U.S. patent application number 14/539780 was filed with the patent office on 2015-05-14 for multilayered coating for downhole tools with enhanced wear resistance and acidic corrosion resistance.
This patent application is currently assigned to National Oilwell DHT, L.P.. The applicant listed for this patent is National Oilwell DHT, L.P.. Invention is credited to Rajagopala N. Pillai, Jiinjen Albert Sue, Unnikrishnan C. Vasudevan.
Application Number | 20150132604 14/539780 |
Document ID | / |
Family ID | 53044052 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150132604 |
Kind Code |
A1 |
Sue; Jiinjen Albert ; et
al. |
May 14, 2015 |
Multilayered Coating for Downhole Tools with Enhanced Wear
Resistance and Acidic Corrosion Resistance
Abstract
A coating for protecting a base material from wear and corrosion
includes a first layer deposited directly onto an outer surface of
the base material. In addition, the coating includes a second layer
deposited directly onto the first layer. The first layer is
positioned between the base material and the second layer. The
first layer includes chromium having a first micro-crack density
and the second layer comprises chromium having a second micro-crack
density that is less than the first micro-crack density.
Inventors: |
Sue; Jiinjen Albert; (The
Woodlands, TX) ; Vasudevan; Unnikrishnan C.;
(Pearland, TX) ; Pillai; Rajagopala N.; (Pasadena,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
National Oilwell DHT, L.P. |
Conroe |
TX |
US |
|
|
Assignee: |
National Oilwell DHT, L.P.
Conroe
TX
|
Family ID: |
53044052 |
Appl. No.: |
14/539780 |
Filed: |
November 12, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61904287 |
Nov 14, 2013 |
|
|
|
Current U.S.
Class: |
428/664 ;
205/104; 205/179; 205/180; 205/184; 428/667 |
Current CPC
Class: |
C23C 18/32 20130101;
C25D 5/12 20130101; C23C 18/1694 20130101; C25D 5/18 20130101; E21B
17/1085 20130101; C23C 18/1653 20130101; E21B 10/00 20130101; Y10T
428/12833 20150115; Y10T 428/12854 20150115; E21B 4/02 20130101;
C25D 5/50 20130101; C25D 7/00 20130101; C25D 5/14 20130101 |
Class at
Publication: |
428/664 ;
205/179; 205/104; 205/180; 205/184; 428/667 |
International
Class: |
E21B 3/00 20060101
E21B003/00; E21B 10/00 20060101 E21B010/00; E21B 4/06 20060101
E21B004/06; C25D 5/12 20060101 C25D005/12; C25D 7/00 20060101
C25D007/00; C25D 5/14 20060101 C25D005/14; C25D 5/50 20060101
C25D005/50; E21B 4/02 20060101 E21B004/02; C25D 5/18 20060101
C25D005/18 |
Claims
1. A coating for protecting a base material from wear and
corrosion, the coating comprising: a first layer deposited directly
onto an outer surface of the base material; and a second layer
deposited directly onto the first layer, wherein the first layer is
positioned between the base material and the second layer; wherein
the first layer comprises chromium having a first micro-crack
density and the second layer comprises chromium having a second
micro-crack density that is less than the first micro-crack
density.
2. The coating of claim 1, wherein the first micro-crack density is
greater than 1000 micro-cracks per inch and the second micro-crack
density is between 400 and 650 micro-cracks per inch.
3. The coating of claim 2, wherein the first layer has a first
thickness measured perpendicular to the outer surface of the base
material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; wherein
the first thickness of the first layer is substantially uniform and
the second thickness of the second layer is substantially
uniform.
4. The coating of claim 2, wherein the second layer has a thickness
less than 0.0050 in. measured perpendicular to the outer surface of
the base material.
5. The coating of claim 2, wherein the second layer has a thickness
between about 0.00050 in. and about 0.0020 in. measured
perpendicular to the outer surface of the base material.
6. The coating of claim 2, wherein the first layer has a first
hardness greater than 1000 HV and the second layer has a second
hardness of about 850 HV.
7. The coating of claim 6, wherein the coating has an inner surface
engaging the outer surface of the base material and an outer
surface distal to the base material, and wherein the coating has a
total thickness less than 0.030 in. measured perpendicularly from
the outer surface of the base material to the outer surface of the
coating.
8. The coating of claim 7, wherein the first layer has a thickness
between about 0.00020 in. and 0.0030 in. measured perpendicular to
the outer surface of the base material.
9. A method for forming a wear and corrosion resistant coating on a
surface of a base material, the method comprising: (a) depositing a
first layer of a first material onto the surface of the base
material; and (b) depositing a second layer of a second material
onto the first layer after (a); wherein the first material or the
second material comprises chromium and is deposited at a current
density of less than about 4.0 A/in2.
10. The method of claim 9, wherein the first material and the
second material each comprise chromium; wherein (a) comprises
depositing the first layer of the first material at a first current
density; and wherein (b) comprises depositing the second layer of
the second material at a second current density that is different
than the first current density.
11. The method of claim 10, wherein one of the second current
density and the first current density is about 3.5 A/in2 and the
other of the first current density and the second current density
is about 1.0 A/in2.
12. The method of claim 10, wherein (a) comprises depositing the
first layer of the first material by pulse current; and wherein (b)
comprises depositing the second layer of the second material by
pulse current.
13. The method of claim 10, wherein (b) comprises depositing the
second layer of the second material until the second layer has a
thickness of about 0.0002 in. to 0.0030 in. measured perpendicular
to the surface of the base material.
14. The method of claim 13, wherein (a) comprises depositing the
first layer of the first material until the first layer has a
thickness of about 0.00020 in. to 0.0030 in. measured perpendicular
to the surface of the base material.
15. The method of claim 9, wherein the first material consists of
chromium and the second material consists of chromium.
16. The method of claim 9, wherein the first material comprises
Ni--P and the second material comprises chromium.
17. The method of claim 16, wherein (a) comprises depositing the
first layer of the first material by an electroless process.
