U.S. patent application number 14/381265 was filed with the patent office on 2015-04-02 for anti-fretting additives for non-lubricated contact surfaces.
The applicant listed for this patent is The Timken Company. Invention is credited to Gary Doll, Peter Drechsler, Ryan Evans, Carl Hager, Paul Shiller.
Application Number | 20150093065 14/381265 |
Document ID | / |
Family ID | 47722549 |
Filed Date | 2015-04-02 |
United States Patent
Application |
20150093065 |
Kind Code |
A1 |
Doll; Gary ; et al. |
April 2, 2015 |
ANTI-FRETTING ADDITIVES FOR NON-LUBRICATED CONTACT SURFACES
Abstract
An anti-fretting rust preventative solution includes a rust
preventative fluid and an anti-fretting additive dissolved in the
rust preventative fluid. The anti-fretting additive includes at
least one compound that is surface-active with steel to produce a
low-shear velocity accommodation layer in a metal-to-metal
interference fit. The anti-fretting rust preventative solution can
be provided in a bearing assembly with metal-to-metal interference
fits, as well as other applications where fretting wear may
otherwise occur.
Inventors: |
Doll; Gary; (Canton, OH)
; Drechsler; Peter; (Canton, OH) ; Hager;
Carl; (Massillon, OH) ; Evans; Ryan;
(Massillon, OH) ; Shiller; Paul; (Youngstown,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Timken Company |
North Canton |
OH |
US |
|
|
Family ID: |
47722549 |
Appl. No.: |
14/381265 |
Filed: |
January 24, 2013 |
PCT Filed: |
January 24, 2013 |
PCT NO: |
PCT/US2013/022904 |
371 Date: |
August 27, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61614364 |
Mar 22, 2012 |
|
|
|
Current U.S.
Class: |
384/625 ;
252/387; 252/388; 252/389.41 |
Current CPC
Class: |
C23F 11/182 20130101;
C23F 11/10 20130101; F16C 19/52 20130101; C23F 11/184 20130101;
C10M 2223/045 20130101; C10M 141/10 20130101; C10N 2030/06
20130101; C10N 2010/12 20130101; C10M 141/12 20130101; C10M
2227/061 20130101; C10N 2030/12 20130101; F16C 33/6688 20130101;
C10N 2040/02 20130101; C23F 11/12 20130101; C10M 169/04 20130101;
F16C 35/06 20130101 |
Class at
Publication: |
384/625 ;
252/387; 252/388; 252/389.41 |
International
Class: |
C23F 11/10 20060101
C23F011/10; C23F 11/18 20060101 C23F011/18; C23F 11/12 20060101
C23F011/12 |
Claims
1. An anti-fretting rust preventative solution comprising: a
non-lubricating rust preventative fluid; and an anti-fretting
additive dissolved in the rust preventative fluid, the
anti-fretting additive including at least one compound that is
surface-active with steel to produce a low-shear velocity
accommodation layer which operates under dry friction principles in
a metal-to-metal interference fit.
2. The anti-fretting rust preventative solution of claim 1, wherein
the rust preventative fluid is a hydrocarbon-based fluid.
3. The anti-fretting rust preventative solution of claim 1, wherein
the at least one compound is surface-active with steel to produce a
low-shear velocity accommodation layer of boric acid.
4. The anti-fretting rust preventative solution of claim 3, wherein
the compound includes at least one of a borate ester, a boronic
ester, and a borinic ester.
5. The anti-fretting rust preventative solution of claim 3, wherein
the at least one compound includes tri-alkyl borate where the alkyl
group is one of an isopropyl group and an n-propyl group.
6. The anti-fretting rust preventative solution of claim 1, wherein
the at least one compound is surface-active with steel to produce a
low-shear velocity accommodation layer of molybdenum disulfide.
7. The anti-fretting rust preventative solution of claim 6, wherein
the at least one compound includes molybdenum dithiophosphate.
8. The anti-fretting rust preventative solution of claim 1, wherein
the amount of the anti-fretting additive is at least 0.5 percent
and less than 50 percent by volume.
9. The anti-fretting rust preventative solution of claim 1, wherein
the amount of the anti-fretting additive is between about 1 percent
and about 10 percent by volume.
10. The anti-fretting rust preventative solution of claim 1,
wherein the amount of the anti-fretting additive is about 5 percent
by volume.
