EN ISO 14577-4:2007

SLOVENSKI STANDARD
01-april-2008
Kovinski materiali - Preskus trdote in lastnosti materialov z instrumentirano
metodo vtiskovanja - 4. del: Preskusna metoda za kovinske in nekovinske prevleke
(ISO 14577-4:2007)
Metallic materials - Instrumented indentation test for hardness and materials parameters
- Part 4: Test method for metallic and non-metallic coatings (ISO 14577-4:2007)
Metallische Werkstoffe - Instrumentierte Eindringprüfung zur Bestimmung der Härte und
anderer Werkstoffparameter - Teil 4: Prüfverfahren für metallische und nichtmetalische
Schichten (ISO 14577-4:2007)
Matériaux métalliques - Essai de pénétration instrumenté pour la détermination de la
dureté et de parametres des matériaux - Partie 4: Méthode d'essai pour les revetements
métalliques et non métalliques (ISO 14577-4:2007)
Ta slovenski standard je istoveten z: EN ISO 14577-4:2007
ICS:
77.040.10 Mehansko preskušanje kovin Mechanical testing of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 14577-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2007
ICS 77.040.10
English Version
Metallic materials - Instrumented indentation test for hardness
and materials parameters - Part 4: Test method for metallic and
non-metallic coatings (ISO 14577-4:2007)
Matériaux métalliques - Essai de pénétration instrumenté Metallische Werkstoffe - Instrumentierte Eindringprüfung
pour la détermination de la dureté et de paramètres des zur Bestimmung der Härte und anderer Werkstoffparameter
matériaux - Partie 4: Méthode d'essai pour les revêtements - Teil 4: Prüfverfahren für metallische und nichtmetalische
métalliques et non métalliques (ISO 14577-4:2007) Schichten (ISO 14577-4:2007)
This European Standard was approved by CEN on 13 April 2007.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the
official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2007 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14577-4:2007: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 14577-4:2007) has been prepared by Technical Committee ISO/TC 164
"Mechanical testing of metals" in collaboration with Technical Committee ECISS/TC 1 "Steel -
Mechanical testing", the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by November 2007, and conflicting national
standards shall be withdrawn at the latest by November 2007.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United
Kingdom.
Endorsement notice
The text of ISO 14577-4:2007 has been approved by CEN as EN ISO 14577-4:2007 without any
modifications.
INTERNATIONAL ISO
STANDARD 14577-4
First edition
2007-05-15
Metallic materials — Instrumented
indentation test for hardness and
materials parameters —
Part 4:
Test method for metallic and non-metallic
coatings
Matériaux métalliques — Essai de pénétration instrumenté pour la
détermination de la dureté et de paramètres des matériaux —
Partie 4: Méthode d'essai pour les revêtements métalliques et non
métalliques
Reference number
ISO 14577-4:2007(E)
©
ISO 2007
ISO 14577-4:2007(E)
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ii © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Symbols and designations . 2
4 Verification and calibration of testing machines. 2
5 Test pieces . 4
5.1 General. 4
5.2 Surface roughness . 4
5.3 Polishing. 5
5.4 Surface cleanliness . 5
5.5 Special requirements for paints and varnishes. 5
6 Procedure . 6
6.1 Test conditions . 6
6.2 Measurement procedure . 9
7 Data analysis and evaluation of results for indentation normal to the surface . 11
7.1 General. 11
7.2 Coating indentation modulus . 12
7.3 Coating indentation hardness . 13
8 Test report . 16
Annex A (normative) Frame compliance calibration procedure . 17
Annex B (normative) Contact point and fully elastic regime. 21
Bibliography . 23

ISO 14577-4:2007(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 14577-4 was prepared by Technical Committee ISO/TC 164, Mechanical testing of metals, Subcommittee
SC 3, Hardness testing.
ISO 14577 consists of the following parts, under the general title Metallic materials — Instrumented
indentation test for hardness and materials parameters:
⎯ Part 1: Test method
⎯ Part 2: Verification and calibration of testing machines
⎯ Part 3: Calibration of reference blocks
⎯ Part 4: Test method for metallic and non-metallic coatings
iv © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
Introduction
The elastic and plastic properties of a coating are critical factors determining the performance of the coated
product. Indeed many coatings are specifically developed to provide wear resistance that is usually conferred
by their high hardness. Measurement of coating hardness is often used as a quality control check. Young’s
modulus becomes important when calculation of the stress in a coating is required in the design of coated
components. For example, the extent to which coated components can withstand external applied forces is an
important property in the capability of any coated system.
