EN ISO 15156-3:2020

SLOVENSKI STANDARD
01-januar-2021
Nadomešča:
SIST EN ISO 15156-3:2015
Industrija za predelavo nafte in zemeljskega plina - Materiali za uporabo v okoljih s
H2S v proizvodnji olja in plina - 3. del: Visokolegirana jekla (CRAs) in druge zlitine
(ISO 15156-3:2020)
Petroleum and natural gas industries - Materials for use in H2S-containing environments
in oil and gas production - Part 3: Cracking-resistant CRAs (corrosion-resistant alloys)
and other alloys (ISO 15156-3:2020)
Erdöl- und Erdgasindustrie - Werkstoffe für den Einsatz in H2S-haltiger Umgebung bei
der Öl- und Gasgewinnung - Teil 3: Hochlegierte Stähle (CRAs) und andere Legierungen
(ISO 15156-3:2020)
Industries du pétrole et du gaz naturel - Matériaux pour utilisation dans des
environnements contenant de l'hydrogène sulfuré (H2S) dans la production de pétrole et
de gaz - Partie 3: ARC (alliages résistants à la corrosion) et autres alliages résistants à
la fissuration (ISO 15156-3:2020)
Ta slovenski standard je istoveten z: EN ISO 15156-3:2020
ICS:
75.180.10 Oprema za raziskovanje, Exploratory, drilling and
vrtanje in odkopavanje extraction equipment
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 15156-3
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2020
EUROPÄISCHE NORM
ICS 75.180.01 Supersedes EN ISO 15156-3:2015
English Version
Petroleum and natural gas industries - Materials for use in
H2S-containing environments in oil and gas production -
Part 3: Cracking-resistant CRAs (corrosion-resistant
alloys) and other alloys (ISO 15156-3:2020)
Industries du pétrole et du gaz naturel - Matériaux Erdöl- und Erdgasindustrie - Werkstoffe für den
pour utilisation dans des environnements contenant de Einsatz in H2S-haltiger Umgebung bei der Öl- und
l'hydrogène sulfuré (H2S) dans la production de Gasgewinnung - Teil 3: Hochlegierte Stähle (CRAs) und
pétrole et de gaz - Partie 3: ARC (alliages résistants à la andere Legierungen (ISO 15156-3:2020)
corrosion) et autres alliages résistants à la fissuration
(ISO 15156-3:2020)
This European Standard was approved by CEN on 12 October 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 15156-3:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 15156-3:2020) has been prepared by Technical Committee ISO/TC 67
"Materials, equipment and offshore structures for petroleum, petrochemical and natural gas industries"
in collaboration with Technical Committee CEN/TC 12 “Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries” the secretariat of which is held by NEN.
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 May 2021, and conflicting national standards shall be
withdrawn at the latest by May 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 15156-3:2015.
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 15156-3:2020 has been approved by CEN as EN ISO 15156-3:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 15156-3
Fourth edition
2020-11
Petroleum and natural gas
industries — Materials for use in H S-
containing environments in oil and
gas production —
Part 3:
Cracking-resistant CRAs (corrosion-
resistant alloys) and other alloys
Industries du pétrole et du gaz naturel — Matériaux pour utilisation
dans des environnements contenant de l'hydrogène sulfuré (H S) dans
la production de pétrole et de gaz —
Partie 3: ARC (alliages résistants à la corrosion) et autres alliages
résistants à la fissuration
Reference number
ISO 15156-3:2020(E)
©
ISO 2020
ISO 15156-3:2020(E)
© 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

ISO 15156-3:2020(E)
Contents Page
Foreword .iv
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 3
4 Symbols and abbreviated terms . 5
5 Factors affecting the cracking-resistance of CRAs and other alloys in H S-containing
environments . 6
6 Qualification and selection of CRAs and other alloys with respect to SSC, SCC, and
GHSC in H S-containing environments . 6
6.1 General . 6
6.2 Evaluation of materials properties . 7
6.2.1 Hardness of parent metals . 7
6.2.2 Cracking-resistance properties of welds. 7
6.2.3 Cracking-resistance properties associated with other fabrication methods . 8
6.3 PREN . 9
7 Purchasing information and marking . 9
7.1 Information that should be supplied for material purchasing . 9
7.2 Marking, labelling, and documentation .10
Annex A (normative) Environmental cracking-resistant CRAs and other alloys (including
Table A.1 — Guidance on the use of the materials selection tables) .11
Annex B (normative) Qualification of CRAs for H S-service by laboratory testing .57
