ASTM E2546-15(2023)

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: E2546 − 15 (Reapproved 2023)
Standard Practice for
Instrumented Indentation Testing
This standard is issued under the fixed designation E2546; 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.
1. Scope* priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.1 This practice defines the basic steps of Instrumented
1.8 This international standard was developed in accor-
Indentation Testing (IIT) and establishes the requirements,
dance with internationally recognized principles on standard-
accuracies, and capabilities needed by an instrument to suc-
ization established in the Decision on Principles for the
cessfully perform the test and produce the data that can be used
Development of International Standards, Guides and Recom-
for the determination of indentation hardness and other mate-
mendations issued by the World Trade Organization Technical
rial characteristics. IIT is a mechanical test that measures the
Barriers to Trade (TBT) Committee.
response of a material to the imposed stress and strain of a
shaped indenter by forcing the indenter into a material and
2. Referenced Documents
monitoring the force on, and displacement of, the indenter as a
2.1 ASTM Standards:
function of time during the full loading-unloading test cycle.
E3 Guide for Preparation of Metallographic Specimens
1.2 The operational features of an IIT instrument, as well as
E74 Practices for Calibration and Verification for Force-
requirements for Instrument Verification (Annex A1), Stan-
Measuring Instruments
dardized Reference Blocks (Annex A2) and Indenter Require-
E92 Test Methods for Vickers Hardness and Knoop Hard-
ments (Annex A3) are defined. This practice is not intended to
ness of Metallic Materials
be a complete purchase specification for an IIT instrument.
E177 Practice for Use of the Terms Precision and Bias in
1.3 With the exception of the non-mandatory Appendix X4,
ASTM Test Methods
this practice does not define the analysis necessary to deter-
E384 Test Method for Microindentation Hardness of Mate-
mine material properties. That analysis is left for other test
rials
methods. Appendix X4 includes some basic analysis tech-
E691 Practice for Conducting an Interlaboratory Study to
niques to allow for the indirect performance verification of an
Determine the Precision of a Test Method
IIT instrument by using test blocks.
E1875 Test Method for Dynamic Young’s Modulus, Shear
1.4 Zero point determination, instrument compliance deter- Modulus, and Poisson’s Ratio by Sonic Resonance
E1876 Test Method for Dynamic Young’s Modulus, Shear
mination and the indirect determination of an indenter’s area
function are important parts of the IIT process. The practice Modulus, and Poisson’s Ratio by Impulse Excitation of
Vibration
defines the requirements for these items and includes non-
mandatory appendixes to help the user define them.
2.2 American Bearing Manufacturers Association Stan-
dard:
1.5 The use of deliberate lateral displacements is not in-
ABMA/ISO 3290-1 Rolling Bearings- Balls-Part 1: Steel
cluded in this practice (that is, scratch testing).
Metal Balls
1.6 The values stated in SI units are to be regarded as
2.3 ISO Standards:
standard. No other units of measurement are included in this
ISO 14577-1, -2, -3, -4 Metallic Materials—Instrumented
standard.
Indentation Tests for Hardness and Material Properties
1.7 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 appro-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
This practice is under the jurisdiction of ASTM Committee E28 on Mechanical the ASTM website.
Testing and is the direct responsibility of Subcommittee E28.06 on Indentation Available from American Bearing Manufacturers Association (ABMA), 2025
Hardness Testing. M Street, NW Suite 800 Washington, DC 20036, http://www.americanbearings.org.
Current edition approved Sept. 1, 2023. Published September 2023. Originally
approved in 2007. Last previous edition approved in 2015 as E2546–15. DOI: Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/E2546-15R23. 4th Floor, New York, NY 10036, http://www.ansi.org.
*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
E2546 − 15 (2023)
ISO 376 Metallic Materials—Calibration of Force-Proving 3.1.8 refined area function, n—area function determined
Instruments for the Verification of Uniaxial Testing Ma- indirectly by a technique such as the one described in Appen-
chines dix X3.
3.1.9 test cycle, n—a series of operations at a single location
3. Terminology
on the test sample specified in terms of either applied test force
or displacement as a function of time.
3.1 Definitions of Terms Specific to This Standard:
3.1.9.1 Discussion—The test cycle may include any of the
3.1.1 contact stiffness, n—the instantaneous elastic response
following operations: approach of the indenter towards the test
of the material over the area of contact with the indenter.
sample, singular or multiple loading, dwell, and unloading
3.1.1.1 Discussion—Contact stiffness can be determined
cycles.
from the slope of line 3 in Fig. 1.
3.1.10 test data, n—for this practice it will consist, at the
3.1.2 force displacement curve, n—a common plot of the
minimum, of a set of related force/displacement/time data
force applied to an indenter and the resultant depth of penetra-
points.
tion.
