ASTM D6425-23

Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils Using SRV Test Machine

SIGNIFICANCE AND USE
5.1 This test method can be used to determine antiwear properties and coefficient of friction of EP lubricating oils at selected temperatures and loads specified for use in applications in which high-speed vibrational or start-stop motions are present for extended periods of time under initial high Hertzian point contact pressures. It has found application as a screening test for lubricants used in gear or cam/follower systems. Users of this test method should determine whether results correlate with field performance or other applications.
SCOPE
1.1 This test method covers an extreme pressure (EP) lubricating oil's coefficient of friction and its ability to protect against wear when subjected to high-frequency, linear oscillation motion. The procedure is identical to that described in DIN 51834.  
1.2 This test method can also be used to determine the ability of a non-EP lubricating oil to protect against wear and its coefficient of friction under similar test conditions.  
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2023
• ICS: 75.100 - Lubricants, industrial oils and related products
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.L0.11 - Tribological Properties of Industrial Fluids and Lubricates

Relations

• Replaces: ASTM D6425-19 - Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils Using SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8503-23 - Standard Test Method for Determining the Scuffing Temperature Limit of Lubricating Oils Using the SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM G115-10(2018) - Standard Guide for Measuring and Reporting Friction Coefficients
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8317-23 - Standard Test Method for Measuring Friction and Wear Properties of Greases Under Rolling Motion Using SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D7755-11(2022) - Standard Practice for Determining the Wear Volume on Standard Test Pieces Used by High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8324-21 - Standard Guide for Selection of Environmentally Acceptable Lubricants for the U.S. Environmental Protection Agency (EPA) Vessel General Permit
• Effective Date: 01-Nov-2023
• Referred By: ASTM D5707-23 - Standard Test Method for Measuring Friction and Wear Properties of Lubricating Grease Using a High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D7594-19 - Standard Test Method for Determining Fretting Wear Resistance of Lubricating Greases Under High Hertzian Contact Pressures Using a High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D8316-20a - Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils with the Roller-Disk Geometry Using SRV Test Machine
• Effective Date: 01-Nov-2023
• Referred By: ASTM D5706-23 - Standard Test Method for Determining Extreme Pressure Properties of Lubricating Greases Using a High-Frequency, Linear-Oscillation (SRV) Test Machine
• Effective Date: 01-Nov-2023

Overview

ASTM D6425-23: Standard Test Method for Measuring Friction and Wear Properties of Extreme Pressure (EP) Lubricating Oils Using SRV Test Machine provides a systematic method for evaluating the antiwear properties and coefficient of friction of extreme pressure (EP) and non-EP lubricating oils under conditions of high-frequency, linear oscillation motion. Applicable to lubricants intended for components subject to high-speed vibrational or start-stop motions, this standard helps in screening and comparing lubricating oils, particularly for applications in gear and cam/follower systems. The procedure is directly aligned with DIN 51834 and incorporates globally recognized testing methodologies.

Key Topics

• Coefficient of Friction: Assesses the lubricating oil's ability to minimize friction under specified oscillatory conditions.
• Antiwear Properties: Measures the wear protection provided by the lubricant, especially in scenarios featuring high Hertzian point contact pressures.
• SRV Test Machine: Utilizes a high-frequency, linear-oscillation device to simulate tribological contacts similar to real-world mechanical operations.
• Test Conditions: Allows for variations in temperature, load, frequency, and stroke, making this method adaptable for different application requirements.
• Screening Test: Serves as a practical screening method for evaluating lubricants before full-scale field testing.
• Precision and Reproducibility: Includes interlaboratory round robin test data to establish reliability and consistency of results.

Applications

ASTM D6425-23 is widely recognized in the tribology and lubrication industry for:

• Quality Control of Lubricating Oils: Supports manufacturers and laboratories in verifying the performance of new or existing extreme pressure lubricants.
• Product Development: Assists in formulation and development of oils for gears, cam followers, and other high-stress contacts.
• Comparative Performance Analysis: Enables direct comparison between different oil products under identical lab conditions.
• Predicting Field Performance: Although primarily a screening tool, results can guide decisions for further field evaluation.
• Industry Sectors:
  • Automotive and truck manufacturing
  • Industrial machinery and equipment
  • Aerospace component suppliers
  • Lubricant testing and certification laboratories

Related Standards

ASTM D6425-23 cites and aligns with several related standards to ensure consistency and broader applicability:

• ASTM D5706: Extreme pressure testing of lubricating greases using an SRV test machine.
• ASTM D7421: Extreme pressure testing for lubricating oils using a high-frequency, linear-oscillation (SRV) test machine.
• ASTM D7755: Procedure for determining the wear volume on standard test pieces with SRV equipment.
• ASTM D4175 & G40: Standard terminologies for petroleum products, lubrication, and wear/erosion processes.
• DIN 51834: The international basis for SRV testing of friction and wear in lubricating oils.
• DIN EN ISO 683-17, DIN 51631, and others: Specifications for steel and solvents used in test implementation.