It is relatively straightforward to determine the hardness and indentation modulus of bulk materials using
instrumented indentation. However, when measurements are made normal to a coated surface, depending on
the force applied and the thickness of the coating, the substrate properties influence the result.
The purpose of this part of ISO 14577 is to provide guidelines for conditions where there is no significant
influence of the substrate, and, where such influence is detected, to provide possible analytical methods to
enable the coating properties to be extracted from the composite measurement. In some cases, the coating
property can be determined directly from measurements on a cross-section.

INTERNATIONAL STANDARD ISO 14577-4:2007(E)

Metallic materials — Instrumented indentation test for hardness
and materials parameters —
Part 4:
Test method for metallic and non-metallic coatings
1 Scope
This part of ISO 14577 specifies a method for testing coatings which is particularly suitable for testing in the
nano/micro range applicable to thin coatings.
This test method is limited to the examination of single layers when the indentation is carried out normal to the
test piece surface, but graded and multilayer coatings can also be measured in cross-section if the thickness
of the individual layers or gradations is greater than the spatial resolution of the indentation process.
The test method is not limited to any particular type of material. Metallic, non-metallic and organic coatings are
included in the scope of this part of ISO 14577.
The application of this part of ISO 14577 regarding measurement of hardness is only possible if the indenter is
a pyramid or a cone with a radius of tip curvature small enough for plastic deformation to occur within the
coating. The hardness of visco-elastic materials, or materials exhibiting significant creep will be strongly
affected by the time taken to perform the test.
NOTE 1 ISO 14577-1, ISO 14577-2 and ISO 14577-3 define usage of instrumented indentation testing of bulk
materials over all force and displacement ranges.
NOTE 2 The application of the method of this part of ISO 14577 is not needed if the indentation depth is so small that
in any possible case a substrate influence can be neglected and the coating can be considered as a bulk material. Limits
for such cases are given.
NOTE 3 The analysis used here does not make any allowances for pile-up or sink-in of indents. Use of Atomic Force
Microscopy (AFM) to assess the indent shape allows the determination of possible pile-up or sink-in of the surface around
the indent. These surface effects result in an under-estimate (pile-up) or over-estimate (sink-in) of the contact area in the
analysis and hence may influence the measured results. Pile-up generally occurs for fully work-hardened materials. Pile-
up of soft, ductile materials is more likely for thinner coatings due to the constraint of the stresses in the zone of plastic
deformation in the coating. It has been reported that the piled up material results in an effective increase of the contact
area for the determination of hardness, while the effect is less pronounced for the determination of indentation modulus,
[1], [2]
since the piled up material behaves less rigidly .
2 Normative references
The following referenced documents are indispensable for the application 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 1514, Paints and varnishes — Standard panels for testing
ISO 2808, Paints and varnishes — Determination of film thickness
ISO 3270, Paints and varnishes and their raw materials — Temperatures and humidities for conditioning and
testing
ISO 14577-4:2007(E)
ISO 4287, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Terms, definitions
and surface texture parameters
ISO 14577-1:2002, Metallic materials — Instrumented indentation test for hardness and materials
parameters — Part 1: Test method
ISO 14577-2, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 2: Verification and calibration of testing machines
ISO 14577-3, Metallic materials — Instrumented indentation test for hardness and materials parameters —
Part 3: Calibration of reference blocks
3 Symbols and designations
The symbols and designations in ISO 14577-1, ISO 14577-2 and ISO 14577-3 and in Table 1 apply.
