ISO/FDIS 14577-2

ISO/TC 164/SC 3 1347
Date: 2025-07-02
ISO/DIS 14577-2:2025(en)
ISO/TC 164/SC 3
Secretariat: DIN BSI
Date: 2026-01-06
Metallic materials — Instrumented indentation test for hardness and
materials parameters —
Part 2:
Verification and calibration of testing machines
Matériaux métalliques — Essai de pénétration instrumenté pour la détermination de la dureté et de
paramètres des matériaux — Partie 2: Vérification et étalonnage des machines d'essai
Partie 2: Vérification et étalonnage des machines d'essai
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FDIS stage
ISO/DISFDIS 14577-2:20252026(en)
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iii
Contents Page
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General conditions . 1
4.1 Requirements . 1
4.2 Preparation . 2
4.3 Functional installation . 2
4.4 Indenter . 2
4.5 Application of the test force . 2
5 Direct verification and calibration . 2
5.1 General . 2
5.2 Calibration of the test force . 3
5.3 Calibration of the displacement measuring device . 3
5.4 Verification and calibration of the machine conformity . 4
5.5 Calibration and verification of the indenter . 5
5.6 Verification of the indenter area function . 13
5.7 Verification of the testing cycle . 14
6 Indirect verification . 14
6.1 General . 14
6.2 Procedure . 16
7 Intervals between calibrations and verifications . 18
7.1 Direct verification and calibration . 18
7.2 Indirect verification . 18
7.3 Routine checking . 18
8 Verification report/Calibration certificate . 18
Annex A (informative) Example of an indenter holder . 20
Annex B (normative) Procedures for determination of indenter area function . 23
Annex C (informative) Examples for the documentation of the results of indirect verification . 26
Annex D (normative) Machine conformity calibration procedure . 31
Bibliography . 36

iv
ISO/DISFDIS 14577-2:20252026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s)
which may be required to implement this document. However, implementers are cautioned that this may not
represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals,
Subcommittee SC 3, Hardness testing., in collaboration with the European Committee for Standardization
(CEN) Technical Committee CEN/TC 459 Test methods for steel (other than chemical analysis),in accordance
with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 14577--2:2015), which has been technically
revised.
The main changes are as follows:
— New procedure for indirect verification.
— New method 6 for machine complianceconformity calibration.
— Replacement of tungsten carbide balls by balls in general.
A list of all parts in the ISO 14577 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
Introduction
Hardness has typically been defined as the resistance of a material to permanent penetration by another
harder material. The results obtained when performing Rockwell, Vickers, and Brinell tests are determined
after the test force has been removed. Therefore, the effect of elastic deformation under the indenter has been
ignored.
[ [2]]
ISO 14577 (all parts) Error! Reference source not found.) has been prepared to enable the user to
evaluate the indentation of materials by considering both the force and displacement during plastic and elastic
deformation. By monitoring the complete cycle of increasing and removal of the test force, hardness values
equivalent to traditional hardness values can be determined. More significantly, additional properties of the
material, such as its indentation modulus and elasto-plastic hardness, can also be determined. All these values
can be calculated without the need to measure the indent optically. Furthermore, by a variety of techniques,
the instrumented indentation test allows to record hardness and modulus depth profiles within a, probably
complex, indentation cycle.
ISO 14577 (all parts) has been written to allow a wide variety of post test data analysis.
Part 2 of ISO 14577 specifies the methods of verification and calibration of instrumented indentation testing
machines.
vi
DRAFT International Standard ISO/DIS 14577-2:2025(en)

Metallic materials — Instrumented indentation test offor hardness
and materials parameters —
Part 2:
Verification and calibration of testing machines
1 Scope
This document specifies the method of verification and calibration of testing machines for carrying out the
instrumented indentation test in accordance with ISO 14577--1.
It specifies a direct verification method for verifying and calibrating the main functions of the testing machine
and an indirect verification method suitable for the determination of the repeatability of the testing machine.
The methods in ISO 14577 are applicable to all systems that comply with the requirements of this part of ISO
14577.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 376, Metallic materials — Calibration of force-proving instruments used for the verification of uniaxial
testing machines
ISO 14577--1, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 1: Test method
ISO 14577--3, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 3: Calibration of reference blocks
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— — ISO Online browsing platform: available at https://www.iso.org/obp
— — IEC Electropedia: available at https://www.electropedia.org/
4 General conditions
4.1 Requirements
There is the requirement that an indirect verification method be used in addition to the direct method and for
the periodic routine checking of the testing machine in service.
