U.S. patent application number 10/151222 was filed with the patent office on 2003-03-27 for highly durable and abrasion resistant composite diamond-like carbon decorative coatings with controllable color for metal substrates.
Invention is credited to Kimock, Fred Michael, Petrmichl, Rudolph Hugo, Rogers, Joseph J., Sydlo, Joseph David, Zeeman, Victor Michael JR..
Application Number | 20030060302 10/151222 |
Document ID | / |
Family ID | 22933002 |
Filed Date | 2003-03-27 |
United States Patent
Application |
20030060302 |
Kind Code |
A1 |
Rogers, Joseph J. ; et
al. |
March 27, 2003 |
Highly durable and abrasion resistant composite diamond-like carbon
decorative coatings with controllable color for metal
substrates
Abstract
Detailed are highly durable and abrasion-resistant composite
diamond-like carbon (DLC) coatings with controllable color ideally,
but not exclusively, suitable as decorative coatings for metal
substrates, for example. The composite DLC coatings typically
include at least a layer of Si-DLC which comprises the elements C,
H, and Si, and color choices include light yellow, bronze,
copper-gold, burgundy, bluish-black, and black.
Inventors: |
Rogers, Joseph J.;
(Hatfield, PA) ; Petrmichl, Rudolph Hugo; (Center
Valley, PA) ; Kimock, Fred Michael; (Macungie,
PA) ; Zeeman, Victor Michael JR.; (Bangor, PA)
; Sydlo, Joseph David; (Whitehall, PA) |
Correspondence
Address: |
JOHN S. PRATT, ESQ
KILPATRICK STOCKTON, LLP
1100 PEACHTREE STREET
SUITE 2800
ATLANTA
GA
30309
US
|
Family ID: |
22933002 |
Appl. No.: |
10/151222 |
Filed: |
May 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10151222 |
May 20, 2002 |
|
|
|
09246976 |
Feb 9, 1999 |
|
|
|
60074297 |
Feb 11, 1998 |
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Current U.S.
Class: |
473/282 |
Current CPC
Class: |
C23C 16/458 20130101;
A63B 2209/02 20130101; C23C 16/30 20130101; A63B 60/00 20151001;
A63B 53/04 20130101; A63B 53/0487 20130101; C23C 16/509 20130101;
A63B 53/12 20130101; A63B 53/0416 20200801; A63B 60/004 20200801;
C23C 16/006 20130101 |
Class at
Publication: |
473/282 |
International
Class: |
A63B 053/00 |
Claims
What is claimed is:
1. An abrasion-resistant coated product comprising an electrically
conductive substrate coated on at least one surface with a
composite diamond-like carbon decorative coating, said decorative
coating comprising at least a first layer of Si-doped diamond-like
carbon containing the elements C, H and Si, using ion-assisted
plasma deposition and using carbon-containing and
silicon-containing precursor gases selected from the group
consisting of hydrocarbon, silane, organosilane, organosilazane and
organo-oxysilicon compounds, and mixtures thereof, the resulting
abrasion-resistant decorative coating having the properties of a
Nanoindentation hardness in the range of about 5 to about 35 GPa
and a thickness in the range of about 1 to about 25
micrometers.
2. The product of claim 1 wherein said color exhibits reflected
light chromaticity coordinate values (x,y) values for x of about
0.25 to about 0.50, and for y of about 0.25 to about 0.45, as
measured with CIE 1931 source C standard illuminant and CIE 1931
2-degree standard observer.
3. The product of claim 2 wherein the color of said decorative
coating is selected from the group consisting of light yellow,
bronze, copper-gold, burgundy, bluish-black, and black.
4. The product of claim 1 wherein said decorative coating also
contains the elements selected from the group of N and O.
5. The product of claim 1 wherein said decorative coating comprises
at least a second layer of diamond-like carbon containing the
elements C and H deposited using ion-assisted plasma deposition
using a hydrocarbon gas.
6. The product of claim 5 wherein said second layer also contains
the element N.
7. The product of claim 1 wherein said substrate is the shaft of a
golf club.
8. The product of claim 1 wherein said substrate the head of a golf
club.
9. The product of claim 8 wherein said golf club is a putter.
10. The product of claim 8 wherein said golf club is a driver.
11. The product of claim 8 wherein said golf club is a wedge.
12. The product of claim 8 wherein said golf club is an iron.
13. An abrasion-resistant coated product comprising the shaft of a
golf club coated on at least a portion of the outer surface with a
composite diamond-like carbon decorative coating, said decorative
coating comprising at least one layer of Si-doped
diamond-like-carbon containing the elements C, H and Si, using
ion-assisted plasma deposition and having the properties of
Nanoindentation hardness in the range of about 5 to about 35 GPa
and thickness in the range of about 1 to about 25 micrometers.
14. The product of claim 13 wherein the color of said decorative
coating is black.
15. An abrasion-resistant coated product comprising the head of a
golf club coated on at least a portion of the outer surface with a
composite diamond-like carbon decorative coating, said decorative
coating comprising at least one layer of Si-doped diamond-like
carbon containing the elements C, H and Si, using ion-assisted
plasma deposition and having the properties of Nanoindentation
hardness in the range of about 5 to about 35 GPa, modulus in the
range of approximately 50 GPa to approximately 300 GPa, and
thickness in the range of about 1 to about 25 micrometers.
16. The product of claim 15 wherein the color of said decorative
coating is black.
17. The product of claim 15 wherein said golf club is a putter.
18. The product of claim 15 wherein said golf club is a driver.
19. The product of claim 15 wherein said golf club is a wedge.
20. The product of claim 15 wherein said golf club is an iron.
21. The product of claim 1 wherein said substrate is selected from
the group consisting of brass hardware, brass fixtures, jewelry,
medical instruments, dental instruments, writing instruments,
musical instruments, eyeglass frames, cigar lighters, cigarette
lighters, automobile ornaments, cycling equipment, fishing
equipment and hunting equipment.
22. The product of claim 1 wherein said hydrocarbon compound is
selected from the group consisting of methane, butane, acetylene,
cyclohexane and mixtures thereof.
23. The product of claim 1 wherein said silane compound is selected
from the group consisting of silane, disilane, diethylsilane,
tetramethylsilane and mixtures thereof.
24. The product of claim 1 wherein said organosilazane compound is
selected from the group consisting of hexamethyldisilazane,
tetramethyldisilazane and mixtures thereof.
25. The product of claim 1 wherein said organo-oxysilicon compound
is selected from the group consisting of hexamethyldisiloxane,
tetramethyldisiloxane, ethoxytrimethylsilane,
octamethycyclotetrasiloxane- , and mixtures thereof.
26. The product of claim 5 wherein said hydrocarbon is selected
from the group consisting of methane, butane, acetylene,
cyclohexane and mixtures thereof.
27. The product of claim 1 wherein said precursor gases consist of
a mixture of tetramethylsilane and cyclohexane.
28. The product of claim 1 wherein said precursor gases consist of
a mixture of hexamethyldisilazane and cyclohexane.
29. A method for producing an abrasion resistant decorative coating
on at least one surface of an electrically conductive substrate by:
ion-assisted plasma depositing from carbon-containing and
silicon-containing precursor gases a composite diamond-like carbon
decorative coating, said decorative coating comprising at least one
layer of Si-doped diamond-like carbon containing the elements C, H
and Si; said precursor gases selected from the group consisting of
hydrocarbon, silane, organosilane, organosilazane and
organo-oxysilicon compounds, and mixtures thereof; using a
substrate bias voltage in the range of about -100 Volts to about
-1000 Volts; recovering a product coated with said abrasion
resistant decorative coating having the properties of a
Nanoindentation hardness in the range of about 5 to about 35 GPa
and a thickness in the range of about 1 to about 25
micrometers.
30. The product of claim 29 wherein said colors exhibit reflected
light chromaticity coordinate values (x, y) values for x of about
0.25 to about 0.50, and for y of about 0.25 to about 0.45, as
measured with CIE 1931 source C standard illuminant and CIE 1931
2-degree standard observer.
31. The product of claim 29 wherein said colors also exhibit
reflected light chromaticity values (Y) of about 5 to about 50.
32. The method of claim 29 wherein the color of said decorative
coating is selected from the group consisting of light yellow,
bronze, copper-gold, burgundy, bluish-black, and black.
