U.S. patent application number 14/058804 was filed with the patent office on 2015-04-23 for method of coating a composite material and a coated edge of a composite structure.
This patent application is currently assigned to The Boeing Company. The applicant listed for this patent is The Boeing Company. Invention is credited to Neha Borkar, Marc J. Froning, William Alan Thompson, Michael H. Ware.
Application Number | 20150111058 14/058804 |
Document ID | / |
Family ID | 52013172 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150111058 |
Kind Code |
A1 |
Thompson; William Alan ; et
al. |
April 23, 2015 |
METHOD OF COATING A COMPOSITE MATERIAL AND A COATED EDGE OF A
COMPOSITE STRUCTURE
Abstract
A method of coating a composite material and an associated
coated composite structure are disclosed to provide increased wear
resistance and surface protection. The edge of the composite
material may be coated so as to provide protection for the edge. A
method of coating a composite material includes applying an
adhesion promotion layer to the composite material. The adhesion
promotion layer includes a binder paint and a plurality of metal
particles within the binder paint. The metal particles may be
irregularly shaped. The method also includes applying a thermal
spray coating to the adhesion promotion layer. The thermal spray
coating may include a twin wire arc bond coating on the adhesion
promotion layer and a high velocity oxygen fuel spray coating on
the twin wire arc bond coating.
Inventors: |
Thompson; William Alan;
(Seattle, WA) ; Ware; Michael H.; (Renton, WA)
; Borkar; Neha; (Newcastle, WA) ; Froning; Marc
J.; (Seattle, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Boeing Company |
Chicago |
IL |
US |
|
|
Assignee: |
The Boeing Company
Chicago
IL
|
Family ID: |
52013172 |
Appl. No.: |
14/058804 |
Filed: |
October 21, 2013 |
Current U.S.
Class: |
428/556 ;
427/455; 428/560 |
Current CPC
Class: |
C23C 4/02 20130101; C23C
4/129 20160101; Y10T 428/12111 20150115; C23C 4/131 20160101; Y10T
428/12083 20150115; C23C 28/00 20130101; C23C 4/18 20130101; C23C
28/341 20130101; C23C 28/321 20130101; C23C 28/322 20130101; C23C
28/345 20130101 |
Class at
Publication: |
428/556 ;
427/455; 428/560 |
International
Class: |
C23C 4/02 20060101
C23C004/02; C23C 4/12 20060101 C23C004/12 |
Claims
1. A method of coating a composite material, the method comprising:
applying an adhesion promotion layer to the composite material,
wherein the adhesion promotion layer comprises a binder paint and a
plurality of metal particles within the binder paint; and applying
a thermal spray coating to the adhesion promotion layer.
2. A method according to claim 1 wherein the plurality of metal
particles comprise a plurality of irregularly shaped metal
particles.
3. A method according to claim 2 further comprising producing the
irregularly shaped metal particles by water atomization.
4. A method according to claim 1 wherein applying an adhesion
promotion layer comprises applying the adhesion promotion layer to
at least an edge of the composite material, and wherein applying
the thermal spray coating comprises applying the thermal spray
coating to the adhesion promotion layer on at least the edge of the
composite material.
5. A method according to claim 4 further comprising processing the
edge of the composite material such that the edge of the composite
material has a rounded or beveled profile prior to application of
the adhesion promotion layer.
6. A method according to claim 1 further comprising removing some
of the binder paint prior to applying the thermal spray coating so
as to expose at least a portion of the metal particles.
7. A method according to claim 1 wherein the plurality of metal
particles have a size between 5 .mu.m and 90 .mu.m.
8. A method according to claim 1 wherein the plurality of metal
particles comprises steel particles.
9. A method according to claim 1 wherein applying a thermal spray
coating comprises applying a high velocity oxygen fuel spray
coating.
10. A method according to claim 9 wherein applying a thermal spray
coating further comprises applying a twin wire arc bond coating to
the adhesion promotion layer prior to applying the high velocity
oxygen fuel spray coating to the twin wire arc bond coating.