3.1.2.1 Discussion—This plot is generated from data col-
3.1.11 zero point, n—the force-displacement-time reference
lected during the entire loading and unloading cycle. (See Fig.
point when the indenter first contacts the sample and the force
1.)
is zero.
3.1.11.1 Discussion—A course zero point is an approximate
3.1.3 indentation radius [a], n—the in-plane radius, at the
value used as part of an analysis to determine a refined value.
surface of the test piece, of the circular impression of an indent
created by a spherical indenter.
3.2 Indentation Symbols and Designations (see Fig. 2 and
3.1.3.1 Discussion—For non-circular impressions, the in-
Table 1):
dentation radius is the radius of the smallest circle capable of
enclosing the indentation. The indentation radius is normally 4. Summary of Practice
used as a guide for spacing of indentations.
4.1 This practice defines the details of the IIT test and the
3.1.4 indenter area function [Λ], n—mathematical function
requirements and capabilities for instruments that perform IIT
that relates the projected (cross-section) area of the indenter tip
tests. The necessary components are defined along with the
to the distance from the apex of the tip as measured along the
required accuracies required to obtain useful results. Verifica-
central axis.
tion methods are defined to insure that the instruments are
performing properly. It is intended that ASTM (or other) Test
3.1.5 instrument compliance, n—the flex or reaction of the
Methods will refer to this practice when defining different
load frame, actuator, stage, indenter, anvil, etc., that is the
calculations or algorithms that determine one or more material
result of the application of a test force to the sample.
characteristics that are of interest to the user.
3.1.6 instrumented indentation test (IIT), n—an indentation
test where the force applied to an indenter and the resultant
5. Significance and Use
displacement of the indenter into the sample are recorded
5.1 IIT Instruments are used to quantitatively measure
during the loading and unloading process for post test analysis.
various mechanical properties of thin coatings and other
3.1.7 nominal area function, n—area function determined
volumes of material when other traditional methods of deter-
from measurement of the gross indenter geometry.
mining material properties cannot be used due to the size or
condition of the sample. This practice will establish the basic
requirements for those instruments. It is intended that IIT based
test methods will be able to refer to this practice for the basic
requirements for force and displacement accuracy,
reproducibility, verification, reporting, etc., that are necessary
for obtaining meaningful test results.
5.2 IIT is not restricted to specific test forces, displacement
ranges, or indenter types. This practice covers the requirements
for a wide range of nano, micro, and macro (see ISO 14577-1)
indentation testing applications. The various IIT instruments
are required to adhere to the requirements of the practice within
their specific design ranges.
6. Apparatus
6.1 General—The force, displacement and time are simul-
taneously recorded during the full sequence of the test. An
analysis of the recorded data must be done to yield relevant
1. Increasing test force
information about the sample. When available, relevant ASTM
2. Removal of the test force
test methods for the analysis should be followed for compara-
3. Tangent to curve 2 at F
max
FIG. 1 IIT Procedure Shown Schematically tive results.
E2546 − 15 (2023)
NOTE 1—The symbols shown are the same for pointed and spherical indenters.
FIG. 2 Schematic Cross-Section of an IIT Indentation
TABLE 1 Symbols and Designations
the estimated uncertainty in the displacement at the zero point
Symbol Designation Unit is larger than both criteria, its value and the influence of its
α Angle, specific to shape of pyramidal indenter ° value on reported mechanical properties shall be noted in the
(see Annex A3)
test report. See Appendix X1 for information on how to
a Radius of indentation (see 3.1.3) μm
determine the zero point.
R Radius of spherical indenter (see Annex A3) μm
F Test force applied to sample N 6.2.2 Sample Positioning—The positioning of the sample
F Maximum value of F N
max
being tested relative to the centerline of the test force is critical
h Indenter displacement into the sample μm
to obtaining good results. The testing instrument shall be
h Maximum value of h μm
max
h Depth over which the indenter and specimen are μm designed to allow the centerline of the test force to be normal
c
in contact during the force application
to the sample surface at the point of indentation.
h Permanent recovered indentation depth after μm
p
6.2.3 Indenters—Indenters normally consists of a contact tip
removal of
test force
and a suitable holder. The tip should have a hardness and
A Surface area of indenter in contact with material μm
s
modulus that significantly exceeds the materials being tested.
A Projected (cross section) area of indenter at μm
p
The holder shall be manufactured to support the contact point
depth h
c
h Point of intersection of line 3 with the h axis (see μm
r without any unpredictable deflections that could affect the test
Fig. 1)
results. The holder shall allow proper mounting in the actuator
S Contact stiffness N/μm
and position the contact point correctly for the application of
t Time relative to the zero point s
the test force. The contact tip and holder could be a one or
multi-piece design. A variety of indenter shapes, such as
pyramids, cones, and spheres, can be used for IIT Testing.