18. The method of claim 17, wherein (b) comprises depositing the
second layer of the second material until the second layer has a
thickness of about 0.0002 in. to 0.0030 in. measured perpendicular
to the surface of the base material.
19. The method of claim 16, further comprising (c) heating the
first layer after (a) and before (b).
20. The method of claim 19, wherein (c) comprises: (c1) heating the
first layer at about 375.degree. F. for about 1.5 hr.; and (C2)
heating the first layer at about 500.degree. F. for about 1 hr
after (c1).
21. The method of claim 20, wherein (c) comprises increasing the
hardness of the first layer to about 50 Rc.
22. A down-hole tool comprising: a body made of a base material; a
protective coating mounted to an outer surface of the base
material, wherein the protective coating comprises: a first layer
deposited directly onto an outer surface of the base material; and
a second layer deposited directly onto the first layer, wherein the
first layer is positioned between the base material and the second
layer; wherein the first layer comprises chromium having a first
micro-crack density and the second layer comprises chromium having
a second micro-crack density that is less than the first
micro-crack density.
23. The tool of claim 22, wherein the first micro-crack density is
greater than 1000 micro-cracks per inch and the second micro-crack
density is between 400 and 650 micro-cracks per inch.
24. The tool of claim 23, wherein the first layer has a first
thickness measured perpendicular to the outer surface of the base
material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; wherein
the first thickness of the first layer is substantially uniform and
the second thickness of the second layer is substantially
uniform.
25. The tool of claim 23, wherein the second layer has a thickness
between about 0.00050 in. and about 0.0020 in. measured
perpendicular to the outer surface of the base material.
26. The tool of claim of claim 25, wherein the coating has an inner
surface engaging the outer surface of the base material and an
outer surface distal the base material, and wherein the coating has
a total thickness less than 0.030 in. measured perpendicularly from
the outer surface of the base material to the outer surface of the
coating.
27. The tool of claim 23, wherein the first layer has a first
hardness greater than 1000 HV and the second layer has a second
hardness of about 850 HV.30.
28. A coating for protecting a base material from wear and
corrosion, the coating comprising: a first layer deposited directly
onto an outer surface of the base material; and a second layer
deposited directly onto the first layer, wherein the first layer is
positioned between the base material and the second layer; wherein
the first layer comprises Ni--P and the second layer comprises
chromium having a micro-crack density between 400 and 650
micro-cracks per inch.
29. The coating of claim 28, wherein the second layer consists of
chromium.
30. The coating of claim 29, wherein the first layer has a first
thickness measured perpendicular to the outer surface of the base
material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; wherein
the first thickness of the first layer is substantially uniform and
the second thickness of the second layer is substantially
uniform.
31. The coating of claim 28, wherein the first layer has a first
thickness measured perpendicular to the outer surface of the base
material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; wherein
the first thickness is between 0.0005 in. and 0.002 in. and the
second thickness is between 0.0002 in. and 0.0030 in.
32. The coating of claim of claim 28, wherein the coating has an
inner surface engaging the outer surface of the base material and
an outer surface distal the base material, and wherein the coating
has a total thickness less than 0.030 in. measured perpendicularly
from the outer surface of the base material to the outer surface of
the coating.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional
Application Ser. No. 61/904,287 filed Nov. 14, 2013, and entitled
"Multilayered Coating for Downhole Tools with Enhanced Wear
Resistance and Acidic Corrosion Resistance," which is hereby
incorporated herein by reference in its entirety.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND
[0003] The present disclosure relates generally to a multi-layered
coating for downhole tools and earth-boring drill bits used to
drill a borehole for the ultimate recovery of oil, gas, or
minerals. More particularly, the present disclosure relates to a
multilayered protective coating that provides enhanced wear
resistance and acid corrosion resistance for downhole tools, such
as, but not limited to mandrels, mud motor rotors and agitator
rotors, and drill bits.
[0004] An earth-boring drill bit is typically mounted on the lower
end of a drill string and is rotated by rotating the drill string
at the surface or by actuation of downhole motors or turbines, or
by both methods. With weight applied to the drill string, the
rotating drill bit engages the earthen formation and proceeds to
form a borehole along a predetermined path toward a target zone.
The borehole thus created will have a diameter generally equal to
the diameter or "gage" of the drill bit.
[0005] The cost of drilling a borehole for recovery of hydrocarbons
is very high, and is proportional to the length of time it takes to
drill to the desired depth and location. The time required to drill
the well, in turn, is affected by the number of times the drill bit
must be changed before reaching the targeted formation. This is the
case because each time the bit is changed, the entire string of
drill pipe, which may be miles long, must be retrieved from the
borehole, section by section. Once the drill string has been
retrieved and the new bit installed, the bit must be lowered to the
bottom of the borehole on the drill string, which again must be
constructed section by section. This process, known as a "trip" of
the drill string, requires considerable time, effort and expense.
Accordingly, it is desirable to employ drill bits that will drill
faster and longer. The length of time that a drill bit may be
employed before it must be changed depends upon a variety of
factors, including the bit's rate of penetration ("ROP"), as well
as its durability or ability to maintain a high or acceptable ROP.
In turn, ROP and durability are dependent upon a number of factors,
including the ability of the bit body to resist abrasion, erosion,
and impact loads.
[0006] Two predominant types of drill bits are roller cone bits and
fixed cutter bits, also known as rotary drag bits. Bit performance
is often limited by selective/localized wear and corrosive damage
to the bit body. Excessive wear and corrosive damage can alter and
negatively affect specific design parameters for optimal cutting
and hydraulic flow paths. For example, excessive localized wear can
alter cutter exposure (i.e., extension height of cutter elements).
As another example, excessive wear and corrosion around cutter
elements can increase the likelihood of such cutter elements being
broken off or otherwise removed from the bit during drilling
operations. In addition, oil and gas wells are often severely
corrosive environments. In particular, oil and natural gas contain
corrosive substances such as carbon dioxide gas, hydrogen sulfide,
and chlorine ions. Prolonged exposure to such corrosive substances
can weaken and damage drill bits, thereby reducing their durability
and useful life.