4.2 Preparation
The machine shall be designed in such a way that it can be verified.
Before verification and calibration of the testing machine, it shall be checked to ensure that the conditions laid
down in 4.34.3 to 4.54.5 are met.
4.3 Functional installation
The testing machine shall be configured to operate in conformity with and shall be installed in an environment
that meets the requirements of this document, ISO 14577--1, and, where applicable, ISO 14577--3. The testing
machine shall be protected from vibrations that would significantly affect the test results. For testing in the
micro and nano ranges, the testing machine shall also be protected from air currents and temperature
fluctuations (see ISO 14577-1:202X, 7.1).
The influence of environment on the data, i.e. the noise floor, shall be estimated by performing a low force (e.g.
equivalent to the usual initial contact force) indentation on a Certified Reference Material (CRM) and analysing
the displacement over time. The force variability is the indent stiffness (obtained from force removal curve)
multiplied by the standard deviation of the displacement once any background drift in mean displacement has
been subtracted. These uncertainties shall then be included in the total combined uncertainty as calculated in
ISO 14577--1:202X, Clause 4, Clause 8 and Annex H.
4.4 Indenter
In order to get repeatable measurements of the force/indentation depth data set, the indenter holder shall be
firmly mounted into the testing machine.
The indenter holder should be designed in such a way that its contribution to the overall
complianceconformity is minimized (see Annex AAnnex A).).
4.5 Application of the test force
The test force shall be applied and removed without shock or vibration that can significantly affect the test
results. It shall be possible to verify the process of increasing, holding, and removal of the test force.
5 Direct verification and calibration
5.1 General
5.1.1 5.1.1 Direct verification and calibration shall be carried out at the temperature of use, which is
typically held at a stable value over the time of measurement in the range 10 °C to 35 °C, but preferably in the
range (23 ± 5) °C. If a range of operating temperatures is required, then direct calibration and verification
should be carried out at suitable points over that temperature range to determine the calibration validity as a
function of temperature. If necessary, a calibration correction function or a set of calibrations valid at specific
operating temperatures can be determined.
5.1.2 5.1.2 The instruments used for direct calibration and verification shall be traceable to National
Standards as far as available.
5.1.3 5.1.3 Direct verification and calibration involves
a) a) calibration of the test force,
b) b) calibration of the displacement measuring device,
c) c) verification and calibration of the machine complianceconformity,
ISO/DISFDIS 14577-2:20252026(en)
d) d) verification of the indenter,
e) e) calibration and verification of the indenter area function, if the indentation depth is less than
6 µm, and
f) f) verification of the test cycle.
5.2 Calibration of the test force
5.2.1 5.2.1 Each range of force used shall be calibrated over the whole force range for both application and
removal of the test force. A minimum of 16 evenly distributed points in the test force range shall be calibrated,
i.e. 16 during application and 16 during removal of the test force. The procedure shall be performed at least
three times. The average of all the measured values at each force point shall be used as the calibration value
for the machine. The difference between the force value from the testing machine and the force value from the
calibration device shall not exceed half of the tolerances given in 0Table 1. .
5.2.2 5.2.2 The test force shall be measured by a traceable method, for example, one of the following:
a) a) measuring by means of an elastic proving-device in accordance with class 1, or better
according to ISO 376;
b) b) balancing against a force with an uncertainty ≤ 0,2 % applied by means of calibrated masses
with mechanical advantage;
c) c) electronic balance with an uncertainty ≤ 0,1 % of the minimum calibrated test force or 10 µg
(0,1 µN) for the nano range.
For each individual measured point used to calculate the calibration value, the difference between the
measured and the nominal test force shall be within the tolerances given in 0Table 1.
Table 1 — Tolerances for test forces
Range of the test force Tolerances
F
N %
F ≥ 2 1,0
0,001 ≤ F < 2 1,0
a
F < 0,001 2,5
a For the nano range, a tolerance of 1 % is strongly recommended.
5.3 Calibration of the displacement measuring device
5.3.1 5.3.1 The resolution required for the displacement measuring device of the testing machine depends
on the size of the smallest indentation depth being measured. For the micro range, this value is by definition
h = 0,2 µm; for the macro range it is typically larger than 2 µm.
