Steel - Determination of the thickness of surface-hardened layers (ISO 18203:2016)

ISO 18203:2016 specifies a method of measuring the case hardening depth, surface hardening depth, nitriding hardness depth and total thickness of surface hardening depth obtained, e.g. thermal (flame and induction hardening, electron beam hardening, laser beam hardening, etc.) or thermochemical (carbonitriding, carburizing and hardening, hardening and nitriding, etc.) treatment.

Stahl - Bestimmung der Dicke gehärteter Randschichten (ISO 18203:2016)

Dieses Dokument legt ein Verfahren zur Messung der Einsatzhärtungstiefe, Randschichthärtungstiefe Nitrierhärtetiefe und Gesamtdicke der erzielten Randschichthärtungstiefe fest, z. B. thermische Behandlung (Flamm- und Induktionshärten, Elektronenstrahlhärten, Laserstrahlhärten usw.) oder thermochemische Behandlung (Carbonitrieren, Aufkohlen und Härten, Härten und Nitrieren usw.).
ANMERKUNG   Gehärtete Randschichten können mittels mechanischer Verfahren (Abstrahlen, Kugelstrahlen usw.) hergestellt werden. Die Dicke dieser Schichten ist üblicherweise gering. Bei der Messung eines Härtungstiefenprofils ist unter Umständen eine geringere Prüfkraft bei der Härteprüfung erforderlich.

Acier - Détermination de l'épaisseur des couches durcies superficielles (ISO 18203:2016)

ISO 18203:2016 spécifie une méthode de mesure de la profondeur de cémentation, la profondeur de durcissement de la surface, la profondeur de la dureté de nitruration et l'épaisseur totale de la profondeur de durcissement de la surface obtenue par exemple, par des traitements thermiques (durcissement par flamme et par induction, durcissement par faisceau d'électrons et par faisceau laser etc.) ou thermochimiques (carbonitruration, cémentation et durcissement, durcissement et nitruration, etc.).

Jekla - Določanje debeline površinsko utrjenih plasti (ISO 18203:2016)

General Information

Status
Published
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
30-Mar-2022
Completion Date
30-Mar-2022

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Standards Content (sample)

SLOVENSKI STANDARD
SIST EN ISO 18203:2022
01-junij-2022
Nadomešča:
SIST EN 10328:2005
SIST EN ISO 2639:2004
Jekla - Določanje debeline površinsko utrjenih plasti (ISO 18203:2016)

Steel - Determination of the thickness of surface-hardened layers (ISO 18203:2016)

Stahl - Bestimmung der Dicke gehärteter Randschichten (ISO 18203:2016)
Acier - Détermination de l'épaisseur des couches durcies superficielles (ISO
18203:2016)
Ta slovenski standard je istoveten z: EN ISO 18203:2022
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.080.20 Jekla Steels
SIST EN ISO 18203:2022 en,fr,de

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

---------------------- Page: 1 ----------------------
SIST EN ISO 18203:2022
---------------------- Page: 2 ----------------------
SIST EN ISO 18203:2022
EN ISO 18203
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2022
EUROPÄISCHE NORM
ICS 77.040.99 Supersedes EN ISO 2639:2002, EN 10328:2005
English Version
Steel - Determination of the thickness of surface-hardened
layers (ISO 18203:2016)

Acier - Détermination de l'épaisseur des couches Stahl - Bestimmung der Dicke gehärteter

durcies superficielles (ISO 18203:2016) Randschichten (ISO 18203:2016)
This European Standard was approved by CEN on 20 March 2022.

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

© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18203:2022 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 18203:2022
EN ISO 18203:2022 (E)
Contents Page

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

---------------------- Page: 4 ----------------------
SIST EN ISO 18203:2022
EN ISO 18203:2022 (E)
European foreword

The text of ISO 18203:2016 has been prepared by Technical Committee ISO/TC 17 "Steel” of the

International Organization for Standardization (ISO) and has been taken over as EN ISO 18203:2022 by

Technical Committee CEN/TC 459/SC 1 “Test methods for steel (other than chemical analysis)” the

secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by September 2022, and conflicting national standards

shall be withdrawn at the latest by September 2022.