Annex C (informative) Information that should be supplied for material purchasing .67
Annex D (informative) Nominated sets of test conditions .69
Bibliography .70
ISO 15156-3:2020(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 67, Materials, equipment and offshore
structures for petroleum, petrochemical and natural gas industries, in collaboration with the European
Committee for Standardization (CEN) Technical Committee CEN/TC 12, Materials, equipment and
offshore structures for petroleum, petrochemical and natural gas industries, in accordance with the
Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This fourth edition cancels and replaces the third edition (ISO 15156-3:2015), which has been
technically revised. The main changes compared to the previous edition are as follows:
— Table A.27 UNS S17400 (17-4PH SS) has new limits. The use of the alloy at the annotated environmental
conditions is now limited to applications where sustained stress is no more than 50 % of SMYS;
— Table A.32 new limits and annotations for UNS N09946 separate from UNS N09945;
— Table A.41 inclusion of UNS R55400 (new a-b Ti alloy);
— Table A.3 UNS S20910 (Nitronic 50) note modifications;
— Tables A.22, A.23, A.26 through A.30, and A.33 temperature conversion corrections;
— Table A.23 new note for maximum design tensile stress for UNS J91540;
— Table A.32 newly added UNS N07718 (high strength Alloy 718, with two-step aging cycle, meeting
API 6A CRA composition and a maximum hardness of 45 HRC) and UNS N09955 requirements and
note letters designation changes on UNS N09925, N09935, N09945 and N09946;
— Table A.40 title modification and note clarification;
— Clause A.13 Cladding, overlays, and wear-resistant alloys modifications;
— Table A.18 and Table A.19 (Martensitic SS) remarks modifications;
— Table A.24 Duplex SS Hot Isostatically Pressed (HIP) inclusion and remarks modification;
iv © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
— the informative Annex D, "Materials chemical compositions and other information", has been
removed due to copyright reasons;
— additions to the bibliography.
A list of all parts in the ISO 15156 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.
ISO 15156-3:2020(E)
Introduction
The consequences of sudden failures of metallic oil and gas field components associated with their
exposure to H S-containing production fluids led to the preparation of the first edition of NACE MR0175
which was published in 1975 by the National Association of Corrosion Engineers, now known as NACE
International.
The original and subsequent editions of NACE MR0175 established limits of H S partial pressure above
which precautions against sulfide stress cracking (SSC) were always considered necessary. They
also provided guidance for the selection and specification of SSC-resistant materials when the H S
thresholds were exceeded. In more recent editions, NACE MR0175 has also provided application limits
for some corrosion-resistant alloys in terms of environmental composition and pH, temperature, and
H S partial pressures.
In separate developments, the European Federation of Corrosion issued EFC Publication 16 in 1995 and
EFC Publication 17 in 1996. These documents are generally complementary to those of NACE, though
they differed in scope and detail.
In 2003, the publication of the ISO 15156 series and NACE MR0175/ISO 15156 was completed for the
first time. These technically identical documents utilized the above sources to provide requirements
and recommendations for materials qualification and selection for application in environments
containing wet H S in oil and gas production systems. They are complemented by NACE TM0177 and
NACE TM0284 test methods.
The revision of this document, i.e. ISO 15156, involves a consolidation of all changes agreed and published
in the Technical Circular 1, ISO 15156-3:2015/Cir.1:2016, the Technical Circular 2, ISO 15156-3:2015/
Cir.2:2018 and the Technical Circular 3, ISO 15156-3:2015/Cir.3:2019, published by the ISO 15156 series
Maintenance Agency secretariat at DIN.
The changes were developed by, and approved by the ballot of, representative groups from within
the oil and gas production industry. The great majority of these changes stem from issues raised by
document users. A description of the process by which these changes were approved can be found at
the ISO 15156 series maintenance website: www .iso .org/ iso15156maintenance.