11. A method of coating a composite material, the method
comprising: applying an adhesion promotion layer to the composite
material, wherein the adhesion promotion layer comprises a binder
paint and a plurality of irregularly shaped metal particles within
the binder paint; applying a twin wire arc bond coating to the
adhesion promotion layer; and applying a high velocity oxygen fuel
spray coating to the twin wire arc bond coating.
12. A method according to claim 11 further comprising producing the
irregularly shaped metal particles by water atomization.
13. A method according to claim 11 further comprising removing some
of the binder paint prior to applying the twin wire arc bond
coating so as to expose at least a portion of the metal
particles.
14. A method according to claim 11 wherein applying an adhesion
promotion layer comprises applying the adhesion promotion layer to
at least an edge of the composite material.
15. A coated composite structure comprising: a composite material;
an adhesion promotion layer on the composite material, wherein the
adhesion promotion layer comprises a binder paint and a plurality
of metal particles within the binder paint; and a thermal spray
coating on the adhesion promotion layer.
16. A coated composite structure according to claim 15 wherein the
plurality of metal particles comprise a plurality of irregularly
shaped metal particles.
17. A coated composite structure according to claim 15 wherein at
least some of the metal particles are exposed through the binder
paint so as to engage the thermal spray coating.
18. A coated composite structure according to claim 15 wherein the
composite material includes an edge, and wherein the adhesion
promotion layer is on the edge of the composite material.
19. A coated composite structure according to claim 15 wherein the
thermal spray coating comprises a high velocity oxygen fuel spray
coating.
20. A coated composite structure according to claim 19 wherein the
thermal spray coating further comprises a twin wire arc bond
coating on the adhesion promotion layer with the high velocity
oxygen fuel spray coating on the twin wire arc bond coating.
Description
TECHNOLOGICAL FILED
[0001] An example aspect of the present disclosure relates
generally to a method of coating a composite material and an
associated coated composite structure and, more particularly, a
method that incorporates a technique for promoting adhesion of a
thermal spray coating on a composite material as well as the
resulting coated composite structure.
BACKGROUND
[0002] Composite materials, such as carbon-fiber reinforced
composite materials, are utilized in a wide variety of applications
as a result of the weight savings provided by composite parts
relative to comparable metal components in combination with the
improved fatigue resistance, strength and corrosion resistance
relative to comparable metal components. For example, composite
materials are utilized by a variety of vehicles, including
aircraft, watercraft and the like, as well as buildings and other
structures, to name but a few applications.
[0003] Some applications that would otherwise utilize composite
materials require more wear resistance or surface protection, such
as erosion resistance, than conventionally provided by composite
materials. As such, metal foils have been bonded to the surface of
composite materials in order to provide improved wear resistance
and surface protection for the composite material. However, the
application of metal foils to composite materials may be somewhat
difficult and may consequently require substantial experience and
skill on the part of a technician in order to properly install the
metal foil. Additionally, in an instance in which the metal foil is
improperly applied, the composite material may have to be reworked,
thereby potentially incurring significant time and expense.
[0004] Some composite materials may be formed of a plurality of
layers, plies or laminates that are stacked upon one another and
bonded together to form an integral structure. In some instances,
edges of the plurality of layers are exposed along an edge of the
composite material. Once deployed and subjected to various forces,
the exposed edges of the plurality of layers of the composite
material may structurally deteriorate more quickly than other
portions of the composite material, thereby potentially limiting
the applications in which the composite material may be
deployed.
BRIEF SUMMARY
[0005] A method of coating a composite material and an associated
coated composite structure are therefore provided in accordance
with an example aspect with the coating being configured to provide
increased wear resistance and surface protection, such as erosion
resistance. In one aspect, the coating provides protection for the
edge of the composite structure, such as the edges of a plurality
of layers of the composite structure. As such, the resulting
composite structure may be utilized in a broad range of
applications including those that may require more wear resistance
or surface protection and/or those that may subject the edge of the
composite structure to forces that might otherwise cause the edges
of the layers of the composite structure to structurally
deteriorate.