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 2639:2002 and EN 10328:2005.

Any feedback and questions on this document should be directed to the users’ national standards body.

A complete listing of these bodies can be found on the CEN website.

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 18203:2016 has been approved by CEN as EN ISO 18203:2022 without any modification.

---------------------- Page: 5 ----------------------
SIST EN ISO 18203:2022
---------------------- Page: 6 ----------------------
SIST EN ISO 18203:2022
INTERNATIONAL ISO
STANDARD 18203
First edition
2016-12-01
Steel — Determination of the
thickness of surface-hardened layers
Acier — Détermination de l’épaisseur des couches durcies
superficielles
Reference number
ISO 18203:2016(E)
ISO 2016
---------------------- Page: 7 ----------------------
SIST EN ISO 18203:2022
ISO 18203:2016(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: 8 ----------------------
SIST EN ISO 18203:2022
ISO 18203:2016(E)
Contents Page

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

Introduction ..................................................................................................................................................................................................................................v

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

2 Normative reference ......................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols, abbreviations and designations .................................................................................................................................. 3

5 Principle ........................................................................................................................................................................................................................ 3

6 Apparatus ..................................................................................................................................................................................................................... 3

7 Test specimen .......................................................................................................................................................................................................... 4

7.1 Selection and preparation of samples ................................................................................................................................. 4

7.2 Preparation of the surface to be examined ..................................................................................................................... 5

8 Method of measurement .............................................................................................................................................................................. 5

8.1 Hardness testing method ............................................................................................................................................................... 5

8.2 Microscopic methods......................................................................................................................................................................... 6

8.2.1 Total thickness of surface hardening depth (THD) ............................................................................ 6

8.2.2 Compound layer thickness (CLT) ....................................................................................................................... 6

9 Evaluation of the results ............................................................................................................................................................................... 7

9.1 Case hardening depth (CHD), surface hardening depth (SHD) and nitriding

hardness depth (NHD) ..................................................................................................................................................................... 7

9.2 Total thickness of surface hardening depth (THD).................................................................................................. 7

9.3 Compound layer thickness (CLT) ............................................................................................................................................ 7

10 Test report ................................................................................................................................................................................................................... 8

Annex A (normative) Interpolation method for determining the case hardening depth .............................9

Annex B (informative) Examples of CLT measurements ...............................................................................................................11

Bibliography .............................................................................................................................................................................................................................12

© ISO 2016 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 18203:2022
ISO 18203:2016(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 17, Steel, Subcommittee SC 7, Methods of testing

(other than mechanical tests and chemical analysis).

This first edition of ISO 18203 cancels and replaces ISO 2639:2002, ISO 3754:1976 and ISO 4970:1979,

which have been technically revised.
iv © ISO 2016 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 18203:2022
ISO 18203:2016(E)
Introduction

In the past, there are three ISO standards for measuring surface-hardened layer. Because those

standards employed almost the same principle of measuring, it is intended to make it easy for

maintenance of the standards and application of test by integrating these three standards.

The method of estimating uncertainty of measurement is not included in this document. In future

revision, uncertainty of measurement may be reflected based on real applications to this test.

© ISO 2016 – All rights reserved v
---------------------- Page: 11 ----------------------
SIST EN ISO 18203:2022
---------------------- Page: 12 ----------------------
SIST EN ISO 18203:2022
INTERNATIONAL STANDARD ISO 18203:2016(E)
Steel — Determination of the thickness of surface-
hardened layers
1 Scope

This document specifies a method of measuring the case hardening depth, surface hardening depth,

nitriding hardness depth and total thickness of surface hardening depth obtained, e.g. thermal (flame

and induction hardening, electron beam hardening, laser beam hardening, etc.) or thermochemical

(carbonitriding, carburizing and hardening, hardening and nitriding, etc.) treatment.

