NLG~
Ashless Multifunctional Additive Technology for
Rolling Element Bearing Grease
William Ward Jr. CLGS and Scott Capitosti, Ph.D., The Lubrizol Corporation, Wickliffe, Ohio, U.S.A.
Presented at NLGI’s 80th Annual Meeting, June, 2013, Tucson, Anzona, USA
speed and the operating environmental conditions (5).
Greases operating at higher temperatures well above
the standard temperature of 70°C, or in wet or dusty
conditions, need to be re-lubricated more frequently
than those operating at normal temperatures in a clean
and dry atmosphere.
Introduction
Lubricant Role
T
ishisintended
paper builds
to provide
upon aprevious
better understanding
work from 2009
onand
the development of long life greases (1). The role of the
lubricant in a rolling element bearing is to help maintain
the bearing’s long-life and anti-friction characteristics.
(2, 3, 4) It does this by minimizing rolling resistance
due to deformation of the rolling elements and raceway
under load by separating the mating surfaces. It is also
there to minimize sliding friction occurring between roll
ing elements, raceways and cage, especially in roller
bearings where much more sliding occurs. In industrial
applications, the performance of the sealing is typically
much less than what is seen in sealed-for-life auto
motive bearings. An important role for grease is the
prevention of contaminant ingress. In many cases, the
grease cannot totally prevent water from entering into
the bearing, and is required to protect the mating sur
faces from water-induced corrosion.
The components of industrial machinery requiring
grease lubrication include bearings, couplings, open
gears and a variety of other moving components. The
widest use of grease is in lubricating bearings, which
are critical elements in equipment used in steel mills,
mining, construction and transportation. In industrial
equipment, both plain and rolling-element bearings are
used. In either case, a robust film of lubricant separat
ing moving surfaces is essential for a long service life.
In many typical industrial applications, the bear
ing is fitted with a lubricator or zerk fitting, and the
maintenance schedule dictates when the bearing is
to be re-lubricated and how much grease needs to
be added to the bearing. The quantity of grease to be
used is a function of the size and type of the bearing.
Furthermore, the re-lubrication interval is defined based
on the size and type of the bearing, the loading, the
Grease Market
In 1990, automotive greases accounted for 50% of
the world’s grease use, but today, it is only around
40% to 45% due to the filled-for-life applications seen
in passenger cars and increased service intervals for
commercial vehicles. The typical life of a passenger car
or light duty truck has increased and vehicle manufac
turers have extended the warranty period from typically
three years and 30,000 miles to 10 years and 100,000
miles. In the same time period, the re-lubrication
intervals of commercial vehicles have increased from
10,000 miles to 25,000 miles. A desired point is that
grease re-lubrication should be the same interval as the
crankcase oil at 40,000 miles. Significantly improved
greases are needed to satisfy this requirement.
Industrial applications comprise the other 55% to
60% of the grease market. There are many different
applications which consist of stationary and rotating
components such as pins, hinges, various types of
bearings and gears. Of interest here are electric motor
bearings and more specifically electric driven motor
systems (EDMS) where electricity is used to drive
motors in a system to convert electricity into rotational
energy. Electric motors are widely used across all sec
tors of the economy, including industrial, commercial,
residential and transportation/agriculture, and in many
applications such as pumps, fans and compressors (6).
Re-lubrication intervals for electric motor rolling element
bearings depend on various factors including tempera
ture, contamination, moisture, vibration, position
(horizontal, vertical, angular) and rolling element type.
—27—
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
NLGil
Bearing Tests
A few rolling element bearing tests are considered for
evaluating the performance of grease, with one of the
most well known in North America being the ASTM
D3527 high temperature bearing test. This test is used
for automotive wheel bearings. Another test which is
used for high temperature applications is the ASTM
D3336, also known as the “Pope Test”. This test is
used for military spindle bearing and electric motor
bearing grease evaluation. Finally, the last test is the
FAG FE9 test which is used to define ISO/DIN grease
performance. Ultimately, performance in these three
test methods are the basis for defining the outcome of
the ashless additive technology described in this paper
as multi-functional for rolling element bearings.
work and selection of components. Matrix testing
involved the separation of the individual components
into their respective functional areas (i.e. sulfur EP,
phosphorus AW, AO, and inhibitors) and preparation
of additive concentrates blended from the appropriate
ratios of additives delivering the same concentrations
to grease as in the typical 4% formulated additive
with base oil replacing the components removed.
This required a total of 16 different combinations to
allow the assessment of each individual additive con
centrate by itself and in combination with the other
additives, while keeping the percent thickener constant
so that additive effects would be observed. Table 1
illustrates the grease additives matrix breakdown used
in this study.
Additional Greases Tested
Experimental
Grease Q: Benchmark urea electric motor bearing
grease for comparative testing.
