) comprises periodically repeated layers, multiple composite layers (where two adjacent composite layers do not contain the same proportion of composite components at all), or both. The method of claim 8, Method of disposing a particular layer in said multilayer coating (14) using physical vapor deposition techniques. The method of claim 7, wherein Chemically depositing an adhesive layer (16) on the substrate (12) and then placing the multilayer coating (14) on the substrate (12).

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