33. The method of claim 29 in wherein the ion-assisted plasma is a
capacitively-coupled RF plasma.
34. The method of claim 29 wherein the ion-assisted plasma is a DC
plasma.
35. The method of claim 29 wherein an ion beam source is used to
generate the ion-assisted plasma.
36. A method for producing an abrasion resistant decorative coating
on at least one surface of an electrically conductive substrate by
ion-assisted sputter depositing a composite diamond-like carbon
decorative coating, said decorative coating comprising at least one
layer of Si-doped diamond-like carbon containing the elements C, H
and Si, said coating having the properties of a Nanoindentation
hardness in the range of about 5 to about 35 GPa and a thickness in
the range of about 1 to about 25 micrometers.
37. The product of claim 36 wherein said colors exhibit reflected
light chromaticity coordinate values (x, y) values for x of about
0.25 to about 0.50, and for y of about 0.25 to about 0.45, as
measured with CIE 1931 source C standard illuminant and CIE 1931
2-degree standard observer.
38. The product of claim 22 wherein said colors also exhibit
reflected light chromaticity values (Y) of about 5 to about 50.
39. The method of claim 22 wherein the color of said decorative
coating is selected from the group consisting of light yellow,
bronze, copper-gold, burgundy, bluish-black, and black.
Description
[0001] This application is based on provisional application Serial
No. 60/074,297, filed on Feb. 11, 1998.
FIELD OF THE INVENTION
[0002] This invention relates generally to highly durable and
abrasion-resistant decorative coatings. More particularly, the
invention relates to a process for depositing a highly durable and
abrasion-resistant composite diamond-like carbon coating with
controllable color. The invention is particularly suited for
applications as a highly durable decorative coating on electrically
conducting substrates which are subjected to high wear environments
including architectural hardware and fixtures made of brass and
other metals, jewelry, medical and dental instruments, writing
instruments such as pens and pencils, musical instruments, eyeglass
frames, cigar and cigarette lighters, automobile hood ornaments and
other components, sporting equipment and other products for leisure
activities such as golf club shafts, golf club heads, cycling
equipment, and fishing and hunting equipment, and other similar
substrates.
BACKGROUND OF THE INVENTION
[0003] There have been many attempts to provide cosmetically
attractive protective coatings onto sporting equipment such as golf
club shafts, golf club heads, cycling equipment, fishing and
hunting equipment, and other hardware. A wide variety of metal
substrate materials are used in these applications, including
steels, stainless steels, aluminum, zinc, brass, titanium, and
specialty alloys such as aluminum alloys, titanium alloys,
magnesium alloys, zinc alloys, and copper alloys. Coatings can
improve the cosmetic appearance of these substrate materials, since
many naturally have a dull finish or drab color. In addition, most
of these substrate materials quickly develop a dull appearance due
surface oxidation or corrosion resulting from exposure to
environmental conditions such as high temperature, humidity, salt,
and acid rain. Therefore, decorative protective coatings are often
applied to these substrates to improve their cosmetic appearance,
and environmental durability.
[0004] Typically, the cosmetic appearance of these coatings falls
into four categories: (i) metal or ceramic coatings with a shiny,
metallic appearance, (ii) ceramic coatings with a white color
appearance, (iii) metal oxide or ceramic coatings with a black
color appearance, and (iv) paints, Which can be of any color.
[0005] Decorative metallic protective coatings with a shiny
cosmetic appearance include chrome and nickel. Titanium nitride is
a ceramic coating which can have the appearance of brass or gold,
depending on the nitrogen content in the material.
[0006] For example, Buettner, U.S. Pat. No. 5,531,444 describes a
golf club head coated with a hard coating of titanium nitride
having a lustrous gold appearance. The titanium nitride coating is
applied at a relatively high substrate temperature in the range of
650.degree. F. to 950.degree. F. (340.degree. C. to 510.degree.
C.), which limits the types of golf head materials which can be
coated to high softening point steels and other hard metals.
Because of this requirement of high substrate temperature to
achieve the desired properties of the coating, substrates which
contain plastic or composite components, such as plastic putter
inserts, cannot be coated.
[0007] Decorative and protective ceramic coatings with a white
color appearance such as aluminum oxide, zirconium oxide, and other
ceramic glazings are also known. These coatings are normally made
from fine powders which are applied to the surface of components,
and then fired to final form. High substrate temperatures are
required to produce a durable finish, and these materials are
brittle and prone to cracking and flaking when the substrate is
subjected to flexure or high impact conditions.
[0008] Decorative and protective metal oxide or ceramic coatings
with a black color appearance such as black chrome oxide and black
aluminum oxide are also known. These coatings typically display a
low-gloss black finish, which has low luster. In addition, these
coatings are easily scratched by abrasives and exhibit
corrosion-resistance which is less than desired.
[0009] Finally, while decorative and protective paints, which can
be of any color, are widely known, such decorative and protective
materials have extremely poor resistance to scratches and abrasion,
and are subject to chipping and cracking when the substrate is
subjected to flexure or high impact conditions.
[0010] Therefore, it is apparent that all of the prior art methods
for producing decorative coatings on metal substrates suffer from
one or more of the following problems:
[0011] (1) insufficient durability and resistance to scratches and
abrasion,
[0012] (2) inadequate resistance to corrosion by environmental
conditions,
[0013] (3) limited choice of appearance color,
[0014] (4) lack of a high luster finish,
[0015] (5) excessively high substrate temperature during
application, and
[0016] (6) inadequate adhesion to the substrate, evidenced by
cracking, flaking or peeling, when subjected to flexure or high
impact conditions.
[0017] The application of coating materials to the surface of
articles to enhance other performance characteristics is also well
known. For example, Kim, U.S. Pat. No. 4,951,953 describes a golf
club coated with a material having a high Young's modulus, or with
a composite material having a high Young's modulus material as a
substantial ingredient in the matrix. The coating may have a
thickness in the range of about 1 to 10 mils (25 microns to 250
microns). The materials of choice have a Young's modulus of 50
million pounds per square inch (psi) or greater, and include
silicon nitride, aluminum oxide, silicon carbide and diamond.
SUMMARY OF THE INVENTION
[0018] The invention provides products having a highly durable and
abrasion-resistant composite diamond-like carbon coating with
controllable color which is ideally suitable as a decorative
coating on metal substrates. The invention also provides the
process for depositing a highly adherent, highly abrasion resistant
diamond-like carbon decorative coating to electrically conductive
substrates. The products of the present invention include sporting
equipment such as shafts and heads of golf clubs (drivers, putters,
irons), cycling equipment, fishing and hunting equipment and other
leisure activity products. The products of the present invention
also include architectural hardware and fixtures made of brass and
other metals, jewelry, medical and dental instruments, writing
instruments such as pens and pencils, musical instruments, eyeglass
frames, cigar and cigarette lighters, automobile hood ornaments and
other components, and other similar metal substrates.
[0019] The composite diamond-like carbon coating structure consists
of at least a first layer of Si-doped diamond-like carbon which is
comprised of the elements C, H, Si and possibly O and N. An
additional coating comprised of layers of Si-doped diamond-like
carbon and diamond-like carbon may be applied over top of the first
Si-doped diamond-like carbon layer. The optional additional layers
of Si-doped diamond-like carbon are also comprised of the elements
C, H, Si and possibly O and N. The optional additional layers of
diamond-like carbon are comprised of the elements C, H and possibly
N.
[0020] The decorative and abrasion-resistant composite diamond-like
carbon coating is deposited by ion-assisted plasma deposition
including capacitive radio frequency plasma and ion-beam
deposition, from carbon-containing and silicon-containing precursor
gases consisting of hydrocarbon, silane, organosilane,
organosilazane and organo-oxysilicon compounds, or mixtures
thereof. The resulting decorative coating has the properties of
Nanoindentation hardness in the range of approximately 5 to 35 GPa,
modulus in the range of approximately 50 to 300 GPa, and thickness
in the range of approximately 1 to 25 micrometers. The colors of
the coating unexpectedly can be varied continuously along the
spectrum of: light yellow to bronze to copper-gold to burgundy to
bluish-black to black. The color range of these coatings is
characterized by reflected light chromaticity coordinate values (x,
y) in the range of approximately 0.25 to 0.50 for x, and in the
range of approximately 0.25 to 0.45 for y as measured with
Commission International de l'Eclairage ("CIE") 1931 source C
standard illuminant and CIE 1931 2-degree standard observer. The
preferred mode of ion-assisted plasma deposition of the decorative
and abrasion-resistant diamond-like carbon coating is
capacitively-coupled radio frequency (RF) plasma deposition.