Materials
This study utilized a commercially manufactured urea
base grease made in Group I, ISO VG 150 base oil.
The greases were all additized as discussed below and
cut to an NLGI Grade #2 using the base oil mixture
while keeping a constant thickener level among all
the greases. The typical grease blending procedure
entailed diluting the base greases at 8000 with the
base oil mixture, mixing in the pre-blended additive
concentrates for ~20 minutes, homogenizing on a triple
roller mill and de-aerating under vacuum. Half-scale
penetrations and dropping points were checked on all
greases to understand any impact of different formula
tion components on the penetration range and drop
ping point.
Additives
The additive under consideration is a new multifunctional ashless package specially formulated to give
the grease a robust ASTM D4950 (7) performance. The
package includes sulfur extreme pressure additives
(S-EP), a phosphorus anti-wear/multi-purpose additive
(P-AW), an antioxidant (AO) and corrosion/rust inhibi
tors (INH). The additives were formulated as a typical
4% by weight treatment based upon the preliminary
Grease R: Benchmark urea electric motor bearing
grease for comparative testing.
Grease S: The additive formulation from matrix Grease
P was blended into a Group II, ISO 150 VG lithium
complex grease and graded with ISO 150 VG oil to
a NLGI #2 consistency using the same scheme as
described above. The grease was then tested for con
formance to D4950 GO-LB requirements for compari
son to Grease P.
Key Tests
ASTM D4950 (7) This test specification covers the
categories for lubricating greases for automotive ser
vice fill. The applications that are covered under this
specification include both chassis grease and wheel
bearing grease. The greases described under this
specification are applicable for automobiles, trucks and
other vehicles. The method describes the specific and
applicable tests and limits to approve a service license
that may be obtained from the National Lubricating
Grease Institute (NLGI).
—28—
VOLUME 77, NUMBER 6
p~r
ASTM Dl 743 (8) This test method covers the determi
nation of the corrosion preventive properties of greases
using grease lubricated tapered roller bearings stored
under wet conditions. New, cleaned and lubricated
bearings are run under a light thrust load for 60 ± 3s to
distribute the lubricant in a pattern that might be found
in service. The bearings are exposed to water and then
stored for 48 ± 0.5 hours at 52 ± 1°C (125 ± 2°F) and
100% relative humidity. After cleaning, the bearing cups
are examined for evidence of corrosion.
ASTM D2266 (9) This test method covers the deter
mination of the wear preventive characteristics of
greases in sliding bearing steel-on-steel contacts. It is
not intended to predict wear characteristics with other
metal combinations nor to evaluate the extreme pres
sure characteristics of the grease. A steel ball is rotated
under load against three stationary steel balls having
grease-lubricated surfaces. The diameters of the wear
scars on the stationary balls are
measured after completion of
the test.
NLG~
ASTM D5483 (11) This test was used to evaluate
the oxidation resistance of experimental greases. The
grease (2.0 ± 0.1 mg) is placed in a small aluminum
pan inside a pressure vessel on a heat flow sensor. An
empty pan is placed on a second sensor and the vessel
is sealed. The chamber is then heated to the highest
test standard temperature of 210°C and 3500 MPa
(500 psi) of oxygen is introduced. The sample is held
isothermally at the test temperature until the grease
starts to oxidize. The resulting exotherm is detected by
the sensor. The point at which the oxidation acceler
ates away is calculated and this is termed the oxidation
induction time (OIT).
ASTM D3527 (12) This wheel bearing grease life test
represents a measure of performance for automotive
service grease under elevated temperature running. It is
used to quantify grease life under the conditions of test
for the GB or GC requirements of the ASTM D4950 (7)
Table 1
Grease Matrix Breakdown
Additive Matrix
ASTM D2596 (10) This test
method covers the determination
of the load carrying properties of
lubricating greases. Three deter
minations are made: 1) last nonseizure load, 2) load-wear index or
LWI (formerly called Mean-Hertz
Load) and 3) weld point. The test is
operated with one steel ball under
load rotating against three steel
balls held stationary in a cup. The
rotating speed is 1770 ± 60rpm.