NOTE 1—The user is encouraged to refer to the manufacturer’s
Annex A3 defines the requirements for the most commonly
instruction manual to understand the exact details of the tests and analysis
used indenters. Whenever they are used the requirements of
performed.
Annex A3 shall be followed. Other indenter shapes can be used
6.2 Testing Instrument—The instrument shall be able to be
provided they are defined in a standardized Method or de-
verified according to the requirements defined in Annex A1 and
scribed in the test report.
have the following features.
NOTE 2—The nominal indenter geometry, as described in Annex A3,
6.2.1 Test Forces/Displacements—The instrument shall be
may be sufficiently accurate for a given analysis. In many cases, however,
able to apply operator selectable test forces or displacements
a refined area function that more accurately represents the shape of the
within its usable range. The controlled parameters can vary
indenter used may be necessary to provide the desired results (see A3.7).
either continuously or step by step. The application of the test
6.2.4 Imaging Device (Optional)—In applications where it
force shall be smooth and free from any unintended vibrations
is desirable to accurately locate the indentation point on the
or abnormalities that could adversely affect the results. The
sample or observe the indent, an imaging device such as an
approach, loading, and data acquisition rates shall be controlled
optical or atomic force microscope may prove helpful. The
to the extent that is required to obtain meaningful estimates of
device should be mounted such that locations can be identified
force and displacement uncertainties at the zero point. The
quickly and accurately.
estimated uncertainty in the force at the zero point shall not
exceed 1 % of the maximum test force (F ) or 2 μN, 6.3 Data Storage and Analysis Capabilities—The apparatus
max
whichever is greater. The estimated uncertainty in the displace- shall have the following capabilities:
ment at the zero point should not exceed 1 % of the maximum 6.3.1 Force/Displacement/Time Measurement—Acquire and
indenter displacement (h ) or 2 nm, whichever is greater. If store raw force, displacement and time data during each test.
max
E2546 − 15 (2023)
6.3.2 Data Correction—When necessary, conversion of the als it is sufficient to locate the test at least six indent radii away
raw data defined in 6.3.1 to corrected force (F), displacement from such features; however, there are exceptions to this rule.
(h), and time (t) data as defined in 3.2. The conversion shall The measurements of elastic properties, for example, are
consider at least the following parameters: Zero point determi- significantly more sensitive and require greater spacing than
nation (see Appendix X1), instrument compliance (see Appen- those for plastic properties. It is the responsibility of the
dix X2) and thermal drift. operator to exercise caution so that such gradients do not affect
6.3.3 Indenter Shape Function—Utilize an appropriate in- the desired results.
denter shape function if necessary (see Appendix X3).
8.4 Define the Test Cycle—The test cycle parameters shall
6.3.4 Test Result Generation:
be chosen with respect to the following considerations:
6.3.4.1 Perform the desired analysis on the raw or corrected
8.4.1 The forces generated by the dynamic motion of the
data to obtain useful test results. When available, relevant
indenter mass shall not adversely affect the accuracy of the
ASTM or ISO 14577 test methods should be used.
results. This is particularly true at the point of contact when the
6.3.4.2 Determine indentation modulus (E ) according to
IT
intentionally applied forces are small.
the Test Method defined in Appendix X4 or another method
8.4.2 The test cycle force and displacement values used in
that produces similar results.
the test result analysis, except those used for zero point
determination, shall be within the verified range of the instru-
7. Test Piece
ment as reported in A1.7.2.4 and A1.7.2.5.
7.1 Surface Finish—The surface finish of the sample will
8.5 Perform the Test Cycle—The test cycle (see 3.1.9) is
directly affect the test results. The test should be performed on
performed according to the specifications of the manufacturer
a flat specimen with a polished or otherwise suitably prepared
or the test method. Force/displacement/time data shall be
surface. Any contamination will reduce the precision and
acquired during each test cycle.
accuracy of the test. The user should consider the indent size
when determining the proper surface finish.
8.6 Correct the Data—The acquired data shall be corrected
according to 6.3.2. The details may be defined by the manu-
7.2 Surface Preparation—The preparation of the surface
facturer or by a test method.
shall be done in a way that minimizes alteration of the
characteristic of the material to be evaluated.
8.7 Analyze Results—The corrected data shall be analyzed
to obtain the desired test results according to 6.3.4. The details
7.3 Sample Thickness—The thickness of the material to be
may be defined by the manufacturer or by a test method.
analyzed may be a critical factor in the ability to obtain the
desired results. The test piece thickness shall be large enough,
9. Report
or indentation depth small enough, such that the test result is
9.1 The report shall include sufficient information about the
not influenced by the test piece support. The test piece
test cycle, indenter, sample and analysis method used to allow
thickness should be at least 10 times the indentation depth or
the final results to be reproduced.
six times greater than the indentation radius; whichever is
greater.