Optimum performance is obtained when the coating layer thickness is
in the range of approximately 2 micrometers to approximately 10
micrometers.
[0021] The elemental composition, refractive index and thickness of
the composite diamond-like carbon coating are chosen to produce the
desired reflected optical color. The deposition process parameters
such as precursor gas composition, plasma power, pressure, and
substrate bias voltage are adjusted to produce coatings with
different elemental composition and refractive indexes, which
change the reflected optical color, and hardness and elastic
modulus, which effect the abrasion resistance and durability of the
coating.
BRIEF DESCRIPTION OF THE DRAWING
[0022] Further features and advantages will become apparent from
the following and more particular description of the preferred
embodiment of the invention, as illustrated in the accompanying
drawing in which:
[0023] FIG. 1 is a diagrammatic view, partially in cross-section,
of an illustrative capacitively-coupled radio frequency plasma
deposition apparatus used to manufacture coated articles of the
present invention.
[0024] FIG. 2 is a diagrammic view, partially in cross-section of
an illustrative plasma ion beam deposition apparatus used to
manufacture coated articles of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention substantially reduces or eliminates
the disadvantages and shortcomings associated with the prior art
techniques by providing for the deposition of a highly durable and
abrasion-resistant composite diamond-like carbon decorative coating
with controllable color which is ideal for metal and other
electrically conductive substrates including architectural hardware
and fixtures made of brass and other metals, jewelry, medical and
dental instruments, writing instruments such as pens and pencils,
musical instruments, eyeglass frames, cigar and cigarette lighters,
automobile hood ornaments and other components, sporting equipment
and other products for leisure activities such as golf club shafts,
golf club heads, cycling equipment, and fishing and hunting
equipment, and other similar metal substrates.
[0026] The mechanical and optical properties of the composite
diamond-like carbon coatings of the present invention can be varied
over a very wide continuous range, and thus the coatings can be
tailored to the needs of many diverse applications.
[0027] The composite diamond-like carbon decorative coatings of the
present invention have the following remarkable performance
characteristics compared to prior art techniques:
[0028] (1) high durability, capable of protecting the substrate
from scratches and abrasion,
[0029] (2) resistance to corrosion by environmental conditions such
as humidity, salt, and acid rain,
[0030] (3) high adhesion to the substrate such that cracking or
flaking does not occur when the substrate is subjected to flexure
or high impact conditions,
[0031] (4) can be made with a variety of attractive colors,
[0032] (5) can be made with high luster, or a low-luster finish if
desired,
[0033] (6) can be applied at low substrate temperature, and
[0034] (7) are amorphous and without the drawbacks of grain
boundaries found in polycrystalline materials.
[0035] It has also been surprisingly discovered that the coatings
of the present invention have a unique ability to hide
fingerprints, when applied over substrates with a variety of
surface finishes.
[0036] For the purposes of the present invention, the term
diamond-like carbon (DLC) is meant to include amorphous materials
composed of carbon, or carbon and hydrogen, whose properties
resemble, but do not duplicate, those of diamond. Some of these
properties are high hardness (HV=about 10 GPa to about 80 GPa), low
friction coefficient (approximately less than 0.2), some
transparency across the majority of the electromagnetic spectrum,
and chemical inertness. At least some of the carbon atoms in DLC
materials are bonded in chemical structures similar to that of
diamond, but without long range crystal order. These DLC materials
can contain up to 50 atomic percent of hydrogen. The diamond-like
carbon materials may also contain dopant atoms such as nitrogen and
silicon. For the purpose of the present invention, DLC materials
which are doped with silicon in the range of approximately 2 atomic
% to approximately 40 atomic % are termed Si-doped diamond-like
carbon, Si-DLC. The Si-DLC materials may also contain nitrogen, and
possibly oxygen.
[0037] The coatings of the present invention are softer and thinner
than those disclosed in Kim, U.S. Pat. No. 4,951,953, yet they can
be remarkably resistant to scratching when deposited on steel
alloys or other metals of comparable hardness. The elastic moduli
of the decorative coatings of the present invention are less than
the 340 GPa (50 million psi) critical value disclosed in the '953
patent, and are typically less than 200 GPa (29 million psi) as
measured by nanoindentation using a Nanoindenter II instrument
manufactured by Nano Instruments, Incorporated (Oak Ridge, Tenn.).
Likewise, the preferred thickness range of the coatings of the
present invention, in the range of approximately 1 micrometer to
approximately 25 micrometers, is below the range of 25 to 250
micrometers described in the '953 patent.
[0038] It has been found that some coatings of the present
invention have surprisingly high resistance to abrasive damage by
SiC sandpaper. For example, it was found that it was very difficult
to damage golf club heads which were coated with black-colored
composite diamond-like carbon decorative coatings, even by vigorous
rubbing of the coated surface with 400 grit SiC sandpaper. This
outstanding degree of resistance to scratching in this test was
unexpected in light of the fact the SiC grit, with expected
hardness of approximately 25 GPa, was substantially harder than the
coatings, which had hardness in the range of approximately 17 to 20
GPa. Probable contributing factors to the outstanding scratch and
abrasion resistance of the composite diamond-like carbon decorative
coatings of the present invention are the very low coefficient of
friction and very low chemical reactivity of the coating
materials.
[0039] These composite diamond-like carbon coatings are resistant
to corrosion by acids and bases, and are also excellent protective
barriers against environmental corrosives such as humidity, salt,
and acid rain. It was discovered, for example, that metals prone to
oxidation and scaling, such as aluminum, zinc-aluminum and
copper-aluminum alloys, are well protected by coatings of the
present invention even during week-long exposure periods in QUV
accelerated weathering tests. In these tests, the samples were
exposed to alternating cycles of high intensity UV-B radiation,
with peak intensity centered at 313 nm, at 50.degree. C. for 4
hours, and then water condensation at 50.degree. C. for 4 hours.
These conditions produced extreme oxidation and scaling on uncoated
aluminum and zinc-aluminum alloys.
[0040] The coatings of the present invention can be made with
excellent adhesion to the substrate such that no delamination
occurs under high impact conditions. Even on a soft material such
as aluminum, which readily deformed when struck with a harder
material, coatings of the present invention adhered so remarkably
well that no flaking was observed in the impact area.
[0041] When applied to metal substrates, the coatings of the
present invention exhibit a variety of unique and attractive
colors. By adjusting the deposition parameters in the process of
the present invention, the color of the composite diamond-like
carbon coating can be varied continuously along the spectrum of:
light yellow, bronze, copper-gold, burgundy, bluish-black, and
black. The appearance of these colors on metal surfaces coated by
the process of the present invention is unexpected, because a
different color spectrum consisting of: nearly water-clear, light
yellow, yellow-brown, brown, and black are obtained on transparent
or partially transparent substrates such as glass or plastics.
Primary process parameters which control the colors of the coating
are the energy of ions bombarding the surface during coating
deposition, the feed gas chemistry, and the thickness of the
coating.
[0042] By increasing the energetics of the deposition process, the
coating color moves along the unique color spectrum of this
invention from the light end, i.e. light colors, to the dark end,
i.e. dark colors. The phrase "energetics of the deposition
process," is defined as the energy delivered to the coating surface
divided by the deposition rate. Energy is delivered to the coating
surface by substrate heating, impacting ions and fast neutral
species, and radiated power from the plasma. For the ion-assisted
plasma deposition process of the present invention, the energetics
of the deposition process can be increased by increasing any of the
following independent process control parameters while holding
others constant: (i) the power, e.g. RF power, applied to the
plasma, (ii) the vacuum system pumping speed, (iii) the area ratio
of the grounded electrode to the powered electrode, and (iv) the
substrate temperature, by increasing the electrode temperature. For
the ion-assisted plasma deposition process of the present
invention, the energetics of the deposition process can be
increased by decreasing the following independent process control
parameters while holding others constant: (v) the total flow rate
of process gases, (vi) the flow rate of the precursor feed gases,
(vii) the molecular weight of the precursor feed gas, and (viii)
the electrically active surface area of the powered electrode and
substrates.