[0006] In one aspect, a method of coating a composite material is
provided that includes applying an adhesion promotion layer to the
composite material. The adhesion promotion layer includes a binder
paint with a plurality of metal particles, such as steel particles,
within the binder paint. The plurality of metal particles may be
irregularly shaped. As such, the method of one aspect may also
include producing the irregularly shaped metal particles by water
atomization. The method also includes applying a thermal spray
coating to the adhesion promotion layer. In this regard, the
thermal spray coating may be applied by applying a high velocity
oxygen fuel spray coating. In one aspect, the thermal spray coating
may be applied by applying a twin wire arc bond coating to the
adhesion promotion layer prior to applying the high velocity oxygen
fuel spray coating to the twin wire arc bond coating.
[0007] The application of the adhesion promotion layer may include,
in one aspect, applying the adhesion promotion layer to at least
one edge of the composite material with the thermal spray coating
then being applied to the adhesion promotion layer on at least the
edge of the composite material. In this aspect, the edge of the
composite material may be processing prior to the application of
the adhesion promotion layer so as to have a rounded or beveled
profile. The method of one aspect may also include removing some of
the binder paint prior to applying the thermal spray coating so as
to expose at least a portion of the metal particles. The plurality
of metal particles of one aspect have a size between 5 .mu.m and 90
.mu.m.
[0008] In another aspect, a method of coating a composite material
is provided that includes applying an adhesion promotion layer to
the composite material including, for example, to at least an edge
of the composite material. The adhesion promotion layer includes a
binder paint and a plurality of irregularly shaped metal particles
within the binder paint. In one aspect, the method may also include
producing the irregularly shaped metal particles by water
atomization. The method also includes applying a twin wire arc bond
coating to the adhesion promotion layer and applying a high
velocity oxygen fuel spray coating to the twin wire arc bond
coating. In one aspect, the method may also include removing some
of the binder paint prior to applying the twin wire arc bond
coating so as to expose at least a portion of the metal
particles.
[0009] In a further aspect, a coated composite structure is
provided that includes a composite material, an adhesion promotion
layer on the composite material and a thermal spray coating on the
adhesion promotion layer. The adhesion promotion layer includes a
binder paint and a plurality of metal particles, such as steel
particles, within the binder paint. In this regard, the plurality
of metal particles may be irregularly shaped. At least some of the
metal particles may be exposed through the binder paint so as to
engage the thermal spray coating.
[0010] The thermal spray coating of one aspect may include a high
velocity oxygen fuel spray coating. In this aspect, the thermal
spray coating may also include a twin wire arc bond coating on the
adhesion promotion layer with a high velocity oxygen fuel spray
coating on the twin wire arch bond coating. The composite structure
of one aspect includes an edge and the adhesion promotion layer is
on at least the edge of the composite structure so as to provide
protection thereto.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] Having thus described aspects of the present disclosure in
general terms, reference will now be made to the accompanying
drawings, which are not necessarily drawn to scale, and
wherein:
[0012] FIG. 1 is a flowchart illustrating operations performed in
accordance with an example aspect of the present disclosure;
[0013] FIG. 2 is a cross-sectional view of a composite material
having an adhesion promotion layer applied thereto in accordance
with an example aspect of the present disclosure;
[0014] FIG. 3 is a cross-sectional view of a composite material and
an adhesion promotion layer following removal of at least some of
the binder paint in accordance with an example aspect of the
present disclosure;
[0015] FIG. 4 is a cross-sectional view of a composite material and
an adhesion promotion layer having a twin wire arc bond coating
applied thereto in accordance with an example aspect of the present
disclosure; and
[0016] FIG. 5 is a cross-sectional view of a composite material, an
adhesion promotion layer and a twin wire arc bond coating having a
high velocity oxygen fuel spray coating applied thereto in
accordance with an example aspect of the present disclosure.