The scale of the displacement measuring device shall be graduated to permit a resolution of indentation depth
measurement in accordance with 0Table 2.
5.3.2 5.3.2 The displacement measuring device of the testing machine shall be calibrated for every range
used by means of a suitable method and a corresponding system traceable to SI. The device shall be calibrated
at a minimum of 16 points in each direction evenly distributed throughout its indentation displacement range.
The procedure shall be performed three times.
Some testing machines have a long-stroke displacement measuring device where the location of the
indentation range of the displacement measuring device varies to suit the sample. For these types of machines,
it shall be verified that the calibration is valid in accordance with 0Table 2 for all of the used measurement
positions in the travel range.
The following methods are recommended for the measurement of the relative displacement of the indenter:
laser interference method, inductive method, capacitive method, and piezotranslator method.
The calibration device shall have an uncertainty of ≤ 0,2 % in the displacement measurement in the applied
measurement range.
For each measured point used for calibration, the difference between the measured and the nominal
displacement shall be within the tolerances given in 0Table 2.
Table 2 — Resolution and tolerances of the displacement measuring device
Resolution of the displacement
Range of application measuring device Tolerances
nm
Macro ≤100 1 % of h
Micro ≤10 1 % of h
a
Nano ≤1 2 nm
a For the nano range, a tolerance of <1 % of h (displacement of the measuring device) is strongly recommended.
5.3.3
5.3.45.3.3 5.3.3 Changes in temperature are commonly a dominant source of displacement drift.
To minimize thermally induced displacement drift, the temperature of the instrument shall be maintained
such that the displacement drift rate remains constant over the time period of one calibration cycle. The drift
rate shall be measured during, immediately before, or immediately after each calibration cycle, e.g. by
monitoring displacement during a suitable hold period. The displacement calibration data shall be corrected
for thermal drift and the product of variation in drift rate and the duration of one calibration cycle shall be less
than the tolerance given in 0Table 2. The drift rate uncertainty shall be included in the displacement
calibration uncertainty calculation.
5.4 Verification and calibration of the machine complianceconformity
5.4.1 General
See normative Annex DAnnex D and ISO 14577--1:202X, Annex C.
This verification and calibration shall be carried out after the test force and the displacement measuring
system have been calibrated in accordance with 5.25.2 and 5.35.3.
5.4.2 Procedure
The calibration and verification of machine complianceconformity is carried out by the measurement of
indentation modulus at a minimum of five different test forces. Method 3 as specified in Annex DAnnex D is
recommended. In all cases, a suitable Certified Reference Material (CRM) shall be mounted into the
instrumented indentation test system in the same way as future test samples will be mounted. This is to ensure
that the CRM provides a faithful reproduction of each particular total machine complianceconformity.
The complianceconformity of the testing machine can be affected by the particular construction and mounting
of an indenter and also the method used to mount a sample. For instance, mounting in plastics (e.g. PVC) can
introduce an extra complianceconformity into the measurement loop. The verification and calibration of
ISO/DISFDIS 14577-2:20252026(en)
machine complianceconformity should be performed using the indenter that will be used for subsequent
measurements.
For contact depths, h > 6 µm, it is not necessary to take into account the real contact area function. For the
c
verification and calibration of the machine complianceconformity, a reference material with certified
indentation modulus, independent from the indentation depth, shall be used. The laboratory for the
certification of the reference material should be certified according to ISO 17025 (Ref [Error! Reference
source not found. [4]).]). A material with a high ratio of 𝐸 ⁄ 𝐻 (such as tungsten) is recommended. The
√
IT IT
range for the test force is defined by the minimum test force that correlates to 6 µm contact depth and the
maximum possible test force of the testing machine. Large indentation depths have the advantage that errors
in the area function are likely to be smaller; however, care shall be taken that the test is not biased by pile-up
in the reference material. The measured complianceconformity of the indentation shall then be compared with
the calculated complianceconformity for the indentation using the certified value of modulus. To recalibrate
machine complianceconformity, the product of the applied force and the detected difference in machine
complianceconformity is applied to the displacement data to refine the estimate of contact depth and,
therefore, the machine complianceconformity estimate at each force. This process is iterated until self-
consistent values of machine complianceconformity and contact depth are reached.