When found necessary by oil and gas production industry experts, future interim changes to this
document will be processed in the same way and will lead to interim updates to this document in
the form of Technical Corrigenda or Technical Circulars. Document users should be aware that such
documents can exist and can impact the validity of the dated references in this document.
The ISO 15156 series Maintenance Agency at DIN was set up after approval by the ISO Technical
Management Board given in document 34/2007. This document describes the makeup of the agency,
which includes experts from NACE, EFC, and ISO/TC 67, and the process for approval of amendments.
It is available from the ISO 15156 series maintenance website and from the ISO/TC 67 Secretariat. The
website also provides access to related documents that provide more detail of the ISO 15156 series
maintenance activities.
vi © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 15156-3:2020(E)
Petroleum and natural gas industries — Materials
for use in H S-containing environments in oil and gas
production —
Part 3:
Cracking-resistant CRAs (corrosion-resistant alloys) and
other alloys
WARNING — CRAs (corrosion-resistant alloys) and other alloys selected using this document
are resistant to cracking in defined HS-containing environments in oil and gas production,
but not necessarily immune to cracking under all service conditions. It is the equipment user's
responsibility to select the CRAs and other alloys suitable for the intended service.
1 Scope
This document gives requirements and recommendations for the selection and qualification of CRAs
(corrosion-resistant alloys) and other alloys for service in equipment used in oil and natural gas
production and natural gas treatment plants in H S-containing environments whose failure can pose
a risk to the health and safety of the public and personnel or to the environment. It can be applied to
help avoid costly corrosion damage to the equipment itself. It supplements, but does not replace, the
materials requirements of the appropriate design codes, standards, or regulations.
This document addresses the resistance of these materials to damage that can be caused by sulfide
stress cracking (SSC), stress corrosion cracking (SCC), and galvanically induced hydrogen stress
cracking (GHSC).
This document is concerned only with cracking. Loss of material by general (mass loss) or localized
corrosion is not addressed.
Table 1 provides a non-exhaustive list of equipment to which this document is applicable, including
exclusions.
This document applies to the qualification and selection of materials for equipment designed and
constructed using load controlled design methods. For design utilizing strain-based design methods,
see ISO 15156-1:2020, Clause 5.
This document is not necessarily suitable for application to equipment used in refining or downstream
processes and equipment.
ISO 15156-3:2020(E)
Table 1 — List of equipment
This document is applicable to materials used for the Exclusions
following equipment
Drilling, well construction, and well-servicing Equipment exposed only to drilling fluids of con-
equipment trolled
a
composition
Drill bits
b
Blowout-preventer (BOP) shear blades
Drilling riser systems
Work strings
c
Wireline and wireline equipment
Surface and intermediate casing
d
Wells including subsurface equipment, gas lift Sucker rod pumps and sucker rods
equipment, wellheads, and christmas trees
Electric submersible pumps
Other artificial lift equipment
Slips
Flow-lines, gathering lines, field facilities, and field Crude oil storage and handling facilities operating
processing plants at
a total absolute pressure below 0,45 MPa (65 psi)
Water-handling equipment Water-handling facilities operating at a total
absolute
pressure below 0,45 MPa (65 psi)
Water injection and water disposal equipment
Natural gas treatment plants —
Transportation pipelines for liquids, gases, and Lines handling gas prepared for general commer-
multi-phase fluids cial
and domestic use
For all equipment above Components loaded only in compression
a
See ISO 15156-2:2020, A.2.3.2.3 for more information.
b
See ISO 15156-2:2020, A.2.3.2.1 for more information.
c
Wireline lubricators and lubricator connecting devices are not excluded.
d
For sucker rod pumps and sucker rods, reference can be made to NACE MR0176.