[0007] To improve the wear and corrosive resistance of bit bodies,
a protective coating can be applied to the base metal (steel) of
the bit body. Hard chromium plating has been used as a protective
coating for downhole tools in oil and gas industry. Conventional
hard chrome plating is applied in areas of need via electroplating
and typically has a thickness of about 0.005 in. As is known in the
art, electroplating refers to the electrolytic deposition of a
layer of metal onto a base metal. Electroplating is performed in a
plating bath containing a liquid solution (or electrolyte)
including the desired plating metal dissolved as microscopic
particles (positive charged ions) suspended in a conductive
solution. The object to be plated is submerged in the plating bath
and a low voltage DC current is applied to the bath. Generally
located at the center of the plating bath, the object to be plated
acts as a negatively charged cathode. The positively charged anodes
complete the DC circuit. A power source known as a rectifier is
used to convert AC power to a carefully regulated low voltage DC
current. The resulting circuit channels the electrons into a path
from the rectifier to the cathode (surface being plated), through
the plating bath to the anode (positively charged) and back to the
rectifier. The positively charged ions at the anodes flow through
the plating bath's metal electrolyte toward the negatively charged
cathode. This movement causes the metal ions in the bath to migrate
toward extra electrons located at the cathode's surface outer
layer. By means of electrolysis, the metal ions are taken out of
solution and are deposited as a layer onto the surface of the
surface of a downhole tool. This process is often termed
"electrodeposition," and the thickness of the electroplated layer
deposited on the surface is determined by the time of plating, the
amount of available metal ions, and the current density
(A/in.sup.2) applied.
BRIEF SUMMARY OF THE DISCLOSED EMBODIMENTS
[0008] In one embodiment disclosed herein, a coating for protecting
a base material from wear and corrosion comprises a first layer
deposited directly onto an outer surface of the base material. In
addition, the coating comprises a second layer deposited directly
onto the first layer. The first layer is positioned between the
base material and the second layer. The first layer comprises
chromium having a first micro-crack density and the second layer
comprises chromium having a second micro-crack density that is less
than the first micro-crack density. In one embodiment of the
coating, the first micro-crack density is greater than 1000
micro-cracks per inch and the second micro-crack density is between
400 and 650 micro-cracks per inch.
[0009] In another embodiment of the coating, the first layer has a
first thickness measured perpendicular to the outer surface of the
base material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; where the
first thickness of the first layer is substantially uniform and the
second thickness of the second layer is substantially uniform. In a
further embodiment of the coating the second layer has a thickness
less than 0.0050 in. measured perpendicular to the outer surface of
the base material, and in a still further embodiment of the coating
the second layer has a thickness between about 0.00050 in. and
about 0.0020 in. measured perpendicular to the outer surface of the
base material.
[0010] In yet another embodiment of the coating, the first layer
has a first hardness greater than 1000 HV and the second layer has
a second hardness of about 850 HV. In another embodiment, the
coating has an inner surface engaging the outer surface of the base
material and an outer surface distal to the base material, and
wherein the coating has a total thickness less than 0.030 in.
measured perpendicularly from the outer surface of the base
material to the outer surface of the coating; and in a further
embodiment the first layer has a thickness between about 0.00020
in. and 0.0030 in. measured perpendicular to the outer surface of
the base material.
[0011] In one embodiment disclosed herein, a method for forming a
wear and corrosion resistant coating on a surface of a base
material comprises (a) depositing a first layer of a first material
onto the surface of the base material. In addition, the method
comprises (b) depositing a second layer of a second material onto
the first layer after (a). The first material or the second
material comprises chromium and is deposited at a current density
of less than about 4.0 A/in2. In a further embodiment of the
method, the first material and the second material each comprise
chromium, wherein (a) comprises depositing the first layer of the
first material at a first current density; and wherein (b)
comprises depositing the second layer of the second material at a
second current density that is different than the first current
density. In a further still embodiment of the method, one of the
second current density and the first current density is about 3.5
A/in2 and the other of the first current density and the second
current density is about 1.0 A/in2. In one embodiment of the method
(a) comprises depositing the first layer of the first material by
pulse current; and (b) comprises depositing the second layer of the
second material by pulse current; in another embodiment (b)
comprises depositing the second layer of the second material until
the second layer has a thickness of about 0.0002 in. to 0.0030 in.
measured perpendicular to the surface of the base material; in a
further embodiment (a) comprises depositing the first layer of the
first material until the first layer has a thickness of about
0.00020 in. to 0.0030 in. measured perpendicular to the surface of
the base material, and in a further still embodiment the first
material consists of chromium and the second material consists of
chromium. In one embodiment of the method, the first material
comprises Ni--P and the second material comprises chromium, and in
another embodiment of the method (a) comprises depositing the first
layer of the first material by an electroless process; in a further
embodiment of the method (b) comprises depositing the second layer
of the second material until the second layer has a thickness of
about 0.0002 in. to 0.0030 in. measured perpendicular to the
surface of the base material; and in a further still embodiment of
the method comprises (c) heating the first layer after (a) and
before (b) wherein (c) comprises: (c1) heating the first layer at
about 375.degree. F. for about 1.5 hr.; and (c2) heating the first
layer at about 500.degree. F. for about 1 hr after (c1). In another
embodiment of the method (c) comprises increasing the hardness of
the first layer to about 50 Rc.