Table 1 — Symbols and designations
Required in the
Symbol Designation Unit
test report
F Test force mN 9
A (h ) Projected area of contact of the indenter at distance h from the tip µm —
p c c
2 b
H Indentation hardness of the coating mN/µm 9
c
a
ν Poisson's ratio of the indenter — —
i
ν Poisson's ratio of the test piece — —
s
a Radius of contact area µm —
t Film thickness µm 9
c
C Frame compliance µm/mN 9
f
C Contact compliance (test piece) µm/mN —
s
C Total measured compliance µm/mN —
t
2 b
E Young's modulus mN/µm —
c 2
E * Plane strain indentation modulus of the coating mN/µm —
c
2 b
E * Plane strain indentation modulus mN/µm 9
IT
2 b
E Reduced modulus of the indentation contact mN/µm —
r
Ra Arithmetic mean deviation from the average height of the assessed µm
profile (see ISO 4287).
a
For diamond ν = 0,07.
i
b
1 mN/µm = 1 GPa.
c
E * = E * (at a/t = 0).
c IT c
4 Verification and calibration of testing machines
The instrument shall be calibrated according to the procedures set out in ISO 14577-2 and Annex A.
Indirect verification using a reference material shall be made to ensure that a new direct verification is not
needed and that no damage or contamination has occurred to the indenter tip. If the results of these initial
indentations indicate the presence of contamination or damage, then the indenter should be cleaned using the
procedure recommended in ISO 14577-1 before further trial indents are made. After cleaning, inspection with
2 © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
an optical microscope at a magnification of greater than 400× 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 according to ISO 14577-2. The procedures for the determination of
the frame compliance C and the area function A (h ) calibration/verification shall be implemented before a
f p c
new indenter is used, see Figure 1.

NOTE A reference indenter is a calibrated indenter used infrequently and only for checking the instrument and test
indenter performance via indirect validation comparison.
Figure 1 — Flow chart of the decisions and actions to be taken in the case of
indirect verification failure
ISO 14577-4:2007(E)
The instrumented indentation instrument shall achieve the required mechanical and thermal stability before
starting an indentation cycle, see 6.2.
Indentation experiments may be performed with a variety of differently shaped indenters which should be
chosen to optimize the plastic and elastic deformation required for a given coating substrate system. Typical
indenter shapes are Vickers, Berkovich, conical, spherical and corner cube.
For the determination of coating plastic properties, pointed indenters are recommended. The thinner the
coating, the sharper the indenter should be. For the determination of coating elastic properties, any geometry
indenter may be used provided that its area function is known. If only the elastic properties of the coating are
required, indentations in the fully elastic regime are recommended (if possible) as this avoids problems due to
fracture, pile up and high creep rates. A larger radius indenter tip or sphere will allow fully elastic indentations
over a larger force range than a smaller radius indenter. However, too large a radius and surface effects will
dominate the measurement uncertainties (roughness, surface layers, etc.). Too small a radius and the
maximum force or displacement before plastic deformation begins, will be very low. The optimum can be
identified by preliminary experiments or modelling (see Clause 7).
5 Test pieces
5.1 General
Generally, surface preparation of the test piece should be kept to a minimum and, if possible, the test piece
should be used in the as-received state if the surface condition conforms to the criteria given in 5.2, 5.3 and
5.4.
The test piece shall be mounted using the same methods as employed for determination/verification of the
instrument frame compliance, and shall be such that the test surface is normal to the axis of the indenter and
such that the local surface at the proposed indentation site is less than ± 5° from the perpendicular to the
indentation axis.
NOTE Possible methods for determining local slope include viewing with a high magnification microscope and
measuring the distance before the surface is out of focus. Knowledge of the depth of focus of the lens gives an estimate of
the local slope; also the perpendicularity and local slope can be checked in practice by imaging the indent if it is made by a
non-spherical indenter.
5.2 Surface roughness
Indentation into rough surfaces will lead to increased scatter in the results with decreasing indentation depth.
Clearly when the roughness value, Ra, approaches the same value as the indentation depth the contact area
will vary greatly from indent to indent depending on its position relative to peaks and valleys at the surface.
The final surface finish should be as smooth as available experience and facilities permit. The Ra value should
be less than 5 % of the maximum penetration depth whenever possible.
NOTE 1 It has been shown that for a Berkovich indenter, the angle that the surface normal presents to the axis of
[3]
indentation has to be greater than 7° for significant errors to result . The important angle is that between the indentation
axis and the local surface normal at the point of contact. This angle may be significantly different from the average surface
plane for rough surfaces, see Note 2.