Practical Value

By standardizing the procedure for friction and wear testing with the SRV machine, ASTM D6425-23 enables:

• Consistent, reproducible results for lubricant performance assessment.
• Reliable screening and benchmarking of oils prior to expensive field trials.
• Accurate comparative analysis, critical for selecting or qualifying lubricants for demanding machinery.
• Support for international trade of lubricating oils through adherence to globally recognized, harmonized test methods.

For developers, quality managers, and end-users in industries where equipment longevity and maintenance are critical, ASTM D6425-23 is a foundational reference for the tribological evaluation of lubricating oils.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6425 − 23
Standard Test Method for
Measuring Friction and Wear Properties of Extreme
Pressure (EP) Lubricating Oils Using SRV Test Machine
This standard is issued under the fixed designation D6425; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method represents the transformation of DIN 51834-2:1997. The DIN working group
implemented changes at its annual meeting in Munich in September 2000. ASTM Committee D02
adopted these modifications as closely as possible. The DIN working group widens the scope of the
standard to accommodate different test conditions and refines repeatability and reproducibility on the
base of four international RR tests. It also introduces the wear volume as a tribological quantity.
1. Scope* 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers an extreme pressure (EP)
A295 Specification for High-Carbon Anti-Friction Bearing
lubricating oil’s coefficient of friction and its ability to protect
Steel
against wear when subjected to high-frequency, linear oscilla-
D235 Specification for Mineral Spirits (Petroleum Spirits)
tion motion. The procedure is identical to that described in DIN
(Hydrocarbon Dry Cleaning Solvent)
51834.
D4175 Terminology Relating to Petroleum Products, Liquid
1.2 This test method can also be used to determine the
Fuels, and Lubricants
ability of a non-EP lubricating oil to protect against wear and
D5706 Test Method for Determining Extreme Pressure
its coefficient of friction under similar test conditions.
Properties of Lubricating Greases Using a High-
1.3 The values stated in SI units are to be regarded as Frequency, Linear-Oscillation (SRV) Test Machine
D7421 Test Method for Determining Extreme Pressure
standard. No other units of measurement are included in this
standard. Properties of Lubricating Oils Using High-Frequency,
Linear-Oscillation (SRV) Test Machine
1.4 This standard does not purport to address all of the
D7755 Practice for Determining the Wear Volume on Stan-
safety concerns, if any, associated with its use. It is the
dard Test Pieces Used by High-Frequency, Linear-
responsibility of the user of this standard to establish appro-
Oscillation (SRV) Test Machine
priate safety, health, and environmental practices and deter-
E45 Test Methods for Determining the Inclusion Content of
mine the applicability of regulatory limitations prior to use.
Steel
1.5 This international standard was developed in accor-
G40 Terminology Relating to Wear and Erosion
dance with internationally recognized principles on standard-
2.2 DIN Standards:
ization established in the Decision on Principles for the
DIN EN ISO 683-17 Heat-treated steels, alloy steels and
Development of International Standards, Guides and Recom-
free-cutting steels—Part 17 : Ball and roller bearing steels
mendations issued by the World Trade Organization Technical
DIN 51631:1999 Mineral spirits; special boiling point spir-
Barriers to Trade (TBT) Committee.
its; requirements
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Subcommittee D02.L0.11 on Tribological Properties of Industrial Fluids and contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Lubricates. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2023. Published January 2024. Originally the ASTM website.
approved in 1999. Last previous edition approved in 2019 as D6425 – 19. DOI: Available from Deutsches Institut für Normung, Beuth Verlag GmbH, Burg-
10.1520/D6425-23. grafenstrasse 6, D-10787 Berlin, Germany.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6425 − 23
DIN 51834 Tribological Test in the Translatory Oscillation 3.1.13 wear, n—damage to a solid surface, generally involv-
Apparatus (Part 2: Determination of Friction and Wear ing progressive loss of material, due to relative motion between
Data for Lubricating Oils) that surface and a contacting substance or substances. G40
DIN EN ISO 13565-2:1998 Geometrical Product Specifica-
3.1.14 Wv, n—wear volume is the loss of volume to the ball
tions (GPS)—Surface Texture: Profile Method; Surfaces
or disk after a test.
having Stratified Functional Properties—Part 2: Height
3.2 Definitions of Terms Specific to This Standard:
Characterization using Linear Material Ratio Curve (re-
3.2.1 seizure, n—localized fusion of metal between the
placement of DIN 4776:1990)
rubbing surfaces of the test pieces. D5706
3. Terminology
3.2.1.1 Discussion—In this test method, seizure is indicated
by a sharp rise in the coefficient of friction, over steady state,
3.1 Definitions:
of greater than 0.2 for over 20 s. In severe cases, a stoppage in
3.1.1 break-in, n—in tribology, an initial transition process
the motor will occur.
occurring in newly established wearing contacts, often accom-
panied by transients in coefficient of friction or wear rate, or
3.3 Abbreviations:
both, that are uncharacteristic of the given tribological sys- 3.3.1 SRV, n—Schwingung, Reibung, Verschleiss, (Ger-
tem’s long term behavior. (Synonym: run-in, wear-in) G40
man); oscillating, friction, wear, (English translation). D5706
3.1.2 coeffıcient of friction μ or f, n—in tribology, the
4. Summary of Test Method
dimensionless ratio of the friction force (F ) between two
f
bodies to the normal force (F ) pressing these bodies together.
n 4.1 This test method is performed on an SRV test machine
G40
using a test ball oscillated at constant frequency and stroke
amplitude and under constant load (F ), against a test disk that
μ 5 F /F (1)
~ ! n
f n
has been moistened with the lubricant specimen. The platform
3.1.3 EP lubricating oil, n—a liquid lubricant containing an
to which the test disk is attached is held at a constant
extreme pressure (EP) additive
temperature.
3.1.4 extreme pressure (EP) additive, n—in a lubricant, a
NOTE 1—The frequency of oscillation, stroke length, test temperature,
substance that minimizes damage to metal surfaces in contact
test load, test duration, and test ball and disk material can be varied from
under high stress rubbing conditions.
those specified in this test method. The test ball yields Hertzian point
3.1.5 Hertzian contact area, n—the apparent area of contact contact geometry. To obtain line or area contact, test pieces of differing
configurations can be substituted for the test ball.
between two nonconforming solid bodies pressed against each
other, as calculated from Hertz’ equations of elastic
4.2 The friction force, F , is measured by a piezo-electric
f
deformation. G40
device in the test disk assembly. Peak values of coefficient of
friction, f, are determined and recorded as a function of time.
3.1.6 Hertzian contact pressure, n—magnitude of the pres-
sure at any specified location in a Hertzian contact area, as
4.3 After a preset test period, the test machine and chart
calculated from Hertz’s equations of elastic deformation. The
recorder are stopped and the wear scar on the ball is measured.
Hertzian contact pressure can also be calculated and reported
If a profilometer is available, a trace of the wear scar on the test
as maximum value P in the centre of the contact or as
max disk can also be used to obtain additional wear information.
P as average over the total contact area. D7421
average
3.1.7 lubricant, n—any substance interposed between two 5. Significance and Use
surfaces for the purpose of reducing the friction or wear
5.1 This test method can be used to determine antiwear
between them. G40
properties and coefficient of friction of EP lubricating oils at
3.1.8 P , n—geometric contact pressure describes the selected temperatures and loads specified for use in applica-
geom.
load carrying capacity at test end.
tions in which high-speed vibrational or start-stop motions are
present for extended periods of time under initial high Hertzian
3.1.9 Ra (C.L.A.), n—in measuring surface finish, the arith-
point contact pressures. It has found application as a screening
metic average of the absolute distances of all profile points
test for lubricants used in gear or cam/follower systems. Users
from the mean line for a given distance.
of this test method should determine whether results correlate
3.1.10 RpK, n—Reduced peak height according to DIN EN
with field performance or other applications.
ISO 13565-2:1998. Half the RpK value is the mean height of
the peak sticking out above the core profile section.
6. Apparatus
3.1.11 RvK, n—Reduced valley height according to DIN EN
6.1 SRV Test Machine illustrated in Figs. 1-4, consists of
ISO 13565-2:1998. RvK is the mean depth of the valley
an oscillation drive, a test chamber (see Fig. 2 and Fig. 4), and
reaching into the material below the core profile section.
3.1.12 Rz (DIN), n—in measuring surface finish, the average
of all Ry values (peak to valley heights) in the assessment
4 The sole source of supply known to the committee at this time is Optimol
length.
Instruments Prüftechnik GmbH, Flößergasse 3, D-81369 München, Germany. If you
are aware of alternative suppliers, please provide this information to ASTM
Amstutz, Hu, “Surface Texture: The Parameters,”Bulletin MI-TP-003-0785, Headquarters. Your comments will receive careful consideration at a meeting of the