9.2 The report shall include the following minimum infor-
mation:
8. Procedure
9.2.1 Date and time,
8.1 Prepare Environment—The test should be carried out
9.2.2 Reference to this practice,
within the temperature range defined by the manufacturer.
9.2.3 Description of instrument—mfg., model, etc.,
Prior to performing any tests the instrument and the test sample
9.2.4 Shape and material of the indenter used,
shall be stabilized to the temperature of the environment.
9.2.5 Temperature,
Temperature change during each test should be less than 1.0°C.
9.2.6 Test sample description,
The test environment shall be clean and free from vibrations,
9.2.7 Description of test cycle,
electromagnetic interference, or other variations that could
9.2.8 Method of zero point determination,
adversely affect the performance of the instrument. Testing
9.2.9 Reference to analytic method used, including values
done outside the specified limits is allowed; however, all
of any model dependent parameters,
deviations shall be specified on the test report.
9.2.10 Number of tests and results,
9.2.11 Details of any occurrence that may have affected the
8.2 Mount Specimen—The sample shall be rigidly supported
results, and
and the test surface shall be positioned normal to the centerline
9.2.12 Define the units of the test results.
of the test force.
NOTE 3—Sample fixtures may add to the compliance of the instrument.
NOTE 4—It is also frequently desirable to describe the location of the
The user should consider the impact of this undesirable effect.
indentation on the test piece as part of the report.
8.3 Select Test Location—The results of indentation tests
10. Keywords
will be adversely affected if the properties being measured vary
within the volume of material being deformed. Extreme 10.1 force displacement curve; indentation hardness; inden-
conditions would be caused by the presence of free surfaces tation modulus; indenter shape function; instrument compli-
such as edges, voids and other indentations. For many materi- ance; instrumented indentation; zero point
E2546 − 15 (2023)
ANNEXES
(Mandatory Information)
A1. INSTRUMENT VERIFICATION
A1.1 Scope (3) Measuring by means of an electronic balance.
A1.3.2.3 If the verification force is applied in the opposite
A1.1.1 This annex specifies procedures for verification of
direction from the force used during a test, the manufacturer
testing machines that conform to the requirements defined in
shall provide documentation confirming that the verification
this practice. The annex describes a direct verification proce-
results would be within the tolerance if the force were applied
dure for checking the main functions of the testing machine
in the test direction.
and an indirect verification procedure suitable for assessing the
A1.3.2.4 If the force calibration is assumed to be indepen-
overall performance of the testing machine. The indirect
dent of indenter position, the manufacturer shall show that this
procedure is used as part of the direct procedure and for the
is the case.
periodic routine checking of the machine in service. This annex
does not cover verification procedures for specific indenter
A1.3.3 Displacement Verification—Each displacement
geometry; such procedures are presented in Annex A3 Indenter
range of the instrument shall be verified as described below.
Requirements. The manufacturer’s recommendations concern-
A1.3.3.1 At least ten verification lengths shall be chosen so
ing instrument calibration and verification should be used as
as to span evenly the defined displacement range. The mea-
long as they do not conflict with the specifications of this
surement of each verification length shall be repeated three
annex.
times. Every measurement shall be within 1 % or 2 nm of its
nominal value, whichever is greater. If the 2nm tolerance is
A1.2 General Conditions
used the maximum indenter displacement (h ) shall be
max
accurate to within 5 % of the stated value. The verified
A1.2.1 Direct and indirect verification procedures shall be
carried out at a temperature of 23 °C 6 5 °C. displacement range of an instrument shall be defined as the
range of lengths from the minimum verified length to the
NOTE A1.1—For both verification and operation, thermal stability of the
instrument is important. During any verification procedure, reasonable
maximum verified length.
care should be taken to ensure that the temperature of the instrument and
A1.3.3.2 The device used for displacement verification shall
its immediate environment are kept at a constant temperature, preferably
be accurate to within 0.25 % or 1 nm of each verified length,
to within a 0.5 °C range over the course of the verification procedure or
whichever is greater. Methods of producing lengths for verifi-
test.
cation include:
A1.3 Direct Verification
(1) Laser interferometers,
(2) Film thickness standards, and
A1.3.1 Direct verification requires assessment of: (1) Force,
(3) Independent actuator or transducer.
