SIST EN ISO 14705:2021
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO 14705:2016)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of monolithic ceramics at room temperature (ISO 14705:2016)
This International Standard specifies a test method for determining the Vickers and Knoop hardness of
monolithic fine ceramics at room temperature.
Hochleistungskeramik - Härteprüfung von monolithischer Keramik bei Raumtemperatur (ISO 14705:2016)
Dieses Dokument legt ein Prüfverfahren zur Bestimmung der Härte von monolithischer Hochleistungskeramik bei Raumtemperatur nach Vickers und Knoop fest.
Céramiques techniques - Méthode d'essai de dureté des céramiques monolithiques à température ambiante (ISO 14705:2016)
Le présent document spécifie une méthode d'essai pour déterminer la dureté Vickers et Knoop des céramiques techniques monolithiques à température ambiante.
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Preskus trdote za monolitno keramiko pri sobni temperaturi (ISO 14705:2016)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 14705:2021
01-marec-2021
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Preskus trdote za
monolitno keramiko pri sobni temperaturi (ISO 14705:2016)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for
hardness of monolithic ceramics at room temperature (ISO 14705:2016)
Hochleistungskeramik - Härteprüfung von monolithischer Keramik bei Raumtemperatur
(ISO 14705:2016)
Céramiques techniques - Méthode d'essai de dureté des céramiques monolithiques à
température ambiante (ISO 14705:2016)
Ta slovenski standard je istoveten z: EN ISO 14705:2021
ICS:
81.060.30 Sodobna keramika Advanced ceramics
SIST EN ISO 14705:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 14705:2021
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SIST EN ISO 14705:2021
EN ISO 14705
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2021
EUROPÄISCHE NORM
ICS 81.060.30
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Test method for hardness of monolithic
ceramics at room temperature (ISO 14705:2016)
Céramiques techniques - Méthode d'essai de dureté Hochleistungskeramik - Härteprüfung von
des céramiques monolithiques à température ambiante monolithischer Keramik bei Raumtemperatur (ISO
(ISO 14705:2016) 14705:2016)
This European Standard was approved by CEN on 20 December 2020.
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-CENELEC 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-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14705:2021 E
worldwide for CEN national Members.
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SIST EN ISO 14705:2021
EN ISO 14705:2021 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 14705:2021
EN ISO 14705:2021 (E)
European foreword
The text of ISO 14705:2016 has been prepared by Technical Committee ISO/TC 206 "Fine ceramics” of
the International Organization for Standardization (ISO) and has been taken over as EN ISO 14705:2021
by Technical Committee CEN/TC 184 “Advanced technical ceramics” the secretariat of which is held by
DIN.
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 July 2021, and conflicting national standards shall be
withdrawn at the latest by July 2021.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
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,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 14705:2016 has been approved by CEN as EN ISO 14705:2021 without any modification.
3
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SIST EN ISO 14705:2021
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SIST EN ISO 14705:2021
INTERNATIONAL ISO
STANDARD 14705
Third edition
2016-12-15
Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for hardness of monolithic
ceramics at room temperature
Céramiques techniques — Méthode d’essai de dureté des céramiques
monolithiques à température ambiante
Reference number
ISO 14705:2016(E)
©
ISO 2016
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle . 2
4.2 Symbols, abbreviated terms and designations . 2
4.3 Significance and use . 4
4.4 Apparatus . 5
4.5 Test pieces . 5
4.6 Procedure . 5
4.7 Accuracy and uncertainties . 7
4.8 Test report . 8
5 Knoop hardness .11
5.1 Principle .11
5.2 Symbols and designations .11
5.3 Significance and use .13
5.4 Apparatus .14
5.5 Test pieces .14
5.6 Procedure .14
5.7 Accuracy and uncertainty .15
5.8 Test report .16
Bibliography .20
© ISO 2016 – All rights reserved iii
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SIST EN ISO 14705:2021
ISO 14705:2016(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.
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 documents 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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on 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 the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 206, Fine ceramics.
This third edition cancels and replaces the second edition (ISO 14705:2008), which has been technically
revised.
iv © ISO 2016 – All rights reserved
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SIST EN ISO 14705:2021
INTERNATIONAL STANDARD ISO 14705:2016(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for hardness of monolithic
ceramics at room temperature
1 Scope
This document specifies a test method for determining the Vickers and Knoop hardness of monolithic
fine ceramics at room temperature.