DETAILED DESCRIPTION
[0017] The present disclosure now will be described more fully
hereinafter with reference to the accompanying drawings, in which
some, but not all aspects are shown. Indeed, the disclosure may be
embodied in many different forms and should not be construed as
limited to the aspects set forth herein; rather, these aspects are
provided so that this disclosure will satisfy applicable legal
requirements. Like numbers refer to like elements throughout.
[0018] A method is provided of coating a composite material to form
a coated composite structure, such as to provide increased wear
resistance and/or surface protection, e.g., erosion protection. In
one aspect, the edge of the composite material may be coated so as
to reduce structural degradation of the edge of the composite
structure following deployment. The composite structure may be
designed for a wide variety of different applications including
vehicular applications in which the coated composite structure
forms various parts of an aircraft, water craft, automobile or the
like. Alternatively, the coated composite structure may be designed
to be used in a building or other structure.
[0019] With respect to an aircraft, for example, the coated
composite structure may have improved erosion resistance and, as a
result, may form the leading edge of a wing or rotor or the forward
edge of a fuselage section. The coated composite structure may also
provide protection from electromagnetic effects (EMEs) so as to
consequently form portions of the wing, fuselage or other
aerodynamic surfaces. As a result of its improved wear resistance,
the coated composite structure may form an actuator. In other
aspects, the coated composite structure may serve as a thermal
barrier by providing heat protection so as to foam a heat shield,
may serve as a durable surface for parts such as a high speed
leading edge for aircraft designed to travel at Mach 1.5 or an
engine nacelle, may serve as a gas diffusion barrier so as to form
a hydrogen storage tank, may serve as a liquid barrier so as to
replace fuel tank paint for jet fuel storage applications and/or
may provide anti-skid properties so as to form a stow bin torque
tube cover.
[0020] Regardless of the intended application, the composite
material of one aspect may include a plurality of layers, laminates
or plies stacked one upon another and bonded to form an integral
structure. The composite material may therefore include a major
surface formed by an outermost composite layer and an edge portion
at which the edges of a plurality of composite layers, plies or
laminates are exposed. The composite material may be formed of a
variety of composite materials. In one aspect, however, each
composite layer is formed of a plurality of carbon fibers disposed
within a resin or matrix material, such as a plastic material.
[0021] In order to provide wear resistance and/or surface
protection for the composite material 20, a thermal spray coating
may be applied on the composite material. In one aspect, the
thermal spray coating is applied not only on the major surface, but
also on the edge of the composite, such as the exposed edges of the
layers of the composite material. However, in some instances, the
thermal spray coating may not readily adhere directly to the
composite material. As such, an adhesion promotion layer 22 may be
applied to the composite material with the thermal spray coating
then applied to the adhesion promotion layer to facilitate reliable
adhesion of the thermal spray coating to the adhesion promotion
layer and, in turn, to the composite material.
[0022] As shown in block 10 of FIG. 1 and also in FIG. 2, an
adhesion promotion layer 22 is initially applied to the composite
material 20 and, in one aspect, to both the edge 20a of the
composite material and a major surface of the composite material,
such as by spraying. In order to facilitate adhesion of the
adhesion promotion layer to the composite material, the surface of
the composite material, including the major surface and/or the edge
surface of the composite material, may be roughened, such as by
being sanded or grit blasted, and then wiped with a cloth that
carries a solvent. Additionally, in an instance in which the edge
initially has sharp corners that could serve to concentrate stress,
the edge may be processed so as to cause the edge to have a rounded
or beveled profile. For example, the edge may be processed by
sanding, routing or other mechanical material processing
techniques. Thereafter, the adhesion promotion layer may be applied
to the composite material including, in one aspect, to an edge of
the composite material.
[0023] The adhesion promotion layer 22 may include a binder paint
24 and a plurality of metal particles 26 within the binder paint.