[0012] In yet another embodiment disclosed herein, a down-hole tool
comprises a body made of a base material. In addition, the
down-hole tool comprises a protective coating mounted to an outer
surface of the base material. The protective coating comprises a
first layer deposited directly onto an outer surface of the base
material and a second layer deposited directly onto the first
layer. The first layer is positioned between the base material and
the second layer. The first layer comprises chromium having a first
micro-crack density and the second layer comprises chromium having
a second micro-crack density that is less than the first
micro-crack density. In one embodiment of the tool, the first
micro-crack density is greater than 1000 micro-cracks per inch and
the second micro-crack density is between 400 and 650 micro-cracks
per inch; in another embodiment of the tool, the first layer has a
first thickness measured perpendicular to the outer surface of the
base material and the second layer has a second thickness measured
perpendicular to the outer surface of the base material; wherein
the first thickness of the first layer is substantially uniform and
the second thickness of the second layer is substantially uniform;
in a further embodiment, the second layer has a thickness between
about 0.00050 in. and about 0.0020 in. measured perpendicular to
the outer surface of the base material; and in a further still
embodiment the coating has an inner surface engaging the outer
surface of the base material and an outer surface distal the base
material, and wherein the coating has a total thickness less than
0.030 in. measured perpendicularly from the outer surface of the
base material to the outer surface of the coating. In another
embodiment of a tool provided for herein, the first layer has a
first hardness greater than 1000 HV and the second layer has a
second hardness of about 850 HV.30.
[0013] In a further embodiment disclosed herein, a coating for
protecting a base material from wear and corrosion comprises a
first layer deposited directly onto an outer surface of the base
material. In addition, the coating comprises a second layer
deposited directly onto the first layer. The first layer is
positioned between the base material and the second layer. The
first layer comprises Ni--P and the second layer comprises chromium
having a micro-crack density between 400 and 650 micro-cracks per
inch. In another embodiment the second layer consists of chromium;
in a further embodiment the first layer has a first thickness
measured perpendicular to the outer surface of the base material
and the second layer has a second thickness measured perpendicular
to the outer surface of the base material; wherein the first
thickness of the first layer is substantially uniform and the
second thickness of the second layer is substantially uniform; and
in a further still embodiment the first layer has a first thickness
measured perpendicular to the outer surface of the base material
and the second layer has a second thickness measured perpendicular
to the outer surface of the base material; wherein the first
thickness is between 0.0005 in. and 0.002 in. and the second
thickness is between 0.0002 in. and 0.0030 in. In another
embodiment, the coating has an inner surface engaging the outer
surface of the base material and an outer surface distal the base
material, and wherein the coating has a total thickness less than
0.030 in. measured perpendicularly from the outer surface of the
base material to the outer surface of the coating.
[0014] Embodiments described herein comprise a combination of
features and advantages intended to address various shortcomings
associated with certain prior devices, systems, and methods. The
foregoing has outlined rather broadly the features and technical
advantages of the invention in order that the detailed description
of the invention that follows may be better understood. The various
characteristics described above, as well as other features, will be
readily apparent to those skilled in the art upon reading the
following detailed description, and by referring to the
accompanying drawings. It should be appreciated by those skilled in
the art that the conception and the specific embodiments disclosed
may be readily utilized as a basis for modifying or designing other
structures for carrying out the same purposes of the invention. It
should also be realized by those skilled in the art that such
equivalent constructions do not depart from the spirit and scope of
the invention as set forth in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a detailed description of the disclosed embodiments of
the invention, reference will now be made to the accompanying
drawings, wherein:
[0016] FIG. 1 is a perspective view of an embodiment of a fixed
cutter drill bit made in accordance with principles described
herein;
[0017] FIG. 2 is a schematic cross-sectional view of the
multilayered protective coating of FIG. 1;
[0018] FIG. 3 is a schematic cross-sectional view of the
multilayered coating of FIG. 1, made in accordance with principles
described herein;
[0019] FIG. 4A is an SEM image of the surface morphology a
conventional hard chromium layer of the prior art comprising a base
material 500, and a hard chrome layer 501;
[0020] FIG. 4B is an SEM image of the surface morphology of a
multilayered chrome coating made in accordance with principles
described herein, and comprising a base material 400, a first
chrome layer 401, and a second chrome layer 402;
[0021] FIG. 5 is a process flow chart illustrating an embodiment of
a method for making a multilayered chromium coating in accordance
with principles described herein; and
[0022] FIG. 6 is a process flow chart illustrating an embodiment of
a method for making a protective coating comprising both Ni--P and
chromium layers in accordance with principles described herein.
DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS
[0023] The following discussion is directed to various exemplary
embodiments of the invention. However, the embodiments disclosed
should not be interpreted, or otherwise used, as limiting the scope
of the disclosure, including the claims. In addition, one skilled
in the art will understand that the following description has broad
application, and the discussion of any embodiment is meant only to
be exemplary of that embodiment, and that the scope of this
disclosure, including the claims, is not limited to that
embodiment.
[0024] The drawing figures are not necessarily to scale. Certain
features and components herein may be shown exaggerated in scale or
in somewhat schematic form and some details of conventional
elements may be omitted in interest of clarity and conciseness.
[0025] Certain terms are used throughout the following description
and claims to refer to particular features or components. As one
skilled in the art will appreciate, different persons may refer to
the same feature or component by different names. This document
does not intend to distinguish between components or features that
differ in name but not function. The drawing figures are not
necessarily to scale. Certain features and components herein may be
shown exaggerated in scale or in somewhat schematic form and some
details of conventional elements may not be shown in interest of
clarity and conciseness.
[0026] In the following discussion and in the claims, the terms
"including" and "comprising" are used in an open-ended fashion, and
thus should be interpreted to mean "including, but not limited to .
. . . " Also, the term "couple" or "couples" is intended to mean
either an indirect or direct connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection, or through an indirect connection via other devices,
components, and connections. In addition, as used herein, the terms
"axial" and "axially" generally mean along or parallel to a central
axis (e.g., central axis of a body or a port), while the terms
"radial" and "radially" generally mean perpendicular to the central
axis. For instance, an axial distance refers to a distance measured
along or parallel to the central axis, and a radial distance means
a distance measured perpendicular to the central axis. As used
herein, the term "about," when used in conjunction with a
percentage or other numerical amount, means plus or minus 10% of
that percentage or other numerical amount. For example, the term
"about 80%," would encompass 80% plus or minus 8%. The term
Chromium, Cr and Chrome may be used interchangeably to describe
some embodiments of the materials described herein. The terms
"plating" and "coating" may be used interchangeably to describe
embodiments of the materials described herein. The term
"substantially" as used herein (unless specifically defined for a
particular context elsewhere or the context clearly dictates
otherwise) means nearly totally or completely, for instance,
satisfying one or more of the following: greater than 50%, 51% or
greater, 75% or greater, 80% or greater, 90% or greater, and 95% or
greater of the condition.