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 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6508-1, Metallic materials — Rockwell hardness test — Part 1: Test method
ISO 6892-1, Metallic materials — Tensile testing — Part 1: Method of test at room temperature
ISO 10423, Petroleum and natural gas industries — Drilling and production equipment — Wellhead and
christmas tree equipment
ISO 11960, Petroleum and natural gas industries — Steel pipes for use as casing or tubing for wells
2 © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
ISO 15156-1:2020, Petroleum and natural gas industries — Materials for use in H S-containing
environments in oil and gas production — Part 1: General principles for selection of cracking-resistant
materials
ISO 15156-2:2020, Petroleum and natural gas industries — Materials for use in H S-containing
environments in oil and gas production — Part 2: Cracking-resistant carbon and low alloy steels, and the
use of cast irons
1)
ASTM A747/A747M , Standard Specification for Steel Castings, Stainless, Precipitation Hardening
ASTM E29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance with
Specifications
ASTM E562, Standard Test Method for Determining Volume Fraction by Systematic Manual Point Count
2)
EFC Publication 17 , Corrosion resistant alloys for oil and gas production: guidelines on general
requirements and test methods for H S service
NACE CORROSION/95 Paper 47, Test methodology for elemental sulfur-resistant advanced materials for oil
and gas field equipment
NACE TM0177: 2016, Laboratory testing of metals for resistance to sulfide stress cracking and stress
corrosion cracking in H S environments
3)
SAE AMS-2430 , Shot Peening
SAE — ASTM, Metals and alloys in the Unified Numbering System
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15156-1, ISO 15156-2 and the
following 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
ageing
change in metallurgical properties that generally occurs slowly at room temperature (natural ageing)
and more rapidly at higher temperature (artificial ageing)
3.2
anneal
heat to and hold at a temperature appropriate for the specific material and then cool at a suitable rate
for such purposes as reducing hardness, improving machineability, or obtaining desired properties
3.3
austenite
face-centred cubic crystalline phase of iron-based alloys
1) www .astm .org
2) www .efcweb .org
3) www .sae .org
ISO 15156-3:2020(E)
3.4
duplex stainless steel
austenitic/ferritic stainless steel
stainless steel (3.13) whose microstructure at room temperature consists primarily of a mixture of
austenite (3.3) and ferrite (3.5)
3.5
ferrite
body-centred cubic crystalline phase of iron-based alloys
3.6
ferritic stainless steel
stainless steel (3.13) whose microstructure at room temperature consists predominantly of ferrite (3.5)
3.7
galvanically induced hydrogen stress cracking
GHSC
cracking that results due to the presence of hydrogen in a metal induced in the cathode of a galvanic
couple and tensile stress (residual and/or applied)
3.8
martensite
hard, supersaturated solid solution of carbon in iron characterized by an acicular (needle-like)
microstructure
3.9
martensitic steel
steel in which a microstructure of martensite (3.8) can be attained by quenching at a cooling rate fast
enough to avoid the formation of other microstructures
3.10
pitting-resistance equivalent number
PREN
F
PREN
number developed to reflect and predict the pitting resistance of a CRA based upon the proportions of
the elements Cr, Mo, W, and N in the chemical composition of the alloy
Note 1 to entry: See 6.3 for further information.
3.11
production environment
natural occurring produced fluids without contamination from chemicals that will temporarily or
continuously reduce the in situ pH
Note 1 to entry: Flow back of chemicals for stimulation and scale removal may temporarily reduce the pH
significantly and some continuously injected chemicals, such as scale inhibitors, can continuously reduce pH.
3.12
solid solution
single crystalline phase containing two or more elements
3.13
stainless steel
steel containing 10,5 % mass fraction or more chromium, possibly with other elements added to secure
special properties
4 © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
4 Symbols and abbreviated terms
AYS actual yield strength
bal balance of composition up to 100 %
BOP blowout preventer
CR c-ring
CRA corrosion-resistant alloy
DCB double cantilever beam (test)
FPB four-point bend (test)
GHSC galvanically induced hydrogen stress cracking
HAZ heat-affected zone
HBW Brinell hardness
HIC hydrogen-induced cracking
HIP hot isostatically pressed
HRB Rockwell hardness (scale B)
HRC Rockwell hardness (scale C)
HSC hydrogen stress cracking
HV Vickers hardness
NDS no data submitted
pCO partial pressure of CO
2 2
pH S partial pressure of H S
2 2
PREN pitting-resistance equivalent number
PWHT post-weld heat treatment
RSRT rippled strain rate test
S elemental sulfur
SCC stress-corrosion cracking
SMYS specified minimum yield strength
SOHIC stress-oriented hydrogen-induced cracking
SSC sulfide stress cracking
SSRT slow strain rate test
ISO 15156-3:2020(E)
SZC soft-zone cracking
UNS unified (alloy) numbering system
UT uniaxial tensile (test)
5 Factors affecting the cracking-resistance of CRAs and other alloys in H S-
containing environments
The cracking behaviour of CRAs and other alloys in H S-containing environments can be affected by
complex interactions of parameters including the following:
— chemical composition, strength, heat treatment, microstructure, method of manufacture, and
finished condition of the material;
— H S partial pressure or equivalent dissolved concentration in the water phase;
— acidity (in situ pH) of the water phase;
— chloride or other halide ion concentration;
— presence of oxygen, sulfur, or other oxidants;
— exposure temperature;
— pitting resistance of the material in the service environment;
— galvanic effects;
— total tensile stress (applied plus residual);
— exposure time.
