ASTM B657-23

Standard Guide for Metallographic Identification of Microstructure in Cemented Carbides

SIGNIFICANCE AND USE
4.1 The microstructure of a cemented carbide affects the material's mechanical and physical properties. This guide is not intended to be used as a specification for carbide grades. Producers and users may use the microstructural information as a guide in developing their own specifications.
SCOPE
1.1 This guide covers apparatus and procedures for the metallographic identification of microstructures in cemented carbides.  
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Precautions applying to use of hazardous laboratory chemicals should be observed for chemicals specified in Table 1.  
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2023
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.06 - Cemented Carbides

Relations

• Refers: ASTM B665-19 - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Nov-2019
• Refers: ASTM B665-08(2012) - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Oct-2012
• Refers: ASTM B665-08 - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Nov-2008
• Refers: ASTM B665-03 - Standard Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 10-Apr-2003
• Refers: ASTM B665-92(1997) - Standard Practice for Metallographic Sample Preparation of Cemented Tungsten Carbides
• Effective Date: 01-Jan-1997

Overview

ASTM B657-23: Standard Guide for Metallographic Identification of Microstructure in Cemented Carbides is an internationally recognized document developed by ASTM International. This guide outlines essential apparatus and procedures for metallographically identifying the microstructural phases present in cemented carbides. Understanding the microstructure of cemented carbides is critical, as different phases and their distributions influence the material's mechanical and physical properties. While not a specification for carbide grades, this standard serves as an invaluable resource for both producers and users in characterizing materials and developing tailored specifications.

Key Topics

• Microstructural Phases: The guide details the identification of principal phases in cemented carbides:
  • α phase (tungsten carbide)
  • β phase (binder, typically cobalt, nickel, or iron, possibly containing alloying elements)
  • γ phase (cubic carbide lattices, such as titanium carbide or tantalum carbide)
  • η-type phases (multiple carbides involving tungsten and binder metals)
• Metallographic Apparatus: Recommendations include the use of a metallographic microscope capable of up to 1500x magnification, ordinary metallurgical laboratory equipment, and specific tools for specimen preparation.
• Etching Techniques: The guide provides best practices for etching, using chemicals like potassium ferricyanide with hydroxide solutions to reveal different microstructural phases.
• Examination Procedures: Step-by-step methods for preparing, etching, and analyzing specimens to distinguish between α, β, γ, and η-type phases.
• Reporting: Guidance on documenting and reporting findings, ensuring clear identification of specimen phases.

Applications

• Materials Research and Development: Metallographers, materials scientists, and quality engineers use ASTM B657-23 procedures to evaluate cemented carbides for research, product development, and quality control.
• Industrial Quality Assurance: Manufacturers apply this standard during production to verify microstructural conformity, detect anomalies, and ensure consistent mechanical properties of cemented carbide tools and components.
• Specification Development: While not a specification itself, the standard provides guidance for producers and end-users creating or updating their own standards for specific applications.
• Troubleshooting and Failure Analysis: Identifying unexpected microstructural features or phase distributions can aid in diagnosing failures or optimizing processing parameters.
• Training and Education: Technical personnel and laboratory staff use this guide to develop expertise in hardmetal microstructure identification.

Related Standards

• ASTM B665 - Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides: Offers detailed procedures for preparing carbide specimens for metallographic analysis.
• ISO 4499 - Hardmetals - Metallographic Determination of Microstructure: An international standard providing similar guidance for identifying and quantifying hardmetal phases.
• Other relevant standards cover safety aspects of laboratory chemical use and general metallographic practices.

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Keywords: cemented carbides, hardmetals, microstructure, metallography, ASTM B657, carbide phases, α phase, β phase, γ phase, η-type phase, powder metallurgy.