[0043] DLC materials made from a pure hydrocarbon precursor feed
gases are black in color, when deposited to thicknesses greater
than about I micrometer, but the color can be shifted to the light
end of the spectrum, i.e. yellow-brown color, by reducing the
energetics of the deposition process. However, for coatings greater
than approximately 1 micrometer which are made from hydrocarbon
precursors only, the color shifts to the yellow-brown range at such
low deposition energy that the resulting coatings are soft and
polymeric in nature, and unsuitable for protecting metal substrates
from abrasion.
[0044] It has unexpectedly been found that for the coatings of the
present invention containing Si-DLC, the coating color can be
controlled by selectively adjusting the precursor feed gas
chemistry. It has been found that a color shift toward the light
end of the spectrum can be induced in the coating under conditions
of high deposition energetics by adding silicon to the
carbon-containing precursor feed gas stream. Appropriate sources of
silicon for the process of the present invention include, but are
not limited to silanes, organosilanes, organosilazanes, and
organo-oxysilicon compounds such as organosiloxanes. Examples of
silicon-containing compounds suitable for the process of the
present invention include, but are not limited to silane, disilane,
diethylsilane, tetramethylsilane, hexamethyldisilazane,
hexamethyldisiloxane, tetramethyldisilazane, tetramethyldisiloxane,
octamethylcyclotetrasiloxane, and ethoxytrimethylsilane. Suitable
carbon-containing precursors for DLC include, but are not limited
to hydrocarbons such as methane, butane, acetylene and cyclohexane,
and mixtures thereof. These carbon-containing precursors may be
used alone or in conjunction with noble gases, hydrogen or nitrogen
for the deposition of DLC, or combined with the silicon-containing
precursor gases for the deposition of Si-DLC. When
silicon-containing and carbon-containing precursor feed gases are
used in the process of the present invention, the coating color can
be further shifted toward the light end of the spectrum by adding
nitrogen, oxygen or hydrogen to the precursor feed gas stream.
[0045] The absorption of light in DLC materials is typically
explained in the prior art by the presence of an extensive sp.sup.2
carbon-carbon bonding network. The inventors speculate that the
presence of bonded Si atoms in the coatings of the present
invention shifts the coating color toward the light end of the
spectrum by effectively diluting the carbon concentration in the
coating, and thereby hindering the formation of this long-range
sp.sup.2 carbon-carbon network. Bonded nitrogen atoms in the
diamond-like carbon material may produce a similar effect. The
inventors also speculate that the presence of oxygen or hydrogen
further reduces the carbon concentration in the coating, by
reacting with the carbon in the feed gas and in the coating and
thereby producing highly volatile, stable and unreactive carbon
byproducts (such as methane and carbon dioxide) that can be readily
removed from the deposition chamber by the vacuum pump.
Additionally, since oxygen atoms readily bond with silicon, when
oxygen is present in the deposition process gas it may reactively
bond into the Si-DLC matrix of the coatings of the present
invention. Since there is no absorption of visible light associated
with Si--O or C--O bonds, as the oxygen content in the coating is
increased, the coating color is shifted toward the lighter end of
the spectrum.
[0046] On metals having mirror-like surface finishes, the coatings
of the present invention which contains Si-DLC exhibit an unusual
luster and depth of color. When viewed at different angles, the
coatings can appear to shift in color. When viewed in sunlight, the
depth of color is accentuated, and the appearance of the coating
can be very different than in artificial light. This effect is also
noticeable at the dark end of the color spectrum, where shades of
purple and blue can be seen in the coatings at certain viewing
angles. DLC coatings made from pure hydrocarbon precursor feed
gases at high energy are also shiny black in color, but lack the
luster achieved by the composite diamond-like carbon decorative
coatings of the present invention which contain silicon.
[0047] The coatings of the present invention can be produced at low
substrate temperatures of less than 150.degree. C., whereas
coatings of the prior art generally require substrate temperatures
greater than 300.degree. C. This enables deposition of the
composite diamond-like carbon coatings on temperature sensitive
alloys and metals, as well as on composite articles with
temperature sensitive components, such as plastic golf putter
inserts. In addition, the low deposition temperature capability of
the process of the present invention means that no special
fixturing concepts, such as direct contact water cooling of the
substrates are required.
[0048] It has also been found that the process of the present
invention can be used to deposit thick and highly durable coatings
at substrate temperatures less than 150.degree. C., without
intimate thermal contact between the substrate and a cooled
surface. This is particularly important for applications where the
majority of the surface area of a substrate needs to be coated, and
therefore cannot be placed in intimate contact with a cooled
mounting surface. Furthermore, this capability greatly simplifies
the fixturing requirements for temperature sensitive substrates
with complex shapes.
[0049] Accordingly, it was discovered that the maximum substrate
temperature reached, in the deposition process of the present
invention, declines significantly when the pressure within the
deposition vacuum chamber is decreased below the typical range of
50.times.10.sup.-3 Torr to 500.times.10.sup.-3 Torr employed in
prior art RF plasma deposition of DLC coatings. This decrease in
substrate temperature was highly unexpected, because the total
power required to deposit coatings of equal thickness and hardness
at different pressures is approximately constant. It has been found
that as the process pressure is decreased, less power is required
to maintain the desired substrate bias voltage, but this effect is
offset by a reduction in the deposition rate. The observed effect
of reduced substrate temperature is too dramatic to be explained by
the increased effectiveness of radiative cooling when the
instantaneous heat load is low. The inventors have observed that
the low pressure deposition plasma is more diffuse than the prior
art plasmas, and it is speculated that at low pressures, the plasma
power may be dissipated more evenly at the boundaries of the
plasma.
[0050] The coatings of the present invention are amorphous, unlike
the coatings on golf clubs described by Kim in the '953 patent. In
crystalline coatings of the prior art, the presence of grain
boundaries and other imperfections degrades the ability of the
coating to protect the substrate from corrosive agents, reduces the
ability of the coating to withstand impact and flexure without
cracking, chipping, or flaking from the substrate. In addition, the
surface morphology of crystalline coatings necessitates
post-deposition polishing to achieve a mirror-like appearance. For
the coatings of the present invention applied to smooth substrates,
no post-deposition processing is required to achieve the
attractive, lustrous surface finish.
[0051] For the present invention, it is preferred that the
thickness of the composite diamond-like carbon coating be greater
than approximately 1 micrometer, which is much greater than the
wavelengths of visible light (approximately 0.5 micrometer). In
this case, the perceived color of the coating is significantly
influenced by the inherent optical color (a combination of
absorption, reflection and refractive index characteristics) of the
coating material, and the reflectivity characteristics of the
substrate. For the case of the present invention, the perceived
color of the coating is not simply generated by thin film optical
interference effects, known to those skilled in the art of optical
coatings. Representative of prior art thin film optical
interference coatings are quarter wavelength stacks of dielectric
layers, which may be combined with thin reflective metal films, to
generate iridescent colors on substrates such as sunglass
lenses.
[0052] For cases where the attenuation of the light through the
coating, via absorption, is so strong that reflected light from the
coating-metal interface is imperceptible, the coating can have a
shiny appearance, but lacks the luster or depth of more transparent
coatings. For hard DLC materials, the threshold coating thickness
for complete absorption is approximately 0.5 micrometer, and above
this threshold, these coatings are black. As the absorption
coefficient is reduced, by reducing the deposition energetics or by
changing the precursor feed gas chemistry as described above, the
maximum thickness for which the luster is apparent increases.
[0053] There are several composite diamond-like carbon coating
structures in the present invention that provide the lustrous
appearance described above, as well as other performance benefits.
The composite diamond-like carbon decorative coatings have hardness
in the range of approximately 5 to 35 GPa, and modulus in the range
of approximately 50 GPa to 300 GPa.
[0054] In the first composite diamond-like carbon coating structure
which provides a lustrous appearance, a single layer of transparent
or partially transparent Si-DLC is deposited on a metal substrate
to a thickness in the range of 1 to 25 micrometers. In addition to
Si, C and H, the Si-DLC may also contain O and N. By controlling
the deposition energetics, the precursor feed gas chemistry, and
the thickness of the coating in the range of approximately 1 to 25
micrometers, lustrous colors can be achieved along the color
spectrum defined by light yellow, bronze, copper-gold, burgundy,
bluish-black and black.