(2) Displacement, and (3) Timing. If available, the devices
used for force and displacement verification shall be traceable
A1.3.4 Timing Verification—The time required for a test
to National Standards.
segment at least ten seconds in duration shall be verified by an
independent timing device. The difference between the time
A1.3.2 Force Verification—Each force range of the instru-
reported by the test equipment and that measured by an
ment shall be verified as described below.
independent timing device must be less than 1.0 seconds. A
A1.3.2.1 At least ten verification forces shall be chosen that
hand-operated, non-traceable, stopwatch is sufficient for this
evenly span the defined force range. The measurement of each
verification.
verification force shall be repeated three times. Every measure-
ment shall be within 1 % or 2 μN of its nominal value,
A1.4 Indirect Verification
whichever is greater. When the 2 μN tolerance is used the
A1.4.1 An independent indirect verification shall be per-
maximum test force (F ) shall be accurate to within 5 % of
max
formed for each force range of the instrument. Indirect verifi-
the stated value. The verified force range of an instrument shall
cation is intended to monitor the total performance of the
be defined as the range of forces from the minimum verified
instrument including force and displacement calibrations, ma-
force to the maximum verified force.
chine compliance, indenter shape function, method of zero-
A1.3.2.2 The device used to verify forces shall be accurate
point determination, and the analysis procedures. Therefore,
to within 0.25 % or 1 μN of each verification force, whichever
these parameters shall remain fixed during indirect verification.
is greater. Examples of techniques for force verification in-
clude: A1.4.2 Procedure—Indirect verification requires determin-
(1) Measuring by means of an elastic proving device in ing the indentation modulus, E , of two materials of known
IT
accordance with Practice E74 (class A), or ISO 376 (class 1), Young’s modulus. The two material’s Young’s modulus shall
(2) Balancing against a force, applied by means of cali- differ by at least a factor of two. Test blocks that comply with
brated masses, and Annex A2 of this practice, should be used.
E2546 − 15 (2023)
NOTE A1.2—The Test Method defined in Appendix X4 is recommended
A1.6.2.2 After any relocation of the instrument, except for
for this procedure.
instruments designed specifically for portable use,
A1.6.2.3 At intervals not to exceed one year,
A1.4.2.1 On each material, five tests shall be performed
A1.6.2.4 When the machine fails routine checking as de-
within each of the following force ranges:
fined in A1.6.3 of this annex, and
(1) A maximum force within the lower 25 % of the verified
A1.6.2.5 When the correction for machine compliance is
force range, and
changed.
(2) A maximum force within the upper 25 % of the verified
force range.
NOTE A1.5—If the correction for machine compliance is known to
A1.4.2.2 The instrument is considered verified if ninety
change in a predictable way, that is, as a function of mounting type or
percent of the values of indentation modulus reported by the sample position, the machine compliance correction may be changed
according to a pre-established algorithm. An indirect verification is not
test equipment match the nominal Young’s modulus, or the
required after such a change.
dynamic Young’s modulus, value assigned to the material to
A1.6.2.6 Following the replacement of a component in
within 65 %.
either the force or displacement measurement system, provided
A1.4.3 Failure of the Indirect Verification—When the re-
that the manufacturer can show that such a replacement does
sults of the indirect verification are unsatisfactory, the manu-
not affect the force or displacement calibration of the complete
facturers’ guidelines for troubleshooting should be followed,
machine.
and the indirect verification repeated. If the results are still not
NOTE A1.6—It is recommended that the indirect verification process be
satisfactory, the instrument fails indirect verification.
used to determine the indenter shape function for a specific indenter.
A1.5 Routine Checking
A1.6.3 Routine Checking—Routine checking shall be per-
formed:
A1.5.1 Routine checking shall be used according to the
A1.6.3.1 Every day that the instrument is used,
schedule defined in A1.6.3 to monitor the performance of the
A1.6.3.2 When an indenter is changed, and
instrument.
A1.6.3.3 After changes in hardware that may affect the
A1.5.2 Procedure—Routine checking requires performing
machine compliance.
at least three tests on a single material of known indentation
A1.6.4 Verification Flowchart—A flowchart showing guide-
modulus. The test parameters, such as maximum force and
lines for verification of the various components is shown in
displacement, should be similar to those that will be used until
Fig. A1.1.
the next routine check. Eighty percent of the values of
indentation modulus reported by the instrument shall match the
A1.7 Reporting Results for Verifications and Routine
expected value to within 65 %.
Checking
NOTE A1.3—The test method used may require additional testing on
test blocks or other reference materials unique to the method.
A1.7.1 Results from all direct and indirect verifications,
including out-of-tolerance data, shall be maintained in a log
A1.5.3 Failure of Routine Checking—When the results of
associated with the instrument.
routine checking are unsatisfactory, the manufacturers’ guide-
lines for troubleshooting should be followed, and the routine
A1.7.2 Direct Verification Report—Reporting for a direct
check repeated. If the results are still not satisfactory, the
verification shall include at least the following information:
instrument fails routine checking.