By following the procedures in ASTM B657-23, users can ensure reliable identification of the microstructural features in cemented carbides, facilitating material optimization, quality assurance, and compliance with international best practices.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: B657 − 23
Standard Guide for
Metallographic Identification of Microstructure in Cemented
Carbides
This standard is issued under the fixed designation B657; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 3. Terminology
3.1 Definitions of Symbols:
1.1 This guide covers apparatus and procedures for the
metallographic identification of microstructures in cemented
Symbol Definition
α phase tungsten carbide
carbides.
β phase binder (for example, Co, Ni, Fe) that may contain alloying
1.2 This standard does not purport to address all of the
elements in solid solution (for example, W, C, Ru, Re, Mo)
γ phase carbide of a cubic lattice (for example, TiC, TaC, NbC)
safety concerns, if any, associated with its use. It is the
that may contain other carbides (for example, WC) in
responsibility of the user of this standard to establish appro-
solid solution
priate safety, health, and environmental practices and deter-
η-type phases multiple carbides of tungsten and at least one metal of the
binder
mine the applicability of regulatory limitations prior to use.
Precautions applying to use of hazardous laboratory chemicals
4. Significance and Use
should be observed for chemicals specified in Table 1.
4.1 The microstructure of a cemented carbide affects the
1.3 This international standard was developed in accor-
material’s mechanical and physical properties. This guide is
dance with internationally recognized principles on standard-
not intended to be used as a specification for carbide grades.
ization established in the Decision on Principles for the
Producers and users may use the microstructural information as
Development of International Standards, Guides and Recom-
a guide in developing their own specifications.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5. Apparatus
5.1 Metallographic Microscope capable of magnifications
2. Referenced Documents
up to 1500 times.
2.1 ASTM Standards:
5.2 Ordinary metallurgical laboratory equipment.
B665 Guide for Metallographic Sample Preparation of Ce-
5.3 Equipment for specimen preparation as outlined in
mented Tungsten Carbides
Guide B665.
2.2 ISO Standard:
ISO 4499 Hardmetals—Metallographic Determination of
6. Specimen Preparation
Microstructure
6.1 A suitable procedure is described in Guide B665.
7. Procedure
This guide is under the jurisdiction of ASTM Committee B09 on Metal
7.1 Examine the microstructure by gradual development of
Powders and Metal Powder Products and is the direct responsibility of Subcom-
the phases by etching. Examples of suitable etching techniques
mittee B09.06 on Cemented Carbides.
are given in Table 1. Examples of the appearance of some
Current edition approved Sept. 1, 2023. Published September 2023. Originally
approved in 1979. Last previous edition approved in 2018 as B657 – 18. DOI:
expected phases, in fine, medium, and coarse grain sizes, are
10.1520/B0657-23.
given in Fig. 1.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
7.2 Determine the presence of η-type phases by lightly
Standards volume information, refer to the standard’s Document Summary page on
etching half the section with Technique 1 (see Table 1).
the ASTM website.
3 Examine the entire section at low magnification and, if
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036. necessary, at magnifications up to 1500 times. Phases of η-type
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B657 − 23
TABLE 1 Etching Techniques
NOTE 1—The separate solutions of potassium hexacyanoferrate (III) and potassium or sodium hydroxide may be stored for a long time. Etchant solution
of potassium hexacyanoferrate (III) and potassium or sodium hydroxide should be discarded a
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: B657 − 18 B657 − 23
Standard Guide for
Metallographic Identification of Microstructure in Cemented
Carbides
This standard is issued under the fixed designation B657; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This guide covers apparatus and procedures for the metallographic identification of microstructures in cemented carbides.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. Precautions applying to use of hazardous laboratory chemicals should be observed for
chemicals specified in Table 1.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
B665 Guide for Metallographic Sample Preparation of Cemented Tungsten Carbides
2.2 ISO Standard:
ISO 4499 Hardmetals—Metallographic Determination of Microstructure
3. Terminology
3.1 Definitions of Symbols:
Symbol Definition
α phase tungsten carbide
β phase binder (for example, Co, Ni, Fe) that may contain alloying
elements in solid solution (for example, W, C, Ru, Re, Mo)
γ phase carbide of a cubic lattice (for example, TiC, TaC, NbC)
that may contain other carbides (for example, WC) in
solid solution
η-type phases multiple carbides of tungsten and at least one metal of the
binder
This guide is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.06
on Cemented Carbides.
Current edition approved April 1, 2018Sept. 1, 2023. Published April 2018September 2023. Originally approved in 1979. Last previous edition approved in 20112018 as
B657 – 11.B657 – 18. DOI: 10.1520/B0657-18.10.1520/B0657-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
B657 − 23
TABLE 1 Etching Techniques
NOTE 1—The separate solutions of potassium hexacyanoferrate (III) and potassium or sodium hydroxide may be stored for a long time, but must be
freshly mixed each day when used.time. Etchant solution of potassium hexacyanoferrate (III) and potassium or sodium hydroxide should be discarded
after a week of use or when etching times exceed recommended times in Table 1.
NOTE 2—The times in the conditions for etching are for concentrations listed. Deviation from these concentrations will affect times required to reveal
desired structures.
Etching
Objective
Tech- Composition of Etchants Conditions of Etching
of Etching
nique
1 Freshly prepared mixture of equal quantities of Etch at approximately 20°C for 2 to 10 s. Flush the test-piece Identification of η
10 %(mass ⁄mass) aqueous solutions of K Fe(CN) (III) section with water immediately, without removing the oxide layer. Dry phase
3 6
(potassium ferricyanide) and potassium the surface carefully with acetone or alcohol without wiping.
or sodium hydroxide
2 A Same as 1A Etch at approximately 20°C for 2 to 4 min. Identification of α, β,
Swabbing surface may enhance the effects of etchant. and γ phases
4. Significance and Use
4.1 The microstructure of a cemented carbide affects the material’s mechanical and physical properties. This guide is not intended
to be used as a specific
...