For contact depths, ≤ 6 µm, the method above shall be applied, except that the actual area of contact, as
calculated from the calibrated indenter area function, shall be used to calculate the contact
complianceconformity using the certified modulus of the CRM.
In many nano and micro range instruments, the machine complianceconformity value is independent of force.
However, if this is not the case, then a machine complianceconformity function may be determined using the
above procedure over a wider range of forces. The range for the test forces is defined by the indentation
depths, >0,5 µm, and the maximum test force of the testing machine or the maximum test force for which no
unusual test piece response (e.g. pile-up of metals or cracking of ceramics or glasses) occurs.
If the machine complianceconformity is recalibrated, then an indirect validation shall be performed before
use.
The calibration procedures detailed in the normative Annex DAnnex D require the use of reference materials
(see ISO 14577--3) that shall be isotropic and homogeneous. It is assumed that the indentation modulus and
Poisson’s ratio are independent of the indentation depth.
5.5 Calibration and verification of the indenter
5.5.1 General
The indenter used for the indentation test shall be calibrated traceable to SI. This requirement may be satisfied
by a calibration certificate from a qualified calibration laboratory or by the user following the verification
methods described in Annex BAnnex B using suitable certified reference materials.
Over time indenters can change shape. Evidence that the indenter continues to complyconform with the
requirements of this part of ISO 14577 is fulfilled by evidence that the indenter passes an indirect verification
over the operating range of indentation depth. This may be provided using the verification methods described
in Annex BAnnex B and suitable certified reference materials.
The indenter shall meet the following requirements:
— — The material shall be homogeneous and fully dense;
— — The elastic modulus and Poisson ratio of the indenter material shall be known;
— — The indenter shall be significantly harder than the sample material. The indenter should have a higher
elastic modulus than the sample material.
— — The indenter geometry shall conform to the requirements of this standard
If the angle of the indenter deviates from the nominal value for an ideal geometry of the indenter, the average
of certified angles for that indenter should be used in all applicable calculations at contact depths h > 6 µm.
c
NOTE An error of 0,2° in the Vickers angle of 136° (2α) results in a 1 % systematic error in area.
Indenters for use in the nano range and in the micro range shall have their area function calibrated over the
relevant indentation depth ranges of use. The indenter performance shall be verified periodically (see
6Clause 6).).
Where non-diamond indenters are used, the values of elastic modulus and Poisson ratio shall be obtained and
used instead of the diamond values in the appropriate analyses.
The angle for pyramidal and conical indenters shall be measured within the indentation depth ranges given in
0Table 3 and illustrated in 0Figure 1.
Table 3 — Values for the measuring ranges for the angle of pyramidal and conical indenters
Dimensions in micrometres
Indentation depth Macro range Micro range
h 6 0,2
Specified max.
h 200
indentation depth
Figure 1 — Illustration of measuring ranges given in 0Table 3
ISO/DISFDIS 14577-2:20252026(en)
5.5.2 Vickers indenter
5.5.2.1 5.5.2.1 The four faces of the right square-based diamond pyramid shall be smooth and
free from surface defects and contaminants that significantly alter the area function. For notes on cleaning of
the indenter surface, see also ISO 14577--1:202X, Annex D.
The surface roughness of the indenter has a similar effect on measurement uncertainty as test piece
roughness. When testing in the nano range, the indenter surface finish should be taken into consideration.
5.5.2.2 5.5.2.2 The angle between the opposite faces of the vertex of the diamond pyramid
shall be 136° ± 0,3° (see 0Figure 2)) (α = 68,0° ± 0,2°).
The angle shall be measured in the range between h and h (see 0Table 3 and 0Figure 1).). The geometry and
1 2
finish of the indenter shall be controlled over the whole calibrated indentation depth range, i.e. from the
indenter tip, h , to the maximum calibrated indentation depth, h .
0 2
5.5.2.3 5.5.2.3 The angle between the axis of the diamond pyramid and the axis of the indenter
holder (normal to the seating surface) should not exceed 0,5°.
5.5.2.4 5.5.2.4 The four faces shall meet at a point. The maximum permissible length of the line
of conjunction between opposite faces is given in 0Table 4 (see also 0Figure 3).).
5.5.2.5 5.5.2.5 The radius of the tip of the indenter shall not exceed 0,5 µm for the micro and
nano range (see 0Figure 4).).