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 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545-2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing
machines
ISO 4545-4, Metallic materials — Knoop hardness test — Part 4: Table of hardness values
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing
machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
Vickers hardness
value obtained by dividing the applied force by the surface area of the indentation computed from the
mean of the measured diagonals of the indentations, assuming that the indentation is an imprint of the
undeformed indenter
Note 1 to entry: Vickers hardness may be expressed in two different units:
2
a) with unit GPa, obtained by dividing the applied force in N by the surface area of the indentation in mm ;
b) Vickers hardness number, obtained by dividing the applied force in kgf by the surface area of the
2
indentation in mm .
© ISO 2016 – All rights reserved 1
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
3.2
Vickers indenter
indenter in the shape of a right-angle pyramid with a square base and an angle between opposite
faces of 136°
Note 1 to entry: See Table 1 and Figure 1.
3.3
Knoop hardness
value obtained by dividing the applied force by the projected area of the indentation computed from the
measurement of the long diagonal of the indentation, assuming that the indentation is an imprint of the
undeformed indenter
Note 1 to entry: The Knoop hardness may be expressed in two different units:
2
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ;
b) Knoop hardness number, obtained by dividing the applied force in kgf by the projected area of the indentation
2
in mm , without units specified.
3.4
Knoop indenter
indenter in the shape of a rhombic-based pyramid with the two angles between the opposite edges at
172,5° and 130°
Note 1 to entry: See Table 3 and Figure 6.
4 Vickers hardness
4.1 Principle
Forcing a diamond indenter in the form of a right-angle pyramid with a square base, and with a specified
angle between opposite faces at the vertex into the surface of a test piece and measuring the length of
the diagonals of the indentation left in the surface after removal of the test force, F. See Figure 1 and
Figure 2.
4.2 Symbols, abbreviated terms and designations
4.2.1 See Table 1, Figure 1 and Figure 2.
4.2.2 The Vickers hardness is denoted by the symbol HV, preceded by the hardness value and followed
by a number representing the test force (see Table 2).
Examples:
a) Use of SI unit (GPa):
15,0 GPa HV 9,807 N represents a Vickers hardness of 15,0 GPa, determined with a test force of
9,807 N (1 kgf)
b) Use of the Vickers hardness number (no units specified):
1 500 HV 1 represents a Vickers hardness number of 1 500, determined with a test force of 9,807 N
(1 kgf).
2 © ISO 2016 – All rights reserved
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
Table 1 — Symbols, abbreviated terms and designations for Vickers hardness testing
Symbol or
abbreviated Designation
term
α Angle between the opposite faces at the vertex of the pyramidal indenter (136° ± 0,5°)
F Test force, in newtons
d Arithmetic mean, in millimetres, of the two diagonals, d and d
1 2
HV Vickers hardness
Test force
=×Constant
Surfaceareaofindentation
a) Units of GPa
136°
2Fsin
F
2
=0,001 =0,001 854
22
d d
b) Hardness number (no units specified)
136°
2Fsin
F
2
=0,102 =0,1891
22
d d
c Arithmetic mean of the half of the two median crack lengths, 2c and 2c
1 2
SD Standard deviation
2
HV −HV
()
∑ n
=
n−1
where
HV
∑ n
HV is the arithmetic mean of the Vickers hardness = ;
n
HV is the HV obtained from nth indentation;
n
n is the number of indentations.
11
NOTE Constant =0,102 , where g is the acceleration due to gravity.
g 9,807
Table 2 — Hardness symbols and the nominal values of test forces, F, for Vickers hardness testing
Test force, F
Hardness symbol
(nominal value)
HV 0,5 4,903 N
HV 1 9,807 N
HV 2 19,61 N
HV 3 29,42 N
HV 5 49,03 N
HV 10 98,07 N
HV 20 196,1 N
© ISO 2016 – All rights reserved 3
==
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
Figure 1 — Vickers indenter (diamond pyramid)
Figure 2 — Vickers indentation
4.3 Significance and use
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal
of Knoop indentations, and the indentation depth is approximately 1,5 times deeper than Knoop
indentations made at the same force. Vickers indentations are influenced less by the specimen surface
flatness, parallelism of the diamond axis to the test piece surface normal, and surface finish than Knoop
indentations, but these parameters should be considered nonetheless. Vickers indentations are much
more likely to cause cracks in fine ceramics than Knoop indentations. Conversion between hardness
scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However,
Vickers indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic
deformation. This difference shall be noted for comparing the hardness of metals and ceramics.
