SUBSTRATES COATED WITH WEAR RESISTANT LAYERS AND METHODS OF APPLYING WEAR RESISTANT LAYERS TO SAME

Abstract

Components with improved erosion resistance are disclosed. A surface of the component or a substrate of the component is modified by coating the substrate with an elastomer layer. The elastomer layer is then modified by embedding hard particles onto an outer side of the elastomer layer. The hard particles exhibit higher fractured toughness providing enhanced erosion protection. The elastic properties of the elastomer experience little reduction because the surface embedded particles are located only at the outer side or outer surface of the elastomer layer. Therefore, the bond between the inner side of the elastomer layer and the substrate or component surface is not interfered with and the potential for electro-chemical corrosion and poor adhesion are not increased by the presence of the hard particles as the hard particles are located away from the inner face between the elastomer layer and the substrate.

Claims

1-5. (canceled)

6. A method of repairing a damaged leading edge of an airfoil, comprising: coating the damaged leading edge of the airfoil with a first uncured elastomeric material; partially curing the first uncured elastomeric material to form a partially cured elastomeric layer, the partially cured elastomeric layer having an inner surface coupled to the damaged leading edge of the airfoil and an outer surface disposed opposite the inner surface; embedding hard particles having a diameter greater than or equal to five microns into the outer surface; further curing the partially cured elastomeric layer to form a matrix, and coating the matrix with a second uncured elastomeric material and curing the second uncured elastomeric material.

7. (canceled)

8. The method of repairing a damaged leading edge according to claim 6 wherein the second uncured elastomeric material is the same as the first uncured elastomeric material.

9. The method of repairing a damaged leading edge according to claim 6 wherein the second uncured elastomeric material is different than the first uncured elastomeric material.

10. The method of repairing a damaged leading edge according to claim 6, wherein the first uncured elastomeric material is selected from the group consisting of polyurethanes, polyureas, silicones, silicone rubbers, fluoropolymers, natural rubber, chlorosulfonated polyethylene, chlorinated polyethylene, ethylene octene copolymers and combinations thereof.

11. The method of repairing a damaged leading edge according to claim 6, wherein the second uncured elastomeric material is selected from the group consisting of polyurethanes, polyureas, silicones, silicone rubbers, fluoropolymers, natural rubber, chlorosulfonated polyethylene, chlorinated polyethylene, ethylene octene copolymers and combinations thereof.

12. The method of repairing damaged leading edge according to claim 6, wherein the partially curing is initiated by mechanism selected from the group consisting of an additional reaction, nucleophilic substitution reaction, nucleophilic aromatic substitution reaction and free radical.

13. The method of repairing a damaged leading edge according to claim 6, wherein the hard particles are selected from the group consisting of alumina, silicon carbide, silicon nitride, boron carbide, tungsten carbide, steel alloys, nickel alloys, diamond, chromium carbide, mullite, zirconia, yttria-stabilized zirconia, magnesium-stabilized zirconia and combinations thereof.

14. The method of repairing a damaged leading edge according to claim 6, wherein the hard particles have a diameter greater than or equal to 100 microns.

15. The method of repairing a damaged leading edge according to claim 6, wherein the hard particles have a diameter greater than or equal to 500 microns.

16. A method of coating an airfoil, comprising: applying a partially crosslinked elastomer to a surface of the airfoil to form an elastomeric layer, the elastomeric layer including an inner surface attached to the surface of the airfoil and an outer surface disposed opposite the inner surface; entrenching hard particles having a diameter greater than or equal to five microns into the outer surface; and crosslinking the elastomeric layer to form a matrix, and coating the matrix with an elastomeric material and crosslinking the elastomeric material.

17. (canceled)

18. The method of coating an airfoil according to claim 16, wherein the hard particles are selected from the group consisting of alumina, silicon carbide, silicon nitride, boron carbide, tungsten carbide, steel alloys, nickel alloys, diamond, chromium carbide, mullite, zirconia, yttria-stabilized zirconia, magnesium-stabilized zirconia and combinations thereof.

19. The method of coating an airfoil according to claim 16, wherein the hard particles have an aspect ratio less than or equal to twenty.

20. The method of coating an airfoil according to claim 16, wherein the hard particles have an aspect ratio less than or equal to 5.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a side sectional view of a substrate coated with an elastomer layer that includes an outer side embedded with particles (surface embedded particles or SEPs).

[0017] FIG. 2 compares, graphically, the mass of the erodent that engages the elastomer layer (x-axis) and the mass of the elastomer layer removed by the erodent (y-axis) for both an untreated elastomer layer and an elastomer layer treated with particles as illustrated in FIG. 1.