11. A bearing assembly with anti-fretting properties, the bearing
assembly comprising: a ring secured to a mating component with a
non-lubricated metal-to-metal interference fit; an anti-fretting
rust preventative solution provided in at least the interference
fit, the anti-fretting rust preventative solution including a
non-lubricating rust preventative fluid and an anti-fretting
additive dissolved in the rust preventative fluid, the
anti-fretting additive including at least one compound that is
surface-active with steel to produce a low-shear velocity
accommodation layer which operates under dry friction
principles.
12. The bearing assembly of claim 11, wherein the rust preventative
fluid is a hydrocarbon-based fluid.
13. The bearing assembly of claim 11, wherein the at least one
compound is surface-active with steel to produce a low-shear
velocity accommodation layer of boric acid.
14. The bearing assembly of claim 13, wherein the at least one
compound includes at least one of a borate ester, a boronic ester,
and a borinic ester.
15. The bearing assembly of claim 13, wherein the at least one
compound includes tri-alkyl borate where the alkyl group is one of
an isopropyl group and an n-propyl group.
16. The bearing assembly of claim 11, wherein the at least one
compound is surface-active with steel to produce a low-shear
velocity accommodation layer of molybdenum disulfide.
17. The bearing assembly of claim 16, wherein the at least one
compound includes molybdenum dithiophosphate.
18. The bearing assembly of claim 11, wherein the amount of the
anti-fretting additive is at least 0.5 percent and less than 50
percent by volume.
19. The bearing assembly of claim 11, wherein the amount of the
anti-fretting additive is between about 1 percent and about 10
percent by volume.
20. The bearing assembly of claim 11, wherein the amount of the
anti-fretting additive is about 5 percent by volume.
21. The bearing assembly of claim 11, wherein the ring is an inner
ring secured with the mating component, a shaft, with the
interference fit, which is a first interference fit, and wherein
the bearing assembly further comprises an outer ring secured in a
bore of a housing with a second interference fit; and the
anti-fretting rust preventative solution is further provided in the
second interference fit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/614,364, filed Mar. 22, 2012, the entire
contents of which are hereby incorporated by reference.
BACKGROUND
[0002] The present invention relates to treatments for
non-lubricated contact surfaces such as "fixed" metal-to-metal
joints in bearing assemblies, for example a shaft fitted into the
bore of an inner ring, or the outer surface of an outer ring fitted
into a housing. These "fixed" joints are typically press-fitted or
shrink-fitted together and generally intended to eliminate movement
therebetween. With small-bore size bearings, it is usually not a
challenge to achieve adequate interference fits (sometimes referred
to as tight fits) to prevent or inhibit fretting wear. However,
achieving sufficient interference fits with large bore bearings can
be significantly more difficult. Repetitive oscillatory movements
of small amplitude can occur between the surfaces of the
interference fit due to certain torque and/or vibration occurrences
during operation of the bearing assembly. In these circumstances,
fretting wear is initiated by adhesion and rupture of contacting
asperities. Fretting wear can also be amplified by oxidation or
corrosion and then manifest as abrasive wear. Thus, fretting wear
is a common concern for interference fits for inner and outer rings
in large bore bearings. Fretting wear can further result in seizure
of components by corrosion and abrasion damage and/or by adhesion
and welding between the parts.
[0003] Because the contact surfaces are not fitted with a running
clearance and generally must not rotate relative to one another,
commercially available greases or lubricants cannot be used to
prevent the fretting wear. As such, these contact surfaces
represent a "dry" friction situation. Typically, the only substance
present in the metal-to-metal joint is a thin coating of rust
preventative oil applied after manufacturing. However, the rust
preventative oil does not have properties that significantly
protect the surfaces from fretting wear damage. A standard practice
used by some bearing manufacturers to reduce the risk of fretting
wear of large bore bearings is to apply a coating of a low friction
material, covering the metal bearing ring surface that is
susceptible to the fretting wear. For example, a Teflon.RTM.-based
coating or a chromium-based coating may be provided such that true
metal-on-metal contact is avoided. Although these coatings are
believed to be effective at reducing the risk of fretting wear,
adding a coating to the bearing ring(s) is costly and adds
complexity to the manufacturing process.
SUMMARY
[0004] In one aspect, the invention provides an anti-fretting rust
preventative solution that includes a rust preventative fluid and
an anti-fretting additive dissolved in the rust preventative fluid.
The anti-fretting additive includes at least one compound that is
surface-active with steel to produce a low-shear velocity
accommodation layer in a metal-to-metal interference fit.