Sheffield Measurement Division, Warner and Swazey, 1985, p. 21. responsible technical committee, which you may attend.
D6425 − 23
FIG. 1 SRV Test Machine (Model III)
1. Oscillation drive rod 6. Electrical resistance heater
2. Test ball holder 7. Resistance thermometer
3. Load rod 8. Test disk holder
4. Test ball 9. Piezoelectric measuring device
5. Test disk 10. Receiving block
FIG. 2 Test Chamber Elements of SRV III
a loading device with a servomotor and a load cell. The 6.1.1 On the firmly mounted receiving block (1) in the test
machine is operated by a control device for the oscillating chamber (see Fig. 2 and Fig. 4), there is a piezoelectric device
drive, a timer, a load control, a frequency control, a stroke (2) to measure the friction force, F , and the friction coefficient,
f
control, a data amplifier to determine the friction coefficient, f; the holder for the test disk (3) with a thermostat-controlled
and a switch and a controller for the heating. An oscilloscope electrical resistance heating element (4); a resistance thermom-
may be used for monitoring. Friction coefficients are recorded eter (5); the oscillation drive rods (6); an exchangeable holder
in relation to time by a chart recorder, or by data acquisition in for the test ball (7); and the load rods of the loading device (8).
a computer.
6.1.2 The design of the receiving block for the test disk
should be such that it has integrated cooling coils, or that
6 cooling coils are wound around it, so that the receiving block
Optimol Instruments supplies an upgrade kit to allow older machines to operate
with 1600 N, if needed. must be capable to maintaining test temperatures down to
D6425 − 23
topography of the disk will be determined by four values:
0.500 μm < Rz < 0.650 μm; 0.035 μm < Ra (C.L.A.) <
0.050 μm, 0.020 μm < Rpk < 0.035 μm and 0.050 μm < Rvk <
0.075 μm, 24 mm 6 0.5 mm diameter by 7.85 mm 6 0.1 mm
thick.
NOTE 2—DIN 17230-1980 was replaced by DIN EN ISO 683-17.
7.3 Cleaning Solvent, single boiling point spirit type 2-A
according to DIN 51631-1999 (published in English).
(Warning—Flammable. Health hazard.)
NOTE 3—In the case of unavailability, please refer to Specification
D235 regarding Type I, Class C (with less than 2 % by volume of
aromatics), mineral spirits.
8. Preparation of Apparatus
8.1 Preparation of SRV I and II Models:
8.1.1 Turn on the test machine and chart recorder and allow
to warm up for 15 min prior to running tests.
8.1.2 Select the friction data to be presented in the crest
peak value position in accordance with the manufacturer’s
directions.
NOTE 4—In most cases, this is accomplished by positioning the sliding
switch on electronic card No. 291.35.20E (front side of electronics behind
front panel) and the sliding switch located on the back panel of the control
FIG. 3 Test Machine (Model IV)
unit.
8.1.3 Turn the amplitude knob to ZERO.
+233 K. The test disk (9) and the test ball (10) are inserted into
8.1.4 Switch the stroke adjustment to AUTO position.
their respective holders (3, 4) (see Fig. 2 and Fig. 4).
8.1.5 Set the frequency to 50 Hz and duration to 2 h, 00 min,
6.1.3 Disks are generally used as the lower test piece. Balls,
30 s in accordance with the manufacturer’s instructions.
cylinders, rings, or specialized shapes may be used, with
8.1.6 Set the load charge amplifier to the setting that
appropriate holders, as the upper test piece (see Fig. 5).
corresponds to the load foreseen for the test in accordance with
the manufacturer’s instructions. The test can be run at constant
6.2 Microscope, equipped with a filar eyepiece graduated in
normal forces selected in +100 N increments starting at
0.005 mm divisions or equipped with a micrometre stage
+100 N.
readable to 0.005 mm. Magnification should be sufficient to
allow for ease of measurement. 8.1.7 Set the desired span, and calibrate the chart recorder in
accordance with the manufacturer’s instructions. Select the
6.3 Syringe, suitable for applying 0.3 mL of the lubricating
desired chart speed.
oil under test.
NOTE 5—In later SRV models, the load charge amplifier is set
6.4 Tweezers, straight, round, about 200 mm long, with
automatically.
non-marring tips.
8.2 Preparation of SRV III, IV, and V Models:
6.5 Torque Wrench, initial torque 0.5 Nm to 5 Nm.
8.2.1 When using SRV III, SRV IV, and SRV V models,
6.6 Ultrasonic Cleaner.
clean and install the specimens as specified under 9.1. Turn on
the test machine and the PC and allow to warm up for 15 min
7. Reagents and Materials
prior to running tests.
7.1 Test Balls, AISI 52100 Steel, 60 HRC 6 2 HRC
8.2.2 Create a set point profile in the SRV control software
hardness, 0.025 μm 6 0.005 μm Ra (C.L.A.) surface finish,
with the following parameters.
10 mm diameter.
NOTE 6—Depending on the software version, names and availability of
7.2 Test Disk, vacuum arc remelted (VAR) AISI 52100 steel
the parameters can vary.