The binder paint may be an organic binder, a spray applied
adhesive, a sealant or the like. In one aspect, the binder paint
may be a polyurethane paint having a base component, an activator
and a hardener. While the binder paint may have various
formulations, the binder paint of one embodiment includes PPG
RW-7042-94A, CA9000B and CA9000C, as the base component, the
activator and the hardener, respectively; all of which are
available from PPG Industries. In an aspect in which the binder
paint is formed of a polyurethane base paint, the polyurethane base
paint may not include pigments so as to improve its capability for
holding the metal particles. For example, PPG RW-7042-94A is a base
component from which the pigments have been removed. The mix ratio
by volume of the binder paint 24 to the metal particles 26 and,
more particularly, the mix ratio of the base, activator, hardener
and metal particles may be varied, but, in one aspect, the mix
ratio by volume of the base, activator, hardener and metal
particles range from about 4:4:1:1.6 to about 4:4:1:2.8. The binder
paint of one aspect has a service temperature range with an upper
end temperature that is sufficiently high so as to withstand the
transient high temperatures to which the binder paint may be
subjected during a thermal spray process. In one aspect, for
example, the binder paint service temperature ranges from about
-65.degree. F. to about +350.degree. F.
[0024] Instead of spherical particles which may not provide
sufficient adhesion for the thermal spray coating or metal flakes
that may lie flat and may protrude little, if any, from the binder
paint 24, the metal particles 26 advantageously have an irregular
shape so as to facilitate subsequent adhesion with the thermal
spray coating. In one aspect, the method may also include producing
the irregularly shaped metal particles by water atomization.
Although the metal particles may be formed of various materials,
the metal particles of one aspect are formed of steel, such as
stainless steel and, more particularly, water atomized 316
stainless steel particles.
[0025] The adhesion promotion layer 22 may be of various
thicknesses and the metal particles 26 may have various sizes. In
one aspect, for example, the metal particles have a size ranging
from about 5 .mu.m to about 90 .mu.m and, more particularly,
ranging from about 20 .mu.m to about 53 .mu.m. In this aspect, the
adhesion promotion layer may have a thickness ranging from about 25
.mu.m to about 50 .mu.m. As described below, the adhesion promotion
layer may be roughened, such as by sanding and/or grit blasting,
the metal particles may have a smaller size, that is, smaller than
about 20 .mu.m, and the adhesion promotion layer may have a
thickness ranging from about 40 .mu.m to about 60 .mu.m, such as
about 50 .mu.m. As such, at least some of the metal particles of
one aspect may be larger in size than the thickness of the adhesion
promotion layer to ensure that at least some of the metal particles
protrude beyond the adhesion promotion layer in order to facilitate
engagement with the thermal spray coating.
[0026] Although a single coat of the adhesion promotion layer 22
may be applied to the composite material 20, a plurality of coats
of the binder paint 24 with the plurality of metal particles 26,
such as a two or three coats of the binder paint with a plurality
of metal particles, may be applied in some aspects in order to form
the adhesion promotion layer. Following application, the adhesion
promotion layer may be cured. While the adhesion promotion layer
may be cured in various manners, the adhesion promotion layer of
one aspect is cured by placement of the composite material
including the adhesion promotion layer in an oven at an elevated
temperature for at least a minimum length of time, such as
placement in an oven maintained at temperature of between
100.degree. F. and 200.degree. F., such as about 160.degree. F.,
for a time of between 1 hour and 4 hours, such as for two
hours.
[0027] The thermal spray coating may then be applied to the
adhesion promotion layer 22. In order to facilitate adherence of
the thermal spray coating to the adhesion promotion layer, at least
some of the binder paint 24 may be removed prior to applying the
thermal spray coating so as to expose (including further exposure
of) as least some of the metal particles 26. See FIG. 3. At least
some of the binder paint may be removed in various manners
including sanding of the surface of the adhesion promotion layer,
thereby sanding the surface of the binder paint. Thereafter, the
sanded surface of the adhesion promotion layer may be wiped with a
cloth that carries a solvent, such as acetone or isopropyl alcohol.