A1.7.2.1 Reference to this standard,
A1.7.2.2 Identification data for the machine,
A1.6 Verification Schedule
A1.7.2.3 Environmental temperature and humidity,
A1.6.1 Direct Verification—Direct verification shall be per- A1.7.2.4 Verified force range of the instrument, as well as
formed: verification forces used and measured values for those forces
(see A1.3.2 of this annex),
A1.6.1.1 When the instrument is first certified to comply
with this standard, A1.7.2.5 Verified displacement range of the instrument, as
well as verification lengths used and measured values for those
A1.6.1.2 Following a major repair or overhaul of the
lengths (see A1.3.3 of this annex),
instrument, including replacement of a component in the force
A1.7.2.6 Identification of devices used for force and dis-
or displacement system, except as described in A1.6.2 of this
placement verification, including any relevant traceability
annex, and
information,
A1.6.1.3 When the instrument fails indirect verification as
A1.7.2.7 Results of timing verification including nominal
defined in A1.4 of this annex.
time of the test segment and measured time, and
NOTE A1.4—It is recommended that direct verification be performed
A1.7.2.8 Name of the verification laboratory and date of
upon installation of an instrument at a new location and at intervals not to
verification.
exceed three years. Instruments intended for portable use cannot easily be
directly verified at each location; therefore they should be verified at a
A1.7.3 Reporting for Indirect Verification—Reporting for an
known stable location.
indirect verification shall include all of the information re-
A1.6.2 Indirect Verification—Indirect verification shall be
quired by standard reporting as described in Section 9. Test
performed:
sample description shall include the nominal dynamic Young’s
A1.6.2.1 Following direct verification, modulus for the test materials.
E2546 − 15 (2023)
FIG. A1.1 Verification Flowchart
A1.7.4 Documentation of Routine Checking—A formal re-
port for routine checking is not required. However, it is
recommended that a log of these results be maintained.
A2. STANDARD REFERENCE BLOCKS
A2.1 Scope A2.2.2 Each test block shall be provided with certified
values of dynamic Young’s modulus and Poisson’s ratio.
A2.1.1 This annex specifies requirements for the production
Instrumented indentation tests shall be used to determine a
and certification of standard reference blocks for use in the
usable range of depth or load for each block. Examples of
indirect verification of instrumented indentation instruments,
material characteristics that might limit the range of appropri-
as described in A1.6.2 of this practice.
ate indentation force include the cracking of a brittle material
above a certain force, or unacceptable scatter in indentation
A2.2 General Requirements
results below a certain indentation force as the result of surface
A2.2.1 Standard reference blocks shall be manufactured
roughness or small-scale nonhomogeneities.
from materials with known values of dynamic Young’s
NOTE A2.1—These minimum and maximum values for force or
modulus, E, and Poisson’s ratio, ν, each determined to an
displacement will in general be indenter-specific. For example, maximum
accuracy better than 1.0 %. loads for blocks of brittle material may be much higher for large-radii
E2546 − 15 (2023)
spheres than for Berkovich tips.
facturer shall confirm, by testing a limited but statistically
significant number of specimens that blocks from various
A2.3 Material Selection
locations within the original batch all meet the general require-
A2.3.1 Materials for standard reference blocks should have
ments given in A2.2.
the following characteristics:
A2.5.2 The test block manufacturer shall determine general
A2.3.1.1 A well-known, uniform composition,
guidelines concerning which indenter geometry’s are suitable
A2.3.1.2 An amorphous or single crystal structure or known
for each test block, and the force or depth range over which the
grain size distribution,
blocks will perform satisfactorily. This information depends
A2.3.1.3 Isotropic elastic properties,
not only on the particular test block material, but on block
A2.3.1.4 A chemically stable surface,
preparation as well.
A2.3.1.5 A melting or glass transition temperature well
A2.5.3 The test block manufacturer shall confirm that the
above room temperature, and
elastic properties of the block at its test surface do not deviate
A2.3.1.6 Little or no pile-up of material about the perimeter
from the bulk values by more than 5 %, due to, for example,
of the indentation site.
any grinding, polishing or annealing processes used in the
A2.4 Manufacture of Reference Blocks
preparation of the blocks. Methods to accomplish this could
include, for example, test indentation by the manufacturer or
A2.4.1 Test Surface Orientation—Reference blocks shall be
measurement of surface elastic properties by surface acoustic
manufactured in such a way that the test surface can be
wave methods.
presented perpendicular to the indenter axis within 0.5 degrees.
For specimens that are intended to be placed with their bottom
A2.5.4 Surface roughness shall be measured on each pol-
surface (that surface opposite the test surface) on a specimen
ishing batch, or on each deposition batch, in the case of a
mounting plate, this requirement shall be met by achieving the
deposited test surface layer. The manufacturer shall report the
necessary 0.5 degree parallelism between top and bottom
method used for surface roughness determination.
surfaces. For specimens that are to be mounted by their sides
A2.5.5 Each block must be marked with it’s own a serial
(that is, a cylindrical reference block clamped in a V-shaped
number or letters. The markings may be on the top or side of
vise), the side surfaces shall be perpendicular to the test surface
the block. If the marking is on the side of the block, the
to within 0.5 degrees.
markings shall be upright when the test surface is the upper
A2.4.2 Test Surface Finish—Test surface roughness can
surface.
seriously degrade the accuracy and reproducibility of indenta-
A2.6 Certification Report
tion test results. Therefore, reference blocks should be prepared
in such a way that the test surface presented is as smooth as is
A2.6.1 The report for each test block shall at contain the
possible for a given material. An acceptable value of average
following minimum information:
surface roughness, R , for many applications is R ≤ 10 nm
A A
A2.6.1.1 The name of the laboratory certifying the block,
measured over a 10 μm trace. Blocks intended specifically for
A2.6.1.2 The certified values for dynamic Young’s modulus,
very-low-force verification will require lower roughness levels.
