Hardmetals - Metallographic determination of microstructure - Part 2: Measurement of WC grain size (ISO 4499-2:2020)

This document gives guidelines for the measurement of hardmetal grain size by metallographic techniques only using optical or electron microscopy. It is intended for WC/Co hardmetals (also called cemented carbides or cermets) containing primarily tungsten carbide (WC[1]) as the hard phase. It is also intended for measuring the grain size and distribution by the linear-intercept technique.
This document essentially covers four main topics:
—     calibration of microscopes, to underpin the accuracy of measurements;
—     linear analysis techniques, to acquire sufficient statistically meaningful data;
—     analysis methods, to calculate representative average values;
—     reporting, to comply with modern quality requirements.
This document is supported by a measurement case study to illustrate the recommended techniques (see Annex A).
This document is not intended for the following:
—     measurements of size distribution;
—     recommendations on shape measurements. Further research is needed before recommendations for shape measurement can be given.
Measurements of coercivity are sometimes used for grain-size measurement, however, this document is concerned only with a metallographic measurement method. It is also written for hardmetals and not for characterizing powders. However, the method can, in principle, be used for measuring the average size of powders that are suitably mounted and sectioned.
[1] DE: Wolframcarbid, EN: tungsten carbide.

Hartmetalle - Metallographische Bestimmung der Mikrostruktur - Teil 2: Messung der WC-Korngröße (ISO 4499-2:2020)

Dieses Dokument gibt Leitlinien für die Messung der Hartmetallkorngröße mittels metallographischer Verfahren ausschließlich unter Anwendung der Licht  oder Elektronenmikroskopie an. Es ist für WC/Co Hartmetalle (auch als Hartmetalle oder Cermets bezeichnet) vorgesehen, die hauptsächlich Wolframcarbid (WC ) als harte Phase haben. Er ist ebenfalls für die Messung der Korngröße und deren Verteilung mit dem Linienschnittverfahren vorgesehen.
Dieses Dokument behandelt im Wesentlichen vier Hauptthemen:
- Kalibrierung von Mikroskopen, um die Genauigkeit der Messungen zu untermauern;
- lineare Analysenverfahren, um ausreichend statistisch aussagekräftige Daten zu erhalten;
- Analysenverfahren zur Berechnung repräsentativer Mittelwerte;
- Berichterstattung, um den modernen Qualitätsanforderungen zu entsprechen.
Dieses Dokument wird durch eine Messfallstudie zur Veranschaulichung der empfohlenen Verfahren unterstützt (siehe Anhang A).
Dieses Dokument ist nicht für Folgendes vorgesehen:
- Messungen von Korngrößenverteilung;
- Empfehlungen für Formmessungen. Weitere Untersuchungen sind erforderlich, bevor Empfehlungen für Formmessung gegeben werden können.
Zur Messung der Korngröße werden mitunter Messungen von Koerzitiv-Feldstärke herangezogen, dieses Dokument befasst sich jedoch ausschließlich mit einem metallographischen Messverfahren. Darüber hinaus ist es für Hartmetalle und nicht zur Charakterisierung von Pulvern vorgesehen. Das Verfahren kann jedoch grundsätzlich zur Messung der mittleren Korngröße von Pulvern, die in geeigneter Weise eingebettet und geteilt sind, herangezogen werden.

Métaux-durs - Détermination métallographique de la microstructure - Partie 2: Mesurage de la taille des grains de WC (ISO 4499-2:2020)

Le présent document donne des lignes directrices relatives au mesurage de la taille des grains de métaux-durs selon des techniques métallographiques utilisant uniquement un microscope optique ou électronique. Il est destiné aux métaux-durs WC/Co (également appelés carbures cémentés ou cermets) contenant principalement du carbure de tungstène (WC[1]) sous la forme d'une phase dure. Il est également destiné au mesurage de la taille des grains et de la distribution au moyen de la technique d'interception linéaire.
Le présent document couvre essentiellement quatre sujets principaux :
—          étalonnage de microscopes, pour appuyer la précision des mesures ;
—          techniques d'analyses linéaires, pour obtenir suffisamment de données statistiquement significatives ;
—          méthodes d'analyse, pour calculer des valeurs moyennes représentatives ;
—          rapports, pour répondre aux exigences modernes de qualité.
Le présent document est étayé par une étude de cas de mesurage destinée à illustrer les techniques recommandées (voir Annexe A).
Le présent document ne traite pas les points suivants :
—          mesurage de la distribution de la taille ;
—          recommandations sur les mesurages de forme. De plus amples recherches sont nécessaires avant de pouvoir établir des recommandations relatives au mesurage de forme.
Des mesurages de coercivité servent parfois au mesurage de la taille des grains, toutefois le présent document ne traite que de la méthode de mesurage métallographique. Il est également rédigé pour les métaux durs et non pour les poudres caractérisantes. Toutefois, la méthode peut, en principe, servir au mesurage de la granulométrie moyenne de poudres convenablement montées et sectionnées.
[1] ALL : Wolframcarbid, AN : tungsten carbide.