These factors shall be considered when using this document for the selection of materials suitable for
environments containing H S in oil and gas production systems.
6 Qualification and selection of CRAs and other alloys with respect to SSC, SCC,
and GHSC in H S-containing environments
6.1 General
CRAs and other alloys shall be selected for their resistance to SSC, SCC, and/or GHSC as required by the
intended service.
Conformance of a CRA or other alloy with this document implies cracking-resistance within defined
environmental service limits. These limits are dependent on the material type or the individual alloy.
To enable qualification and/or selection of CRAs and other alloys, the equipment purchaser can be
required to provide information on the proposed conditions of exposure to the equipment supplier.
In defining the severity of H S-containing environments, exposures that can occur during system
upsets or shutdowns, etc. shall also be considered. Such exposures can include unbuffered, low pH
condensed water. The limits given in the tables in Annex A are for production environments and do not
cover conditions occurring during injection or flowback of chemicals that can reduce the in situ pH.
CRAs and other alloys shall be selected using Annex A or following qualification by successful
laboratory testing in accordance with Annex B. Qualification based on satisfactory field experience is
also acceptable. Such qualification shall conform with ISO 15156-1.
6 © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
In Annex A, materials are identified by materials groups. Within each group, alloys are identified by
materials type (within compositional limits) or as individual alloys. Acceptable metallurgical conditions
and environmental limits are given for which alloys are expected to resist cracking. Environmental
limits are given for H S partial pressure, temperature, chloride concentration, and elemental sulfur.
A CRA or other alloy can be qualified by testing for use under operating conditions that are more severe
than the environmental limits given in Annex A. Similarly, a CRA or other alloy can be qualified for use
in different metallurgical conditions (higher strength, alternative heat treatment, etc.) to those given in
Annex A.
The documentation of qualifications performed in accordance with Annex B shall meet the requirements
in ISO 15156-1:2020, Clause 9.
The equipment user shall verify qualifications (see B.2.2) and retain documentation supporting the
materials selections made.
6.2 Evaluation of materials properties
6.2.1 Hardness of parent metals
If hardness measurements on parent metal are specified, sufficient hardness tests shall be made
to establish the actual hardness of the CRA or other alloy being examined. Individual HRC readings
exceeding the value permitted by this document may be considered acceptable if the average of several
readings taken within close proximity does not exceed the value permitted by this document and no
individual reading is greater than 2 HRC above the specified value. Equivalent requirements shall
apply to other methods of hardness measurement when specified in this document or referenced in a
manufacturing specification.
The conversion of hardness readings to or from other scales is material-dependent. The user may
establish the required conversion tables.
NOTE The number and location of hardness tests on parent metal are not specified in ISO 15156 (all parts).
6.2.2 Cracking-resistance properties of welds
6.2.2.1 General
The metallurgical changes that occur when welding CRAs and other alloys can affect their susceptibility
to SSC, SCC, and/or GHSC. Welded joints can have a greater susceptibility to cracking than the parent
material(s) joined.
The equipment user may allow the cracking susceptibility of weldments to govern the limits of safe
service conditions for a fabricated system.
Processes and consumables used in welding should be selected in accordance with good practice and to
achieve the required corrosion and cracking resistances.
Welding shall be carried out in conformance with appropriate codes and standards as agreed between
the supplier and the purchaser. Welding procedure specifications (WPSs) and procedure qualification
records (PQRs) shall be available for inspection by the equipment user.