In one aspect, the resulting surface of the adhesion promotion
layer may then be roughened, such as by grit blasting the surface
at a relatively low pressure, such as ranging between about 20 psi
and about 40 psi, and at a relatively high angle, such as ranging
between about 30.degree. and about 60.degree.. The resulting grit
residue may then be removed, such as by subjecting the surface to a
blast of compressed air.
[0028] Thereafter, the thermal spray coating may be applied to the
adhesion promotion layer 22. In one aspect, the thermal spray
coating is applied to that portion of the adhesion promotion layer
that covers a major surface of the composite material 20 and/or to
that portion of the adhesion promotion layer that covers an edge
20a of the composite material. As such, the thermal spray coating
may be applied to the major surface of the composite material
and/or to the edge portions of the plurality of layers that
comprise the composite material. In one aspect, the thermal spray
coating includes a single coating, such as a twin wire arc coating
or an air plasma coating. In this aspect, the single coating is
configured to provide the desired functionality. For example, the
single coating may be formed of or otherwise include a metal, such
as copper, such that the resulting copper provides protection from
electromagnetic effects (EME's), such as protection from lightning
strikes.
[0029] As described below, however, the thermal spray coating of
other aspects may be comprised of a plurality of coatings, such as
two or more coatings. In this regard, the thermal spray coating may
include a relatively thick functional coating to provide the
desired wear resistance and/or surface protection, such as erosion
protection, as well as an intermediate coating between the adhesion
promotion layer 22 and the thicker functional coating to further
facilitate the adherence of the thicker functional coating to the
adhesion promotion layer and, in turn, to the underlying composite
material 20.
[0030] In the illustrated aspect, the thermal spray coating may
include first coating 28 that facilitates the adherence of a second
functional coating 30, different than the first coating, to the
adhesion promotion layer 22. See block 12 of FIG. 1 as well as FIG.
4. Although the first coating will be described hereinafter by way
of example as a twin wire arc bond coating that is applied to the
adhesion promotion layer, the first coating may be another type of
thermal spray coating, such as an air plasma coating, such that
subsequent reference to a twin wire arc bond coating is by way of
example, but not of limitation. For example, the twin wire arc bond
coating may be applied to the adhesion promotion layer that covers
the major surface of the composite material 20 and, in one aspect,
also to the adhesion promotion layer that covers the edge 20a of
the composite material. The twin wire arc bond coating may be
applied at a relatively low deposition rate such that the resulting
twin wire arc bond coating has a relatively low residual stress
which facilitates the adherence of the twin wire arc bond coating
to the adhesion promotion layer and reduces any tendency for the
twin wire arc bond coating to peel away from the adhesion promotion
layer, particularly at the edges of the twin wire arc bond coating.
The twin wire arc bond coating may be rough so as to facilitate the
subsequent adhesion of the thicker functional coating to the twin
wire arc bond coating. Further, the twin wire arc bond coating is
generally thinner than the subsequent functional layer, but should
be sufficiently thick so as to withstand the heat incurred during
the application of the subsequent functional layer and, in one
aspect, may have a thickness ranging from about 50 .mu.m to about
150 .mu.m. The twin wire arc bond coating may be formed of a
variety of materials, but, in one aspect, may be formed of metals
including, but not limited to, Ni, Al, NiAl, e.g., the combination
of 95% Ni and 5% Al, NiCr, Inconel.RTM. alloy 625, nickel alloy
718, Fe, Co, Mo, Cr, Ti, Ta, Cu, Zn, Sn, Ag, Au, Pt and alloys
thereof. Oxides, such as Al.sub.2O.sub.3, TiO.sub.2, CrO.sub.3 or
the like; carbides, such as CrC, WC, TiC or the like; and/or
silicides, such as TiSi.sub.2, SiC, MoSi.sub.2 or the like could
alternatively be incorporated using a cored wire process. Among
other functions, the twin wire arc bond coating may provide thermal
protection to the composite material during the subsequent
application of the functional layer so as to permit higher thermal
spray temperatures during the application of the functional layer
without material degradation, such as without damaging the
composite material.