4 © ISO 2016 – All rights reserved
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
4.4 Apparatus
4.4.1 Testing machine, capable of applying a predetermined test force in the range of 4,903 N (0,5 kgf)
to 98,07 N (10 kgf), preferably 9,807 N (1 kgf), in accordance with ISO 6507-2. Verification of the test
force shall be carried out in accordance with ISO 6507-2.
4.4.2 Diamond indenter, in the shape of a right-angle pyramid with a square base, as specified in
ISO 6507-1 and ISO 6507-2. Verification of the indenter shall be carried out in accordance with ISO 6507-2.
4.4.3 Measuring device, capable of measuring the indentation diagonals with a readout resolution
of ±0,2 µm or finer. A numerical aperture (NA) between 0,60 and 0,95 for the objective lens for the
microscope is recommended. Verification of the measuring device shall be carried out in accordance
with ISO 6507-2.
NOTE Indirect verification can be carried out by means of standardized blocks calibrated in accordance
with ISO 6507-3, following ISO 6507-2, or other approved and traceable ceramic standard reference blocks.
4.5 Test pieces
4.5.1 The test shall be carried out on a surface which is smooth, flat and free from foreign matter. The
test piece shall be polished to permit accurate measurement of the diagonal lengths of the indentation.
Preparation shall be carried out in such a way that any alteration of the surface hardness is minimized.
Surfaces shall not be thermally or chemically etched. If applicable, residual surface stresses shall be
removed by suitable polishing or annealing procedures.
4.5.2 The thickness of the test piece shall be at least 0,5 mm. It shall be at least 1,5 times the diagonal
of the indentation, d, and at least 2 times the crack length, c, whichever is greater. No indentation damage
shall be visible at the back of the test piece upon completion of the test.
4.6 Procedure
4.6.1 In general, the test shall be carried out at room temperature within the limits of 10 °C to 35 °C.
Tests carried out under controlled conditions shall be made at a temperature of 23 °C ± 5 °C.
4.6.2 The test force shall be 9,807 N (1 kgf). In cases where significant chipping or lateral crack-spalling
occurs or where the impression is too faint, the test forces within the range 4,903 N (0,5 kgf) to 196,1 N
(20 kgf), listed in Table 2, may be used. Other instances where a heavier load may be required are where
the grain structure is very coarse and the indentation area at lower loads may contact only a few grains
of the material (e.g. a multiphase material).
4.6.3 The following items shall be confirmed before the test.
a) Check the zero of the measuring system.
b) Check the measuring system using a calibrated scale or certified indentation in a test block.
c) Check the operation of the loading system by performing a test on a certified test block.
d) Check the condition of the indenter by examining the indentation made in the test block. Replace
the indenter, if necessary, by taking into account the conditions given in 4.6.10.
e) A test block with high hardness has to be used in order to obtain impressions in the same size
range as expected during tests on ceramics.
4.6.4 The indenter shall be cleaned prior to and during the test series, as ceramic powders or fragments
from the ceramic test piece can adhere to the diamond indenter.
© ISO 2016 – All rights reserved 5
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
4.6.5 The test piece shall be placed on a rigid support. The support surface shall be clean and free from
foreign matter. It is important that the test piece lies firmly on the support, so that displacement cannot
occur during the test.
4.6.6 Carefully adjust the illumination and focusing conditions, in order to obtain the optimum view
and clarity of the indentation. Both indentation tips shall be in focus at the same time. Do not change the
focus when measuring the distance from tip to tip.
4.6.7 Bring the indenter into contact with the test surface and apply the test force in a direction
perpendicular to the surface, without shock or vibration, until the applied force attains the specified
value. The time from the initial application of the force until the full test force is reached shall not be less
than 1 s nor greater than 5 s. The duration of application of the constant maximum test force shall be 15 s.
4.6.8 Throughout the test, the apparatus shall be protected from shock or vibration.
4.6.9 The distance between the centre of any indentations and the edge of the test piece shall be at
least 2,5 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack,
as shown in Figure 3. The distance between the centres of two adjacent indentations shall be at least
4 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack, as shown
in Figure 3. If two adjacent indentations differ in size and crack length, the spacing shall be based on the
mean diagonal of the larger indentation and the longer crack length.