[0055] In the second composite diamond-like carbon coating
structure which provides a lustrous appearance, multiple layers of
transparent or partially transparent Si-DLC of different elemental
composition are sequentially deposited on the metal substrate. In
addition to Si, C and H, all layers in this coating may also
contain O and N. The coating structure can be tailored to the
requirements of the application. For example, the first layer may
be enriched with silicon in order to maximize the adhesion to the
substrate. Alternately, several thin layers with varying refractive
indices may be included at the top of the coating (away from the
coating-metal interface) in order to control or reduce any thin
film interference effects that may be present.
[0056] In the third composite diamond-like carbon coating structure
which provides a lustrous appearance, a coating is produced by
first depositing on a metal substrate one or more layers of the
transparent or partially transparent Si-DLC, containing Si, C, H
and optionally O and N, and then depositing at least one layer of
DLC, consisting essentially of C and H, and optionally N. The
thickness of the single DLC layer, or multiple DLC layers, is less
than the maximum for complete absorption of visible light within
the composite coating, and the total thickness of the composite
coating is in the range of approximately 1 to 25 micrometers The
third composite diamond-like carbon coating structure has the
advantage that the composite coating with the DLC top layer
generally affords maximum chemical resistance, with the exception
of oxidizing environments, for which the Si-DLC top layer is
preferred. The DLC layers in this structure may be further refined
to suit the mechanical requirements of the application by adding
small amounts of other elemental constituents. For example, small
amounts of metal may be incorporated in the top DLC layer to reduce
the friction of the coating in high humidity environments.
[0057] In the fourth composite diamond-like carbon coating
structure which provides a lustrous appearance, a nontransparent
layer of DLC, consisting essentially of C, H and optionally N, is
deposited between layers of transparent Si-DLC, consisting of Si,
C, H, and optionally O and N. The purpose of the Si-DLC layer
adjacent to the metal interface is to provide good adhesion, while
the purpose of the top layer of Si-DLC is to provide luster and
depth of color to the coating. While visible light entering the DLC
layer or layers is completely absorbed, some of the light impinging
on the interface between the Si-DLC and the DLC is reflected due to
refractive index mismatch. The advantage of the fourth composite
diamond-like carbon coating structure is that a shiny black coating
with luster and depth of color is produced.
[0058] Finally, a highly durable shiny black composite diamond-like
carbon decorative coating having a structure of a first layer of
Si-DLC consisting of Si, C, H, and optionally O and N, and at least
a second layer of DLC consisting essentially of C, H and optionally
N, which DLC layer is thick enough and of sufficient optical
density to not allow visible light to reach the Si-DLC layer can be
made by the ion-assisted plasma deposition process of the present
invention. The top layer of DLC in this structure has a thickness
of greater than 0.5 micrometer, and the total thickness of the
composite coating is in the range of approximately 1 to 25
micrometers. This type of composite diamond-like carbon coating has
the properties of outstanding adhesion, superior abrasion
resistance, corrosion resistance, but has a shiny black color,
rather than the lustrous colors of the Si-DLC containing coatings
of the present invention. In addition, these shiny black composite
diamond-like carbon coatings can have high hardness in the range of
approximately 15 to 35 GPa, and high modulus, in the range of
approximately 120 GPa to 300 GPa, both of which are at the upper
end of the range of these properties for the coatings of the
present invention. The characteristics and appearance of this shiny
black composite diamond-like carbon decorative coating is ideal for
sporting equipment including golf club shafts, and golf club heads
such as putters, drivers and irons.
[0059] It has been found that deposition of the first layer of
Si-DLC material, having a Si concentration between approximately 2
atomic percent and 40 atomic percent prior to the deposition of a
DLC layer, results in highly adherent composite diamond-like carbon
decorative coatings with outstanding adhesion to the substrate and
outstanding abrasion-resistance properties. It is currently
believed that reaction between the Si atoms in the Si-DLC layer and
the substrate is critical for the composite diamond-like carbon
coating to exhibit excellent adhesion to the substrate. It is
currently believed that reaction between the Si atoms in the Si-DLC
layer and the carbon atoms in the DLC layer is critical for the
outstanding adhesion between these two layers.
[0060] For structures in which a second coating, consisting of at
least one additional layer of DLC or Si-DLC, is deposited on top of
the first Si-DLC layer, the thickness of the first Si-DLC layer is
in the range of approximately 0.1 to 15 micrometers. This thickness
range has been found to produce the best adhesion to the substrate
for the multiple-layer coatings of the present invention.
[0061] The preferred method of the present invention comprises the
following steps. The substrate is first chemically cleaned to
remove contaminants. In the second step, the substrate is inserted
into a vacuum coating chamber and the air in the chamber is
evacuated. Next, in the third step, the substrate surface is
sputter-etched by a flux of energetic ions or other reactive
species to assist in the removal of residual contaminants such as
residual hydrocarbons and surface oxides, and to activate the
surface. In the fourth step, after the substrate surface has been
etched and activated, at least a first layer of Si-DLC is deposited
by an ion-assisted plasma deposition process, preferably
capacitively-coupled RF plasma deposition, from carbon-containing
and silicon-containing precursor gas compounds. Upon completion of
the formation of the Si-DLC first coating layer, an additional
coating, consisting of at least one layer of DLC or Si-DLC may be
deposited by an ion-assisted plasma deposition process, preferably
capacitively-coupled RF plasma deposition, from precursor gases.
The deposition of the desired thickness and number of DLC and
Si-DLC layers, is continued until the desired optical color and
total coating thickness is achieved, at which point the deposition
process on the substrates is terminated. Then, the vacuum chamber
pressure is increased to atmospheric pressure, and the coated metal
substrates having a highly durable and abrasion-resistant composite
diamond-like carbon decorative coating are removed from the vacuum
chamber.
[0062] It is understood that the process of the present invention
can be carried out in a batch-type vacuum deposition system, in
which the main vacuum chamber is evacuated and vented to atmosphere
after processing each batch of parts; a load-locked deposition
system, in which the main vacuum deposition chamber is maintained
under vacuum at all times, but batches of parts to be coated are
shuttled in and out of the deposition zone through vacuum-to-air
load locks; or in-line processing vacuum deposition chambers, in
which parts are flowing constantly from atmosphere, through
differential pumping zones, into the deposition chamber, back
through differential pumping zones, and returned to atmospheric
pressure.
[0063] It is possible to perform ion-assisted plasma deposition of
DLC materials using a variety of methods, including
capacitively-coupled RF plasma deposition, DC plasma deposition,
ion beam plasma deposition and ion-assisted sputter deposition.
However, since the decorative coatings of the present invention are
ideally suited to a variety of substrates with highly curved
surfaces, the RF plasma or DC plasma deposition methods are
preferred with the RF plasma method most preferred. It is known
that properties of DLC materials deposited by direct ion beam
deposition are very sensitive to the angle of incidence of the ion
beam onto the substrate. At incident angles in the range of
approximately 60 degrees to 90 degrees, highly smooth, dense and
hard DLC films are deposited. However, when the ion beam is
directed onto the substrate at a grazing angle of incidence less
than approximately 45 degrees, the films become rougher, and the
density and hardness decrease. This effect becomes much worse as
the angle of incidence approaches 0 degrees. Therefore, complex
fixturing is required for obtaining uniform DLC materials of
optimum quality on highly curved surfaces, such as golf club heads,
using ion beam deposition. For the case of ion-assisted sputter
deposition of DLC and Si-DLC coatings, the deposition rate of these
materials is typically much lower than that achieved by
capacitively-coupled RF plasma deposition. In addition, complex
fixturing is required for obtaining uniform diamond-like carbon
materials of optimum quality on highly curved surfaces, such as
golf club heads, using ion-assisted sputter deposition.
[0064] A preferred ion-assisted plasma deposition apparatus for
producing the preferred embodiment of the present invention by
capacitively-coupled RF plasma deposition, in accordance with
Holland, U.S. Pat. No. 4,382,100, which is incorporated herein by
reference, is illustrated schematically in FIG. 1. The process is
carried out inside vacuum chamber 10, which is fabricated according
to techniques known in the art. Vacuum chamber 10 is evacuated by
first pumping with a rough vacuum pump (not shown) and then by an
optional high vacuum pump (not shown). Use of a high vacuum pump
allows for removal of greater levels of air and contaminants from
the chamber prior to initiating the deposition process, and also
enables operation of the plasma at lower pressures than can be
achieved with a rough vacuum pump. The high vacuum pump can be a
diffusion pump, turbomolecular pump, or other high vacuum pumps
known in the art.