DETAILED DESCRIPTION

[0018] Referring to FIG. 1, a substrate 10 is illustrated that includes an outer surface 12 that is at least partially covered by an elastomer layer 14. The elastomer layer 14 includes an inner side 16 that covers, is bonded to, affixed to or engaged with the outer surface 12 of the substrate 10. The elastomer layer 14 also includes an outer side 18 that is at least partially covered with a plurality of particles 20. An additional embodiment is also disclosed in FIG. 1 which includes dual elastomer layers 114, 214. In this example, the lower elastomer layer 214 can be applied to the outer surface 12 of the substrate 10 and may be allowed to cure. Then, the upper layer 114 is prepared and, optionally, the particles 20 may be mixed with the elastomer of the upper layer 114 and applied to the lower layer 214 thereby providing a dual layer 114, 214 structure wherein the outer layer 114 includes the plurality of hard particles but which cannot migrate to the inner layer 214 as the inner layer 214 is cured or at least substantially cured by the time the outer layer 114 is applied onto the inner 214. The properties of the layers 14, 114 and 214 can be selected to provide a preferred combination of bonding, erosion protection and thermal and environmental resistance to the coated substrate 10.

[0019] Other techniques for applying the particles 20 to the elastomer layer 14 include partially-curing the elastomer layer 14 and spraying or pressing the particles 20 onto the outer side 18 of the partially-cured elastomer layer. The particles 20 may also be strategically placed on the outer side 18 of the elastomer layer 14 by using a screen or mesh 22 and pressing or spraying or otherwise delivering the particles 20 through the screen or mesh 22 onto the outer side 18 of the partially-cured elastomer layer 14.

[0020] Depending on the type of elastomer and desired properties, the particles 20 may be fabricated from materials selected from the group consisting of alumina, silicon carbide, silicon nitride, boron carbide, tungsten carbide, steel alloys, nickel alloys, diamond, chromium carbide, mullite, zirconia, yttria stabilized zirconia, magnesium stabilized zirconia and combinations thereof. If the particles 20 and the elastomer layer 14 are not inherently compatible, it may be necessary to add a known coupling agent to the elastomer in order to combine the elastomer and the particles. For that matter, the elastomer layer 14 should be selected so that it is compatible with the substrate 10 and, when cured onto the substrate 10, the elastomer layer 14 should be mechanically and/or chemically bonded to the substrate 10.

[0021] It is preferable that the elastomer has a strain to failure of at least 20% and a tensile strength of at least 1,000 PSI. Even more preferable, the elastomer may have a strain to failure of at least 100% and a tensile strength of at least 3,000 PSI. It is still more preferable that the elastomer has a strain to failure of at least 1000% and a tensile strength of at least 5,000 PSI. Elastomers such as polyurethanes, polyureas, silicones or silicone rubbers and fluoropolymers can satisfy these requirements. Other suitable elastomers may include, but are not limited to natural rubber, polyurethanes, chlorosulfonated polyethylene, chlorinated polyethylene and ethylene-propylene copolymers and terpolymers.

[0022] One example of a possible polyurethane is a product manufactured by AIR PRODUCTS under the trade name Airthane. Examples of potentially suitable fluoropolymers include those manufactured by Dupont Dow Elastomers under the tradenames Viton and Kalrez. E.I. Dupont de Nemours Company also manufactures Teflon fluoropolymer. Another example of a possible fluoropolymer includes that which is manufactured by the Minnesota, Mining & Manufacturing Company (3M) under the tradenames Fluorel. Further examples of potential elastomers include Engage polyolefin, Ascium and Hypalon chlorinated polyethylenes, and Tyrin chlorinated polyethylene, all manufactured by Dupont Dow Elastomers. Another example of a possible polymer is a fluorinated polymer, such as polychlorotrifluoroethylene manufactured by 3M under the tradename Kel-F. Examples of a potential silicone include NuSil R-2180, fluorosilicone and polydimethylsiloxane.

[0023] It is preferable that the hard particles 20 have a diameter ranging from about 5 microns to about 3000 microns. It is even more preferable that the hard particles 20 have a diameter ranging from about 100 microns to about 1000 microns. It is especially preferable that the hard particles 20 have a diameter ranging from about 500 microns to about 800 microns. It is also preferable that the hard particles 20 have an aspect ratio ranging from about 1 to about 20. It is even more preferable that the hard particles 20 have an aspect ratio ranging from about 1 to about 10, and it is especially preferable that the hard particles 20 have an aspect ratio ranging from about 1 to about 5. It is also preferable that the hard particles 20 have favorable mechanical and chemical properties, such as high hardness, abrasion resistance, high modulus of stiffness, high compressive strength, water resistance, and thermal stability. It is also preferable that the hard particles 20 account for from about 1% to about 50% of the volume of the elastomer/particle layer 14. It is even more preferable that the hard particles 20 account for from about 1% to about 25% of the volume of the elastomer/particle layer 14, and it is especially preferable that the hard particles 20 account for from about 5% to about 20% of such volume.