Trdine - Metalografsko določevanje mikrostrukture - 2. del: Merjenje velikosti zrn volframovega karbida (WC) (ISO 4499-2:2020)

General Information

Status
Published
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
05-Aug-2020
Completion Date
05-Aug-2020

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SLOVENSKI STANDARD
SIST EN ISO 4499-2:2020
01-oktober-2020
Nadomešča:
SIST EN ISO 4499-2:2010

Trdine - Metalografsko določevanje mikrostrukture - 2. del: Merjenje velikosti zrn

volframovega karbida (WC) (ISO 4499-2:2020)

Hardmetals - Metallographic determination of microstructure - Part 2: Measurement of

WC grain size (ISO 4499-2:2020)

Hartmetalle - Metallographische Bestimmung der Mikrostruktur - Teil 2: Messung der WC

Korngröße (ISO 4499-2:2020)

Métaux-durs - Détermination métallographique de la microstructure - Partie 2: Mesurage

de la taille des grains de WC (ISO 4499-2:2020)
Ta slovenski standard je istoveten z: EN ISO 4499-2:2020
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.160 Metalurgija prahov Powder metallurgy
SIST EN ISO 4499-2:2020 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 4499-2:2020
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SIST EN ISO 4499-2:2020
EN ISO 4499-2
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2020
EUROPÄISCHE NORM
ICS 77.040.99; 77.160 Supersedes EN ISO 4499-2:2010
English Version
Hardmetals - Metallographic determination of
microstructure - Part 2: Measurement of WC grain size
(ISO 4499-2:2020)

Métaux-durs - Détermination métallographique de la Hartmetalle - Metallographische Bestimmung der

microstructure - Partie 2: Mesurage de la taille des Mikrostruktur - Teil 2: Messung der WC Korngröße

grains de WC (ISO 4499-2:2020) (ISO 4499-2:2020)
This European Standard was approved by CEN on 1 August 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

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4499-2:2020 E

worldwide for CEN national Members.
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SIST EN ISO 4499-2:2020
EN ISO 4499-2:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST EN ISO 4499-2:2020
EN ISO 4499-2:2020 (E)
European foreword

This document (EN ISO 4499-2:2020) has been prepared by Technical Committee ISO/TC 119 "Powder

metallurgy" in collaboration with Technical Committee CEN/SS M11 “Powder metallurgy” the

secretariat of which is held by CCMC.

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 February 2021, and conflicting national standards

shall be withdrawn at the latest by February 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.

This document supersedes EN ISO 4499-2:2010.

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 4499-2:2020 has been approved by CEN as EN ISO 4499-2:2020 without any

modification.
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SIST EN ISO 4499-2:2020
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SIST EN ISO 4499-2:2020
INTERNATIONAL ISO
STANDARD 4499-2
Second edition
2020-07
Hardmetals — Metallographic
determination of microstructure —
Part 2:
Measurement of WC grain size
Métaux-durs — Détermination métallographique de la
microstructure —
Partie 2: Mesurage de la taille des grains de WC
Reference number
ISO 4499-2:2020(E)
ISO 2020
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms, definitions, symbols and abbreviated terms ....................................................................................................... 2

3.1 Terms and definitions ....................................................................................................................................................................... 2

3.2 Symbols and abbreviated terms............................................................................................................................................... 3

4 General information ......................................................................................................................................................................................... 3

5 Apparatus ..................................................................................................................................................................................................................... 4

6 Calibration .................................................................................................................................................................................................................. 5

7 Grain-size measurement by the linear-intercept method ......................................................................................... 5

7.1 General ........................................................................................................................................................................................................... 5

7.2 Sampling ....................................................................................................................................................................................................... 6

7.2.1 Sampling of products ................................................................................................................................................... 6

7.2.2 Sampling of microstructure .................................................................................................................................... 6

7.3 Measurement errors .......................................................................................................................................................................... 7