[0005] In another aspect, the invention provides a bearing assembly
with anti-fretting properties. The bearing assembly includes a
shaft, an inner ring secured to the shaft with a first interference
fit, a housing including a bore, an outer ring secured in the bore
of the housing with a second interference fit, and an anti-fretting
rust preventative solution provided in at least the first and
second interference fits. The anti-fretting rust preventative
solution includes a rust preventative fluid and an anti-fretting
additive dissolved in the rust preventative fluid. The
anti-fretting additive including at least one compound that is
surface-active with steel to produce a low-shear velocity
accommodation layer.
[0006] Other aspects of the invention will become apparent by
consideration of the detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 illustrates conformal fretting wear test friction
results of 5 percent tri-isopropyl borate in a rust preventative
oil.
[0008] FIG. 2 illustrates conformal fretting wear test temperature
results of 5 percent tri-isopropyl borate in a rust preventative
oil.
[0009] FIG. 3 is an illustrative summary of the conformal fretting
testing of 5 percent tri-isopropyl borate in a rust preventative
oil.
[0010] FIG. 4 is a perspective view of a conventional bearing
assembly.
DETAILED DESCRIPTION
[0011] Before any embodiments of the invention are explained in
detail, it is to be understood that the invention is not limited in
its application to the details of construction and the arrangement
of components set forth in the following description or illustrated
in the following drawings. The invention is capable of other
embodiments and of being practiced or of being carried out in
various ways.
[0012] FIG. 4 illustrates a typical bearing assembly 10 including
an inner ring 12, a shaft 14 secured within a bore 12A of the inner
ring 12, an outer ring 16, and a housing 18 having a bore 18A in
which the outer ring 16 is secured. The inner ring 12 and the outer
ring 16 have a low friction coupling therebetween, such as rolling
elements (not shown). The bore 12A of the inner ring 12 has an
interference fit with the shaft 14 to inhibit relative rotation
between the inner ring 12 and the shaft 14. Likewise, the outer
ring 16 has an interference fit with the bore 18A of the housing 18
to inhibit relative rotation between the outer ring 16 and the
housing 18. The interference fits can be achieved by press-fitting
or shrink-fitting. In either case, the interference fit between the
inner ring 12 and the shaft 14 and the interference fit between the
outer ring 16 and the housing 18 both result in metal-to-metal
surface contact. In some constructions, the bearing assembly 10 can
be a large size bearing assembly in which the bore 12A of the inner
ring 12 is greater than about 200 mm. It should be understood that
certain applications may require only one bearing ring, and thus a
single metal-to-metal interference fit.
[0013] To prevent or inhibit corrosion on at least the inner and
outer rings 12, 16, a rust preventative (RP) fluid is provided on
the surfaces of the inner and outer rings 12, 16. The RP fluid may
also be provided on one or both of the shaft 14 and the housing 18.
The RP fluid can be a hydrocarbon-based fluid (or water-based rust
preventative fluid) that wets the surfaces of the inner and outer
rings 12, 16. Hydrocarbon-based fluids can include petroleum-based
fluids (e.g., a thin oil with kerosene-like consistency) or
non-petroleum-based fluids (e.g., vegetable or plant oils,
synthetics, etc.) or water soluble oil or water-based synthetic
rust preventative solution. Examples of suitable RP's include but
are not limited to Quaker FERROCOTE.RTM. 5856 BF and Quaker
FERROCOTE.RTM. 5856 BF T1. To provide an anti-fretting property to
the metal-to-metal surface contacts, at least one additive is added
to the RP to form a solution. Such additives can include at least
one of a boron compound (e.g., boric acid, salts of boric acid such
as sodium borate, a borate ester, a boronic ester, or a bonnie
ester) and an extreme pressure (EP) additive (e.g., molybdenum
dithiophosphate "MoDTP"). For example, the additive can include at
least one tri-alkyl borate where the alkyl group is any straight or
branched alkyl group similar to but not limited to ethyl, n-butyl,
iso-butyl, tert-butyl, n-pentyl, iso-pentyl, etc. (e.g., tri-alkyl
borates like tri-isopropyl borate or tri-propyl borate). Regardless
of the exact type, the anti-fretting additive stays in solution in
the RP fluid so that fretting wear protection is provided when at
least one of the inner ring 12 and the shaft 14, which are
assembled into the first interference fit, and at least one of the
outer ring 16 and the housing 18, which are assembled into the
second interference fit, are wetted with the RP. In some
constructions, one or both of the inner ring 12 and the shaft 14
and one or both of the outer ring 16 and the housing 18 are steel,
and the anti-fretting additive can be surface-active with steel
(i.e., subject to a chemical reaction in a steel-on-steel
concentrated contact) to produce a shear deformation layer, or
"low-shear velocity accommodation layer", such that when two
surfaces move relative to each other, the sliding interface resides
in the low-shear velocity accommodation layer. Low-shear velocity
accommodation layers are discussed in detail in Y. Berthier, M.