5.5.2.6 5.5.2.6 The verification of the shape of the indenter shall be carried out using
microscopes or other suitable devices. If the indenter is used for testing in the micro or nano range, a
verification by a closed loop controlled atomic-force-microscope (AFM) is recommended.
NOTE An area function derived by indentation in a certified reference material has high uncertainty in the nano
range.
Table 4 — Maximum permissible length of the line of conjunction
Range of the contact depth Maximum permissible length
of the line of conjunction
µm µm
h > 30 1
c
a
30 ≥ h > 6 0,5
c
b
hc ≤ 6 ≤ 0,5
a This can be assumed to have been achieved when there is no detectable conjunction when the indenter is verified by an optical
microscope at 400 × magnification.
b This shall be included when the correction of the shape of the indenter is taken into account; see ISO 14577--1:202X, C.2.
Figure 2 — Angle of the Vickers diamond pyramid

Key
a line of conjunction
a
Line of conjunction.
Figure 3 — Line of conjunction on the tip of the indenter — Schematic
ISO/DISFDIS 14577-2:20252026(en)

Figure 4 — Radius of the tip of the indenter
5.5.3 Berkovich, modified Berkovich, and corner cube indenters
5.5.3.1 5.5.3.1 In practice, there are two types of Berkovich pyramidal diamond indenters in
common use. The Berkovich indenter (see Reference [Error! Reference source not found.[5])]) is designed
to have the same surface area as a Vickers indenter at any given indentation depth. The modified Berkovich
indenter (see Reference [Error! Reference source not found.[11])]) is designed to have the same projected
area as the Vickers indenter at any given indentation depth. The most common Berkovich geometry in use is
the modified Berkovich indenter. This is often for convenience referred to as a “Berkovich” indenter.
5.5.3.2 5.5.3.2 The three faces of the triangular based diamond pyramid shall be smooth and
free from surface defects and from contaminations that significantly alter the area function. For notes on
cleaning of the surface, see also ISO 14577--1:202X, Annex D.
The surface roughness of the indenter has a similar effect on measurement uncertainty as does test piece
roughness. When testing in the nano range, the indenter surface finish should be taken into consideration.
5.5.3.3 5.5.3.3 The radius of the tip of the indenter shall not exceed 0,5 µm for the micro range
and shall not exceed 0,2 µm for the nano range (see 0Figure 4).).
5.5.3.4 5.5.3.4 The angle between the axis of the diamond pyramid and the three faces is
designated α. The angle between edges of the triangular base of the diamond pyramid shall be 60° ± 0,3° (see
0Figure 5).).
a
α = 65,03° ± 0,30° for Berkovich indenter.
α = 65,27° ± 0,30° for modified Berkovich indenter.
α = 35,26° ± 0,30° for corner cube indenters.

a
α = 65,03° ± 0,30° for Berkovich indenter.
α = 65,27° ± 0,30° for modified Berkovich indenter.
α = 35,26° ± 0,30° for corner cube indenters.
Figure 5 — Angle of the Berkovich and corner cube indenters
NOTE The most common Berkovich geometry in use is the modified Berkovich indenter. This is often for
convenience referred to as a “Berkovich” indenter.
5.5.3.5 5.5.3.5 The verification of the shape of the indenter shall be carried out using
microscopes or suitable devices. If the indenter is used for testing in the micro and nano range, a measurement
by a closed-loop controlled atomic-force-microscope (AFM) is recommended.
NOTE An area function derived by indentation in a certified reference material has high uncertainty in the nano
range.
5.5.4 Ball indenters
The balls shall have a certified geometry. Batch certification methods are sufficient. The certificate shall show
the diameter of the average value of at least three measured points of different positions. If any value differs
from the permissible values of the nominal diameter (see 0Table 5),), the ball (and/or the batch) shall not be
used as an indenter.
Table 5 — Tolerances for ball indenters
Dimensions in millimetres
Ball diameter Tolerance
10 ±0,005
5 ±0,004
2,5 ±0,003
1 ±0,003
0,5 ±0,003
5.5.5 Spheroconical indenters
The characteristics of spheroconical indenters shall be as given in 0Table 6 (see also 0Figure 6).).