[0031] Thereafter, a second coating 30 that may serve as a
functional layer to provide the desired wear resistance and/or
surface protection may be formed upon the twin wire arc bond
coating 28 including that portion of the twin wire arc bond coating
that covers the major surface of the composite material 20 and/or
the edge 20a of the composite material. Although the second coating
will be described hereinafter by way of example as a high velocity
oxygen fuel spray coating that is applied to the twin wire arc bond
coating, the second coating may be another type of thermal spray
coating, different than the first coating, that provides the
desired functionality, such as wear resistance, erosion protection
or the like, such as a plasma applied coating, a cold sprayed
coating or the like. As such, subsequent reference to a high
velocity oxygen fuel spray coating is by way of example, but not of
limitation.
[0032] In one example, the functional layer may be a high velocity
oxygen fuel spray coating 30 that is applied to, e.g., deposited
upon, and that adheres to the twin wire arc bond coating 28. See
block 14 of FIG. 1 as well as FIG. 5. In order to facilitate the
adherence of the high velocity oxygen fuel spray coating to the
twin wire arc bond coating, the surface of the twin wire arc bond
coating may be prepared prior to the application of the high
velocity oxygen fuel spray coating. In one aspect, the surface of
the twin wire arc bond coating may be sanded so as to increase the
planarity of the surface of the twin wire arc bond coating, such as
by reducing the high spots, such that the surface of the twin wire
arc bond coating varies in height by no more than a predetermined
amount, such as no more than about 1,000 .mu.in. Following the
sanding, the surface of the twin wire arc bond coating may be wiped
with a cloth that carries a solvent. In one aspect, the surface of
the twin wire arc bond coating, including, for example, the surface
of the twin wire arc bond coating on the edge 20a of the composite
material, may then be roughened to facilitate the adherence of the
high velocity oxygen fuel spray coating thereto. The surface of the
twin wire arc bond coating may be roughened, for example, by grit
blasting the surface of the twin wire arc bond coating, such as at
a relatively low pressure ranging, for example, from about 20 psi
to about 40 psi and at a relatively high angle ranging, for
example, from about 30.degree. to about 60.degree.. Thereafter, the
grit residue may be removed, such as by blasting the surface of the
twin wire arc bond coating with compressed air.
[0033] Once the surface of the twin wire arc bond coating 28 has
been prepared, the high velocity oxygen fuel spray coating 30 may
be applied, as shown in block 14 of FIG. 1. The high velocity
oxygen fuel spray coating may be thicker than the twin wire arc
bond coating and, in one aspect, may have a thickness ranging from
about 150 82 m to about 400 .mu.m. Additionally, the high velocity
oxygen fuel spray coating may be denser than the twin wire arc bond
coating so as to provide the desired wear resistance and/or surface
protection. During the application of the high velocity action fuel
spray coating, the temperature of the composite material and the
coatings thereon, such as the adhesion promotion layer, is
generally maintained at a temperature of no more than a predefined
threshold temperature, such as at a temperature of no more than
130.degree. F. as measured from the backside of the composite
material, such as the side of the composite material opposite the
major surface that is being coated.
[0034] The high velocity oxygen fuel spray coating 30 may be formed
of various materials including various metals, such as, for
example, Ni, Al, NiAl, NiCr or an austenitic nickel-base
superalloy, such as Ni 625, e.g., INCONEL.RTM. alloy 625,
consisting of 61.0% nickel, 21.5% chromium, 9.0% molybdenum, 3.6%
niobium and 2.5% iron; oxides, such as Al.sub.2O.sub.3, TiO.sub.2,
CrO.sub.3 or the like; carbides, such as CrC, WC, TiC or the like;
and/or silicides, such as TiSi.sub.2, SiC, MoSi.sub.2 or the like.