with an inclusion rating using method D, Type A, as severity
8.2.2.1 Start conditions (thermostatic stabilization):
level number of 0,5 according to Test Methods E45 and
Temperature: for example, 50 °C ± 1 K or 80 °C ± 1 K or 120 °C ±1 K
Specification A295 or a inclusion sum value K1 ≤ 10 according
Test load: 50 N ± 1 N
to DIN EN ISO 683-17 and spherodized annealed to obtain
Start delay: 600 s (is displayed by all versions of the SRV software)
globular carbide, 62 HRC 6 1 HRC hardness, the surfaces of
8.2.2.2 Cut-off criteria for friction, if occurs:
the disk being lapped and free of lapping raw materials. The
Coefficient of friction, f (cut-off value for permanent increase of level):
0.3 during t > 20 s
Coefficient of friction, f (cut-off value for one-off increase of level): 0.35
ASM Handbook, “Friction, Lubrication, and Wear Technology,” Vol 18,
October 1992. 8.2.3 Test parameters:
D6425 − 23
1. Base of the receiving block 7. Upper specimen holder
2. Piezo force measurement elements 8. Drive rods of the load unit
3. Supporting surface (head plate) of the receiving block 9. Test disk
4. Lower specimen holder 10. Test ball
5. Position of the electrical resistance heating and resis- F Normal force (test load)
n
tance thermometer
6. Oscillation drive rods F Friction force
f
FIG. 4 Test Chamber Elements of SRV Models IV and V
9.1.3 Place 0.3 mL of the lubricating oil to be tested on the
Frequency: 50 Hz
Stroke: 1.00 mm
cleaned disk. Then install the disk (place on the block). Tighten
Temperature: for example, 50 °C or 80 °C or 120 °C
the fastening screw until resistance just begins.
Pre-load: 50 N for 30 s
Test load: running-in under 50 N for 30 s, then constant load of 300 N 9.1.4 Place the cleaned ball, using the tweezers, in the
disassembled, cleaned, and dried ball holder. Tighten the
8.2.4 Sample rates for result-relevant measurement chan-
fastening screw until resistance just begins.
nels:
9.1.5 Install the ball holder and test ball in the test chamber.
Coefficient of friction, f: #32 ms
Stroke: #2 s
Procedure for SRV III, IV, and V Models
Test load: #2 s
Frequency: #2 s
9.2 Procedure for SRV III, IV, and V Models:
Temperature: #2 s
9.2.1 Open the Assistant for starting a test in the SRV
NOTE 7—For SRV V models, it is recommended to do one sampling per
control software. Select the created set-point profile and, if
period (that is, 20 ms) for coefficient of friction and stroke.
necessary (for example, SRV V), the data logger configuration
and proceed through the Assistant until the pre-load has been
9. Procedure
applied.
Procedure for All SRV Models
9.2.2 Then set the test load unit to 50 N and release and
re-tighten the ball and disk clamps to a torque of 2.5 Nm.
9.1 Installation of the Test Pieces and Lubricating Oil
9.2.3 The heater control starts automatically and heats up to
Specimen in the Test Chamber:
the pre-set and desired temperature: 50 °C, 80 °C, or 120 °C.
9.1.1 Using solvent resistant gloves, clean the test ball, ball
9.2.4 Follow the directions in the Assistant for starting a
holder, and disk by wiping the surfaces with laboratory tissue
test in the SRV control software until the automated test run
soaked with cleaning solvent (single boiling point spirit type
mode (waiting for reaching st
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6425 − 19 D6425 − 23
Standard Test Method for
Measuring Friction and Wear Properties of Extreme
Pressure (EP) Lubricating Oils Using SRV Test Machine
This standard is issued under the fixed designation D6425; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
This test method represents the transformation of DIN 51834-2:1997. The DIN working group
implemented changes at its annual meeting in Munich in September 2000. ASTM Committee D02
adopted these modifications as closely as possible. The DIN working group widens the scope of the
standard to accommodate different test conditions and refines repeatability and reproducibility on the
base of four international RR tests. It also introduces the wear volume as a tribological quantity.
1. Scope*
1.1 This test method covers an extreme pressure (EP) lubricating oil’s coefficient of friction and its ability to protect against wear
when subjected to high-frequency, linear oscillation motion. The procedure is identical to that described in DIN 51834.
1.2 This test method can also be used to determine the ability of a non-EP lubricating oil to protect against wear and its coefficient
of friction under similar test conditions.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A295 Specification for High-Carbon Anti-Friction Bearing Steel
D235 Specification for Mineral Spirits (Petroleum Spirits) (Hydrocarbon Dry Cleaning Solvent)
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.L0.11 on Tribological Properties of Industrial Fluids and Lubricates.
Current edition approved Dec. 15, 2019Nov. 1, 2023. Published February 2020January 2024. Originally approved in 1999. Last previous edition approved in 20172019