7.3.1 Systematic and random errors ............................................................................................................................ 7

7.3.2 Large WC grain sizes..................................................................................................................................................... 7

7.3.3 Smallest measurable intercept ............................................................................................................................ 7

8 Reporting ...................................................................................................................................................................................................................... 8

Annex A (informative) Measurement case study ..................................................................................................................................10

Annex B (informative) Report proforma .......................................................................................................................................................15

Bibliography .............................................................................................................................................................................................................................17

© ISO 2020 – All rights reserved iii
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(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 of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 119, Powder metallurgy, Subcommittee

SC 4, Sampling and testing methods for hardmetals, in collaboration with the European Committee for

Standardization (CEN) Technical Committee CEN/SS M11, Powder metallurgy, in accordance with the

Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 4499-2:2008), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— former 3.1 has been removed;
— 3.2 has been expanded;
— in Clause 5, “Electron back scatter diffraction (EBSD)” has been added;
— in 7.2.1, the list has been revised;

— in 7.3.3, Table 1, row “Electron back scatter diffraction” has been added and in the row “Scanning

electron microscope”, the value for the “Minimum visible intercept length” has been corrected from

200 nm into 400 nm.
A list of all parts in the ISO 4499 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
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SIST EN ISO 4499-2:2020
INTERNATIONAL STANDARD ISO 4499-2:2020(E)
Hardmetals — Metallographic determination of
microstructure —
Part 2:
Measurement of WC grain size
1 Scope

This document gives guidelines for the measurement of hardmetal grain size by metallographic

techniques only using optical or electron microscopy. It is intended for WC/Co hardmetals (also called

cemented carbides or cermets) containing primarily tungsten carbide (WC ) as the hard phase. It is

also intended for measuring the grain size and distribution by the linear-intercept technique.

This document essentially covers four main topics:
— calibration of microscopes, to underpin the accuracy of measurements;

— linear analysis techniques, to acquire sufficient statistically meaningful data;

— analysis methods, to calculate representative average values;
— reporting, to comply with modern quality requirements.

This document is supported by a measurement case study to illustrate the recommended techniques

(see Annex A).
This document is not intended for the following:
— measurements of size distribution;

— recommendations on shape measurements. Further research is needed before recommendations

for shape measurement can be given.

Measurements of coercivity are sometimes used for grain-size measurement, however, this document

is concerned only with a metallographic measurement method. It is also written for hardmetals and not

for characterizing powders. However, the method can, in principle, be used for measuring the average

size of powders that are suitably mounted and sectioned.
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 3369, Impermeable sintered metal materials and hardmetals — Determination of density

ISO 3738-1, Hardmetals — Rockwell hardness test (scale A) — Part 1: Test method

ISO 3738-2, Hardmetals — Rockwell hardness test (scale A) — Part 2: Preparation and calibration of

standard test blocks
ISO 4489:2019, Hardmetals — Sampling and testing
1) DE: Wolframcarbid, EN: tungsten carbide.
© ISO 2020 – All rights reserved 1
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)
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

ISO 6507-3, Metallic materials — Vickers hardness test — Part 3: Calibration of reference blocks

ISO 6507-4, Metallic materials — Vickers hardness test — Part 4: Tables of hardness values

3 Terms, definitions, symbols and abbreviated terms
3.1 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:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
nano
with WC grain size <0,2 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.2
ultrafine
with WC grain size 0,2 µm to 0,5 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.3
submicron
with WC grain size 0,5 µm to 0,8 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.4
fine
with WC grain size 0,8 µm to 1,3 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.5
medium
with WC grain size 1,3 µm to 2,5 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.6
coarse
with WC grain size 2,5 µm to 6,0 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in this document.

3.1.7
extra coarse
with WC grain size >6,0 µm

Note 1 to entry: Measured by the mean-linear-intercept method described in document.

2 © ISO 2020 – All rights reserved
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)
3.2 Symbols and abbreviated terms

For the purposes of this document, the following symbols, abbreviations and units apply.

is the area, in square millimetres (mm )
d is the arithmetic mean linear intercept of WC grains, in micrometres (µm)
ECD
is the equivalent circle diameter, in millimetres (mm)
is the line length, in millimetres (mm)
LI is the arithmetic mean-linear-intercept distance, in micrometres (µm)
l is the measured length of individual intercepts, in micrometres (µm)
is the sum of the measured length of each individual intercept
∑ i
N is the number of grain boundaries traversed
n is the number of WC grains intercepted
is the magnification
m is the maximum magnification
max
m is the minimum magnification
min
s is the measured size, in millimetres (mm)
s is the actual size, in millimetres (mm)
EBSD is electron back scatter diffraction
SEM is scanning electron microscopy
FESEM is field emission SEM
TEM is transmission electron microscopy
LOM is low magnification
4 General information

This document addresses the issue of good practice for the measurement of a mean value for WC grain

size. It recommends the use of a linear-intercept technique for obtaining data. The measurements shall

be made using good practice for the preparation of suitable microstructures for examination outlined

in ISO 4499-1.