[0027] As previously described, hard chromium plating has been used
as a protective coating for downhole tools in oil and gas industry
to improve the wear and corrosive resistance of bit bodies, a
protective coating can be applied to the base metal (steel) of the
bit body. While hard chrome plating enhances the wear and corrosion
resistance, the conventional plating technique often introduces
defects or cracks into the coating, for example when internal
stress exceeds the tensile stress of the chromium. Further, in
addition to the desired reaction resulting in the metallic chromium
formation, many undesired side reactions occur. One of these is the
formation of hydrogen gas, which can become entrapped and cause
internal stresses, as well as subsequent cracking, as it seeks to
escape the deposit. The width, depth, and population density of
these cracks varies widely and is influenced by the following: the
type of plating chemistry used (single-catalyst, mixed catalyst,
proprietary), chromic acid concentration, type and concentration of
catalyst, chromium-to-catalyst ratio, plating current-density, bath
temperature, concentration of bath impurities (iron, copper, zinc,
nickel, trivalent chromium, etc.), and the chromium deposit
thickness surface condition of substrate.
[0028] Generally speaking, a micro-crack structure comprised of a
high population density of narrow, shallow cracks is preferred
because the deposit tends to have a lower stress, higher lubricity,
good wearability and better corrosion resistance. If the conditions
during plating cause the cracks to be coarse in nature, often
referred to as macro-cracks, they may be visible to the naked eye.
Usually, chromium with a microstructure comprising macro-cracks
exhibits less desirable properties in service. For instance,
corrosive fluids can more easily access the underlying substrate
material through large macro-cracks than smaller micro-cracks.
[0029] A thin dense chromium (TDC) coating with thickness of 0.0001
in. or 0.0003 in. has less structural defects as compared to hard
chrome plating, and is often void of micro-cracks. Thus, TDC
usually exhibits better corrosion resistance than hard chrome
plating. Thin dense chromium plating has been used in various
coating applications such as bearing races, seal surfaces, pump
piston, valves and pump housings, due primarily to its high surface
hardness, low friction coefficient and high corrosion resistance.
However, TDC is typically limited to a maximum thickness of about
0.0005 in., which results in a marked reduction in abrasion,
erosion, abrasive wear, scuffing and galling. Therefore, TDC is
less than ideal for highly abrasive and corrosive environments.
[0030] Embodiments disclosed herein provide coatings, compositions,
and methods to protect and improve the wear and corrosive
resistance downhole tools in oil and gas industry while offering
the potential to overcome some of the foregoing challenges.
[0031] Referring now to FIG. 1, an embodiment of a downhole tool
100 in accordance with the principles described herein is shown. In
this embodiment, tool 100 is a fixed cutter PDC bit adapted for
drilling through formations of rock to form a borehole. Bit 100 has
a central axis 105 about which it is rotated in a cutting direction
106 to drill the borehole. In addition, bit 100 includes a bit body
110, a shank 111, and an externally threaded connection or pin 112
attached to shank 111. Pin 112 connects bit 100 to a drill string
(not shown). Bit body 110 has a bit face 120 formed on the end of
the bit 100 that faces the formation and is generally opposite pin
112.
[0032] A cutting structure 121 is provided on face 120 and includes
a plurality of circumferentially-spaced blades 130 that extend from
bit face 120. In this embodiment, cutting structure 121 includes
six angularly-spaced blades 130. Blades 130 are integrally formed
as part of, and extend from, bit body 110 and bit face 120. Each
blade 130 includes a cutter-supporting surface 131 for mounting a
plurality of cutter elements 132. Each cutter element 132 comprises
a cutting face 133 attached to an elongated and generally
cylindrical support member or substrate 134, which is received and
secured in a pocket formed in surface 131 of the corresponding
blade 130 to which it is fixed. Each cutting face 133 is made of a
very hard material, such as a polycrystalline diamond material,
suitable for engaging and shearing the formation.
[0033] Bit 100 also includes circumferentially-spaced gage pads 140
disposed about the circumference of bit 100. In this embodiment,
gage pads 140 are integrally formed as part of the bit body 110,
with each gage pad 140 extending axially from a corresponding blade
130. Each gage pad 140 has a radially outer gage-facing surface 141
that slidingly engages the borehole sidewall during drilling to
help maintain the size of the borehole and stabilize bit 100
against vibration. In certain embodiments, gage pads 140 include
flush-mounted or protruding cutter elements embedded in gage-facing
surfaces 141 to resist pad wear and assist in reaming the borehole
sidewall.
[0034] To enhance the durability and operating lifetime of bit 100,
select regions of bit body 110 are provided with a multilayered
coating for protecting the base material (for example the metal
forming bit body 110) from wear and corrosion, thereby providing
enhanced wear resistance and corrosion resistance as described
herein. Since formation facing surfaces 131 of blades 130 and
gage-facing surfaces 141 of pads 140 are particularly susceptible
to wear and damage, in this embodiment, a multilayered protective
coating 150 that enhances resistance to wear and corrosion is
provided on the entire formation facing surface 131 of each blade
130 and the entire gage-facing surface 141 of each gage pad 140. In
other embodiments, additional surfaces of the bit body (e.g., bit
body 110) can comprise multilayered protective coatings.
[0035] Referring now to FIG. 2, coating 150 is shown applied to the
outer surface 154 of the base metal or material 153 of bit body
110. In general, coating 150 functions to protect underlying base
material 153 from wear and corrosion during downhole operations.
Coating 150 includes a plurality of layers, and thus, may also be
referred to as "multilayered." In particular, coating 150 includes
a first layer 151 deposited directly onto the outer surface 154 of
base material 153 and a second layer 152 deposited directly onto
the first layer 151. Thus, first layer 151 is positioned between
base material 153 and second layer 152.