as D6425 – 17.D6425 – 19. DOI: 10.1520/D6425-19.10.1520/D6425-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6425 − 23
D5706 Test Method for Determining Extreme Pressure Properties of Lubricating Greases Using a High-Frequency, Linear-
Oscillation (SRV) Test Machine
D7421 Test Method for Determining Extreme Pressure Properties of Lubricating Oils Using High-Frequency, Linear-Oscillation
(SRV) Test Machine
D7755 Practice for Determining the Wear Volume on Standard Test Pieces Used by High-Frequency, Linear-Oscillation (SRV)
Test Machine
E45 Test Methods for Determining the Inclusion Content of Steel
G40 Terminology Relating to Wear and Erosion
2.2 DIN Standards:
DIN EN ISO 683-17 Heat-treated steels, alloy steels and free-cutting steels—Part 17 : Ball and roller bearing steels
DIN 51631:1999 Mineral spirits; special boiling point spirits; requirements
DIN 51834 Tribological Test in the Translatory Oscillation Apparatus (Part 2: Determination of Friction and Wear Data for
Lubricating Oils)
DIN EN ISO 13565-2:1998 Geometrical Product Specifications (GPS)—Surface Texture: Profile Method; Surfaces having
Stratified Functional Properties—Part 2: Height Characterization using Linear Material Ratio Curve (replacement of DIN
4776:1990)
3. Terminology
3.1 Definitions:
3.1.1 break-in, n—in tribology, an initial transition process occurring in newly established wearing contacts, often accompanied
by transients in coefficient of friction or wear rate, or both, that are uncharacteristic of the given tribological system’s long term
behavior. (Synonym: run-in, wear-in) G40
3.1.2 coeffıcient of friction μ or f, n—in tribology, the dimensionless ratio of the friction force (F ) between two bodies to the
f
normal force (F ) pressing these bodies together. G40
n
μ 5 F /F (1)
~ !
f n
3.1.3 EP lubricating oil, n—a liquid lubricant containing an extreme pressure (EP) additive
3.1.4 extreme pressure (EP) additive, n—in a lubricant, a substance that minimizes damage to metal surfaces in contact under high
stress rubbing conditions.
3.1.5 Hertzian contact area, n—the apparent area of contact between two nonconforming solid bodies pressed against each other,
as calculated from Hertz’ equations of elastic deformation. G40
3.1.6 Hertzian contact pressure, n—magnitude of the pressure at any specified location in a Hertzian contact area, as calculated
from Hertz’s equations of elastic deformation. The Hertzian contact pressure can also be calculated and reported as maximum value
P in the centre of the contact or as P as average over the total contact area. D7421
max average
3.1.7 lubricant, n—any substance interposed between two surfaces for the purpose of reducing the friction or wear between them.
G40
3.1.8 P , n—geometric contact pressure describes the load carrying capacity at test end.
geom.
3.1.9 Ra (C.L.A.), n—in measuring surface finish, the arithmetic average of the absolute distances of all profile points from the
mean line for a given distance.
3.1.10 RpK, n—Reduced peak height according to DIN EN ISO 13565-2:1998. Half the RpK value is the mean height of the peak
sticking out above the core profile section.
3.1.11 RvK, n—Reduced valley height according to DIN EN ISO 13565-2:1998. RvK is the mean depth of the valley reaching into
the material below the core profile section.
Available from Deutsches Institut für Normung, Beuth Verlag GmbH, Burggrafenstrasse 6, D-10787 Berlin, Germany.
Amstutz, Hu, “Surface Texture: The Parameters,”Bulletin MI-TP-003-0785, Sheffield Measurement Division, Warner and Swazey, 1985, p. 21.
D6425 − 23
3.1.12 Rz (DIN), n—in measuring surface finish, the average of all Ry values (peak to valley heights) in the assessment length.
3.1.13 wear, n—damage to a solid surface, generally involving progressive loss of material, due to relative motion between that
surface and a contacting substance or substances. G40
3.1.14 Wv, n—wear volume is the loss of volume to the ball or disk after a test.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 seizure, n—localized fusion of metal between the rubbing surfaces of the test pieces. D5706
3.2.1.1 Discussion—
In this test method, seizure is indicated by a sharp rise in the coefficient of friction, over steady state, of greater than 0.2 for over
20 s. In severe cases, a stoppage in the motor will occur.
3.3 Abbreviations:
3.3.1 SRV, n—Schwingung, Reibung, Verschleiss, (German); oscillating, friction, wear, (English translation). D5706
4. Summary of Test Method
4.1 This test method is performed on an SRV test machine using a test ball oscillated at constant frequency and stroke amplitude
and under constant load (F ), against a test disk that has been moistened with the lubricant specimen. The platform to which the
n
test disk is attached is held at a constant temperature.