NOTE 2 While Ra has been recommended as a practical and easily understood roughness parameter, it should be
borne in mind that this is an average and thus single peaks and valleys may be greater than this as defined by the Rz
value, although the likelihood of encountering the maximum peak, for example, on the surface is small. Modelling to
investigate the roughness of the coating surface has concluded that there are two limiting situations for any Ra value.
When the ‘wavelength’ of the roughness (in the plane of the coating surface) is much greater than the indenter tip radius,
the force-penetration response is determined by the local coating surface curvature, but when the wavelength is much less
than the tip radius, asperity contact occurs and the effect is similar to having an additional lower modulus coating on the
surface.
NOTE 3 In cases where coatings are used in the as-received condition, random defects (such as nodular growths or
scratches) might be present. Where an indentation site imaging system is included in the testing machine, it is
recommended that “flat” areas away from these defects be selected for measurement.
4 © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
The roughness profilometer probe radius should be comparable to the indenter radius. If the roughness
parameter Ra is determined with an AFM on a scan area, the size of this area should be agreed upon between
the customer and the measurement laboratory. A scan area of 10 µm × 10 µm is recommended.
Some instruments are capable of scanning the indentation site before indentation. In this case areas with the
required local slope and roughness may be selected for indentation in surfaces that might otherwise, on
average, be too rough.
5.3 Polishing
It should be appreciated that mechanical polishing of surfaces can result in a change in the work hardening
and/or the residual stress state of the surface and consequently the measured hardness. For ceramics, this is
less of a concern than for metals, although surface damage can occur. Grinding and polishing shall be carried
out such that any stress induced by the previous stage is removed by the subsequent stage, and the final
stage shall be with a grade of polishing medium appropriate to the displacement scale being used in the test.
If possible, electrochemical polishing should be used.
NOTE 1 Many coatings replicate the surface finish of the substrate. If it is acceptable to do so, surface preparation
problems can be reduced by ensuring that the substrate has an appropriate surface finish, thus eliminating the need to
prepare the surface of the coating. In some cases, however, changing the substrate surface roughness may affect other
coating properties therefore care should be taken when using this approach.
NOTE 2 In coatings, it is common to get relatively large residual stresses (e.g. arising from thermal expansion
coefficient mismatch between the coating and the substrate and/or stress induced by the coating deposition process).
Thus, a stress free surface would not normally be expected. Furthermore, stress gradients in coatings are not uncommon,
so that removal of excessive material during a remedial surface preparation stage may result in a significant departure
from the original surface state.
NOTE 3 Polishing reduces the coating thickness and so the effects of the substrate will be enhanced when indenting
normal to the surface. Where the data analysis requires an accurate knowledge of the coating thickness indented,
polishing will require re-measurement of coating thickness. This again emphasises the need to carry out minimum
preparation.
5.4 Surface cleanliness
Generally, provided the surface is free from obvious surface contamination, cleaning procedures should be
avoided. If cleaning is required, it shall be limited to methods that minimise damage, for example
⎯ application of dry, oil-free, filtered gas stream,
⎯ application of subliming particle stream of CO (taking care not to depress the surface temperature below
the dew point), and
⎯ rinsing with a solvent (which is chemically inert to the test piece) and then drying.
If these methods fail and the surface is sufficiently robust, the surface may be wiped with a lintless tissue
soaked in solvent to remove trapped dust particles, then the surface shall be rinsed in a solvent as above.
Ultrasonic methods are known to create or increase damage to coatings and should be used with caution.
5.5 Special requirements for paints and varnishes
5.5.1 Substrate
Permitted substrates are steel, glass, aluminium, plastic and wood. Prepare the test panels as described in
5.5.2 and 5.5.3. Their surface should be free of visible damages. If samples are drawn from coated articles,
care should be taken that they are plane and will not be bent when being cut. The test panels should, when
under load, not yield or start to vibrate.
Small samples should be adequately supported to prevent deformation of the test sample during
measurement.
ISO 14577-4:2007(E)
5.5.2 Preparation and coating of the substrate
The substrate for the test shall be prepared as described in ISO 1514 and shall be coated with the product or
system to be tested according to the procedure laid down. Coating thickness should be more than ten times
the indentation depth when values specific for the material should be determined.
5.5.3 Drying and conditioning of the test coating
The coated test panel should be dried, hardened and aged for the established time and under the established
conditions, with at least 24 h storage under standard conditions as described in ISO 3270. Coating thickness
should be determined according to one of the methods specified in ISO 2808.