[0036] First layer 151 comprises a first material 151a and has a
first thickness T.sub.151 measured perpendicular to outer surface
154, and second layer 152 comprises a second material 152a and has
a second thickness T.sub.152 measured perpendicular to outer
surface 154. In this embodiment, first material 151a and second
material 152a each comprise chromium. As will be described in more
detail below, each chrome layer 151, 152 is applied via an
electrolytic process at a different, discrete current density
(e.g., A/in.sup.2).
[0037] In this embodiment, thickness T.sub.151 of layer 151 is
substantially constant and uniform moving laterally along coating
150, and thickness T.sub.152 of layer 152 is substantially constant
and uniform moving laterally along coating 150. The thickness of
each layer 151, 152, respectively, is preferably less than 0.0050
in. More specifically, thickness T151 is preferably between about
0.00020 in. and 0.0030 in. and thickness T152 is preferably between
about 0.00050 in. and about 0.0050 in. Each layer 151, 152 includes
a plurality of micro-cracks. In general, the micro-cracks in a
given layer 151, 152 can be oriented substantially parallel to the
outer surface 154 of the base material or substantially
perpendicular to the outer surface 154 of the base material 153.
and/or oriented substantially perpendicular to the outer surface of
the base material. The quantity or volume of micro-cracks in each
layer 151, 152 can be characterized in terms of a "micro-crack
density", which refers to the average number of micro-cracks per
unit length (e.g., micro-cracks per inch). A micro-crack is as
known in the art, a crack in the material that is not visible to
the naked eye, thus requiring a microscope (such as but not limited
to SEM) to visualize the crack. A macro-crack in comparison is
visible to naked eye (unaided human visual perception), and is thus
greater than about 55 micrometers). In general, the micro-crack
density of a layer or material can be measured or determined by
microscope or such techniques familiar to one skilled in the art.
The micro-crack density is inversely related to the current density
at which the material is deposited, wherein a low current density
will create a high micro-crack density, and high current density
will produce a low micro-crack density.
[0038] In this embodiment, first layer 151 has a first micro-crack
density, and second layer 152 has a second micro-crack density that
is less than the first micro-crack density. In other words, second
layer 152 has more micro-cracks per unit length than first layer
151. More specifically, in this embodiment, the first micro-crack
density (of layer 151) is greater than 1000 micro-cracks per inch
and the second micro-crack density (of layer 152) is between 400
and 650 micro-cracks per inch.
[0039] Referring still to FIG. 2, coating 150 has an inner surface
156 engaging outer surface 154 of base material 153, an outer
surface 158 distal to the base material 153, and a total thickness
T.sub.150 measured perpendicular to outer surface 154 from inner
surface 156 to outer surface 158. Total thickness T.sub.150 is less
than 0.030 in. As previously described, thicknesses T.sub.151,
T.sub.152 are substantially uniform, and thus, total thickness
T.sub.150 is also substantially constant or uniform moving
laterally along coating 150. The first layer 151 of protective
coating 150 has a first hardness that is greater than 1000 HV and
the second layer 152 of coating 150 has a second hardness of about
850 HV.
[0040] Although coating 150 is shown and described as including two
layers 151, 152, in other embodiments, the multilayered protective
coating (e.g., coating 150) includes more than two layers. However,
in such embodiments, each layer preferably has a thickness less
than 0.005 in. (measured perpendicular to the outer surface of the
underlying base metal or material), and the coating preferably has
a total thickness less than about 0.030 in. (measured perpendicular
to the outer surface of the underlying base metal or material).
[0041] Referring now to FIG. 3, an embodiment of a multilayered
coating 170 for protecting an underlying base metal or material 173
is shown. For example, coating 170 can be used in place of coating
150 previously described to enhance the wear and corrosion
resistance of a downhole tool. In this embodiment, coating 170
includes a first layer includes a first layer 171 deposited
directly onto the outer surface 174 of base material 173 and a
second layer 172 deposited directly onto the first layer 171. Thus,
first layer 171 is positioned between base material 173 and second
layer 172. First layer 171 comprises a first material 171a and has
a first thickness T.sub.171 measured perpendicular to outer surface
174, and second layer 172 comprises a second material 172a and has
a second thickness T.sub.172 measured perpendicular to outer
surface 174. In this embodiment, first material 171a comprises
Ni--P deposited onto surface 174 via a electroless process, and
second material 172a comprises chromium deposited by an
electrolytic process directly onto first layer 171 at a discrete
current density (A/in.sup.2).
[0042] In this embodiment, thickness T.sub.171 of layer 171 is
substantially constant and uniform moving laterally along coating
170, and thickness T.sub.172 of layer 172 is substantially constant
and uniform moving laterally along coating 170. Thickness
T.sub.171, T.sub.172 of each layer 171, 172, respectively, is
preferably less than 0.0050 in. More specifically, thickness
T.sub.171 is preferably between about 0.00020 in. and 0.0030 in.
and thickness T.sub.172 is preferably between about 0.00050 in. and
about 0.0050 in.
[0043] Coating 170 has an inner surface 176 engaging outer surface
174 of base material 173, an outer surface 178 distal to the base
material 173, and a total thickness T.sub.170 measured
perpendicular to outer surface 174 from inner surface 176 to outer
surface 178. Total thickness T.sub.170 is less than 0.030 in. As
previously described, thicknesses T.sub.171, T.sub.172 are
substantially uniform, and thus, total thickness T.sub.170 is also
substantially constant or uniform moving laterally along coating
170. In addition, second layer 172 has a micro-crack density
between 400 and 850 micro-cracks per inch, and more specifically
between 400 and 650 micro-cracks per inch.
[0044] Although coating 170 is shown and described as including two
layers 171, 172, in other embodiments, the multilayered protective
coating (e.g., coating 170) includes more than two layers. However,
in such embodiments, each layer preferably has a thickness less
than 0.005 in. (measured perpendicular to the outer surface of the
underlying base metal or material), the coating preferably has a
total thickness less than about 0.030 in. (measured perpendicular
to the outer surface of the underlying base metal or material), and
the layers of Ni--P and chromium are preferably arranged in an
alternating fashion.