NOTE Surface-hardened layer can be produced by mechanical method (shot blasting, shot peening, etc.). The

depth of these layers is generally shallow. Measuring a profile of hardened depth may require lower test force of

hardness test.
2 Normative reference

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 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
case hardening depth
CHD

perpendicular distance between the surface and the layer having a hardness of 550 HV in accordance

with ISO 6507-1 or equivalent Knoop hardness in accordance with ISO 4545-1

Note 1 to entry: For steels which present a hardness greater than 450 HV at a distance of three times the case

hardening depth (determined with a limiting hardness value of 550 HV) from the surface, a limiting hardness

value greater than 550 HV, in steps of 25 units, can be selected for the determination of the case hardening depth

by agreement between interested parties.

Note 2 to entry: In general, case hardening consists of carburizing or carbonitriding followed by quench

hardening (see ISO 4885).
© ISO 2016 – All rights reserved 1
---------------------- Page:
...

SLOVENSKI STANDARD
oSIST prEN ISO 18203:2022
01-januar-2022
Jekla - Določevanje in preverjanje cementacijske in kalilne globine (ISO
18203:2016)

Steel - Determination of the thickness of surfacehardened layers (ISO 18203:2016)

Stahl - Bestimmung der Dicke gehärteter Randschichten (ISO 18203:2016)
Acier - Détermination de l'épaisseur des couches durcies superficielles (ISO
18203:2016)
Ta slovenski standard je istoveten z: prEN ISO 18203
ICS:
77.040.99 Druge metode za Other methods of testing of
preskušanje kovin metals
77.080.20 Jekla Steels
oSIST prEN ISO 18203:2022 en,fr,de

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

---------------------- Page: 1 ----------------------
oSIST prEN ISO 18203:2022
---------------------- Page: 2 ----------------------
oSIST prEN ISO 18203:2022
INTERNATIONAL ISO
STANDARD 18203
First edition
2016-12-01
Steel — Determination of the
thickness of surface-hardened layers
Acier — Détermination de l’épaisseur des couches durcies
superficielles
Reference number
ISO 18203:2016(E)
ISO 2016
---------------------- Page: 3 ----------------------
oSIST prEN ISO 18203:2022
ISO 18203:2016(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 18203:2022
ISO 18203:2016(E)
Contents Page

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

Introduction ..................................................................................................................................................................................................................................v

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

2 Normative reference ......................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols, abbreviations and designations .................................................................................................................................. 3

5 Principle ........................................................................................................................................................................................................................ 3

6 Apparatus ..................................................................................................................................................................................................................... 3

7 Test specimen .......................................................................................................................................................................................................... 4

7.1 Selection and preparation of samples ................................................................................................................................. 4

7.2 Preparation of the surface to be examined ..................................................................................................................... 5

8 Method of measurement .............................................................................................................................................................................. 5

8.1 Hardness testing method ............................................................................................................................................................... 5

8.2 Microscopic methods......................................................................................................................................................................... 6

8.2.1 Total thickness of surface hardening depth (THD) ............................................................................ 6

8.2.2 Compound layer thickness (CLT) ....................................................................................................................... 6

9 Evaluation of the results ............................................................................................................................................................................... 7

9.1 Case hardening depth (CHD), surface hardening depth (SHD) and nitriding

hardness depth (NHD) ..................................................................................................................................................................... 7

9.2 Total thickness of surface hardening depth (THD).................................................................................................. 7

9.3 Compound layer thickness (CLT) ............................................................................................................................................ 7

10 Test report ................................................................................................................................................................................................................... 8

Annex A (normative) Interpolation method for determining the case hardening depth .............................9

Annex B (informative) Examples of CLT measurements ...............................................................................................................11

Bibliography .............................................................................................................................................................................................................................12

© ISO 2016 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 18203:2022
ISO 18203:2016(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 17, Steel, Subcommittee SC 7, Methods of testing

(other than mechanical tests and chemical analysis).