6 Procedure
6.1 Test conditions
6.1.1 The indenter geometry, maximum force and/or displacement and force displacement cycle (with
suitable hold periods) shall be selected by the operator to be appropriate to the coating to be measured and
the operating parameters of the instrument used, see Figure 2.
Hardness values are only valid if plastic deformation has occurred and there is a residual indentation after
force removal.
NOTE 1 A typical ‘small’ radius for hardness measurement is that of a Berkovich indenter (< 250 nm). A typical ‘large’
radius for modulus measurement is < 25 µm. In certain cases, a change of indenter can be avoided by force selection. The
range of elastic deformation can be estimated by the formulas of Annex B.
NOTE 2 An example of a simplified stress analysis is given in 7.3, Note 4.
6.1.2 Where multiple indentations normal to the surface or indentations in cross-section are planned, each
indent shall be positioned and separated according to ISO 14577-1:2002, 7.7.
NOTE Coatings can display a high degree of anisotropy, and thus the orientation of the indenter within the plane and
the direction of indentation (normal or cross-section) can significantly alter the measured value of the hardness and
sometimes the modulus.
6.1.3 The parameters of the instrumented indentation test are defined according to ISO 14577-1:2002, 7.4.
The following parameters of coating/substrate influencing the measurement result should be considered:
a) substrate hardness, Young’s modulus and Poisson’s ratio;
b) coating thickness;
c) surface roughness;
d) adhesion of the coating to the substrate (delamination of the coating should be avoided).
All these parameters should be kept constant if a direct comparison is to be made between two or more test
pieces.
The time dependence of the material parameter being measured should be taken into account.
[4] to [8]
NOTE 1 Hardness and Young’s modulus values can be affected by adhesion .
NOTE 2 Variations in test piece parameters other than hardness or modulus can affect measurement of these
quantities. If the indentation depth is a sufficiently small fraction of the coating thickness, or the coating thickness may be
reasonably well estimated and is constant for all indentation sites on a particular sample, it is possible to measure E * and
c
H , without an accurate thickness measurement. If, however, the properties as a function of relative indentation depth are
c
to be compared, an accurate thickness determination may be necessary. The exact limits depend on the ratio of properties
of coating and substrate.
Normalizing procedures shall always be used when determining coating properties from coatings of different
thickness.
6 © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
a)  For indentation hardness of coating
ISO 14577-4:2007(E)
b)  For indentation modulus of coating
Figure 2 — Flow chart for selection of indenter geometry and indentation parameters to measure
coating properties
8 © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
6.2 Measurement procedure
6.2.1 General
Introduce the prepared test piece and position it so that testing can be undertaken at the desired location.
Carry out the predetermined number of indentation cycles using the selected test conditions.
6.2.2 Force control experiments
A single force application and removal cycle shall be used. A decision tree to assist in estimating the drift
during the experiment is shown in Figure 3. If the drift rate is significant, the displacement data shall be
corrected by measuring the drift rate during a hold at as close to zero force as is practicable or during a hold
at a suitable place in the force removal curve (e.g. after 90 % of the force has been removed). If a contact in
the fully elastic regime (see Annex B) can be obtained, a hold at initial contact is preferred. In this way,
material influences (creep, visco-plasticity, cracking) can be avoided. The hold period shall be sufficient to
allow determination of the average displacement drift rate due to the instrument (e.g. due to temperature
changes) and a linear correction shall be applied. The drift rate correction obtained in this way is only valid if
the drift (as opposed to noise) in the displacement values determined during the hold period (wherever it is in
the indentation cycle) is believed to result from purely instrumental effects (such as temperature) and not from
indentation induced responses from the material (e.g. visco-elastic or anelastic creep, fracture, pressure
induced phase transformations, etc.).
If material influences cannot be avoided, drift rates shall be measured before and after each indentation (e.g.
using an elastic contact with a hard reference surface). Either the average linear drift rate may be calculated
or the drift rate linearly interpolated over the time between the two measurements. The hold period shall be
sufficient to allow determination of the drift in displacement due to temperature fluctuations. Drift (as opposed
to noise) in displacement values determined during the hold period at 90 % force removal or at close to zero is
believed to result from temperature changes and a linear correction should be applied.