[0045] Embodiments described herein also include methods for making
or forming a wear and corrosion resistant coating on an outer
surface of a base metal or material. In one embodiment, the method
comprises: (a) depositing a first layer of a first material onto
the surface of the base material; and (b) depositing a second layer
of a second material onto the first layer after (a); wherein the
first material or the second material comprises chromium and is
deposited at a current density of less than about 4.0 A/in.sup.2.
In some embodiments, the first material (e.g., material 151a) and
the second material (e.g., material 152a) each comprise chromium;
wherein (a) comprises depositing the first layer of the first
material at a first current density; and wherein (b) comprises
depositing the second layer of the second material at a second
current density that is different than the first current density.
In another embodiment, one of the second current density and the
first current density is about 3.5 A/in.sup.2 and the other of the
first current density and the second current density is about 1.0
A/in.sup.2. In further embodiments, the first current density may
be about 3.0 A/in.sup.2, 2.5 A/in.sup.2, 2.0 A/in.sup.2, 1.5
A/in.sup.2, 1.0 3 A/in.sup.2, and 0.5 A/in.sup.2. In still further
embodiments, the second current density may be about 3.0
A/in.sup.2, 2.5 A/in.sup.2, 2.0 A/in.sup.2; 1.5 A/in.sup.2, 1.0
A/in.sup.2, and 0.5 A/in.sup.2.
[0046] In another embodiment, depositing the first layer of the
first material may be by pulse current; and depositing the second
layer of the second material may also by pulse current.
[0047] In some embodiments of a method of coating a base surface,
the second layer formed from a second material is deposited until
the layer has a thickness of about 0.0002 in. to 0.0003 in.
measured perpendicular to the surface of the base material.
Similarly, in some embodiments, the first layer of the first
material is deposited until the first layer has a thickness of
about 0.00020 in. to 0.0003 in. also measured perpendicular to the
surface of the base material. Embodiments of such a method wherein
the first material consists of chromium and the second material
consists of chromium are illustrated in FIGS. 2 and 4(B).
[0048] Referring now to FIG. 5, an embodiment of a method 200 for
making coating 150 as previously described is schematically shown.
Beginning in block 201 of method 200, first material 151a
comprising chromium is deposited onto base material 153 by a pulsed
or alternative current electroplating to form layer 151. The
chromium of first material 151a is applied to the base material 153
at a first current density, in for example a Heef.RTM. 25 bath,
where the length of time that the current is applied and the
concentration of chromium ions determines the thickness of the
layer. Next in block 202, a second material 152a comprising
chromium is deposited onto first layer 151 by a pulsed or
alternative current electroplating to form layer 152. The chromium
of second material 152a is applied to first layer 151 at a second
current density that is different than the first current density at
which first material 151a is applied, however, each of the current
densities is preferably less than 4.0 A/in.sup.2.
[0049] As shown in block 203, blocks 201 and 202 may be repeated as
necessary to produce a coating on surface 154 comprising any
desired number of discrete layers (e.g., layers 151, 152) of
chromium, as well as any desired total thickness (e.g., total
thickness T.sub.150) that is preferably less than 0.03 in.
[0050] Referring now to FIG. 6, an embodiment of a method 300 for
making protective coating 170 as previously described is
schematically shown. Beginning in block 301 of method 300, a first
material 171a comprising Ni--P is deposited onto base material 173
by an electroless process. In block 303, the Ni--P (first layer
171) is heated at about 375.degree. F. for about 1.5 hr., and
further heated at 500.degree. F. for about 1 hr, wherein the first
layer 171 is heated for a total of 2.5 hrs. In this embodiment, the
resultant layer 171 is about 0.0010 to about 0.0020 inches thick,
has an increased hardness of about 50 Rc. Next, in block 303,
Second material 172a comprising chromium is deposited on first
layer 171 by a pulsed or alternative current electroplating to form
second layer 172. The current density at which second material 172a
is applied is preferably less than 4.0 A/in.sup.2.
[0051] As shown in block 304, blocks 301, 302, 303 may be repeated
as necessary to produce a coating on surface 174 comprising any
desired number of discrete layers (e.g., layers 171, 172) of Ni--P
and chromium, and any desired total thickness (e.g., total
thickness T.sub.170) that is preferably less than 0.03 in.
[0052] Although coating 150 was shown and described in connection
with bit body 110, in general, embodiments of coatings described
herein (e.g., coatings 150, 170) can be applied to the surface of
any downhole tool such as but not limited to mandrels, mud motor
rotors, and agitator rotors. In one embodiment a down-hole tool
comprises a body made of a base material and a protective coating
is mounted to an outer surface of the base material. The protective
coating comprises a first layer deposited directly onto an outer
surface of the base material; and a second layer deposited directly
onto the first layer, wherein the first layer is positioned between
the base material and the second layer; wherein the first layer
comprises chromium having a first micro-crack density and the
second layer comprises chromium having a second micro-crack density
that is less than the first micro-crack density.
[0053] In another embodiment, the first micro-crack density is
greater than 2500 micro-cracks per inch and the second micro-crack
density is between 1000 and 1500 micro-cracks per inch, in a
further embodiment, the first micro-crack density is greater than
1500 micro-cracks per inch and the second micro-crack density is
between 500 and 850 micro-cracks per inch, and in a preferred
embodiment the first micro-crack density is greater than 1000
micro-cracks per inch and the second micro-crack density is between
400 and 650 micro-cracks per inch.
[0054] In some embodiments of the tool described herein, the first
layer has a first thickness measured perpendicular to the outer
surface of the base material, and the second layer has a second
thickness measured perpendicular to the outer surface of the base
material; wherein the first thickness of the first layer is
substantially uniform and the second thickness of the second layer
is substantially uniform. In another embodiment, the second layer
has a thickness between about 0.00005 in. and about 0.020 in.
measured perpendicular to the outer surface of the base material,
and in a preferred embodiment second layer has a thickness between
about 0.00050 in. and about 0.0020 in. measured perpendicular to
the outer surface of the base material.