Key
1 edge of test piece
2 indentations
c length from the centre of indentation to the end of crack
d length of indent diagonal
l distance between centres of indentations
1
l ≥ 4d and 5c
1
l distance from centre of indentation to the edge of sample
2
l ≥ 2,5d and 5c
2
Figure 3 — Closest permitted spacing between indentations and from indentation to the test
piece edge for Vickers indentations
6 © ISO 2016 – All rights reserved
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SIST EN ISO 14705:2021
ISO 14705:2016(E)
4.6.10 The satisfactory condition of the indenter shall be verified frequently. Any irregularities in the
shape of the indentation may indicate chipping, cracking or other deterioration of the indenter. If the
examination of the indenter confirms this, then the test shall be rejected and the indenter replaced.
4.6.11 If there is excessive cracking from the indentation tips and sides, then the indentation shall be
rejected and go unmeasured. If one of the tips of an indentation falls into a pore, the indentation shall be
rejected. If the indentation lies in or on a large pore, the indentation shall be rejected. Figure 4 provides
guidance on this assessment.
4.6.12 Measure the length of the two diagonals to within 0,2 µm for diagonals less than 50 µm, or to
within 0,5 µm for diagonals equal to or more than 50 µm. The arithmetical mean of two readings shall
be taken for the calculation of the Vickers hardness. If the difference of the two diagonals is more than
5 % of the mean value (see Figure 4), the result shall be rejected, and a check made of the parallelism and
flatness of the test piece, and of the alignment of the indenter. Follow the manufacturer’s instructions
very carefully, with regards to the proper usage of the measuring crosshairs. Figure 5 is provided for
guidance. The use of optical methods to enhance contrast (like Nomarski interferences) is not permitted.
4.6.13 At least five valid indentations shall be made for obtaining a mean result in accordance with this
document.
4.6.14 Calculate the Vickers hardness, HV, for each valid indentation, using the formula in Table 1.
Calculate the mean hardness for all valid indentations and the standard deviation. The calculated Vickers
hardness shall be expressed with three significant numbers (e.g. 15,4 GPa HV 9,807 N or 1540 HV 1)
4.6.15 Alternatively, see ISO 6507-4 for conversion tables for use in tests made on flat surfaces.
4.7 Accuracy and uncertainties
The principal errors arising in a Vickers hardness test on advanced monolithic technical ceramics
vary in magnitude according to the size of the indentation, and thus the indentation force used. The
Vickers diamond geometry was originally chosen because natural cleavage planes of the diamond were
employed. Variations in geometry between indenters are therefore small, and can usually be ignored
except when indentations are of less than 20 µm diagonal length where the tip and edges near the
tip may be variable between indenters. In particular, the edges may have flats up to 1 µm across on
them, and this has the effect of cutting the corners off the indentation. The error that this introduces is
insignificant if the indentation is larger than about 30 µm, but increases rapidly in importance as the
size is reduced.
Determination of the diagonal lengths using cross-wires or other device attached to the instrument
relies on the operator positioning them at the “true” opposing corners of the indentation. There is a
subjective element in performing this task which increases with poor optical contrast and reducing
size of the indentation. The possible errors can be reduced by experience, and by consistent use of
high-hardness, preferably ceramic or hardmetal, test blocks to familiarize the eye at the start of
measurement sessions. In this way, any systematic measurement bias can be reduced. In a round-robin
[4]
exercise on high-alumina ceramics , it was found that when two individuals measure the same set
of indentations on different measurement equipment, a poor correlation was obtained unless the true
sizes of the indentations varied by more than ±1 µm. It follows that, discounting differences between
machines, it cannot be guaranteed that any two observers will agree that one material is significantly
harder than another unless the average indentation sizes are systematically smaller by more than
1 µm. Thus, even if it is possible to measure the indentation diagonal length to an apparent precision of
0,1 µm, or the optical resolution limit if larger, the ability to discriminate between materials is limited
to an order of magnitude greater in size. Errors of this size assume significance when the indentation
size is less than about 20 µm. In addition, there is the actual scatter in indentation sizes as a result of
local microstructure variations such as grain size, grain orientation, secondary phase content, micro-
cracking, porosity, etc. In a very uniform and homogeneous, hard, fine-grained material, the scatter
...