The properties and performance of hardmetals are directly dependent on the microstructure developed

during manufacture, which in turn is controlled by the character of the starting powder batch.

Understanding the microstructure is the key to controlling or improving properties, and therefore the

measurement of microstructural features, particularly grain size and size distribution, is of paramount

importance.

Methods of metallographic preparation and etching techniques are as important as the grain-size

measurement method (see References [1] to [6]), and are included in ISO 4499-1. The principal type of

hardmetal considered is WC with a Co binder. However, the procedure can be used for hardmetals that

contain cubic carbides or which are based on TiC or Ti(C, N).
© ISO 2020 – All rights reserved 3
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)

The most direct way to measure the WC grain size is to polish and etch a cross-section of the

microstructure and then to use quantitative metallographic techniques to measure a mean value for

the grain size, either by area counting or by linear-intercept techniques.

There are three ways by which the mean size by number of the WC grains can be defined:

— by length (of a line across a 2D section of a grain);
— by area (of 2D sections of grains);
— by volume (of individual grains).

A number average is obtained by counting each measurement of the parameter of interest (length, area

or volume) and dividing the total value of the parameter (length, area or volume) by the number of this

parameter counted.

The value most used to date has been a length parameter. This can be obtained in several ways, for

[14]
example, by parallel lines or circles as described in ASTM E112 :

— by linear intercept, called the Heyn method, from a straight line drawn across the structure;

— by the equivalent circle diameter: this is obtained by measuring grain areas and then taking the

diameter of a circle of equivalent area. It is possible, for equiaxed grains, to convert an equivalent

circle diameter (ECD) grain size to a linear intercept (LI) value using Formula (1).

LI==A π/4ECD (1)
Thus ECD = 1,13 LI.
This expression is discussed in References [1] and [7].

An additional method is that established by Jefferies, where the number of grains per unit area can be

counted. This can, if required, be converted to an equivalent circle diameter.
It shall be noted that
— point/area counting provides no information on distribution, and

— the Jefferies method is not intended for use on multiphase materials such as hardmetals.

The recommended technique for measurement of hardmetal grain size is the linear-intercept method.

5 Apparatus
[12]

Grain-size measurements are obtained from images of the microstructure. ISO 4499-1, ASTM B657

[13]

and ASTM B665 should be consulted for best practice in the preparation of surfaces for imaging.

Hardmetal structural images are usually generated by either optical microscopy, scanning electron

microscopy (SEM) or electron back scatter diffraction (EBSD). For accurate measurements, it is better

to use scanning electron-microscopic images. Even in coarse-grained materials, the imaged surface

cuts through a substantial number of the corners of grains, giving a proportion of small intercepts that

can only be measured accurately using the scanning electron microscope.

Measurements of intercept lengths from the acquired images can be obtained manually or

semiautomatically using image analysis. Automatic image analysis can be used in some circumstances

when the images are fairly coarse and good contrast can be obtained, but for many materials, especially

those with very fine grain sizes, good images are difficult to acquire and are generally not amenable to

automatic analysis.

For the ultrafine and nano grades, good images are particularly difficult to acquire using conventional

scanning electron microscopes with tungsten-filament electron sources. For these materials, it is

4 © ISO 2020 – All rights reserved
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)

recommended that a field emission SEM (FESEM) be used. These systems give significantly higher

resolution images, sufficient to measure materials with mean intercept sizes of about 0,1 µm to 0,2 µm.

For materials with ever smaller grain sizes, it might be necessary to use transmission electron

microscopy (TEM). However, the problems of sampling and specimen preparation are particularly

severe (see Reference [9]). Careful specimen preparation for good images is vital for these materials,

and often a combination of etching methods is helpful (see ISO 4499-1).
6 Calibration

To give reliable quantitative measurements, images shall be calibrated against a stage micrometer or

scale traceable to a national reference standard. The most commonly used stage micrometers for SEMs

are the SIRA grids. These are ruled lines which form a grid and are available with 19,7 lines per mm and

2 160 lines per mm. However, these shall also be calibrated and certified as being traceable to a national

reference standard.