[0065] Within electrically grounded metal vacuum chamber or glass
vacuum chamber 10 with electrically grounded electrode 12,
substrates 13 (for example, golf club heads, as shown) are mounted
either in recessed holes directly in the powered electrode, or
equivalently in recessed holes 14 in electrically conductive
mounting block 15 which in turn rests on powered electrode 20.
Alternatively, substrates 13 may be mounted on metal mounting studs
16, which are in electrical contact with powered electrode 20 and
may or may not be recessed into mounting block 15. Powered
electrode 20 may be stationary, or may incorporate a rotation
mechanism. Powered electrode 20 is shown with cooling water inlet
22 and cooling water outlet 24 of a typical cooling system 25 for
RF chamber 10. RF power circuit 30 is electrically connected to
grounded electrode 12 and powered electrode 20 via cables or
connectors as shown by means well known in the art. Electrically
grounded dark space shield 32 is separated from powered electrode
20 by a small gap 34. DC blocking capacitor 36 in RF power circuit
30 allows the entire electrode assembly, i.e., substrates 13,
mounting block 15, mounting studs 16, and powered electrode 20, to
develop a negative voltage (also known in the art as DC self-bias
voltage) upon ignition of plasma 37 by application of suitable RF
power from RF generator 38 in the presence of process gases. The
process gases, which may include argon for sputter-etching of the
substrates prior to coating deposition, and precursor gases for
deposition, pass through gas line 40 into shower head distributor
42 and out through orifices 44 into chamber 10. The effluent gases
are exhausted through exhaust pumping port 50. An automated
variable throttle valve in the exhaust port (not shown in FIG. 1)
is used to control the rate of gas removal from the vacuum chamber.
The pressure in the chamber is thus controlled by throttle valve
position and total gas flow into the chamber. RF blocking inductor
52 in circuit 30 permits measurement of the DC bias voltage via
voltmeter 54. Matching network 56 in circuit 30 is tuned to assure
optimum delivery of RF power into plasma 37. Typical process
operating conditions include gas pressure in the range of
approximately 1.times.10.sup.-3 Torr to 500.times.10.sup.-3 Torr,
RF frequency of 13.56 MHz, peak-to-peak RF voltages in the range of
approximately 500 to 2000 Volts, and DC self-bias voltages in the
range of approximately -100 to -1,000 Volts.
[0066] In capacitively-coupled RF plasma systems such as that
illustrated in FIG. 1, the surface area of grounded surfaces is
normally substantially larger than the surface area of powered
electrode 20 and substrates 13. In such asymmetric systems, ion
bombardment energies and fluxes are much larger on the powered
electrode than they are on the grounded surfaces including grounded
electrode 12. Bombardment by positive ions from an inert gas (e.g.
Ar) plasma results in sputter-etching of the exposed surfaces of
the substrate assembly which includes substrates 13, mounting block
15, mounting studs 16, and powered electrode 20. Likewise, ion
bombardment by positive ions of the precursor gases, such as
hydrocarbon gases (e.g. methane, acetylene, butane, cyclohexane,
etc.), results in deposition of a DLC coating on all exposed
surfaces of the substrate assembly, including substrates 13,
mounting block 15, mounting studs 16 and powered electrode 20.
[0067] Deposition on the edges and backside of the powered
electrode is commonly avoided in capacitive RF plasma systems by
the use of dark space shield 32 shown in FIG. 1. As illustrated,
grounded metal shield 32 is separated from powered electrode 20 by
thin vacuum gap 34. Gap 34 is thinner than the width of the plasma
dark space adjacent the exposed surface of powered electrode 20,
and thus a self-sustaining plasma will not develop in gap 34.
[0068] Additionally, it is possible to employ the electronic
masking method of Petrmichl et al., U.S. Pat. No. 5,653,812, which
is incorporated herein by reference to minimize deposition of
coating onto mounting block 15 and on other surfaces inside chamber
10 where deposition is undesirable.
[0069] Finally, it is also possible to mount the metal substrates
to be coated on a vertical powered electrode assembly (not shown).
In this configuration, many individual substrates are attached to
metal mounting poles which connect to a common center post, much
like the branches on a pine tree connect to the tree trunk. The
center post is an intimate part of the powered electrode assembly.
This configuration is commonly referred to as a "Christmas tree"
configuration in the prior art, and has advantages of higher
substrate packing density compared to the horizontal fixturing
arrangement shown in FIG. 1.
[0070] The apparatus of FIG. 1 may also be used to perform DC
plasma deposition by replacing RF power circuit 30 with a DC power
supply. In this configuration, the negative terminal of the DC
power supply is connected to electrode 20, and a DC plasma is
ignited between the substrates and the grounded components such as
electrode 12 within vacuum chamber 10. DC power supplies capable of
negative bias voltages up to -3000 Volts are suitable for the DC
plasma deposition method. The advantage of the DC plasma method of
ion-assisted plasma deposition is the simplicity of the power
supply configuration. However, this configuration is susceptible to
formation of arcs during the deposition of insulating Si-DLC and
DLC coatings. The arcs may be overcome by using arc suppression
method known in the art.
[0071] In the ion-assisted plasma deposition process carried out in
an apparatus such as that illustrated in FIG. 1, the primary
control parameters are the precursor composition and flow rate, the
bias voltage, and the substrate temperature. The useful range of
the latter is, however, limited for metal alloy substrates of low
melting point or softening point, and substrates which contain
temperature sensitive components, such as plastic inserts which are
used in golf putters. Other process parameters that affect the
coating properties in the ion-assisted plasma process are the total
flow rate, discharge power, pressure, size and shape of electrodes,
and the presence of external magnetic fields.
[0072] Alternatively, the apparatus illustrated in FIG. 2 may be
utilized to perform the ion-assisted deposition process of the
present invention by plasma ion beam deposition. As shown in FIG.
2, the process is carried out inside vacuum chamber 61, which is
pumped by high vacuum pump 62 which is typically a turbomolecular
pump or diffusion pump. Fixture 63 is used to hold substrates 71,
in this case on rotating drum 70. As illustrated in FIG. 2, drum 70
and substrates 71 both rotate in opposite directions, but the type
and degree of substrate rotation is chosen depending on the
configuration of the substrates, to obtain adequate uniformity of
the coating thickness and properties. Deposition of the Si-DLC and
DLC layers is carried out by ion plasma beam deposition using ion
source 64, which is operated on inert gases introduced via inlet
65, and silicon-containing and carbon-containing precursor gases
which may be introduced via inlets 66 or 67. Inlets 68 and 69 are
available for adding dopant gases such as oxygen, nitrogen and
hydrogen to the chamber during deposition to modify the properties
of the depositing Si-DLC or DLC layer. An example of the use of
FIG. 2 for the decorative coatings of the present invention would
be in the coating of golf club shaft substrates 71, mounted on
rotating spindles 70 of drum planetary fixture 63. The long axis of
the golf club shafts would be perpendicular to the plane of the
drawing of FIG. 2.
[0073] Additionally, ion source 64 could be replaced by a magnetron
sputtering cathode to perform deposition of the coatings of the
present invention by ion-assisted sputter deposition. In this case,
the carbon-containing and silicon-containing deposition flux is
achieved by sputtering from carbon-containing and
silicon-containing cathode materials such as carbon, silicon, and
silicon carbide.
[0074] According to the method of the present invention, the
substrate is first chemically cleaned to remove contaminants, such
as residual hydrocarbons and other contaminants, from the substrate
manufacturing and handling processes. Ultrasonic cleaning in
solvents, or other aqueous detergents as known in the art is
effective. Details of the cleaning procedure depend upon the nature
of the contamination and residue remaining on the part after
manufacture and subsequent handling. It has been found that it is
critical for this chemical cleaning step to be effective in
removing surface contaminants and residues, or the resulting
adhesion of the coating will be poor.