SLOVENSKI STANDARD
oSIST prEN ISO 14705:2020
01-oktober-2020
Fina keramika (sodobna keramika, sodobna tehnična keramika) - Preskus trdote za
monolitno keramiko pri sobni temperaturi (ISO 14705:2016)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for
hardness of monolithic ceramics at room temperature (ISO 14705:2016)
Hochleistungskeramik - Härteprüfung von monolithischer Keramik bei Raumtemperatur
(ISO 14705:2016)
Céramiques techniques - Méthode d'essai de dureté des céramiques monolithiques à
température ambiante (ISO 14705:2016)
Ta slovenski standard je istoveten z: prEN ISO 14705
ICS:
81.060.30 Sodobna keramika Advanced ceramics
oSIST prEN ISO 14705:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 14705:2020
---------------------- Page: 2 ----------------------
oSIST prEN ISO 14705:2020
INTERNATIONAL ISO
STANDARD 14705
Third edition
2016-12-15
Fine ceramics (advanced ceramics,
advanced technical ceramics) — Test
method for hardness of monolithic
ceramics at room temperature
Céramiques techniques — Méthode d’essai de dureté des céramiques
monolithiques à température ambiante
Reference number
ISO 14705:2016(E)
©
ISO 2016
---------------------- Page: 3 ----------------------
oSIST prEN ISO 14705:2020
ISO 14705:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 14705:2020
ISO 14705:2016(E)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Vickers hardness . 2
4.1 Principle . 2
4.2 Symbols, abbreviated terms and designations . 2
4.3 Significance and use . 4
4.4 Apparatus . 5
4.5 Test pieces . 5
4.6 Procedure . 5
4.7 Accuracy and uncertainties . 7
4.8 Test report . 8
5 Knoop hardness .11
5.1 Principle .11
5.2 Symbols and designations .11
5.3 Significance and use .13
5.4 Apparatus .14
5.5 Test pieces .14
5.6 Procedure .14
5.7 Accuracy and uncertainty .15
5.8 Test report .16
Bibliography .20
© ISO 2016 – All rights reserved iii
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oSIST prEN ISO 14705:2020
ISO 14705:2016(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.
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents 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).
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The committee responsible for this document is ISO/TC 206, Fine ceramics.
This third edition cancels and replaces the second edition (ISO 14705:2008), which has been technically
revised.
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INTERNATIONAL STANDARD ISO 14705:2016(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for hardness of monolithic
ceramics at room temperature
1 Scope
This document specifies a test method for determining the Vickers and Knoop hardness of monolithic
fine ceramics at room temperature.
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 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545-2, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing
machines
ISO 4545-4, Metallic materials — Knoop hardness test — Part 4: Table of hardness values
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-2, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing
machines
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
Vickers hardness
value obtained by dividing the applied force by the surface area of the indentation computed from the
mean of the measured diagonals of the indentations, assuming that the indentation is an imprint of the
undeformed indenter
Note 1 to entry: Vickers hardness may be expressed in two different units:
2
a) with unit GPa, obtained by dividing the applied force in N by the surface area of the indentation in mm ;
b) Vickers hardness number, obtained by dividing the applied force in kgf by the surface area of the
2
indentation in mm .
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3.2
Vickers indenter
indenter in the shape of a right-angle pyramid with a square base and an angle between opposite
faces of 136°
Note 1 to entry: See Table 1 and Figure 1.
3.3
Knoop hardness
value obtained by dividing the applied force by the projected area of the indentation computed from the
measurement of the long diagonal of the indentation, assuming that the indentation is an imprint of the
undeformed indenter
Note 1 to entry: The Knoop hardness may be expressed in two different units:
2
a) with units of GPa, obtained by dividing the applied force in N by the projected area of the indentation in mm ;
b) Knoop hardness number, obtained by dividing the applied force in kgf by the projected area of the indentation
2
in mm , without units specified.
3.4
Knoop indenter
indenter in the shape of a rhombic-based pyramid with the two angles between the opposite edges at
172,5° and 130°
Note 1 to entry: See Table 3 and Figure 6.
4 Vickers hardness
4.1 Principle
Forcing a diamond indenter in the form of a right-angle pyramid with a square base, and with a specified
angle between opposite faces at the vertex into the surface of a test piece and measuring the length of
the diagonals of the indentation left in the surface after removal of the test force, F. See Figure 1 and
Figure 2.
4.2 Symbols, abbreviated terms and designations
4.2.1 See Table 1, Figure 1 and Figure 2.
4.2.2 The Vickers hardness is denoted by the symbol HV, preceded by the hardness value and followed
by a number representing the test force (see Table 2).
Examples:
a) Use of SI unit (GPa):
15,0 GPa HV 9,807 N represents a Vickers hardness of 15,0 GPa, determined with a test force of
9,807 N (1 kgf)
b) Use of the Vickers hardness number (no units specified):
1 500 HV 1 represents a Vickers hardness number of 1 500, determined with a test force of 9,807 N
(1 kgf).