NOTE 1—The frequency of oscillation, stroke length, test temperature, test load, test duration, and test ball and disk material can be varied from those
specified in this test method. The test ball yields Hertzian point contact geometry. To obtain line or area contact, test pieces of differing configurations
can be substituted for the test ball.
4.2 The friction force, F , is measured by a piezo-electric device in the test disk assembly. Peak values of coefficient of friction,
f
f, are determined and recorded as a function of time.
4.3 After a preset test period, the test machine and chart recorder are stopped and the wear scar on the ball is measured. If a
profilometer is available, a trace of the wear scar on the test disk can also be used to obtain additional wear information.
5. Significance and Use
5.1 This test method can be used to determine antiwear properties and coefficient of friction of EP lubricating oils at selected
temperatures and loads specified for use in applications in which high-speed vibrational or start-stop motions are present for
extended periods of time under initial high Hertzian point contact pressures. It has found application as a screening test for
lubricants used in gear or cam/follower systems. Users of this test method should determine whether results correlate with field
performance or other applications.
6. Apparatus
6.1 SRV Test Machine illustrated illustrated in Figs. 1-4, consists of an oscillation drive, a test chamber (see Fig. 2 and Fig. 4),
and a loading device with a servomotor and a load cell. The machine is operated by a control device for the oscillating drive, a
timer, a load control, a frequency control, a stroke control, a data amplifier to determine the friction coefficient, and a switch and
a controller for the heating. An oscilloscope may be used for monitoring. Friction coefficients are recorded in relation to time by
a chart recorder, or by data acquisition in a computer.
6.1.1 On the firmly mounted receiving block (1) in the test chamber (see Fig. 2 and Fig. 4), there is a piezoelectric device (2) to
measure the friction force, F , and the friction coefficient, f; the holder for the test disk (3) with a thermostat-controlled electrical
f
The sole source of supply known to the committee at this time is Optimol Instruments Prüftechnik GmbH, Flößergasse 3, D-81369 München, Germany. If you are aware
of alternative suppliers, please provide this information to ASTM Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical
committee, which you may attend.
Optimol Instruments supplies an upgrade kit to allow older machines to operate with 1600 N, if needed.
D6425 − 23
FIG. 1 SRV Test Machine (Model III)
1. Oscillation drive rod 6. Electrical resistance heater
2. Test ball holder 7. Resistance thermometer
3. Load rod 8. Test disk holder
4. Test ball 9. Piezoelectric measuring device
5. Test disk 10. Receiving block
FIG. 2 Test Chamber Elements of SRV III
resistance heating element (4); a resistance thermometer (5); the oscillation drive rods (6); an exchangeable holder for the test ball
(7); and the load rods of the loading device (8).
6.1.2 The design of the receiving block for the test disk should be such that it has integrated cooling coils, or that cooling coils
are wound around it, so that the receiving block must be capable to maintaining test temperatures down to +233 K. The test disk
(9) and the test ball (10) are inserted into their respective holders (3, 4) (see Fig. 2 and Fig. 4).
6.1.3 Disks are generally used as the lower test piece. Balls, cylinders, rings, or specialized shapes may be used, with appropriate
holders, as the upper test piece (see Fig. 5).
6.2 Microscope, equipped with a filar eyepiece graduated in 0.005 mm divisions or equipped with a micrometre stage readable to
0.005 mm. Magnification should be sufficient to allow for ease of measurement.
6.3 Syringe, suitable for applying 0.3 mL of the lubricating oil under test.
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FIG. 3 Test Machine (Model IV)
6.4 Tweezers, straight, round, about 200 mm long, with non-marring tips.
6.5 Torque Wrench, initial torque 0.5 Nm to 5 Nm.
6.6 Ultrasonic Cleaner.
7. Reagents and Materials
7.1 Test Balls, AISI 52100 Steel, 60 HRC 6 2 HRC hardness, 0.025 μm 6 0.005 μm Ra (C.L.A.) surface finish, 10 mm diameter.
7.2 Test Disk, vacuum arc remelted (VAR) AISI 52100 steel with an inclusion rating using method D, Type A, as severity level
number of 0,5 according to Test Methods E45 and Specification A295 or a inclusion sum value K1 ≤ 10 according to DIN EN ISO
683-17 and spherodized annealed to obtain globular carbide, 62 HRC 6 1 HRC hardness, the surfaces of the disk being lapped
and free of lapping raw materials. The topography of the disk will be determined by four values: 0.500 μm < Rz < 0.650 μm;
0.035 μm < Ra (C.L.A.) < 0.050 μm, 0.020 μm < Rpk < 0.035 μm and 0.050 μm < Rvk < 0.075 μm, 24 mm 6 0.5 mm diameter
by 7.85 mm 6 0.1 mm thick.