Godet & M. Brendle (1989): Velocity Accommodation in Friction,
Tribology Transactions, 32:4, 490-496, which is incorporated by
reference herein. For example, this reference describes in detail
the differences between simple thick film lubricants, which operate
only through fluid shear according to predictable fluid dynamic
principles, and "dry" friction, which operates through numerous,
more complex mechanisms to accommodate movement between two bodies
or surfaces. In dry friction, an oil film may be present, but the
mechanisms of velocity accommodation do not adhere to the simple
fluid principle of shear alone. As used herein, "velocity
accommodation layer" refers to a layer between two bodies or
surfaces that enhances the ability for movement (i.e., non-zero
velocity) therebetween. In some constructions, boron compounds
dissolved in the RP fluid can be surface-active with steel to
produce a velocity accommodation layer of boric acid. Also, MoDTP
as an additive is surface-active with steel to produce a velocity
accommodation layer of molybdenum disulfide MoS.sub.2. Boron
compounds such as tri-isopropyl borate and tri-propyl borate and
some EP additives like MoDTP have been observed in the inventors'
labs to function well as velocity accommodation layers in the kind
of reciprocating contact that causes fretting. Experimental testing
has shown this methodology to be extremely effective at inhibiting
fretting wear without sacrificing the inherent corrosion protection
of the RP.
[0014] Two methods of testing were used to determine the efficacy
of the additives and also demonstrate the use. The first was the
Fafnir Fretting Oxidation test (ASTM D-4170-97), which is a
standard test for fretting wear. The second was an oscillating
conformal fretting test that emulates a ring on shaft application.
Although not limiting, the testing disclosed herein was conducted
on four different solutions. The four solutions were created by
combining (e.g., dissolving) one of two additives (tri-isopropyl
borate and 2-ethylhexyl molybdenum dithiophosphate) as a solute at
5 percent by total volume with one of two RP fluids (FERROCOTE.RTM.
5856 BF T1 and FERROCOTE.RTM. 5856 BF) as a solvent. The
FERROCOTE.RTM. 5856 BF T1 RP fluid is the same as or similar to the
FERROCOTE.RTM. 5856 BF, further diluted with a solvent. The tests
were replicated at least twice. The Fafnir test was run according
to the ASTM procedure and the conformal fretting wear test was run
according to the following parameters: [0015] Clearance:
.about.0.254 mm (0.010 inches) [0016] Inner Ring Dia.: .about.49.23
mm (1.938 inches) [0017] Outer Ring Bore: .about.49.48 mm (1.948
inches) [0018] Contact Width: .about.13.07 mm (0.515 inches) [0019]
Load: .about.4480N (1000 lbs) [0020] Contact Stress: .about.53 MPa
(7.7 ksi) [0021] Inner Ring Surface Finish: .about..mu.m (pin)
[0022] Outer Ring Surface Finish: .about.0.813 .mu.m (32 pin)
[0023] Oil: 0.1 mL of FERROCOTE.RTM. 5856BF in the contact [0024]
Oscillation: 5 degrees at 13.3 Hz [0025] Duration: 22 hours or when
test is suspended by temperature (100 deg. C.) or friction (110
lbs).
[0026] The Fafnir test is most commonly used as a grease test so
the preparation was modified to give testing conditions closer to
that of the actual rust preventative conditions in the field.
Samples were ultrasonically cleaned in Hexanes and Isopropanol. A
thin layer of FERROCOTE.RTM. 5856 BF or FERROCOTE.RTM. 5856 BF plus
5 percent tri-isopropyl borate was applied to the surfaces of the
inner and outer ring. All excess was wiped off or allowed to drip
off (e.g., for 5 minutes). Once the inner ring was mounted on the
Falex spindle, a 0.1 mL drop of the test solution was placed on the
top of the test ring prior to mounting the outer ring. Multiple
tests were conducted on each solution.