E, and Poisson’s ratio, ν, along with the uncertainty of each,
For guidelines on the preparation on metallographic
A2.6.1.3 The method by which E and ν were determined,
specimens, see for example Guide E3.
including identification of the equipment used and relevant
traceability information for that method and equipment,
A2.4.3 Reference Block Compliance—In some cases, the
reference block may consist of a smaller piece of test material A2.6.1.4 The serial number of the block,
in a larger, integral mount, or a deposited surface layer on a A2.6.1.5 The date of certification,
substrate. If this is the case, care must be taken by the test block A2.6.1.6 The regions of the block surface that is not
manufacturer to ensure that the stiffness of that integral mount available to the user for indentation; examples of such regions
or substrate is sufficiently high that its compliance does not include areas that are too close to an edge, or regions that were
significantly affect the measured elastic properties of the test used by the manufacturer for indentation or other quality
material. control testing that might have altered the surface properties,
A2.6.1.7 The indenter geometries for which the block is
A2.5 Certification Procedure
appropriate, and range of indentation force or depth over which
A2.5.1 The test block manufacturer shall determine both the the block may be expected to perform satisfactorily for each
specified indenter geometry,
dynamic Young’s modulus and Poisson’s ratio for the test block
material, each to within 1.0 % accuracy, using the current A2.6.1.8 The surface roughness of the test surface, includ-
ing a precise definition of the roughness quantity reported and
versions of Test Methods E1875 or E1876. This process may
be performed either on each block or on a larger batch of a description of how it was determined, and
material prior to sectioning or separation of individual test A2.6.1.9 An expiration date, if one is appropriate for a given
blocks. If such “batch certification” is performed, the manu- test material.
E2546 − 15 (2023)
A3. INDENTER REQUIREMENTS
A3.1 Scope
A3.1.1 This annex will define the requirements for the
various indenters typically used for IIT. The physical dimen-
sions and manufacturing tolerances of the most common
indenters will be defined along with the requirements for
certification.
A3.2 General Requirements
A3.2.1 The indenters used for IIT can be many different
shapes to suit the test method used. All indenters shall meet the
following requirements:
A3.2.1.1 The part of the indenter that contacts the sample
shall be made from a hard material and have a defined shape.
They can be a one piece or multi-piece design.
A3.2.1.2 The surface of the indenter that contacts the
sample shall be highly polished and free from chips, pits,
contamination and any other imperfections that may affect its
final use. The surface shall be observed under a microscope
with a magnification of least 50×.
FIG. A3.1 Angle of the Vickers Diamond Pyramid
NOTE A3.1—Spherical indenters that meet the requirements of ABMA/
ISO 3290-1 Grade 24 do not have to be inspected optically.
A3.2.1.3 Each indenter shall have a unique serial number. In A3.4 Three Sided Pyramidal Pointed Indenters
the case of a ball indenter, the holder only shall be serialized.
A3.4.1 There are three commonly used three sided pyrami-
The serial number shall be marked on the indenter or holder in
dal indenters used for IIT. They shall meet the following
a manner that cannot be easily removed. Indenters that are too
requirements:
small to be easily marked shall have the serial number marked
A3.4.1.1 Berkovich and Modified Berkovich—There are two
on its container.
types of Berkovich pyramidal diamond indenters in use. The
A3.2.1.4 The indenters shall be measured to verify their
original Berkovich indenter was designed to have the same
conformance to the dimensional requirements. A nominal
surface area as a Vickers indenter at any given indentation
indenter area function at the maximum usable indentation
depth. The modified Berkovich indenter is more commonly
depth shall be calculated based on the actual dimensions of the
used and has the same projected area as a Vickers indenter at
indenter.
any given indentation depth. The angles and tolerances for a
A3.2.1.5 Spherical indenters that are part of a batch of balls Berkovich indenter shall meet the angle and tolerance require-
from a lot that meet the requirements of ABMA/ISO 3290-1 ments defined in Fig. A3.3.
Grade 24 do not have to be individually measured or have a A3.4.1.2 Cube Corner—The angles and tolerances for a
cube corner indenter shall meet the angle and tolerance
indenter area function determined.
requirements defined in Fig. A3.3.