Lubricating greases are brought to
27 ± 8°C (80 ± 15°F) and then sub
jected to a series of steps of 1 Os
duration at increasing loads until
welding occurs. This test method,
used for specification purposes,
differentiates between lubricating
greases having low, medium and
high level of extreme-pressure
properties.
iditive not present; 1 =additive is present)
Grease Identification
P-AW
S-EP
INH
0
0
0
0
1
0
0
0
0
0
1
0
0
0
1
1
0
0
0
1
0
0
0
1
1
1
0
~
0
0
1
1
1
~
1
0
0
1
1
1
0
1
1
1
1
1
1
~
1
—29 —
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
NLGI
requires a minimum of four, preferably five bearings to
be run to failure and the L10 (F10) & L50 (F50) lives in hours
are calculated by using Weibull statistics (14). The
conditions chosen are described under results. A L50
of 100 hours under a given set of conditions is defined
as the acceptable criteria to meet DIN and ISO grease
standards for rolling element bearings under DIN 51825
(15) and ISO 12924 (16) as read in conjunction with
ISO 6743-9 (17).
standard classification. The test is considered a bear
ing oxidation/degradation test for grease. Two tapered
roller bearings are run under a low axial load of 1 11 N
at 1000 rpm. Temperature in the bearing housing is
controlled to 160°C. Based on the bearing torque after
a running in period, a cut-off torque is calculated and
if the grease breaks down and the torque reaches the
cut-off, the test is stopped and the number of running
hours to failure is recorded. The bearings are run for
20 hours and then undergo a four hour rest period.
At the end of the rest period the bearings are restarted.
Normally on start up after a rest period there is an
increase in torque. If the torque does not drop to below
the cut-off torque within a short period of time (typically
30 to 90 seconds), the test rig shuts itself off and the
grease is considered to have failed at the end of the
20 hour running period, and the number of hours to
failure is reported.
DIN51 821 (13) This is
the FAG FF9 test and
is widely used to define
grease oxidation life in
bearings. The test utilizes
62 mm outer diameter
angular contact ball bear
ings (ISO designation
7206) mounted in hous
ings in which thrust and
axial loads are applied.
The test equipment is
defined by DIN51 821
part 1 and the test
method is defined in
part 2 of the same stan
dard. There is a choice
of three axial loads 1500,
3000, 4500 N, and
two speeds, 3,000 and
6,000 rpm and of stan
dard temperatures: 120,
140, 160, 180, 200°C.
In order to generate
meaningful data, the test
Grease
Identification
A
B
C
D
F
F
G
H
I
J
K
L
AO
0
1
0
0
0
1
1
1
0
0
0
1
_____________
_______
____________
______
____________
_______
_____________
_______
_______
ASTM D3336 (18) This test method covers the evalu
ation of the performance of lubricating greases in ball
bearings operating at high speeds and elevated tem
peratures. A grease lubricated 6204 deep groove ball
bearing is rotated at 10,000 rpm under light axial and
radial loads at a specified elevated temperature. Tests
are continued until failure or completion of a specified
number of hours of running time. This test method can
Table 2
Penetration and Dropping Point
Additive Matrix
(0=additive not present; 1 =additive is present)
P-AW
S-EP
INH
Dl 403
D2265
wO I w60
(°C)
0
0
0
249/265
285
0
0
0
279/275
290
1
0
0
275/291
312
0
1
0
273/273
297
0
0
1
275/281
305
1
0
0
275/291
314
0
1
0
279/279
297
0
0
1
265/283
316
1
1
0
265/285
301
1
0
1
255/277
312
0
1
1
259/275
303
1
1
0
259/283
302
M
1
0
1
1
259/275
293
___________
N
______
1
1
0
1
265/285
315
_____________
0
_______
0
1
1
1
265/285
303
P
1
1
1
1
265/281
296
~ —
~
—30
—
VOLUME 77, NUMBER 6
— ~—
NLGI
Table Al summarizes all test data. Not surprisingly,
Grease A (no additives) resulted in the largest wear
scar of 0.79 mm. Explanation of antiwear is almost as
easy as bearing rust. Seven of eight greases contain
ing P-EP have wear scars less than 0.6mm and the
last one gave a borderline wear scar of 0.61 mm. Less
understood is the reason why AO alone and in com
bination with 5-EP and INH at the same time deliver
adequate antiwear. One explanation of this might be
that the polarity helps to maintain a reasonable film of
the component. The results show that of the greases
containing AO, nearly 63% of them pass wear but
70% of the time P-EP is present to confound a firm
conclusion. The higher wear results of Greases D, E,
K and H suggest that either S-EP or INH antagonizes
antiwear. Grease 0 (containing P-AW, S-EP and INH)
performed the best, and the data indicated that the
AO component is not necessary to achieve good wear
performance. Furthermore, while Greases B and C did
meet the GO-LB wear limit, it appears that a robust
D2266 pass requires at the very least a combina
tion of P-AW and 5-EP components. If these two addi
tive types are present together the wear result is good
no matter if the other additive types are present or not.
Table 4 shows passing wear greases and components
sorted from lowest to highest wear scar.
be used to evaluate the ability of grease to provide
adequate lubrication for extended periods of ball bear
ings operating under light loads at high speeds and
elevated temperatures.
Testing Results and Discussion
Initial Evaluations
As discussed above, 16 greases with identical thick
ener content were prepared as outlined in Table 1.