ISO/DISFDIS 14577-2:20252026(en)
Table 6 — Tolerances for spheroconical indenters
Feature Tolerance
R ≤ 50 µm 0,4 R
av av
a
500 µm > R > 50 µm 0,2 R
av av
Cone included angle, 2α
a
120° 5°
90° 5°
60° 5°
Cone flank angle, α
60° 2.,5°
45° 2,5°
30° 2,5°
[ [1]
a Rockwell diamond indenters (see ISO 6508--2) Error! Reference source not found.)
]
fulfil this requirement.
The centreline of the cone to the centreline of the mount shall be within 0,01 mm.
The instantaneous radius of curvature, R(h), of the spherical cap at any indentation depth, h, measured from
the point of first contact shall not vary by more than a factor of two from the average radius, R , as given by
av
the condition in 0Formula (1)::
0,5 ≤ |R(h)/R | ≤ 2 (1)
av
Indentation analysis that requires an accurate radius shall use a radius function R(h ).
c
Indenters with a spherical tipped cone shape are useful for many applications. These indenters are normally
made from diamond but can also be made from other materials, e.g. ruby, sapphire, or hardmetal (WC-Co
cemented carbide). If Hertzian contact mechanics are being used to interpret the indentation response, the
value used for the indenter radius is critical. It is, therefore, recommended that the shape of each indenter be
determined directly by a suitable measurement system, or indirectly by indentation into a certified reference
material.
Surface roughness, Ra, should be minimized. Roughness causes an uncertainty in the actual area of contact
and in the definition of the first contact point of the indenter with the test piece. Asperities have radii of contact
vastly different from the average radius of the spherical cap and, therefore, behave very differently. If possible,
the Ra of the diamond surface should be less than 1/20 of the usual indentation depth for an indenter.
NOTE Geometry suggests that the depth of the spherical cap, h , on a cone of included angle, 2α, and radius, R , is
s av
given by 0Formula (2)::
h = R [1 − sin(α)] (2)
s av
In practice, there is a gradual transition from spherical cap to cone geometry that is hard to specify. Given this and the
uncertainties in R and α allowed (see 0Table 6),), caution should be exercised whenever the depth exceeds 0,5 h .
av s
a
α angle between the axis of the cone and its face.
h depth of the spherical cap.
s
h local depth.
R(h) local radius.
R radius of the spherical cap.
av
ISO/DISFDIS 14577-2:20252026(en)

a
α angle between the axis of the cone and its face.
hs depth of the spherical cap.
h local depth.
R(h) local radius.
Rav radius of the spherical cap.
Figure 6 — Representation of the features of spheroconical indenters
5.6 Verification of the indenter area function
5.6.1 General
See ISO 14577--1:202X, Annex C.
5.6.2 Procedure
Procedures for the determination of indenter area function are given in Annex BAnnex B.
The verification of the indenter area function consists of a comparison of the measured indenter area function
with a documented indenter area function determined for the newly certified and calibrated indenter.
NOTE The indenter area function and machine complianceconformity correction can be determined simultaneously
using an iterative procedure and multiple reference materials (see Reference [Error! Reference source not
found.[8]).]).
The indenter area function shall be recalibrated when the area function used for the measurement of a
reference material generates modulus results that deviate by more than 5 % from the specified reference
modulus value.
A pyramidal indenter shall no longer be used in the nano- or micro-ranges when the tip radius significantly
exceeds the respective values given in 5.5.25.5.2 and 5.5.35.5.3. In the macro range the indenter should be
discarded when the face angle significantly deviates from the respective values given in 4.5.2 and 4.5.3.
A ball or spherical indenter shall be discarded when the calibrated tip radius deviates more than 3 times the
specified tip radius tolerances in 0table 5 and 06.
5.7 Verification of the testing cycle
The testing machine shall be able to acquire data with a valid time stamp. The testing cycle (application of the
test force, holding of the maximum test force, and removal of the test force) shall be measured with a tolerance
not greater than 0,1 s. The duration of each part of the testing cycle during the experiment shall meet the
requirements of ISO 14577--1.
6 Indirect verification
6.1 General
Indirect verification shall be carried out at the temperature of use by means of reference blocks calibrated for
elastic modulus using non-indentation methods in accordance with ISO 14577-3 and within the temperature
range for which the calibration of the reference blocks is valid, typically (23 ± ± 5) °C. Indirect verification
using a reference material shall be made to ensure the direct verification is valid and that no damage or
contamination has occurred to the indenter tip.