[0075] In the second step of the process, the substrate is inserted
into a vacuum chamber, and the air in the chamber is evacuated. The
vacuum chamber is then typically evacuated to a pressure of
approximately 1.times.10.sup.-3 Torr or less. The exact level of
vacuum is dependent upon the nature of the substrate material, the
sputter-etching rate of the substrate, the constituents present in
the vacuum chamber residual gas, and the details of the coating
process. It is not desirable to evacuate to lower pressures than
necessary, as this increases the overall process cycle time, and
reduces the throughput of the coating system.
[0076] In the third step of the process, non-depositing gases such
as argon, xenon, krypton, nitrogen and hydrogen are flowed into the
chamber, and a plasma is initiated by applying RF power to the
substrates. Ions in the plasma are extracted by the bias voltage on
the substrates, and impact the substrate with sufficient energy to
sputter-etch the substrate surface to remove residual contaminants,
such as hydrocarbons, surface oxides and other unwanted materials
not removed in the first cleaning step, and to activate the
surface. This sputter-etching of the substrate surface generates an
atomically clean surface, and is required to achieve high adhesion
between the substrate surface and the coating. Typically, in order
to achieve efficient and rapid ion sputter-etching, the bias
voltage is set to -500 V or more, and the chamber pressure is
maintained as low as possible (less than approximately
50.times.10.sup.-3 Torr) by completely opening the automated
throttle valve in the exhaust port. Bias voltages as high as
approximately -2000 Volts can be used, but lower bias voltages are
usually used in order to minimize heating of the substrate.
[0077] In the fourth step of the process, immediately after the
substrate surface has been sputter-etched, at least a first layer
of Si-DLC is deposited by ion-assisted plasma deposition,
preferably capacitively-coupled RF plasma deposition, from
carbon-containing and silicon-containing precursor gases which are
introduced into the vacuum chamber. These carbon-containing and
silicon-containing precursor gases consist of hydrocarbon, silane,
organosilane, organosilazane and organo-oxysilicon compounds, or
mixtures thereof. The flow of non-depositing gas or gases used to
sputter-etch the substrate may be shut off entirely at this point
in the process, or alternatively, may continue along with the flow
of precursor gases. Other gases, such as nitrogen, hydrogen or
oxygen, may be added to the precursor gas flow in order to modify
the optical and mechanical properties of the depositing Si-DLC
coating.
[0078] Upon completion of the deposition of the Si-DLC first
coating layer, a second coating consisting of at least one layer of
DLC or Si-DLC may be deposited by ion-assisted plasma deposition,
preferably capacitively-coupled RF plasma deposition, from
precursor gases. DLC is deposited from hydrocarbon precursor gases,
and possibly nitrogen, hydrogen, and inert gases. Additional layers
of Si-DLC are deposited from carbon-containing and
silicon-containing precursor gases, including hydrocarbon, silane,
organosilane, organosilazane and organo-oxysilicon compounds, or
mixtures thereof. Other gases, such as nitrogen, hydrogen or
oxygen, may be added to the precursor gas flow in order to modify
the optical and mechanical properties of the additional layers of
Si-DLC.
[0079] The thickness, refractive index, and number of the layers in
the composite coating are chosen to produce the desired optical
color, as well as the required durability characteristics such as
resistance to scratches and abrasion. The physical thickness of
individual layers in the second coating is typically approximately
0.5 micrometer or greater. If a shiny black coating is desired, the
thickness of the DLC layer in the second coating is greater than
0.5 micrometer. Optimally, the additional layer of DLC or Si-DLC is
deposited immediately after completion of the first coating layer,
in the same vacuum chamber and in the same vacuum cycle. This
eliminates the added cost of additional pumpdown cycles, and
improves the quality of the interface between the first coating
layer and the second coating.
[0080] The deposition of the desired thickness and number of DLC
and Si-DLC layers is continued until the desired optical color and
total coating thickness in the range of approximately 1 to 25
micrometers is achieved, at which point the deposition process on
the substrates is terminated. Then, the vacuum chamber pressure is
increased to atmospheric pressure, and the substrates having a
highly durable and abrasion-resistant composite diamond-like carbon
decorative coating having thickness in the range of approximately 1
to 25 micrometers, hardness in the range of approximately 5 to 35
GPa, and modulus in the range of approximately 50 to 300 GPa is
removed from the vacuum chamber.
[0081] Appropriate types of precursor feed gases for the process
for depositing the decorative composite diamond-like carbon
coatings of the present invention include, but are not limited to
hydrocarbon compounds, silanes, organosilanes, organosilazanes, and
organo-oxysilicon compounds such as organosiloxanes. Examples of
specific compounds suitable for the process of the present
invention include, but are not limited to carbon-containing
precursors such as methane, butane, cyclohexane and acetylene, and
silicon-containing precursors such as silane, disilane,
diethylsilane, tetramethylsilane, hexamethyldisilazane,
tetramethyldisilazane, hexamethyldisiloxane, tetramethyldisiloxane,
and ethoxytrimethylsilane. Noble gases such as argon, krypton and
xenon, and other gases such as nitrogen, oxygen and hydrogen may be
added to the flow of precursor gases to modify the properties of
the depositing coatings. Note that some of the silicon-containing
precursors such as diethylsilane and tetramethylsilane also contain
carbon atoms, some of the silicon-containing precursors such as
hexamethyldisilazane and tetramethyldisilazane also contain C and N
atoms, and some of the silicon-containing precursors such as
hexamethyldisiloxane, tetramethyldisiloxane, and
ethoxytrimethylsilane also contain C and O atoms.
[0082] The examples which follow illustrate the superior
performance of the method of this invention. The examples are for
illustrative purposes only and are not meant to limit the scope of
the claims in any way.
EXAMPLE A
[0083] Golf club shafts and shafts with attached heads including a
driver and iron all made of steel and other metal alloys, including
a driver and iron, were coated with shiny black, highly durable,
highly abrasion-resistant and corrosion-resistant decorative
composite diamond-like carbon coatings by ion-assisted plasma
deposition. The coatings were deposited in a capacitively-coupled
RF plasma deposition apparatus, consisting of a 24-inch
diameter.times.36-inch high vacuum chamber with a 6-inch diameter
water-cooled powered electrode. The vacuum chamber was evacuated by
a roots blower/mechanical pump combination, and a turbomolecular
high vacuum pump. The golf clubs, including shafts and heads, were
cleaned by wiping with isopropyl alcohol, allowed to dry, and then
were mounted vertically, with the handle end attached to the
powered electrode by a simple metal mounting stud. Individual golf
club shafts and golf club shafts with attached heads were coated
one at a time.
[0084] The chamber was evacuated to less than 1.times.10.sup.-3
Torr, and then argon was introduced at a flow of 25 sccm and the
pressure increased to 22.times.10.sup.-3 Torr. A plasma was
initiated by applying RF power to the powered electrode and golf
club, and the RF power was increased to 360 W until a -625 V
substrate bias was achieved. The golf clubs were sputter-etched in
the argon plasma for 3 minutes, before 25 sccm of tetramethylsilane
was added to the argon gas flow. The pressure increased to
28.times.10.sup.-3 Torr, and the power was increased to 400 W to
maintain the -625 V bias. In the following 10 minutes, a first
layer of Si-DLC was deposited from the tetramethysilane/argon
mixture to a thickness of about 0.5 micrometer. Next, 25 sccm
cyclohexane was introduced, and the argon and tetramethylsilane
flows were both shut off, to initiate the deposition of DLC. The
pressure decreased to 27.times.10.sup.-3 Torr, and the power was
adjusted to 390 W to maintain the -625 V bias. The DLC deposition
was continued for a total of 30 minutes, to achieve a top layer of
DLC which was approximately 2 micrometers thick. Then, the RF power
and the cyclohexane flow was then turned off, the chamber was
vented, and the coated golf clubs were removed. The coated golf
club shafts and heads had a uniform shiny black appearance, and
were highly resistant to scratching with 400 grit SiC
sandpaper.
EXAMPLE B
[0085] Golf club putters and coupons made of several different
metals were coated by the ion-assisted plasma deposition method of
the present invention, using a variety of process conditions to
generate highly adherent and durable composite diamond-like carbon
coatings with a variety of colors. All of the coating deposition
runs were carried out in the same coating chamber used in Example
A. The metal coupons were prepared with several surface finishes:
mirror-polished, a "satin" machined finish, an as-machined finish
and a bead-blasted finish.