Table 2 shows the detailed penetration and dropping
point results. As expected, all greases met NLGI
Grade #2 criteria with high dropping points. The com
plete matrix of greases was then subjected to evalua
tion in some of the key property tests of ASTM D4950,
and the results of these studies are presented below.
Key Property Test 1: Water Corrosion
To better understand the contribution of each additive
type toward corrosion protection, each grease in the
matrix was tested in ASTM Dl 743, with a pass being
required in order to meet ASTM D4950. All test data
is shown in Table Al. Grease A (with no additive) gave
a Fail Light result, as did Grease B (only AO), Grease
D (only S-EP), Grease E (only INH), Grease G (AO
and S-EP), Grease H (AO and INH), Grease K (S-EP
and INH) and Grease M (AO, S-EP and INH). All other
greases provided passing results. This data clearly
Table 3
indicates that the AO, S-EP and INH components
ASTM Dl 743 Pass Data
of this additive package, either alone or in any
combination with each other, are detrimental to
Additive Matrix
Grease
(0=not
present; 1 =present)
water corrosion protection. To further help with
Identification
differentiation, Table 3 shows the passing results
AO P-AW S-EP INH
sorted from the fail results. The P-AW multifunctional
0
0
1
0
0
component was a necessary ingredient for bearing
F
1
1
0
0
rust protection.
I
0
1
1
0
J
0
1
0
1
Key Property Test 2: Four-Ball Wear
L
1
1
1
0
Next, the grease samples were evaluated by a
N
1
1
0
1
four-ball wear tester to assess the additive contri
butions toward antiwear performance. The ASTM
0
0
1
1
1
D4950 specification requires a maximum of a
P
1
1
1
1
~
0.6 mm wear scar as acceptable for GO-LB.
—
—31
—
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
—
Dl 743
Rating
Pass
Pass
Pass
Pass
Pass
Pass
Pass
Pass
NLGII
Key Property Test 3 Four-BaIl EP
ASTM D2596 was used to assess comparative EP
performance of the greases. All data is summarized in
Table Al and passing data is summarized in Table 5.
As expected, the grease without additives (Grease A)
did not meet either requirement. The S-EP component
proved to be necessary to achieve a GO-LB passing
result almost 90% of the time, shown by the results of
Greases I, M, G, D, 0, P and L. The only additive type
to perform well every time was the S-ER Grease K was
the only anomaly found as it contained
all other additives and only missed S-ER
Upon closer inspection the data indicated
that all two-way interactions of additives
where S-EP is not one of the components
Grease
Identification
provided low Elb characteristics. As the
number of components increase, as in
the Grease K example, the EP may be
weakly compensated to the minimum
requirement of GO-LB.
Key Property Test 4 Pressure
Differential Scanning Calorimetry
The ASTM D5483 test is not included
under standard D4950 specifications, but
is instead an additional test that can be
used to further differentiate grease prod
ucts. It is commonly used as a screening
tool, but also as a product differentiator
for oxidative stability. In this case, it was
desired to screen greases to help shorten
the time frame of testing since much of
the work was done in parallel by assess
ing the oxidation characteristics. Of the
three standard isotherms
1 55°O, 1 80°O
and 21000
the 16 greases were all run
under a 21000 isotherm, and the results
are shown in Table Al with individual
results plotted in Figure 1. The 210°O
isotherm was chosen because of test
experience and realization that testing
at 1 80°O might take an extended time.
Grease A (no additives) almost instanta
neously oxidized. The S-EP component
—
—
alone (Grease D) showed a substantial improvement in
OIT with a result of nearly 24 minutes. As was demon
strated in the D2596 test, the S-EP additives appeared
necessary to achieve good performance in this test.
Adding the AO component to the S-EP (Grease G)
resulted in an OIT nearly double that of the S-EP alone.
Oxidative stability of a grease is an important factor
in D5483 performance (11, 19). Not only do sulfur
components function in EP performance, but they also
have well-documented benefits in terms of antioxidant
behavior (20). Thus, it is not surprising that the PDSO
Table 4
ASTM D2266 Data
Additive Matrix
(0=not present; 1 =present)
AC P-AW S-EP INH
1
1
1
0.42
0
1
1
0
0.43
1
1
0
1
0.44
~
1
1
1
0.44
•!__
1
1
0
0.46
i__
1
0
0
0
1
0
1
0.52
0.54
0
1
0
1
0.58
0
0.59
0
0~0’~W~
Grease
Identification
D2266 Avg. Scar
Diam. (mm)
1
0
~tth~A4k~~
,A~t ~#~ra~d4
~ A4S
Table 5
ASTM 02596 Data
Additive Matrix
(O=not present; 1 =present)
AO P-AW S-EP INH
D2596 Weld
Point (kgf) I LWI
I
0
1
1
0
250/46
M
1
0
1
1
250/40.7
G
1
0
1
0
250/32.9
D
0
0
1
0
250/32.9
0
0
1
1
1
200/44.3
P
L
1
1
1
1
1
1
1
0
200/37.8
200/32.5
K
0
1
0
1
1
0
1
1
200/31.8
200/28.3
N
-~
~.