[0027] The Fafnir test measures weight loss. The larger the weight
loss, the larger the fretting wear. The results are tabulated
here.
TABLE-US-00001 TABLE 1 Average weight loss: Baseline 5856BF T1
3.475 mg 5% TIPB/5856BF T1 0.875 mg 5% MoDTP/5856BF T1 -0.075
mg
TABLE-US-00002 TABLE 2 Average weight loss: Baseline 5856BF 1.075
mg 5% TIPB/5856BF 0.250 mg 5% MoDTP/5856BF 0.450 mg
[0028] ASTM D-4170 is designed to test greases and the statistical
evaluation in the documentation is correct for grease. This testing
was performed on oil rust preventatives rather than grease, so we
rely on statistical data drawn from the measurements. The range of
values found for the studies with FERROCOTE.RTM. 5856BF T1 for the
baseline sample was 1.8 mg. The range for the baseline sample in
the FERROCOTE.RTM. 5856BF tests was 0.38 mg. The trend is similar
in both tests that the additives did reduce fretting wear.
[0029] The result of the conformal fretting wear test is a time to
the suspension of the test due to friction or temperature. When the
test conditions reach the cutoff for friction or temperature the
film protecting the surfaces from fretting has failed. The longer
the film lasts, the better the protection. The results are
summarized in Table 3 below.
TABLE-US-00003 TABLE 3 Falex Test Results - Time to 65 lbs Friction
Cutoff Time (hrs) Time (hrs) Solution Test 1 Test 2 RP Baseline 2.1
2.0 RP w/5% TIPB 10.5 8.9 RP w/5% MoDTP 11.4 10.5
[0030] Since the additized RP solution is intended to be first and
foremost a corrosion inhibitor, the rust preventative properties of
the additized RP solution were tested. A long-term humidity cabinet
test was also conducted according to ASTM 1748. Samples coated with
a solution of 5 percent by volume tri-isopropyl borate in Quaker
FERROCOTE.RTM. 5856 T1 did not display corrosion after four months
exposure to 120 degrees Fahrenheit at 90 percent relative humidity.
Thus, it was determined that the anti-fretting additive had no
detrimental effect on the corrosion prevention ability of the RP
fluid itself Other additives, such as the MoDTP, are lubricant
additives and because of their use in bearings are understood to
have no ill effect on the corrosion protection of an RP fluid.
[0031] RP fluids additized as described herein can be direct
replacements for RP fluids already in use. The amount of the
additives in an RP solution can be about, or at least about, 0.1,
0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 percent by total volume (v/v),
and about or less than about, 90, 80, 70, 60, 50, 40, 30, 20, or 10
percent by total volume (v/v), but other amounts can also be
effective. In some constructions, the amount can be between about 1
percent and about 10 percent by total volume (v/v), and more
particularly, can be about 5 percent by total volume (v/v) in some
constructions. Although there is not necessarily an upper limit, at
very high concentrations of additive, the rust preventing
properties of the base RP fluid may begin to be sacrificed. In
other words, the additives will not cause corrosion, but there
should be a minimum amount (e.g., about, or at least about, 10, 20,
30, 40, 50, 60, 70, 80 or 90 percent) of the base RP fluid
necessary to perform the basic function of inhibiting corrosion.
The additized RP solution can be applied in any manner as RP fluids
are typically applied. In some constructions, the parts are dipped
and allowed to drain. Although FERROCOTE.RTM. 5856BF and
FERROCOTE.RTM. 5856BF T1 are given as examples herein, there is not
necessarily a preference between the two, and those of ordinary
skill in the art will realize that other known RP fluids can also
be modified into solutions with anti-fretting additives as
described herein.
[0032] Another aspect of equal importance is that false brinelling,
or fretting can occur between the rolling elements and the raceways
of a bearing prior to installation in the application. An
anti-fretting RP solution as described herein can also reduce the
risk of this type of wear occurring during shipping and storage,
for example. The fretting wear prevention due to the additives in
RP solutions as described herein may also be used to mitigate
fretting wear in other situations besides interference fits of
bearing rings, and in metal components besides bearings altogether.
Shipping of metallic parts often requires some form of fretting
wear protection--either a lubricant such as grease or a physical
barrier like plastic or cardboard. The fretting wear protection
from an anti-fretting RP solution as described herein can be great
enough to be used alone in place of these other forms of fretting
wear protection at a lower cost.
* * * * *