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Table 1 — Symbols, abbreviated terms and designations for Vickers hardness testing
Symbol or
abbreviated Designation
term
α Angle between the opposite faces at the vertex of the pyramidal indenter (136° ± 0,5°)
F Test force, in newtons
d Arithmetic mean, in millimetres, of the two diagonals, d and d
1 2
HV Vickers hardness
Test force
=×Constant
Surfaceareaofindentation
a) Units of GPa
136°
2Fsin
F
2
=0,001 =0,001 854
22
d d
b) Hardness number (no units specified)
136°
2Fsin
F
2
=0,102 =0,1891
22
d d
c Arithmetic mean of the half of the two median crack lengths, 2c and 2c
1 2
SD Standard deviation
2
HV −HV
()
∑ n
=
n−1
where
HV
∑ n
HV is the arithmetic mean of the Vickers hardness = ;
n
HV is the HV obtained from nth indentation;
n
n is the number of indentations.
11
NOTE Constant =0,102 , where g is the acceleration due to gravity.
g 9,807
Table 2 — Hardness symbols and the nominal values of test forces, F, for Vickers hardness testing
Test force, F
Hardness symbol
(nominal value)
HV 0,5 4,903 N
HV 1 9,807 N
HV 2 19,61 N
HV 3 29,42 N
HV 5 49,03 N
HV 10 98,07 N
HV 20 196,1 N
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Figure 1 — Vickers indenter (diamond pyramid)
Figure 2 — Vickers indentation
4.3 Significance and use
Vickers indentation diagonal lengths are approximately 2,8 times shorter than the long diagonal
of Knoop indentations, and the indentation depth is approximately 1,5 times deeper than Knoop
indentations made at the same force. Vickers indentations are influenced less by the specimen surface
flatness, parallelism of the diamond axis to the test piece surface normal, and surface finish than Knoop
indentations, but these parameters should be considered nonetheless. Vickers indentations are much
more likely to cause cracks in fine ceramics than Knoop indentations. Conversion between hardness
scales shall not be made.
Vickers indentations on metallic materials are mainly formed by the plastic deformation. However,
Vickers indentations on fine ceramics are formed by micro-cracking and micro-fracture, besides plastic
deformation. This difference shall be noted for comparing the hardness of metals and ceramics.
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4.4 Apparatus
4.4.1 Testing machine, capable of applying a predetermined test force in the range of 4,903 N (0,5 kgf)
to 98,07 N (10 kgf), preferably 9,807 N (1 kgf), in accordance with ISO 6507-2. Verification of the test
force shall be carried out in accordance with ISO 6507-2.
4.4.2 Diamond indenter, in the shape of a right-angle pyramid with a square base, as specified in
ISO 6507-1 and ISO 6507-2. Verification of the indenter shall be carried out in accordance with ISO 6507-2.
4.4.3 Measuring device, capable of measuring the indentation diagonals with a readout resolution
of ±0,2 µm or finer. A numerical aperture (NA) between 0,60 and 0,95 for the objective lens for the
microscope is recommended. Verification of the measuring device shall be carried out in accordance
with ISO 6507-2.
NOTE Indirect verification can be carried out by means of standardized blocks calibrated in accordance
with ISO 6507-3, following ISO 6507-2, or other approved and traceable ceramic standard reference blocks.
4.5 Test pieces
4.5.1 The test shall be carried out on a surface which is smooth, flat and free from foreign matter. The
test piece shall be polished to permit accurate measurement of the diagonal lengths of the indentation.
Preparation shall be carried out in such a way that any alteration of the surface hardness is minimized.
Surfaces shall not be thermally or chemically etched. If applicable, residual surface stresses shall be
removed by suitable polishing or annealing procedures.
4.5.2 The thickness of the test piece shall be at least 0,5 mm. It shall be at least 1,5 times the diagonal
of the indentation, d, and at least 2 times the crack length, c, whichever is greater. No indentation damage
shall be visible at the back of the test piece upon completion of the test.
4.6 Procedure
4.6.1 In general, the test shall be carried out at room temperature within the limits of 10 °C to 35 °C.
Tests carried out under controlled conditions shall be made at a temperature of 23 °C ± 5 °C.
4.6.2 The test force shall be 9,807 N (1 kgf). In cases where significant chipping or lateral crack-spalling
occurs or where the impression is too faint, the test forces within the range 4,903 N (0,5 kgf) to 196,1 N
(20 kgf), listed in Table 2, may be used. Other instances where a heavier load may be required are where
the grain structure is very coarse and the indentation area at lower loads may contact only a few grains
of the material (e.g. a multiphase material).