—32—
VOLUME 77, NUMBER 6
~f~_~c1
-~-~
—~-
——
~-~—-—-~
-~
NLG~
result of Grease D is further enhanced by the addi
tion of an AO component. The other high performing
greases include Grease M (AO, S-EP and INH) and the
fully formulated Grease P. The importance of oxidative
stability is further substantiated by the fact that no real
benefit in OIT was observed over Grease G when the
INH was added (Grease M) or in the fully formulated
grease (Grease P). A half normal probability plot of the
data is shown in Figure Al indicating that S-EP, AO and
their interaction, as well as the interactions of P-AW
with each AO and S-EP were significant when statisti
cally analyzing the data.
of other components cannot be ignored. Interestingly,
on three occasions the presence of AO is not neces
sary for long life. P-AW is present 83% of the time
when the life is >160 hours. Statistical analysis of the
data showed that only P-AW was significant in attain
ing longer grease life. A half normal probability plot is
appended as Figure A2 showing that only P-AW was
significant. The R2 was very low when trying to corre
late effects and interactions to the grease life data.
D3527 life data is plotted versus D5483 PDSC OIT in
Figure 2. The plot shows that there is no clear relation
ship between wheel bearing life testing and screening
Key Property Test 5 Wheel Bearing Life
The most difficult requirement of the GO classifi
cation is the 80 hours minimum life in the wheel
Grease
bearing life test. Therefore, it is of utmost impor
tance to evaluate the additive contributions of this
ashless package toward a passing wheel bearing
life test (see Table Al). Grease A (no additives)
only achieved 60 hours, while each of the additive
concentrates on their own were able to surpass
the 80 hour mark. Of particular interest is the result
for Grease C (P-AW only), which ran for 320 hours
before the test was stopped to allow the testing of
other greases to continue. Grease C
was tested again for confirma
tion and an identical result was
E
obtained. The other greases gave
A
credible wheel bearing life in other
performance areas and were
20
B
shown to be deficient. In Table 6,
F
I
the D3527 data is sorted from
H
longest life to shortest life with a
I
10
cut-off of >160 hours of durability.
The rationale for this is to highlight
only formulations that provide more
0
than double the durability of the
test method with the thought that a
focus on these formulations result
in robust bearing oxidation life.
1~0
20
P-AW was shown to be an impor
Exo Up
tant factor to provide long life
Figure 1 Composite Plot of D5483 Data
performance, but the importance
1
Table 6
ASTM 03527 Data
Additive Matrix
(0~not present; 1 =present)
AO P-AW S-EP INH
q__
D3527
(hrs)
1
1
1
0
1
0
0
>320
240
1
0
1
1
200
0
1
1
1
1
200
1
1
1
200
0
1
0
1
180
~ —
20
N
P
G
M
0
30
D
40
Time (mm)
—
—33—
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
101
L
0
K
5•0
60
70
-10
Universal V4.5A TA Instru,nents
-z
NLGI
using pressure scanning differential calorimetry for
this particular base grease and additive matrix test
ing. Hence, one needs to be critical when interpreting
screening results as an indicator of actual bearing
life results.
D1N51821 FE9 Bearing Tests
The FF9 test is used to evaluate upper operating tem
perature for both DIN 51825 and ISO 12924 specif ca
tions where bearing grease is desired. To accomplish
this, the grease is run on four or five bearings at the
desired upper operating temperature and must give a
L50 (F50 used interchangeably) of at least 100 hours. In
the current study, Grease P was tested at two different
operating temperatures, 160°C and 177°C (Table 7).
The data clearly indicates better performance at 160°C,
and this temperature also correlates to the temperature
used in ASTM D3527, for which Grease P also per
formed well. These FF9 results clearly illustrate the sig
nificant impact that temperature has on bearing life and
that will meet an upper operating temperature of 160°C
from an ISO/DIN perspective. The 177°C was actually
run first as the D3336 results discussed below were run
Overall Multipurpose Performance
D4950 GC-LB Performance
As previously mentioned, the ashless package dis
cussed herein is able to provide robust GC-LB perfor
mance when formulated into a suitable base grease.