The high velocity oxygen fuel coating generally includes a
plurality of metal particles, such as nickel alloy 625 particles,
that are fed to a high velocity oxygen fuel gun that directs the
metal particles to the surface to be coated while melting the metal
particles. In one aspect, the size of the metal particles may range
from, for example, about 5 .mu.m to about 90 .mu.m. In order to
increase the number of metal particles that are melted prior to
contact with the twin wire arc bond coating 28, the metal particles
may have a smaller size distribution ranging from, for example,
about 20 .mu.m to about 45 .mu.m.
[0035] A variety of different types of high velocity oxygen fuel
guns may be utilized in order to apply the high velocity oxygen
fuel coating 30 including a high velocity oxygen fuel gun that
utilizes fuel, e.g., kerosene or hydrogen fuel. In addition, while
the metal particles may be fed to the high velocity oxygen fuel gun
in a radial manner, the metal particles of one aspect may be fed to
the high velocity oxygen fuel gun in an axial manner. Regardless,
the high velocity of such a high velocity oxygen fuel gun is
established by the jet velocity at the exit of the barrel of the
high velocity oxygen fuel gun being generally greater than the
speed of sound and typically exceeding 1000 m/s prior to the
introduction of the metal particles. In one aspect, the composite
material 20 may be cooled during the application of the high
velocity oxygen fuel coating, such as by liquid nitrogen or liquid
carbon dioxide, so as to avoid or reduce material degradation
attributable to elevated temperatures.
[0036] In one aspect, the surface of the high velocity oxygen fuel
coating 30 may also be finished following its application. For
example, the surface of the high velocity oxygen fuel coating of
one aspect may be processed, such as by being sanded and/or ground,
so as to flatten the surface of the high velocity oxygen fuel
coating. In one aspect, the surface of the high velocity oxygen
fuel coating may be sanded or ground in a progressive manner with
decreasing grit sizes, such as beginning with a relatively low grit
paper, such as an 80 grit paper, and moving progressively to
smaller grit sizes. In order to avoid localized heating during the
sanding or grinding process, a wet sanding of the surface of the
high velocity oxygen fuel coating may be employed so as to avoid
any softening or warping of localized portions of the high velocity
oxygen fuel coating that may occur in instances in which the
sanding or grinding belt contacts only a few high spots of the high
velocity oxygen fuel coating and causes localized heat build-up.
Although the surface of the high velocity oxygen fuel coating may
be finished to within various tolerances, the surface of the high
velocity oxygen fuel coating of one aspect may be finished such
that the average surface roughness Ra is within a predefined range,
such as by having an average surface roughness Ra that ranges from
about 8 .mu.in to about 24 .mu.in.
[0037] In one aspect, the surface of the high velocity oxygen fuel
coating 30 may thereafter be sealed. Additionally or alternatively,
the surface of the high velocity oxygen fuel coating may optionally
be surface treated and/or painted.
[0038] By coating the composite material 20 with a thermal spray
coating, such as the high velocity oxygen fuel coating 30, the
resulting coated composite structure may have a relatively high
hardness and low porosity so as to provide increased wear
resistance and surface protection, such as erosion resistance,
thereby permitting the resulting coated composite structure to be
utilized in a broad range of applications. The thermal spray
coating of one aspect may also advantageously provide EME
protection for a resulting coated composite structure. In one
aspect in which the edge 20a of the composite material is also
coated, such as with a metal, including the edges of the layers
that comprise the composite material, the edge of the composite
material is no longer exposed and, as such, is protected from
structural degradation by the thermal spray coating.
[0039] Many modifications and other aspects of the disclosure set
forth herein will come to mind to one skilled in the art to which
this disclosure pertains having the benefit of the teachings
presented in the foregoing descriptions and the associated
drawings. For example, the first and second coatings may be formed
of other types of thermal spray coatings if so desired. Therefore,
it is to be understood that the disclosure is not to be limited to
the specific aspects disclosed and that modifications and other
aspects are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
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