Figure 3 — Decision tree to assist in estimating the drift during a force controlled experiment
ISO 14577-4:2007(E)
If no elastic contact can be obtained, there is no generally recommendable method. Depending on the
material under investigation, a hold at initial force (e.g. visco-elastic material) or at 90 % removed force (e.g.
soft material) may be preferred. Because of the stiffer contact (higher contact area) at 90 % removed force,
dispersion of the data when using this method is generally lower. For difficult materials, a hold period at both
ends of the indentation cycle may be included. It is recommended that the hold period be for at least the force
application time, and the first 10 s to 20 s of the hold data should be discarded for the analysis since these
initial data may be significantly influenced by time-dependent effects (material time-dependent deformation,
[9], [10]
formation of capillary surface layers) .
A further hold period shall be performed at maximum force to allow for completion of any time dependent
deformation. The minimum hold period length is therefore dependent on the instrument capability and the
material being tested. The hold period shall be long enough and/or the time to remove force shall be short
enough such that:
q > 10 × q /C
F C t
where
q is the force removal rate;
F
q is the creep rate.
C
The creep rate is defined as the linear fit to the displacement vs. time for the last > 30 data points before force
removal begins.
NOTE 1 The error in measured compliance (due to the creep rate at the point of force removal) depends on the range
of force removal data fitted, the fit algorithm used, the absolute contact compliance and the rate of force removal. An
estimate of the worst case error in the measured contact compliance can be calculated using the following formula:
q
C
error=× 100 % (1)
⎡⎤
⎛⎞
πHF1d
⎛⎞
⎢⎥⎜⎟
⋅⋅ ⋅
⎜⎟
⎜⎟
⎢⎥2dEtF
⎝⎠
r
max
⎝⎠
⎣⎦
The hardness (and modulus) may be depth dependent particularly if a non-self-similar indenter is used.
NOTE 2 When visco-elastic materials are tested, the drift rate will not necessarily reduce by increasing the hold at
maximum force. Even if it does, the drift rate will reverse when the force is removed as visco-elastic recovery begins. The
practice of using a measurement of creep rate just before force removal to apply a creep rate correction to the force
removal data is not recommended. The elastic modulus of visco-elastic materials is better tested using an indentation
cycle faster than the visco-elastic time constant or by using dynamic (ac) indentation methods.
Force application and removal rates may be the same but it is recommended that the removal rate should be
higher than the application rate (if possible) to minimize the influence of creep. Slower force application
reduces the hold period length required at F to achieve the necessary reduction in creep rate.
max
[9]
NOTE 3 The influence of the material creep behaviour on hardness and modulus results has been reported . The
results show that, especially for materials with low hardness-to-modulus ratio (which includes most metals) the modulus
results are not reliable if the hold period is too short. A modulus error, due to creep, of more than 50 % can arise. The
variation of the hold period produced a hardness change of up to 18 %. Reference [9] proposes hold periods dependent
on the material type that range from 8 s for fused quartz to 187 s for aluminium. The criterion used was that the creep rate
should have decayed to a value where the depth increase in one minute is less than 1 % of the indentation depth. It
should be noted that creep of 1 % of the total indentation depth may cause a large change in the apparent contact
stiffness in nearly perfectly plastic materials such as metals.
It is recommended that the creep rate be assessed in preliminary experiments. The force removal rate should
be the highest possible that still ensures sufficient force removal data for the subsequent analysis.
6.2.3 Displacement control experiments
Hold periods shall be imposed as for the force control experiments by holding at constant force to determine
drift. Target displacement rates should be corrected for the displacement drift rate. These rates should also be
corrected for frame compliance.
10 © ISO 2007 – All rights reserved

ISO 14577-4:2007(E)
7 Data analysis and evaluation of results for indentation normal to the surface
7.1 General
Before the data obtained during the indentation experiments can be analysed, it is necessary to have
corrected the displacement data for significant thermal drift, determined the values of A (h ) and obtained C
p c s
(the contact compliance) by correcting the data for the instrument frame compliance, C . The hardness and
f
indentation modulus of the test piece can then be calculated using equations in ISO 14577-1:2002, Annex A.