The select tests discussed above showed good
bearing rust, antiwear, FP, oxidation and bearing life
performance capability for Grease P. Grease P was
completed perThe D4950 classification. The results
shown in Table A2 indicate that Grease A is able to
deliver acceptable D4950 perfor
mance while significantly exceed
Table 7
ing the limits specified for several
DIN 51821-2 (Method A/l 500/6000) FE9 Results for Grease P
GC-LB tests. Examples include
Bearing Fail Hours
1 .25% water washout (Dl 264),
L50 Life Estimate
Temp (°C)
0.8% oil separation (Dl 742), 200
~11o
160
hours bearing life (D3527), <1 .0 mg
62
88
177
average mass loss fretting wear
(D41 70), 5.7 g wheel bearing leak
age (D4290) and 7.42 Nm low tem
•A RBACXD )~E•F~G -H ~l,J SKALXM
perature torque (D4693) results.
350
A
Supplemental Tests
300
Supplemental test results of
250
~
Grease P are shown in Table A3.
The Timken OK load exceeds
~ 200
40 pounds indicating that as an
[~~
i50
EP-grease this depending upon
CO
Q
how one defines it. For example,
~ ioo~(
some manufacturers use the
50
D2596 or other four ball EP
methods, and others use the
0•
Timken OK load test. The
0
10
20
30
40
50
D4048 copper corrosion rating
D5483, PDSC at 21 0°C Isotherm, minutes
of 1 B indicates yellow metal
compatibility.
Figure 2 D3527 vs D5483
__________
,–
,~.
I
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~
—34—
VOLUME 77, NUMBER 6
NLGI
in advance of the FF9 testing, so it was anticipated that
the FE9 might provide an upper operating temperature
of 177°C.
ASTM D3336 Benchmark Tests
Grease P was tested for applicability for electric motor
bearings. To accomplish this, screen testing was done
in advance of D3336 high speed bearing tests versus
two leading field electric motor bearing greases. Screen
testing was performed in a variety of different tests not
reported here. One test of interest included the D2595
high temperature volatility. The data is shown in
Table 8 below. The D5283 and D2266 are shown on
Grease P versus benchmark urea Greases Q and R.
High ASTM D3336 life and good anti-wear properties
are a general requirement for electric motor bearings
unless the bearings have an applied thrust load in
which case an EP additive may be required (21). The
results show that the ashless grease provides at least
the level of performance found in today’s electric motor
greases on the market.
extreme pressure characteristics in the Timken OK
load test, and testing of the urea grease was extended
to the FAG FF9 standard conditions for European
bearing grease, showing acceptable Weibull statistics
that pass DIN 51825 and ISO 6743-9 requirements.
A comparison to industry benchmark electric motor
greases in high temperature, high speed bearing tests
further validated the multi-functionality of this ashless
performance package. The ashless additive technology
was shown to provide the performance needed for a
wide range of rolling element bearings when formulated
in suitable base grease.
Acknowledgements
The authors wish to acknowledge many co-workers and
departments within The Lubrizol Corporation for their
contributions to this work. In particular, Allison Rajakumar
who performed the statistical analysis of the data, Glenn
Sabruno and Chris Hsu for their grease preparation
work, and the Lubrizol Applications Testing group.
References
Lithium Complex Grease Testing
Grease S represents the same additive formulated into
lithium complex grease. The GC-LB tests run in the
LiX grease passed all requirements. It was noted that
EP weld performance was significantly better.
Conclusions
1) Ward, Jr., W. C., and Fish, Gareth. “Development of
Greases with Extended Grease and Bearing Life Using
Pressure Differential Scanning Calorimetry and Wheel
Bearing Life Testing.” NLGI Spokesman (2010) Vol
74(5) p14-27.
2) Cann, P.M. “Grease Lubricant Film Distribution in
Rolling Contacts” NLGI Spokesman (1997) Vol 61(2)
p22 29.
The use of several key D4950 performance tests
has allowed for the characterization and component
3) Cann, FM. and Hurley, S “Grease Composition and
breakdown of a new multi-functional, ashless addi
Film Thickness in Rolling Contacts” NLGI Spokesman
tive. The individual performance contributions of four
(1999) Vol 63(1) p12-22.
additive component types were determined for several
key tests, showing that the
Table 8
components used to formu
D3336
and
Comparative Tests
late urea grease could be
Test
Grease P Grease Q Grease R
extended to lithium complex
grease, providing robust
D2595 (Evaporation Loss) 177°C, 22hr, %
5.53
3.79
4.11
D4950 performance from
D2266 (4-Ball Wear) scar diameter, mm
0.44
0.48
0.53
a rolling element bearing
D5483 (210°C), OIT (mm.)
41.6
14.9
36.3
perspective. Supplemental
D3336 (High Temperature Bearing Test)
425
290
304
tests highlighted good yel
10,000rpm, 177°C, F50, hr
low metal protection and
~ ~
—
—35 —
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
NLGI
4) Lugt, Piet M. “A Review on Grease Lubrication in
Rolling Bearing” Tribology Transactions (2009) Vol. 52,
470-480.
of Lubricating Grease (Four-Ball Method).” ASTM
International, West Conshohocken, PA.