[0086] All of the substrates were chemically cleaned in an aqueous
soap solution in an ultrasonic bath, then rinsed with isopropyl
alcohol, air dried, and then mounted onto the powered electrode.
Putters were attached to the powered electrode via a mounting stud
as illustrated in FIG. 1. Metal coupons were attached to the side
of an aluminum mounting block, which simulated the shape of a golf
club putter, which was attached to powered electrode. After
evacuation of the air in the vacuum chamber to a pressure of less
than 1.times.10.sup.-3 Torr, argon gas was introduced into the
chamber at a flow rate of 90 sccm, to produce a pressure of
approximately 20.times.10.sup.-3 Torr. A plasma was ignited at a RF
frequency of 13.56 MHz, and a power of approximately 400 Watts,
resulting in a self-bias voltage of -700 Volts on the powered
electrode and the substrates. The substrates were sputter-etched
for a period of 10 minutes under these conditions to remove
residual hydrocarbon contamination and oxide layers from the
surface. Then, composite diamond-like carbon coatings containing at
least one layer of Si-DLC were deposited using ion-assisted plasma
deposition from silicon-containing precursor gases, using the
conditions presented in Table 1 below. Properties of the deposited
composite diamond-like carbon coatings on polished aluminum, ZA12
zinc-aluminum alloy, and stainless steel substrates are also
summarized in Table 1.
[0087] The hardness and modulus values for each of the coatings
presented in Table 1 were obtained by nanoindentation using a Nano
Instruments, Incorporated (Oak Ridge, Tenn.) Nano II nanoindenter.
A Berkovich style indentation tip was used. Indents were made at
three depths: 50 nm, 100 nm, and 150 nm. The reported hardness and
modulus values are the average of five indents at each of the three
depths. A Si (100) single crystal standard (hardness 10.5 GPa) was
used to calibrate the instrument.
1TABLE 1 Flow Rate and Precursor; Bias Flow Rate and Voltage for
Si-DLC First Precursor; Bias Second Layer Coating Hardness: Run
Si-DLC First Layer Thickness Voltage for Thickness Modulus No.
Layer (microns) Second Layer (microns) (GPa) Color 16 100 sccm 3.4
None -- 8.5; 68 Lustrous TMS + 25 burgundy sccm Ar; -300 V 9 100
sccm 3.7 None -- 14; 118 Lustrous TMS + 25 bluish- sccm Ar; -500
black V 15 100 sccm 5.9 None -- 17; Lustrous TMS + 153 blusih- 25
sccm Ar; black -700 V 32 25 sccm 3.6 None -- 7.7; Lustrous HMDSN;
62 copper- -500 V gold 31 25 sccm 3.6 None -- 11; Lustrous HMDSN;
93 burgundy -700 V 28 25 sccm 3.1 None -- 9.7; Lustrous TMDSN + 86
copper- 25 sccm Ar; gold -700 V 24 25 sccm 5.4 None -- 8.0;
Lustrous TMDSN + 68 copper- 25 sccm Ar; gold -700 V 30 25 sccm 0.6
100 sccm 1.7 13.5; Shiny TMDSN + cyclohexane; 110 black 25 sccm Ar;
-500 V -700 V 27 100 sccm 2.5 100 sccm 0.7 17.2; Shiny TMDSN +
cyclohexane; 137 black 25 sccm Ar; -700 V -700 V Note: TMS =
tetramethylsilane; HMDSN = hexamethyldisilazane; TMDSN =
tetramethyldisilazane.
[0088] The coatings presented in Table 1 demonstrated excellent
adhesion in boiling water-to-ice water thermal shock adhesion
tests, and in impact tests in which the coated substrate were
impacted with a sharp corner of a hard metal wedge golf club head,
to simulate aggressive banging together of unprotected golf club
heads.
[0089] Reflected light chromaticity coordinates of the coupons were
measured using a Hunter UltraScan XE dual beam, xenon source, flash
spectrophotometer with a wavelength range of 360 to 750 nm. A
six-inch diameter, barium coated integrating sphere was used to
measure reflected light. Tristimulus integrations using CIE 1931
source C standard illuminant and CIE 1931 2-degree standard
observer were performed to obtain the chromaticity coordinates were
based on a triangular bandpass of 10 nm and a wavelength interval
of 10 nm. The appearance color, and chromaticity coordinate data
for the test coupons are presented in Table 2 below.
2TABLE 2 Coating Chromaticity Chromaticity Hardness; Appear- Values
of Values of Run Modulus ance coated Al coupon coated SS coupon No.
(GPa) Color (Y, x, y) (Y, x, y) 16 8.5; Lustrous 20.4, 0.375, 0.338
17.0, 0.354, 0.328 68 burgundy 9 14; Lustrous 18.7, 0.323, 0.311
17.3, 0.310, 0.310 118 bluish- black 15 17; Lustrous 19.71, 0.305,
0.311 18.7, 0.306, 0.312 153 bluish- black 32 7.7; Lustrous 28.6,
0.406, 0.378 21.9, 0.382, 0.356 62 copper- gold 31 11; Lustrous
20.3, 0.376, 0.338 18.6, 0.350, 0.326 93 burgundy 28 9.7; Lustrous
23.8, 0.392, 0.353 20.2, 0.372, 0.344 86 copper- gold 24 8.0;
Lustrous 24.0, 0.408, 0.364 19.8, 0.395, 0.356 68 copper- gold 30
13.5; Shiny 13.8, 0.316, 0.323 14.9, 0.312, 0.318 110 black 27
17.2; Shiny 15.2, 0.313, 0.319 15.8, 0.313, 0.319 137 black Note:
SS = stainless steel coupon.
[0090] From examination of the data in Table 2, it is apparent that
the shiny black composite diamond-like carbon decorative coatings
with a DLC top layer deposited in Run No. 27 and 30 have the lower
values of Y than do all of the other coatings which have Si-DLC as
the top layer. For the case of the coatings from Run No. 27 and 30,
the values of Y were 15.2 and 13.8, respectively, whereas for all
the other coatings which have Si-DLC as the top layer, the values
of Y were between 18 and 29. This indicates that the coatings with
the Si-DLC top layer are more reflective than the coatings with a
DLC top layer which is greater than 0.5 micrometer thick.
Therefore, the Si-DLC coatings appear to have higher luster, i.e.
are lustrous, than do the coatings with a DLC top layer which is
greater than 0.5 micrometer thick.
[0091] The chromaticity coordinate values of (x,y) in Table 2 also
indicate some of the representative color coordinates for the
lustrous bronze, copper-gold, burgundy, bluish-black, and shiny
black coatings of the present invention. However, the range of
chromaticity coordinates presented in Table 2 is only a subset of
the range of colors which can be made by the present invention. For
the present invention, the range of chromaticity coordinate values
for x are from approximately 0.25 to 0.50, and for y are from
approximately 0.25 to 0.45, and values for Y are from approximately
5 to 50.
[0092] The previous discussion, Examples and the results presented
in Table 1 demonstrate that highly durable and abrasion-resistant
composite diamond-like carbon coatings with controllable color can
be applied to a variety of metal substrates by the ion-assisted
plasma deposition process of the present invention. For example,
coated golf club heads such as drivers, putters and irons, which
have high abrasion resistance and a shiny black color, or lustrous
colors such as bronze, copper-gold, burgundy, bluish-black and
black can be produced. Because of the high coating deposition rates
which can be attained, the invention provides an economical
manufacturing process.
[0093] From the foregoing description, one of ordinary skill in the
art can easily ascertain that the present invention provides an
improved method for producing highly durable, lustrous protective
coatings on a variety of metal substrates. Highly important
technical advantages of the ion-assisted plasma deposited composite
diamond-like carbon coatings present invention includes attractive
cosmetic appearance with a variety of colors, tailorable shiny,
high-luster or low-luster finish, outstanding adhesion and
durability, outstanding resistance to scratches, abrasion and
corrosion, and ease and flexibility of mass production.
[0094] Without departing from the spirit and scope of this
invention, one of ordinary skill in the art can make various
changes and modifications to the invention to adapt it to various
usages and conditions. As such, these changes and modifications are
properly, equitably, and intended to be, within the full range of
equivalents of the following claims.
* * * * *