Annex A of this part of ISO 14577 describes the determination of C and C . The properties thus calculated
s f
according to ISO 14577-1 are composite properties for the coating/substrate combination. 7.2 and 7.3 provide
methods for extracting the hardness and indentation modulus of the coating from the composite properties
measured assuming that the coating properties are constant with depth.
NOTE 1 For indentation into a cross-section, the values obtained using ISO 14577-1 can be considered to be those of
the coating, provided that the recommendations in 6.1.2 have been followed.
NOTE 2 Empirical guidelines are given in Reference [11] for hardness measurement of electroplated coatings on steels,
where it is recommended that the indentation depth does not exceed one tenth the thickness of the coating, while for paint
[12]
films penetration of up to one third the coating thickness may be allowed. These approximations can be unsatisfactory
in many cases and only apply to hardness measurements.
Test parameters for ductile and brittle coatings shall be considered separately.
For indentation normal to the surface, elastic deformation of the substrate will always occur for all coatings,
even though this could be negligibly small for a thick compliant coating on a stiff substrate. Thus the measured
modulus will always be the composite modulus of the coating and substrate and the value obtained will be a
function of indentation depth.
For hardness measurement, it is recommended to use as small a radius indenter as possible (i.e. as sharp as
possible) to limit the plastic deformation to be within the coating. A measurement of the uncoated substrate
hardness is a useful guide to the appropriate choice of analysis (soft vs. hard). In some circumstances, it is
possible to identify a range of indentation depth over which the measured hardness is constant (i.e. before the
onset of substrate plastic deformation) and then carry out indentation experiments within this range.
Estimates of coating hardness and modulus may be extracted from the composite values E *, H obtained
IT IT
from indentation normal to the surface by expressing those composite values as a function of contact radius a
or contact depth h normalized to coating thickness. Measurement of coating thickness, t , is not required to
c c
obtain an accurate intercept value. However, if data from different thickness coatings are to be plotted
together, or the maximum range of indentation depth for valid data is to be used, it is recommended to make a
measurement of actual coating thickness to ensure the best reproducibility of results. For indenters of different
geometries (e.g. Berkovich, Vickers, spherical, cone, etc.), a is approximated by the radius of a circle having
the same area as the projected area of contact with the indenter:
A
p
a= (2)
π
This value has exact equivalence for a spherical or conical indenter but becomes increasingly less physically
meaningful as the axial symmetry of the indenter reduces, i.e. cone = sphere > Vickers > Berkovich.
NOTE 3 It is relatively easy to measure the hardness of ductile coatings or the elastic modulus of brittle coatings. It is
more difficult to determine the hardness of brittle or hard coatings or the elastic modulus of ductile coatings.
NOTE 4 Where t is not measured, nominal values of t may be used but comparison of data between coatings of
c c
different thicknesses will be less accurate.
ISO 14577-4:2007(E)
7.2 Coating indentation modulus
In the case of force-controlled cycles and test pieces of unknown indentation response, a set of trial
indentations shall be performed (e.g. at two widely spaced forces) and analysed to obtain estimates of the test
force required for the range of a/t specified below. See Figure 2 b) for the selection of suitable indenter
c
geometry and indentation parameters.
In the case of soft/ductile coatings, indentation force or displacement and indenter geometry shall be chosen
such that data shall be obtained in the region where a/t < 1,5. The plane strain indentation modulus of the
c
coating E * is obtained by taking a series of measurements at different indentation depths and extrapolating a
c
linear fit to plane strain indentation modulus vs. a/t to zero, see Figure 4.
c
Key
1 spherical indenter
2 Berkovich indenter
3 Vickers indenter
Figure 4 — Plane strain indentation modulus vs. normalized contact radius of Au on Ni, selected data
for spherical, Berkovich and Vickers indenter
In the case of hard/brittle coatings, the indentation force or displacement and the indenter geometry shall be
chosen such that data is obtained in the region a/t < 2. The plane strain indentation modulus of the coating,
c
E *, is obtained by taking a series of measurements at different indentation depths and extrapolating a linear
c
fit to the measured test piece plane strain indentation modulus, E *, vs. a/t to zero, see Figure 5.
IT c
NOTE 1 A linear fit to plane strain indentation modulus vs. a/t to zero is a first approximation. However, in g
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