NOTE 2—DIN 17230-1980 was replaced by DIN EN ISO 683-17.
7.3 Cleaning Solvent, single boiling point spirit type 2-A according to DIN 51631-1999 (published in English). (Warning—
Flammable. Health hazard.)
NOTE 3—In the case of unavailability, please refer to Specification D235 regarding Type I, Class C (with less than 2 % by volume of aromatics), mineral
spirits.
ASM Handbook, “Friction, Lubrication, and Wear Technology,” Vol 18, October 1992.
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1. Base of the receiving block 7. Upper specimen holder
2. Piezo force measurement elements 8. Drive rods of the load unit
3. Supporting surface (head plate) of the receiving block 9. Test disk
4. Lower specimen holder 10. Test ball
5. Position of the electrical resistance heating and resis- F Normal force (test load)
n
tance thermometer
6. Oscillation drive rods F Friction force
f
FIG. 4 Test Chamber Elements of SRV Models IV and V
8. Preparation of Apparatus
8.1 Preparation of SRV I and II Models:
8.1.1 Turn on the test machine and chart recorder and allow to warm up for 15 min prior to running teststests.
8.1.2 Select the friction data to be presented in the crest peak value position in accordance with the manufacturer’s directions.
NOTE 4—In most cases, this is accomplished by positioning the sliding switch on electronic card No. 291.35.20E (front side of electronics behind front
panel) and the sliding switch located on the back panel of the control unit.
8.1.3 Turn the amplitude knob to ZERO.
8.1.4 Switch the stroke adjustment to AUTO position.
8.1.5 Set the frequency to 50 Hz and duration to 2 h, 00 min, 30 s in accordance with the manufacturer’s instructions.
8.1.6 Set the load charge amplifier to the setting that corresponds to the load foreseen for the test in accordance with the
manufacturer’s instructions. The test can be run at constant normal forces selected in +100 N increments starting at +100 N.
8.1.7 Set the desired span, and calibrate the chart recorder in accordance with the manufacturer’s instructions. Select the desired
chart speed.
NOTE 5—In later SRV models, the load charge amplifier is set automatically.
8.2 Preparation of SRV III, IV, and V Models:
8.2.1 When using SRV III, SRV IV, and SRV V models, clean and install the specimens as specified under 9.1. Turn on the test
machine and the PC and allow to warm up for 15 min prior to running teststests.
8.2.2 Create a set point profile in the SRV control software with the following parameters.
D6425 − 23
FIG. 5 Test Pieces and Holders for Standard Tribological Contacts
NOTE 6—Depending on the software version, names and availability of the parameters can vary.
8.2.2.1 Start conditions (thermostatic stabilization):
Temperature: for example, 50 °C ± 1 K or 80 °C ± 1 K or 120 °C ±1 K
Test load: 50 N ± 1 N
Start delay: 600 s (is displayed by all versions of the SRV software)
8.2.2.2 Cut-off criteria for friction, if occurs:
Coefficient of friction, f (cut-off value for permanent increase of level):
0.3 during t > 20 s
Coefficient of friction, f (cut-off value for one-off increase of level): 0.35
8.2.3 Test parameters:
D6425 − 23
Frequency: 50 Hz
Stroke: 1.00 mm
Temperature: for example, 50 °C or 80 °C or 120 °C
Pre-load: 50 N for 30 s
Test load: running-in under 50 N for 30 s, then constant load of 300 N
8.2.4 Sample rates for result-relevant measurement channels:
Coefficient of friction, f: #32 ms
Stroke: #2 s
Test load: #2 s
Frequency: #2 s
Temperature: #2 s
NOTE 7—For SRV V models, it is recommended to do one sampling per period (that is, 20 ms) for coefficient of friction and stroke.
9. Procedure
Procedure for All SRV Models
9.1 Installation of the Test Pieces and Lubricating Oil Specimen in the Test Chamber:
9.1.1 Using solvent resistant gloves, clean the test ball, ball holder, and disk by wiping the surfaces with laboratory tissue soaked
with cleaning solvent (single boiling point spirit type 2-A according to DIN 51631). (Warning—This mixture is flammable and
a health hazard.) Repeat wiping until no dark residue appears on the tissue. Immerse the ball and disk in a beaker of the cleaning
solvent under ultrasonic vibration (if available) for 10 min. Dry the ball holder. Dry the test ball and disk with a clean tissue,
ensuring that no streaking occurs on the surface.
9.1.2 Ensure that the test load unit is in the release position (refer to your operating manual for details).
9.1.3 Place 0.3 mL of the lubricating oil to be tested on the cleaned disk. Then install the disk (place on the block). Tighten the
fastening screw until resistance just begins.
9.1.4 Place the cleaned ball, using the tweezers, in the disassembled, cleaned, and dried ball holder. Tighten the fastening screw
until resistance just begins.
9.1.5 Install the ball holder and test ball in the test chamber.
Procedure for SRV III, IV, and V Models
9.2 Proced
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