ASTM B657-05

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Designation: B657 – 05
Standard Guide for
Metallographic Identification of Microstructure in Cemented
1
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* not intended to be used as a specification for carbide grades.
Producersandusersmayusethemicrostructuralinformationas
1.1 This guide covers apparatus and procedures for the
a guide in developing their own specifications.
metallographic identification of microstructures in cemented
carbides.
5. Apparatus
1.2 This standard does not purport to address all of the
5.1 Metallographic Microscope capable of magnifications
safety concerns, if any, associated with its use. It is the
up to 1500 times.
responsibility of the user of this standard to establish appro-
5.2 Ordinary metallurgical laboratory equipment.
priate safety and health practices and determine the applica-
5.3 Equipment for specimen preparation as outlined in
bility of regulatory limitations prior to use. Precautions apply-
Guide B665.
ing to use of hazardous laboratory chemicals should be
observed for chemicals specified in Table 1.
6. Specimen Preparation
6.1 A suitable procedure is described in Guide B665.
2. Referenced Documents
2
2.1 ASTM Standards:
7. Procedure
B665 Guide for Metallographic Sample Preparation of Ce-
7.1 Examine the microstructure by gradual development of
mented Tungsten Carbides
3 the phases by etching. Examples of suitable etching techniques
2.2 ISO Standard:
are given in Table 1. Examples of the appearance of some
ISO 4499 Hardmetals—Metallographic Determination of
expected phases, in fine, medium, and coarse grain sizes, are
Microstructure
given in Fig. 1.
3. Terminology 7.2 Determine the presence of h-type phases by lightly
etching half the section with Technique 1 (see Table 1).
3.1 Definitions of Symbols:
Examine the entire section at low magnification and, if
Symbol Definition
necessary, at magnifications up to 1500 times. Phases of h-type
a phase tungsten carbide
b phase binder (for example, Co, Ni, Fe)
are colored orange to brown in the etched portion, and white to
g phase carbide of a cubic lattice (for example, TiC, TaC, NbC)
light gray in the unetched portion. g-Phase may also etch
that may contain other carbides (for example, WC) in
lightlyandappearbrownishintheetchedportion,butwillhave
solid solution
h-type phases multiple carbides of tungsten and at least one metal of the
a brown/gold color even in the unetched portion, thereby
binder
differentiating it from h-phase. The other phases remain
unetched. Etching by Technique 1 does not preclude subse-
4. Significance and Use
quent etching byTechnique 2. Note and record the existence of
4.1 The microstructure of a cemented carbide affects the
h-type phases and their distribution.
material’s mechanical and physical properties. This guide is
7.3 Determine the presence of g phases by etching with
Technique 2 (Table 1). This phase appears light yellowish
1
This guide is under the jurisdiction of ASTM Committee B09 on Metal
brown and has a typically rounded shape (see Fig. 1). Examine
Powders and Metal Powder Products and is the direct responsibility of Subcom-
the etched section and note and record the existence of a g
mittee B09.06 on Cemented Carbides.
Current edition approved Oct. 1, 2005. Published October 2005. Originally phase.
approved in 1979. Last previous edition approved in 2000 as B657 – 92 (2000).
7.4 Determine the presence of a phase in the same etched
DOI: 10.1520/B0657-05.
specimen as in 7.3. The a phase appears gray, angular
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
(idiomorphic), and straight-slided (see Fig. 1). Examine the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
etched section and note and record the presence of a phase.
the ASTM website.
3
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.
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B657 – 05
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.
Etching
Objective
Tech- Composition of Etchants Conditions of Etching
of Etching
nique
1 Fres
...