11) ASTM D5483-05 “Standard Test Method for
5) Johnson, M. “Lubricant Application: Grease
Volumes and Frequencies” Tribology and Lubrication
Technology, April 2009, 2-8.
Oxidation Induction Time of Lubricating Greases by
6) Waide, P, and Brunner, C. (2011). Energy-Efficiency
Policy Opportunities for Electric Motor-Driven
Systems. Office of Energy Efficiency and Renewable
Energy. U.S. Department of Energy.
12) ASTM D3527-07 “Standard Test Method for Life
Performance of Automotive Wheel Bearing Grease”
ASTM International, West Conshohocken, PA.
Pressure Differential Scanning Calorimetry” ASTM
International, West Conshohocken, PA.
13) DIN 51821 -2 “Testing of lubricants; test using the FAG
roller bearing grease testing apparatus FE9.” 1989.
7) ASTM D4950-08 “Standard Classification and
Specification of Automotive Service Greases.” ASTM
International, West Conshohocken, PA.
14) Weibull, W. “The Phenomenum of Rupture in Solids”
IngeniorsVetenskaps Akedemien (1939). No. 153
as cited in Life Factors for Rolling Bearings. Second
Edition edited by E.V Zaretsky. Copyright 1999.
Society of Tribologist and Lubrication Engineers.
8) Dl 743 10, “Standard Test Method for Determining
Corrosion Preventive Properties of Lubricating
Greases,” ASTM International, West Conshohocken, PA.
—
9) D 2266-01, “Standard Test Method for Wear
Preventative Characteristics of Lubricating Grease
(Four-Ball Method).” 2001: ASTM International, West
Conshohocken, PA.
15) DIN 51825. “Type K lubrication greases; classifica
tion, requirements and testing.” (2004). Deutsches
Institut für Normung e. V (1991).
16) ISO 12924:2010.”Lubricants, industrial oils and related
products (Class L) Family X (Greases) Specification”
International Standards Organization (2010),
10) ASTM D2596-97(2008), “Standard Test Method
for Measurement of Extreme-Pressure Properties
–
–
Table Al
Additive Matrix
(0=not present; 1 ~present)
D2265
(°C)
Dl 743
rating
D2266 Avg.
Scar Diam.
(mm)
D2596 Weld
Point (kgf) I
LWI
D3527
(hrs)
D5483 OIT
(mm.)
60
320
2
0
0
1
0
273/273
297
Fail Light
0.63
250/32.9
120
23.9
0
0
0
1
275/281
305
Fail Light
0.65
160/25.4
100
<1
1
1
1
0
0
1
0
0
275/291
279/279
314
297
Pass
Fail Light
0.61
0.61
160/28.1
250/32.9
140
140
10.2
42.6
1
0
0
1
265/283
316
Fail Light
0.70
126/23.8
120
2
16.9
0
1
1
0
265 / 285
301
Pass
0.43
250 / 46
140
0
1
0
1
255/277
312
Pass
0.58
160/28
180
2
0
0
1
1
259/275
303
Fail Light
0.68
200/31.8
160
19.9
1
1
0
1
1
0
1
259 / 283
259 / 275
302
293
Pass
Fail Light
0.46
0.54
200 / 32.5
250 / 40.7
240
200
46.4
41.6
1
1
0
1
1
1
265/285
265/285
315
303
Pass
Pass
0.44
0.42
200/28.3
200/44.3
142
200
8.8
19.3
1
1
1
265 / 281
265
Pass
0.44
200 / 37.8
200
41,5
1
1
0
1
,~v,,
~
~
~
~‘ ~
—36 —
VOLUME 77, NUMBER 6
~
~
NLGI
17) Iso 6743-9. (2003) “Lubricants, industrial oils and
related products (class L) Classification Part 9:
Family X (Greases)” International Standards
Organization (2007).
19) Rhee, 1.-S., “The Development of a New Oxidation
Stability Test Method for Greases Using Pressure
Differential Scanning Calorimetry (PDSC)”, NLGI
Spokesman, (1991) Vol 55, p123-132.
18) D3336 05. “Standard Test Method for Life of
Lubricating Greases in Ball Bearings at Elevated
Temperatures” ASTM International, West
Conshohocken, PA.
20) “Lubricant Additives: Chemistry and Applications”,
Second Edition, edited by Leslie R. Rudnick.
—
—
—
21) “Guide to Electric Motor Bearing Lubrication.” (2002).
ExxonMobil Corporation.