Welding PQRs shall include documented evidence demonstrating satisfactory cracking resistance
under conditions at least as severe as those of the proposed application. Such evidence shall be based
upon one or more of the following:
— conformance with the requirements and recommendations for the specific materials group of
Annex A (see also 6.2.2.2 and 6.2.2.3);
— weld cracking-resistance qualification testing in accordance with Annex B;
ISO 15156-3:2020(E)
— documented field experience modelled upon that specified for parent materials in ISO 15156-1.
The requirements and recommendations given in Annex A might not be appropriate for all combinations
of parent and weld metals used in the fabrication of equipment and components. The equipment user
may require evidence of successful cracking-resistance testing as part of the welding procedure
qualification to ensure the weldment produced provides adequate resistance to SSC, SCC, and GHSC for
the application.
6.2.2.2 Qualification of welding procedures in accordance with Annex A based upon hardness
6.2.2.2.1 General
The qualification of welding procedures for sour service shall, if specified in Annex A, include hardness
testing in accordance with 6.2.2.2.2, 6.2.2.2.3 and 6.2.2.2.4.
6.2.2.2.2 Hardness testing methods for welding procedure qualification
Unless otherwise approved by the user, hardness testing for welding procedure qualification shall be
carried out using Vickers HV 10 or HV 5 methods in accordance with ISO 6507-1 or the Rockwell 15N
method in accordance with ISO 6508-1.
NOTE For the purposes of this document, ASTM E384 is equivalent to ISO 6507-1 and ASTM E18 is equivalent
to ISO 6508-1.
6.2.2.2.3 Hardness surveys for welding procedure qualification
Hardness surveys for butt welds, fillet welds, repair, and partial penetration welds and overlay welds
shall be carried out as described in ISO 15156-2:2020, 7.3.3.3.
6.2.2.2.4 Hardness acceptance criteria for welds
Weld hardness acceptance criteria for CRAs or other alloys given in Annex A shall apply to alloys
selected using Annex A.
Hardness acceptance criteria can also be established from successful cracking-resistance testing of
welded samples. Testing shall be in accordance with Annex B.
6.2.2.3 Qualification of welding procedures in accordance with Annex A by other means of testing
Where appropriate, requirements and recommendations to ensure adequate cracking-resistance of
welds using other means of testing are provided in the materials groups of Annex A.
6.2.3 Cracking-resistance properties associated with other fabrication methods
For CRAs and other alloys that are subject to metallurgical changes caused by fabrication methods
other than welding, cracking-resistance qualification testing of the material affected by fabrication
shall be specified as part of the qualification of the fabrication process.
Qualification testing shall be specified as part of the qualification of burning and cutting processes if
any HAZ remains in the final product.
The requirements and acceptance criteria of 6.2.2 shall apply to the qualification testing of both
fabrication methods and burning/cutting processes subject to the suitable interpretation of the
hardness survey requirements of 6.2.2.2.3 for the fabrication method or burning/cutting process.
The form and location of the samples used for evaluation and testing shall be acceptable to the
equipment user.
8 © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
6.3 PREN
For the purpose of determining conformance with the requirements of this document, all F limits
PREN
specified in this document shall be considered absolute limits as defined in ASTM E29. With the absolute
method, an observed value or a calculated value is not to be rounded, but is to be compared directly
with the specified limiting value. Conformance or non-conformance with the specification is based on
this comparison.
The F calculation is based on actual composition, not nominal composition. Nominal composition is
PREN
used for general classification only.
The PREN (F )shall be calculated as given in Formula (1):
PREN
Fw=+33,,ww+05 +16w (1)
()
PREN Cr Mo WN
where
w is the mass fraction of chromium in the alloy, expressed as a percentage mass fraction of
Cr
the total composition;
w is the mass fraction of molybdenum in the alloy, expressed as a percentage mass fraction
Mo
of the total composition;
w is the mass fraction of tungsten in the alloy, expressed as a percentage mass fraction of the
W
total composition;
w is the mass fraction of nitrogen in the alloy, expressed as a percentage mass fraction of the
N
total composition.
NOTE There are several variations of the PREN. All were developed to reflect and predict the pitting
resistance of Fe/Ni/Cr/Mo CRAs in the presence of dissolved chlorides and oxygen, e.g. in sea water. Though
useful, these indices are not directly indicative of corrosion resistance in H S-containing oil field environments.