[0024] Depending upon the type of elastomer and the desired properties, the hard particles may comprise a material from the group consisting of alumina, silicon carbide, silicon nitride, boron carbide, tungsten carbide, steel alloys, nickel alloys, diamond, chromium carbide, mullite, zirconia, yttria-stabilized zirconia, magnesium-stabilized zirconia and combinations thereof. It is desired to include particles having a hardness generally higher than that of incoming erodent particles such as sand.

[0025] The elastomer serves as a matrix for the hard particles, which add the desired physical properties to the elastomer, thereby increasing the toughness and/or stiffness of the elastomeric matrix. Incorporating hard particles into the elastomeric matrix allows an additional pathway for the elastomer to dissipate impact energy over a larger relative volume because the sizes of the particulate matter (sand or water) impacting the elastomer are significantly less than the size of the hard particles within the elastomeric matrix. It is anticipated that the smaller erodent particle will impact the reinforcement particle within the elastomer or with the elastomer itself. If the reinforcement particle is impacted, the force will be transferred into both the reinforcement particle and the elastomeric matrix. The elastomer layer(s) is, thereby, less susceptible to erosion than a pure elastomer. The particle-embedded elastomer layer 14, therefore, will typically have a longer useful life compared to a pure elastomer layer. The elastomer layer 14 will also have a longer life expectancy than an elastomeric matrix reinforced with conventional reinforcing particles because the disclosed elastomer layer 14 with hard particles 20 embedded on its outer side 18 can absorb a particulate matter's impact energy over a significantly greater volume. Applying the particle-coated or particle-embedded elastomer layer 14 onto a substrate such as an airfoil, rotor or fan, especially a leading edge, reduces the energy density absorbed by the elastomer layer 14, thereby reducing its potential for eroding which, in turn, increases the component's erosion resistance.

[0026] The particles 20 may be partially or totally embedded in the elastomer layers 14, 114 as illustrated in FIG. 1, but are most effective when particles are disposed partially on or just below the outer side 18 of elastomer layers 14, 114. The elastomer layers 14, 114 may have particles deposited to a depth ranging from about 1% to about 99% of the overall thickness of the layer or layers 14, 114. Other suitable particle depth ranges can range from about 1% to about 50% or from about 5% to about 10%. At least about 1% of the outer layer 14, 114 thickness would have embedded particles with an upper limit of about 99% of the outer thickness of the layers 14, 114 would have embedded particles. One preferred range is from about 5% to about 10% of the outer layer thickness.

[0027] Turning to FIG. 2, simulated data for an untreated elastomer layer and a treated elastomer layer 14 is presented graphically. The line 30 represents an untreated elastomer layer that is being bombarded with an erodent in the form of sand particles and/or water particles. The initial dip in the curve is evidence of a weight gain as the erodent particles are embedded into the untreated elastomer layer. However, as the untreated elastomer layer erodes, it loses weight as indicated by the upswing of the curve 30. The curve 32 represents a treated elastomer layer 14 like that shown in FIG. 1. The treated elastomer layer 14 also gains weight as it is initially bombarded with particles, but at an initially slower rate than the untreated elastomer, and then slowly begins to lose weight as it erodes. The reader will note the substantial offset between the curves 30 and 32 thereby establishing that the treated elastomer layer 14 will take longer to erode than the untreated elastomer layer represented by the curve 30.

INDUSTRIAL APPLICABILITY

[0028] Various components that are susceptible to erosion by sand or dirt particles and/or water particles may be provided with a superior erosion-resistant coating in the form of an elastomer layer 14 with hard particles 20 embedded into or onto the outer side 18 of the elastomer layer 14. The inner side 16 of the elastomer layer 14 that engages the substrate 10 is free of particles and therefore the bond between the inner side 16 and the outer surface 12 of the substrate 10 will not be interfered with by the hard particles 20. Further, the risk of causing electro-chemical corrosion and/or adhesion problems at the interface between the inner sides 16 of the elastomer layer 14 and the upper surface 12 of the substrate 10 is avoided by keeping the hard particles 20 away from this interface.

[0029] The modified elastomer layer 14 as shown in FIG. 1 or the dual layer 114, 214 with the modified outer layer 114 can be applied to a variety of components including, but not limited to a propeller, a helicopter rotor blade, an airfoil, a compressor blade of a gas turbine, a fan blade of a gas turbine and a rotor blade of a pump, a rotor blade of a compressor, a fan blade of a heating-ventilation-air conditioning unit (HVAC) and other components as will be apparent to those skilled in the art.