This first edition of ISO 18203 cancels and replaces ISO 2639:2002, ISO 3754:1976 and ISO 4970:1979,

which have been technically revised.
iv © ISO 2016 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 18203:2022
ISO 18203:2016(E)
Introduction

In the past, there are three ISO standards for measuring surface-hardened layer. Because those

standards employed almost the same principle of measuring, it is intended to make it easy for

maintenance of the standards and application of test by integrating these three standards.

The method of estimating uncertainty of measurement is not included in this document. In future

revision, uncertainty of measurement may be reflected based on real applications to this test.

© ISO 2016 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST prEN ISO 18203:2022
---------------------- Page: 8 ----------------------
oSIST prEN ISO 18203:2022
INTERNATIONAL STANDARD ISO 18203:2016(E)
Steel — Determination of the thickness of surface-
hardened layers
1 Scope

This document specifies a method of measuring the case hardening depth, surface hardening depth,

nitriding hardness depth and total thickness of surface hardening depth obtained, e.g. thermal (flame

and induction hardening, electron beam hardening, laser beam hardening, etc.) or thermochemical

(carbonitriding, carburizing and hardening, hardening and nitriding, etc.) treatment.

NOTE Surface-hardened layer can be produced by mechanical method (shot blasting, shot peening, etc.). The

depth of these layers is generally shallow. Measuring a profile of hardened depth may require lower test force of

hardness test.
2 Normative reference

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 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
case hardening depth
CHD

perpendicular distance between the surface and the layer having a hardness of 550 HV in accordance

with ISO 6507-1 or equivalent Knoop hardness in accordance with ISO 4545-1

Note 1 to entry: For steels which present a hardness greater than 450 HV at a distance of three times the case

hardening depth (determined with a limiting hardness value of 550 HV) from the surface, a limiting hardness

value greater than 550 HV, in steps of 25 units, can be selected for the determination of the case hardening depth

by agreement between interested parties.

Note 2 to entry: In general, case hardening consists of carburizing or carbonitriding followed by quench

hardening (see ISO 4885).
© ISO 2016 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST prEN ISO 18203:2022
ISO 18203:2016(E)
3.2
surface hardening depth
SHD

distance between the surface and the layer where HV is equal to the value specified by the term

“hardness limit”

Note 1 to entry: Hardness limit is a function of the minimum surface hardness required for the part, given by the

following formula:
hardness limit (HV) = A × minimum surface hardness (HV)
Note 2 to entry: 0,80 is usually used for A. Other values can be applied.

Note 3 to entry: SHD measurement should be applied for parts which, in the surface hardened condition, have a

hardness less than (hardness limit – 100 HV) at a distance 3 × SHD from the surface. Where these conditions are

not satisfied, the definition of SHD should be agreed between interested parties.

Note 4 to entry: Recommended hardness limit values are listed in Table 1.
Table 1 — Recommended hardness limit values of SHD
Minimum surface hardness Hardness limit
HV HV
300 to 330 250
335 to 355 275
360 to 385 300
390 to 420 325
425 to 455 350
460 to 480 375
485 to 515 400
520 to 545 425
550 to 575 450
580 to 605 475
610 to 635 500
640 to 665 525
670 to 705 550
710 to 730 575
735 to 765 600
770 to 795 625
800 to 835 650
840 to 865 675
3.3
compound layer thickness
CLT

thickness of the surface layer formed during the thermochemical treatment and made up of the chemical

compounds formed by the elements introduced during the treatment and certain elements from the

base metal
2 © ISO 2016 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 18203:2022
ISO 18203:2016(E)
3.4
nitriding hardness depth
NHD

distance from the surface of nitride layer to the point where the material hardness limit is 50 HV above

core hardness

Note 1 to entry: The core hardness is determined by at least three hardness measurements and rounded to the

nearest multiple of 10 HV.
3.5
total thickness of surface hardening depth
THD

distance from the examined surface to the limit that shows the same hardness as the matrix hardness

Note 1 to entry: The distance is often m
...

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