7 Purchasing information and marking
7.1 Information that should be supplied for material purchasing
7.1.1 The preparation of material purchasing specifications can require cooperation and exchange of
data between the equipment user, the equipment supplier, and the material manufacturer to ensure that
the material purchased conforms with ISO 15156-1 and this document.
7.1.2 The following information shall be provided:
— preferred materials types and/or grades (if known);
— equipment type (if known);
— reference to this document, i.e. ISO 15156-3:2020;
— acceptable bases for selection of materials for cracking-resistance (see Clause 6).
ISO 15156-3:2020(E)
7.1.3 The equipment user and the equipment supplier/material manufacturer may agree that CRAs
and other alloys other than those described and or listed in Annex A may be selected subject to suitable
qualification testing.
If the purchaser intends to make use of such agreements, extensions, and qualifications, the appropriate
additional information shall be clearly indicated in the materials purchasing specification. This
information includes the following:
— requirements for SSC, SCC, and/or GHSC testing (see Clause 6 and Annex B);
— service conditions for the specific sour service application.
7.1.4 The information required for material purchasing shall be entered on suitable data sheets.
Suggested formats are given in Annex C.
7.2 Marking, labelling, and documentation
Materials conforming with this document shall be made traceable, preferably by marking, before
delivery. Suitable labelling or documentation is also acceptable.
For materials qualified and selected for a special application in accordance with Annex B, traceability
shall include reference to the environmental conditions of the special application.
The equipment user may request the equipment or materials supplier to provide documentation of the
materials used in equipment or components and their environmental service limits as defined in this
document.
The tables in Annex C provide designations that can be used.
10 © ISO 2020 – All rights reserved

ISO 15156-3:2020(E)
Annex A
(normative)
Environmental cracking-resistant CRAs and other alloys
(including Table A.1 — Guidance on the use of the materials
selection tables)
A.1 General
A.1.1 Materials groups
The materials groups used to list CRAs or other alloys (see 6.1) are as follows:
— austenitic stainless steels (identified as material type and as individual alloys) (see A.2);
— highly alloyed austenitic stainless steels (identified as material types and as individual alloys)
(see A.3);
— solid-solution nickel-based alloys (identified as material types and as individual alloys) (see A.4);
— ferritic stainless steels (identified as material type) (see A.5);
— martensitic stainless steels (identified as individual alloys) (see A.6);
— duplex stainless steels (identified as material types) (see A.7);
— precipitation-hardened stainless steels (identified as individual alloys) (see A.8);
— precipitation-hardened nickel-based alloys (identified as individual alloys) (see A.9);
— cobalt-based alloys (identified as individual alloys) (see A.10);
— titanium and tantalum (identified as individual alloys) (see A.11);
— copper, aluminium (identified as materials types) (see A.12).
Subject to A.1.2, A.1.3, A.1.4, and A.1.5 below, the CRAs and other alloys listed in Table A.1 to
Table A.42 may be used without further testing for SSC, SCC, and GHSC cracking-resistance within the
environmental limits shown.
Information on the use of copper and aluminium alloys is contained in A.12.
A.13 contains recommendations on the use of cladding, overlays, and wear-resistant alloys.
4)
NOTE The materials listed and the restrictions shown are those originally listed in NACE MR0175: 2003
except for balloted changes introduced since 2003.
A.1.2 Limits of chemical composition
The user of a CRA or other alloy shall ensure that the chemical analysis of the material used meets the
material analysis requirements shown for the material in SAE — ASTM, Metals and alloys in the Unified
Numbering System.
The material shall also meet any provision shown in the text and/or tables of its materials group.
4) Withdrawn.
ISO 15156-3:2020(E)
A.1.3 Environmental and metallurgical limits for cracking-resistance
A.2.2 to A.11.2 contain materials selection tables showing the environmental limits of the materials
when used for any equipment or component. These subclauses also often contain materials selection
tables showing the less restrictive environmental limits of the materials when used for named
equipment or components.
− 0
The tables show the application limits with respect to temperature, pH S, Cl , pH, S . These limits apply
collectively. The pH used in the tables corresponds to the minimum in situ pH.
NO
...