[0055] In a further embodiment of the tool described herein, the
coating has an inner surface engaging the outer surface of the base
material and an outer surface distal the base material, and wherein
the coating has a total thickness less than 0.050 in. measured
perpendicularly from the outer surface of the base material to the
outer surface of the coating; in a further still embodiment, the
coating has an inner surface engaging the outer surface of the base
material and an outer surface distal the base material, and wherein
the coating has a total thickness less than 0.030 in. measured
perpendicularly from the outer surface of the base material to the
outer surface of the coating. In another embodiment of the tool the
first layer has a first hardness greater than 1100 HV and the
second layer has a second hardness of about 500 HV; in a further
embodiment the first layer has a first hardness greater than 1000
HV and the second layer has a second hardness of about 650 HV; and
in a preferred embodiment the first layer has a first hardness
greater than 1000 HV and the second layer has a second hardness of
about 850 HV.
EXAMPLES
Example 1
[0056] Production of a wear and corrosion resistant coating on the
surface of a downhole tool (e.g., surface 150) in accordance with
principles described herein.
[0057] In one embodiment herein described, a 6.75 inch agitator was
hard chrome plated in a Heef.RTM. 25 bath with alternative current
densities of 2.0 and 4.0 A/in.sup.2. The coated agitator was
subjected to field runs in conditions: water based mud of 8.4 to
10.25 ppg with pH of 7.8 to 11 at 170-176.degree. F. The mud
contained 0.2 to 13.9% solid, 0.25% sand, and 154,000 to 160,000
mg/l of chlorides content. The conventional hard chrome plated
agitator rotor is not recommended to run in chloride concentrations
of >100,000 mg/l. The total run time of alternated current hard
chrome plated agitator rotor was 456 hours of 10 field test
runs
Example 2
[0058] Production of a wear and corrosion resistant coating on a
base material (e.g., coating 150) in accordance with principles
described herein.
[0059] Alternative current electrolytic plating as described herein
was used to create a multilayer Chromium coating (FIG. 5B), and the
microstructure of the coating was compared to a single layer hard
chrome plating of the prior art (FIG. 5A). The coating comprising
of multiple layers of Cr plating can be visualized in the SEM image
of FIG. 5(B). Micro-cracks in the cross-sectional polished surface
of each of the coatings were enhanced by etching with Mable
reagent.
[0060] The Cr plating of the prior art (FIG. 5A) was deposited with
current density of 2 A/in.sup.2. The micro-cracks in the
conventional hard Cr plating were large, and in the deposition
(grow) direction, perpendicular to the surface of the base
material.
[0061] In the embodiment of the protective coating described
herein, the multilayer Cr plating (the darker layer or first chrome
layer) was deposited at 3.5 A/in.sup.2; while the lighter layer or
second chrome layer) was deposited at 1.0 A/in.sup.2. The low
current density layer (second layer) has a denser microstructure,
as evidenced in the FIG. 5B; this is due to the fact that the lower
the current density, the slower the metal ion deposit time, the
dense the product, and the greater the number of micro-cracks per
inch. Further, it can be seen in the first layer that was plated at
a current density of 3.5 A/in.sup.2, that some cracks seemed to
orientate parallel to the plating surface. As is described herein,
the concentration of metal ions, length of deposition, and current
density can all be varied to create a coating that satisfies the
required wear and corrosion resistance.
SUMMARY OF FEATURES AND ADVANTAGES
[0062] Embodiments of the invention described herein provide for
various coatings for application to downhole tools, wherein the
coating provides enhanced wear and corrosion resistant coatings.
Methods for producing such coatings are also provided.
[0063] Various embodiments of current density are employed to
produce a plurality of layers that in some embodiments comprise
chrome, each can be of a different thickness and/or micro-crack
density. Micro-cracks are thus specific to one layer, rather than
to the entire coating (as seen in prior art hard chrome coatings
that comprise one layer), and function to reduce the degree to
which corrosive fluids (for example from drilling environments) can
penetrate the entire thickness of the coating and access the base
material of the underlying tool, causing corrosive and wear
damage.
[0064] Hence the presence of multiple layers in the coating reduce
the degree to which the coating is susceptible to wear and erosion.
Further such a microstructure comprising the described micro-crack
densities are desirable, because the deposited surfaces also have
lower stress, higher lubricity, and enhanced wearability.
[0065] In one embodiment of the method of making a coating for
protecting a base material, the base material is a matrix drill
body, and in a further embodiment, the coating may be applied to
any surface in need of improved corrosive resistance, and or wear
resistance, such as but not limited to downhole drilling equipment
or tools.
[0066] Therefore it is believed that the protective coatings made
by the methods described herein and exemplified in examples
described herein, will impart to a surface and such downhole tools
as drill bit bodies and wear surfaces to which said materials are
applied, improved wear resistance and corrosive resistance as
compared to some conventional protective coatings, downhole tools,
bit bodies and wear surfaces.
[0067] While preferred embodiments have been shown and described,
modifications thereof can be made by one skilled in the art without
departing from the scope or teachings herein. The embodiments
described herein are exemplary only and are not limiting. Many
variations and modifications of the systems, apparatus, and
processes described herein are possible and are within the scope of
the invention. For example, the relative dimensions of various
parts, the materials from which the various parts are made, and
other parameters can be varied. Accordingly, the scope of
protection is not limited to the embodiments described herein, but
is only limited by the claims that follow, the scope of which shall
include all equivalents of the subject matter of the claims. Unless
expressly stated otherwise, the steps in a method claim may be
performed in any order. The recitation of identifiers such as (a),
(b), (c) or (1), (2), (3) before steps in a method claim are not
intended to and do not specify a particular order to the steps, but
rather are used to simplify subsequent reference to such steps.
* * * * *