A3.2.1.6 Indenters for use at indentation depths ≤0.006 mm
shall have their area function defined over the relevant inden-
A3.5 Spherical Ball Indenters
tation depth range of use per A3.7.
A3.5.1 The ball shall be harder than the test piece. Carbide
A3.3 Vickers Indenters
balls with hardness not less than 1500 HV10 and having the
chemical composition defined in Table A3.1 are recommended.
A3.3.1 Vickers indenters that are used for IIT are similar to
A3.5.2 The balls shall meet the tolerance defined in Table
the indenters defined in Test Methods E384 and E92. They
A3.2. It is permissible to certify their compliance to the
shall meet the following requirements:
requirements of this section by using batch inspection tech-
A3.3.1.1 The angle between the opposite faces of the vertex
niques.
of the diamond pyramid shall be (136° 6 0.3°) (see Fig. A3.1).
NOTE A3.2—Balls that conform to ABMA/ISO 3290-1 Grade 24 satisfy
A3.3.1.2 The angle between the axis of the diamond pyra-
these requirements.
mid and the axis of the indenter holder (normal to the seating
A3.6 Spherical Tipped Conical Indenters
surface) shall not exceed 0.5°.
A3.3.1.3 The four faces should meet at a sharp point. The A3.6.1 Indenters with a spherical tipped cone shape are
maximum permissible length of the line of conjunction, c, useful for many applications. These indenters are normally
between opposite faces shall be 0.001 mm (see Fig. A3.2). made from diamond but may also be made from other
E2546 − 15 (2023)
FIG. A3.2 Line of Conjunction at the Tip of the Indenter, Schematically
TABLE A3.2 Tolerances for Ball Indenters
Ball Indenter Diameter, Tolerance,
mm mm
10 ±0.005
5 ±0.004
2.5 ±0.003
1 ±0.003
0.5 ±0.003
TABLE A3.3 Tolerances for Sphero-Conical Indenters
Feature Tolerance
Average Radius (R ) # 0.050 mm ±0.25 R
av av
0.500 > R > 0.050 mm ±0.10 R
av av
Cone included angle (2α)
120° ±5°
90° ±5°
60° ±5°
Cone flank angle (α) to centerline of mount
60° ±5°
45° ±2.5°
α = 65.03° 6 0.3° for Berkovich indenter
30° ±2.5°
α = 65.27° 6 0.3° for modified Berkovich indenter
Point of intersection of cone flanks to within 0.01 mm
α = 35.26° 6 0.3° for corner cube indenters
centerline of mount
FIG. A3.3 Angle of the Berkovich and Cube Corner Indenters
TABLE A3.1 Carbide Ball Chemical Composition
point of first contact should not vary by more than a factor of
Chemical Percent
two from the average radius, that is, 0.5 < R(h)/R < 2.
av
Cobalt (Co) 5.0 to 7.0 %
NOTE A3.3—Geometry suggests that the depth of spherical cap h on a
s
Total other carbides 2.0 %
cone of included angle 2α and radius R is given by:
av
Tungsten Carbide (WC) balance
h 5 R 1 2 sin α (A3.1)
~ ~ !!
s av
A3.6.3 In practice, there is a gradual transition from spheri-
materials, for example, ruby, sapphire or hard metal as long as
cal cap to cone geometry, which is hard to specify. Given this
the material is significantly harder than the sample being
and the uncertainties in R and α allowed (see Table A3.3),
av
tested. They are intended to indent only with the spherical tip.
caution should be exercised whenever the depth exceeds 0.5 h .
s
The characteristics of spherical tipped conical indenters shall
be as given in Table A3.3. A3.7 Indenter Area Function
A3.6.2 The instantaneous radius of curvature (R(h)) of the A3.7.1 Most of the results determined from an IIT test are
spherical cap at any indentation depth h measured from the based on the projected contact area of the indenter. However,
E2546 − 15 (2023)
usually, only the indentation depth is measured. When the A3.8.1.1 Date of verification,
maximum contact depth, h , is less than 6 μm, the relationship
c A3.8.1.2 Verifying laboratory,
between depth and projected contact area may be significantly
A3.8.1.3 Description of indenter,
different from that predicted by the nominal area function.
A3.8.1.4 Reference to this practice,
Therefore, when the indenter is used in this regime, a refined
A3.8.1.5 Unique serial number,
area function shall be determined. Either of the following
techniques is recommended:
A3.8.1.6 Geometrical data with an uncertainty statement,
A3.7.1.1 A direct measurement method using a traceable
A3.8.1.7 Nominal area function and maximum valid depth,
atomic force microscope (AFM).
A3.8.1.8 Refined area function (if determined) and valid
A3.7.1.2 Indirectly by utilizing indentations into a material
depth range, and
of known Young’s modulus (see Appendix X3).
A3.8.1.9 Description of technique used to determine refined
A3.8 Report
area function (if determined).
A3.8.1 At least the followin
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