Before measuring on the reference block, it is recommended to inspect and clean the indenter first using the
procedure recommended in ISO 14577--1:202X, Annex D. If the results of these initial indentations indicate
the presence of contamination or damage, then the indenter should be cleaned again before further trial
indentations are made. If after further cleaning, indentation into the reference material still indicates the
presence of contamination or damage, then inspection with an optical microscope at a magnification of 400x
is recommended. Detection of sub-microscopic damage or contamination is possible using appropriate
microscopy of indents or the indenter. Where damage is detected, the indenter shall be replaced.
For an indirect validation decision tree, see 0Figure 7. The procedures for the determination of the machine
complianceconformity, C , and the area function, A (h ), calibration/verification shall be implemented
F p,UL c
before a new indenter is used. If, after applying the currently valid correction for machine
complianceconformity and indentation area function (obtained using a variable epsilon and a radial
displacement correction, ISO 14577--1:202X, Annex I), a measured value from a reference block deviates from
the certified value of the test piece by more than the maximum permissible amount of the limits specified in
0Table 7 (see Note 2) and repetition of the procedure using a newly verified and certified indenter and valid
machine complianceconformity correction corresponding to that indenter) also fails to reproduce the certified
value, the testing machine shall be serviced and a full, direct calibration be performed.
NOTE 1 The use of control charts is a sensitive way to determine changes in performances before a control limit is
breached (see Annex CAnnex C).).
ISO/DISFDIS 14577-2:20252026(en)

Start
( ) and C
f
Indirect verification on
Pass
validation if
Certified Reference Materials
indenter is new
Fail
Recalibrate
Change or
Calibrate indenter Clean
recalibrate
indenter
indenter
Inspect
e ect
Damaged
indenter
indenter
magni ication
Undamaged
Pass
Repeat indirect verification on
Certified Reference Materials
Fail
Pass
Choose
Indirect verification on
between direct
Certified Reference Materials
calibration and or indenter
using reference indenter
change vs. reference
indenter
Fail
Keep indenter
Change indenter
Repeat indirect verification on
Direct
Pass
calibration Certified Reference Materials
F , h, test cycle
using test indenter
Fail
Proceed
with test
Figure 7— — Flow chart of decisions and actions to be taken for indirect verification
NOTE 2 A reference indenter is a calibrated indenter used infrequently and only for checking the instrument and test
indenter performance through indirect validation comparison.
6.2 Procedure
6.2.1 6.2.1 Indirect verification shall be carried out on at least one reference block of a CRM. It is highly
recommended to use two reference blocks, and the certified values of these blocks differ significantly, e.g. by
ISO/DISFDIS 14577-2:20252026(en)
a factor of two. The indirect verification shall be carried out at two or more test forces that are an order of
magnitude different or at least span the range of indentation forces or depths being measured. This shall be
done on each reference block used for the verification. For tests with indentation depths ≤ 6 µm, this provides
some verification of the contact area function.
For the indirect verification in the nano and micro range, only CRMs certified for elastic modulus shall be used.
6.2.2 6.2.2 If a testing machine is used only at one test force, it may be verified only at this test force on at
least two reference blocks with certified values that span the range of values of the test pieces being tested.
6.2.3 6.2.3 On each reference block, at least five measurements shall be made in accordance with
ISO 14577--1. For contact depths <6 µm, at least 10 measurements at each test force on each block are
recommended to reduce the uncertainty in repeatability of the measurement mean.
NOTE When a CRM is used for daily check of testing machine before routine measurements, three to five
indentations are considered sufficient.
6.2.4 6.2.4 For each reference block, an arithmetic mean value, ,𝑞¯, from n values q , ., q (where q
1 n
represents the materials parameters) is calculated as given in 0Formula (3)::
𝑞 + ⋯ + 𝑞
1 𝑛
𝑞¯ =
𝑛
(3)
The relative deviation, R , of an individual measured value is expressed as a percentage, given by
i
0Formula (4)::
(4)
𝑞  − 𝑞¯
𝑖
6.2.5 𝑅 =     × 100
𝑖
𝑞¯
(4)
6.2.5 The repeatability of the testing machine is assessed by making 10 sequential measurements of a CRM,
preferably at the same position or within a region of minimal samp
...