For images obtained from an optical microscope, an image of the calibration graticule shall also be

obtained using the same objectives (and internal magnification step changers or zoom position) and

illuminating technique. The microscope shall be set up for Köhler illumination to obtain the maximum

resolution (see Reference [10]).

For images obtained from a scanning electron microscope, images of the graticule should be obtained

under the same conditions (accelerating kV, working distance, illumination aperture) as those used for

the hardmetal.
7 Grain-size measurement by the linear-intercept method
7.1 General

It is recommended that the arithmetic mean-linear-intercept be used as the parameter to define WC

grain size. This is the simplest procedure to use and has the added advantage of providing data that can

be used to quantify distribution width.

This method requires a straight line to be drawn across a calibrated image. In a single-phase material

the length of line (L), starting at a random position, traversing a number of grain boundaries (N), and

ending at another random position, is measured. The mean-linear-intercept distance LI is specified in

Formula (2):
LI=LN/ (2)

As can be seen from the Formula (2), only the the mean-linear-intercept distance is calculated, there is

no information obtained on grain-size distribution.

For a nominally two-phase material such as a hardmetal (α and β phase), the linear-intercept technique

is less straightforward because each phase shall be measured independently, but it can provide

information on grain-size distribution. A line is drawn across a calibrated image of the microstructure

of a hardmetal. Where this line intercepts a grain of WC, the length of the line (l ) is measured using a

calibrated rule (where i = 1, 2, 3, …, n, for the 1st, 2nd, 3rd, …, nth grain). It is advisable to count at least

100 grains, preferably at least 200 grains in order to reduce the uncertainty to below 10 %.

The mean-linear-intercept grain size is defined as Formula (3):
dl= /n (3)
wc ∑i

Hardmetal grain sizes generally fall in the range 0,1 µm to 10 µm. Because of the uncertainties of

measurement, it is good practice to report the the mean-linear-intercept grain size to one decimal place

for values > 1,0 µm and to two decimal places for values < 1,0 µm, i.e. the results are reported to two

significant figures, such as 3,4 µm or 0,18 µm.
© ISO 2020 – All rights reserved 5
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SIST EN ISO 4499-2:2020
ISO 4499-2:2020(E)
A worked example is given in Annex A.
7.2 Sampling
7.2.1 Sampling of products

Sampling is the procedure whereby an item of hardmetal or a region within an item is chosen for testing.

Random sampling is defined such that, in selecting an individual from a population, each individual in

the population has the same chance of being chosen (see Reference [11]).

ISO 4489:2019, Clause 4 states: “For confirmation of the grade of hardmetal, it is usually sufficient

to take a test sample of one unit”. The following tests shall be carried out in accordance with the

International Standardards given in ISO 4489:2019, 5.1:
— Determination of coercivity no standard available;
— Determination of density ISO 3369;
— Determination of Rockwell hardness HRA ISO 3738-1 and ISO 3738-2;
— Determination of Vickers hardness HV ISO 6507-1, ISO 6507-2,
ISO 6507-3 and ISO 6507-4.
and tests which may be carried out in special cases:
— Determination of microstructure ISO 4499 (all parts);
— Determination of porosity and uncombined carbon ISO 4499-4.
7.2.2 Sampling of microstructure

Sampling for microstructural purposes should be carefully considered depending on the reason for

undertaking the measurements.
a) General check measurement of a sectioned isolated object

— The images chosen for analysis should be representative of the whole section and should be

obtained by random positioning. The number of images to be prepared is recommended to be at

least four, which can be intensively analysed so that in total, at least 200 grains are measured.

b) Determination of homogeneity of grain size

— In this case, a systematic set of images from defined locations within the section shall be

obtained and intensively analysed so that at least 200 grains are measured from each location.

This allows for example, trends in grain size greater than the likely error of measurement at

each position (fractional error is proportional to 1/ N , where N is the number of grains at

each location) to be determined.
c) Inhomogeneous materials

— In cases where the microstructure is inhomogeneous from one field of view to the next, it is

good practice to increase the number of images evaluated, but to evaluate them less intensively,

while still achieving a total feature count of > 200.

The magnification of the image obtained should be such that there are between 10 WC and 20 WC grains

across the field of view, permitting individual intercepts to be measured to better than 10 % accuracy.

This will usually allow 3 or 4 linear-intercept lines to be drawn across the image without intercepting

any in
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