4.6.3 The following items shall be confirmed before the test.
a) Check the zero of the measuring system.
b) Check the measuring system using a calibrated scale or certified indentation in a test block.
c) Check the operation of the loading system by performing a test on a certified test block.
d) Check the condition of the indenter by examining the indentation made in the test block. Replace
the indenter, if necessary, by taking into account the conditions given in 4.6.10.
e) A test block with high hardness has to be used in order to obtain impressions in the same size
range as expected during tests on ceramics.
4.6.4 The indenter shall be cleaned prior to and during the test series, as ceramic powders or fragments
from the ceramic test piece can adhere to the diamond indenter.
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4.6.5 The test piece shall be placed on a rigid support. The support surface shall be clean and free from
foreign matter. It is important that the test piece lies firmly on the support, so that displacement cannot
occur during the test.
4.6.6 Carefully adjust the illumination and focusing conditions, in order to obtain the optimum view
and clarity of the indentation. Both indentation tips shall be in focus at the same time. Do not change the
focus when measuring the distance from tip to tip.
4.6.7 Bring the indenter into contact with the test surface and apply the test force in a direction
perpendicular to the surface, without shock or vibration, until the applied force attains the specified
value. The time from the initial application of the force until the full test force is reached shall not be less
than 1 s nor greater than 5 s. The duration of application of the constant maximum test force shall be 15 s.
4.6.8 Throughout the test, the apparatus shall be protected from shock or vibration.
4.6.9 The distance between the centre of any indentations and the edge of the test piece shall be at
least 2,5 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack,
as shown in Figure 3. The distance between the centres of two adjacent indentations shall be at least
4 times the mean diagonal of the indentation, and at least 5 times the mean length of the crack, as shown
in Figure 3. If two adjacent indentations differ in size and crack length, the spacing shall be based on the
mean diagonal of the larger indentation and the longer crack length.
Key
1 edge of test piece
2 indentations
c length from the centre of indentation to the end of crack
d length of indent diagonal
l distance between centres of indentations
1
l ≥ 4d and 5c
1
l distance from centre of indentation to the edge of sample
2
l ≥ 2,5d and 5c
2
Figure 3 — Closest permitted spacing between indentations and from indentation to the test
piece edge for Vickers indentations
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4.6.10 The satisfactory condition of the indenter shall be verified frequently. Any irregularities in the
shape of the indentation may indicate chipping, cracking or other deterioration of the indenter. If the
examination of the indenter confirms this, then the test shall be rejected and the indenter replaced.
4.6.11 If there is excessive cracking from the indentation tips and sides, then the indentation shall be
rejected and go unmeasured. If one of the tips of an indentation falls into a pore, the indentation shall be
rejected. If the indentation lies in or on a large pore, the indentation shall be rejected. Figure 4 provides
guidance on this assessment.
4.6.12 Measure the length of the two diagonals to within 0,2 µm for diagonals less than 50 µm, or to
within 0,5 µm for diagonals equal to or more than 50 µm. The arithmetical mean of two readings shall
be taken for the calculation of the Vickers hardness. If the difference of the two diagonals is more than
5 % of the mean value (see Figure 4), the result shall be rejected, and a check made of the parallelism and
flatness of the test piece, and of the alignment of the indenter. Follow the manufacturer’s instructions
very carefully, with regards to the proper usage of the measuring crosshairs. Figure 5 is provided for
guidance. The use of optical methods to enhance contrast (like Nomarski interferences) is not permitted.
4.6.13 At least five valid indentations shall be made for obtaining a mean result in accordance with this
document.
4.6.14 Calculate the Vickers hardness, HV, for each valid indentation, using the formula in Table 1.
Calculate the mean hardness for all valid indentations and the standard deviation. The calculated Vickers
hardness shall be expressed with three significant numbers (e.g. 15,4 GPa HV 9,807 N or 1540 HV 1)
4.6.15 Alternatively, see ISO 6507-4 for conversion tables for use in tests made on flat surfaces.
4.7 Accuracy and uncertainties
The principal errors arising in a Vickers hardness test on advanced monolithic technical ceramics
vary in magnitude according to the size of the indentation, and thus the indentation force used. The
Vickers diamond geometry was originally chosen because natural cleavage planes of the diamond were
employed. Variations in geometry between indenters are therefore small, and can usually be ignored
except when indentations are of less than 20 µm diagonal length where the tip and edges near the
tip may be variable between indenters. In particular, the edges may have flats up to 1 µm across on
them, and this has the effect of cutting the corners off the indentation. The error that this introduces is
insignificant if the indentation is larger than about 30 µm, but increases rapidly in importance as the
size is reduced.
