ISO 14705:2008
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for hardness of monolithic ceramics at room temperature
Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for hardness of monolithic ceramics at room temperature
ISO 14705:2008 specifies a test method for determining the Vickers and Knoop hardness of monolithic fine ceramics at room temperature.
Céramiques techniques — Méthode d'essai de dureté des céramiques monolithiques à température ambiante
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 14705
Second edition
2008-02-01
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 14705:2008(E)
©
ISO 2008
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ISO 14705:2008(E)
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ii © ISO 2008 – All rights reserved
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ISO 14705:2008(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, abbreviations and designations.2
4.3 Significance and use .4
4.4 Apparatus.5
4.5 Test pieces.5
4.6 Procedure.5
4.7 Test report.7
5 Knoop hardness.10
5.1 Principle.10
5.2 Symbols and designations .10
5.3 Significance and use .12
5.4 Apparatus.12
5.5 Test pieces.13
5.6 Procedure.13
5.7 Test report.14
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ISO 14705:2008(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 14705 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
This second edition cancels and replaces the first edition (ISO 14705:2000), which has been technically
revised.
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INTERNATIONAL STANDARD ISO 14705:2008(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Test method for hardness of monolithic ceramics
at room temperature
1 Scope
This International Standard specifies a test method for determining the Vickers and Knoop hardness of
monolithic fine ceramics at room temperature.
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 4545-1:2005, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 4545-2:2005, Metallic materials — Knoop hardness test — Part 2: Verification and calibration of testing
machines
ISO 4545-3:2005, Metallic materials — Knoop hardness test — Part 3: Calibration of reference blocks
ISO 4545-4:2005, Metallic materials — Knoop hardness test — Part 4: Table of hardness values
ISO 6507-1:2005, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-2:2005, Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing
machines
ISO 6507-3:2005, Metallic materials — Vickers hardness test — Part 3: Calibration of reference blocks
ISO 6507-4:2005, Metallic materials — Vickers hardness test — Part 4: Tables of hardness values
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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 Vickers hardness may be expressed in two different units:
2
a) with units of GPa, obtained by dividing the applied force, in kN, 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 indentation, in
2
mm , without the units specified.
NOTE 2 Use of Vickers hardness with units of GPa is preferred.
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ISO 14705:2008(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°
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 Knoop hardness may be expressed in two different units:
2
a) with units of GPa, obtained by dividing the applied force, in kN, 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, in
2
mm , without units specified.
NOTE 2 The use of Knoop hardness with units of GPa is preferred.
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°
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 Figures 1 and 2.
4.2 Symbols, abbreviations and designations
4.2.1 See Table 1 and Figures 1 and 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 the 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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ISO 14705:2008(E)
Table 1 — Symbols, abbreviations and designations for Vickers hardness testing
Symbol or
Designation
abbreviation
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
Surface area of indentation
(1) units of GPa (preferred)
136°
2sF in
F
2
==0,001 0,001854
22
dd
(2) hardness number (no units specified)
136°
2sF in
F
2
==0,102 0,189 1
22
dd
c Arithmetic mean of the half of the two median crack lengths 2c and 2c
1 2
S.D. 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 4,903 N or HV 0,5 4,903 N
HV 9,807 N or HV 1 9,807 N
HV 19,61 N or HV 2 19,61 N
HV 29,42 N or HV 3 29,42 N
HV 49,03 N or HV 5 49,03 N
HV 98,07 N or HV 10 98,07 N
HV 196,1 N or HV 20 196,1 N
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ISO 14705:2008(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 are 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 hardnesses of metals and ceramics.
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ISO 14705:2008(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) of 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.
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 on 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 recommended test force is 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 examination of the indentation made in the test block. Replace the
indenter, if necessary, by taking into account the conditions given in 4.6.10.
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.
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.
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ISO 14705:2008(E)
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
...
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