TableA2
ASTM D4950 Performance Data for Greases P and S
Test
Grease P
Grease S
D21 7 (full scale penetration)
Dl 264
Dl 742
Dl 743
D2265
D2266
GC-LB Limits
Unworked Pen
265
Worked Pen
281
276
220-340
(% Water Washout)
(% Oil Separation)
1 .25
5.3
15% (max)
0.8
1.8
6% (max)
(Rust Protection)
(Dropping Point)
(Four-Ball Wear)
Pass
Pass
Pass
265
255
220°C (mm)
0.44
0.55
0.6 mm (max)
Load Wear Index
37.8
46.8
3okgf(min)
Weld Point, kg
200
315
200 kgf (mm)
200
120
80 hrs (mm)
0.75
7.2
10 mg (max)
15.8 / -6
13.6 / -7
0 to 30 / 0 to -10
1 1 .9/-2
9.7/-4
-5 to +30 / -15 to +2
5.7
3.2
10 g (max)
7.42
3.8
15.5 Nm (max)
Avg. Scar Diameter (mm)
D2596 (Four-Ball EP)
D3527 (Wheel Bearing Life, hours)
D41 70 (Fretting Wear)
Avg. Mass Loss, mg
D4289 (Elastomer Compatibility)
AMS 3217/3C
(Vol. Change % / Hardness Change)
AMS 321 7/2C
(Vol. Change % / Hardness Change)
D4290 (Wheel Bearing Leakage, g)
D4693 (Low Temp Torque, -40°C, Nm)
-~——~ ~ ~
TableA3
Additional Performance Data for Grease P
Test
Grease P
Desired
I D2509 (Timken OK Load), lbs.
~ D4048 (Copper Corrosion)
~-~—-~
—37
—
NLGI SPOKESMAN, JANUARY/FEBRUARY 2014
j
NLGI
p
Half Normal Plot of the Standardized Effects
(response is 05483, Alpha
=
0.10)
Figure Al
Estimated Effects and coefficients for D5483 (coded units)
C
Term
constant
AO
P-AW
5-EP
AO*P~AW
AO*S~EP
P~AW*S~EP
Effect
13.813
1.462
27.713
2.862
9.213
-2.437
S=1.67831
R-Sq = 99.41%
Absolute Standardized Effect
0oef
17.656
6.906
0.731
13.856
1.431
4.606
-1.219
SE coef
0.4196
0.4196
0.4196
0.4196
0.4196
0.41 96
0.4196
PRESS=80.1205
R-Sq(pred) = 98.12%
T
42.08
16.46
1.74
33.02
3.41
10.98
-2.90
P
0.000
0.000
0.115
0.000
0.008
0.000
0.017
R-Sq(adj) =99.01%
Half Normal Plot of the Effects
(response is Ln 03527, Alpha
=
0.10)
C
C
U
Figure A2
Estimated Effects and coefficients for Ln D3527 (coded units)
Term
0onstant
AO
P-AW
A0*P~AW
Absolute Effect
Lenth’s PSE
=
Effect
0.1103
0.41 83
-0.2415
S = 0.31 8981
R-Sq = 44.57%
0.191853
coef
5.0256
0.0551
0.2091
-0.1207
SE coef
0.07975
0.07975
0.07975
0.07975
PRESS = 2.17065
R-Sq(pred) = 1.46%
T
63.02
0.69
2.62
-1.51
R-Sq(adi)
=
P
0.000
0.503
0.022
0.156
30.71%
ABOUT THE AUTHORS
The
Lubrizol Corporation Ward obtained
his B.S. in Chemistry from Lake Erie
College (1979) in Painesville, Ohio and
his Masters in Chemical Engineering
from Cleveland State University (1985).
Bill is currently a Global Commercial
Manager in grease. He has over 37
years of experience in fuels and lubri
cants at Lubrizol, including chemical
synthesis, two stoke oil, natural gas
engine oil additive development, and Technology Manager for
automatic transmission fluid development. He holds several
patents and has authored several grease related papers. He
received the NLGI Fellow Award (2006), NLGI Author Award
(2011), and the Clarence E. Earle Award (2012). He is a member
of SAE, STLE and NLGI.
William C. Ward Jr., CLGS
—
Lubrizol Corporation Capitosti received
his B.S. Chemistry from the University
of Pittsburgh; Johnstown (2000), and
Ph.D. Synthetic Organic Chemistry from
the University of Virginia (2004). He is
currently the R&D Technology Manager
of Industrial Products serving the grease,
hydraulic, and industrial gear oil areas
—
—
with Lubrizol on the commercialization
of many different additive components, including antioxidants,
friction modifiers, and ashless TBN boosters for heavy duty diesel
and passenger car formulations. Prior to Lubrizol, he worked for
7 years in the Pharmaceutical/Biotechnology industry as a syn
thetic organic chemist, where he obtained 8 published patents.
He is a member of ACS, SAE and NLGI.
—38—
VOLUME 77, NUMBER 6