Determination of the diagonal lengths using cross-wires or other device attached to the instrument
relies on the operator positioning them at the “true” opposing corners of the indentation. There is a
subjective element in performing this task which increases with poor optical contrast and reducing
size of the indentation. The possible errors can be reduced by experience, and by consistent use of
high-hardness, preferably ceramic or hardmetal, test blocks to familiarize the eye at the start of
measurement sessions. In this way, any systematic measurement bias can be reduced. In a round-robin
[4]
exercise on high-alumina ceramics , it was found that when two individuals measure the same set
of indentations on different measurement equipment, a poor correlation was obtained unless the true
sizes of the indentations varied by more than ±1 µm. It follows that, discounting differences between
machines, it cannot be guaranteed that any two observers will agree that one material is significantly
harder than another unless the average indentation sizes are systematically smaller by more than
1 µm. Thus, even if it is possible to measure the indentation diagonal length to an apparent precision of
0,1 µm, or the optical resolution limit if larger, the ability to discriminate between materials is limited
to an order of magnitude greater in size. Errors of this size assume significance when the indentation
size is less than about 20 µm. In addition, there is the actual scatter in indentation sizes as a result of
local microstructure variations such as grain size, grain orientation, secondary phase content, micro-
cracking, porosity, etc. In a very uniform and homogeneous, hard, fine-grained material, the scatter in
actual indentation sizes may be less than the potential measurement errors, and thus not be discernible.
In a less-homogenous material, the true indentation size may vary significantly. In such a case, the
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mean result may be determined by the choice of measurement position, deliberate or inadvertent.
The certainty of mean result can be improved only by increasing the number of indentations, but the
possibility of a human bias remains. The discrimination between inhomogeneous materials is poorer
than for homogeneous ones. The use of the scanning electron microscope is not recommended for a
number of reasons. The principal ones are that the topographic contrast produced by an indentation is
not great, that the edges and corners are not always clearly defined, and that the actual magnification
of the image requires careful calibration and checking for distortion in both directions.
In summary, the systematic and material inhomogeneity errors may be minimized by employing the
highest possible measurement force consistent with no chipping or displacement of corners of the
indentation. Under such conditions, the discrimination between materials is greatest. Tests at HV 1,0
represent an optimum force in terms of the range of materials which can give acceptable indentations.
At greater forces, problems with quality of indentations can make measurement impossible for many
materials, even though errors may be proportionately smaller. Even so, the possible errors contribute
typically ±0,7 GPa in hardness (±70 in hardness number) as a confidence level. Microhardness tests are
subject to much larger overall errors, typically ±2,0 GPa in hardness (±200 in hardness number) (10 %
to 15 %) can be expected at HV 0,2, and greater at lower forces, and should not be used for any test
required for a specification.
4.8 Test report
The test report shall include the following information:
a) a reference to this document, i.e. ISO 14705:2016;
b) an information on the test piece;
c) the test conditions, i.e.:
1) thickness of test piece;
2) test force, if different from 9,807 N (1 kgf), substatiate;
3) surface condition (polishing method; describe other treatments);
4) test temperature, or certification that the test was done at “room temperature”;
5) the number of valid indentations and the total number of indentations made to obtain these
valid indentations;
6) magnification of microscope;
d) the result obtained:
1) individual valid Vickers hardness values;
2) arithmetic mean of the Vickers hardness;
3) standard deviation (SD) of the Vickers hardness;
e) all operations not specified by this document or regarded as optional;
f) details of any circumstances (such as extensive cracking or chipping, porosity, multiphase nature
of the material, coarse grain size, etc.) which may have affected the result.
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a) Acceptable indentations
b) Unacceptable indentations
Key
1 bowed edges 6 tip region displaced
2 porosity 7 chipping and ragged edges
3 large tip cracks 8 ragged edges (grain displacement, pullouts)
4 asymmetrical 9 pore at tip
5 spalled edges 10 indentation on a large pore
a
Permissible degree of asymmetry, as defined in 4.6.12.
Figure 4 — Guidelines for the acceptability of Vickers indentations
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a) Incorrect, crosshair completely covers the tip.
b) Correct, double crosshair measurement system. The indentation is intended to be measured be-
tween two crosshairs or measuring lines. Indentation tips should be on the inside edge (in the fr
...
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