ASTM B276.pdf
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Designation: B 276 – 05
Standard Test Method for
Apparent Porosity in Cemented Carbides
1
This standard is issued under the fixed designation B 276; 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 (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope*
1.1 This test method specifies procedures for the metallo-
graphic determination of apparent porosity in cemented car-
bides.
NOTE 1—The term “apparent porosity” is construed to mean all
microstructures observed on a properly prepared, unetched surface,
including structures resulting from uncombined carbon, non-metallic
inclusions, etc., as well as true, inherent porosity.
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 appro-
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
2
B 243 Terminology of Powder Metallurgy
B 665 Guide for Metallographic Sample Preparation of
Cemented Tungsten Carbides
2.2 ASTM Adjunct:
3
ADJB0276A Apparent Porosity (5 prints of 5 photomicro-
graphs each)
3. Terminology
3.1 Definitions—Definition of powder metallurgy terms can
be found in Terminology
B 243.
4. Significance and Use
4.1 Cemented carbide materials may contain small voids
that, depending on the application, may affect the performance
of the product. To assist users in specifying the maximum
acceptable level of porosity, this test method illustrates a broad
range of porosity levels for each of three porosity types. This
test method is not intended to be used as a specification, but the
levels shown here may be cited in specifications written by
producers and users of cemented carbides.
5. Interferences
5.1 Lack of adequate pressure on the specimen during
polishing may result in material being torn from the surface of
the specimen. This condition may be erroneously interpreted as
porosity.
6. Apparatus
6.1 A metallographic microscope permitting observation
and measurement up to a magnification of 2003.
6.2 Equipment for the metallographic preparation of test
specimens.
7. Specimen Preparation
7.1 Where possible, specimens should be metallographi-
cally mounted in a plastic material, so that they can be polished
without rounding the edges. Larger specimens may be polished
without mounting. When the specimens are too large, they
shall be sectioned using a diamond cut-off wheel or by
fracturing (appropriate safety precautions shall be utilized
when fracturing a specimen). The area selected for examina-
tion should represent, as nearly as possible, the entire cross
section.
7.2 The specimen shall be prepared for metallographic
examination. A suitable procedure is described in Practice
B 665.The surface to be examined shall be unetched and free of
grinding and polishing marks.
8. Procedure
8.1 Pore size shall be defined as the maximum dimension of
the pore. Make special reference to the presence of cracks and
slits, as well as nonmetallic inclusions.
8.2 Classification of Type “A” and “C” apparent porosity is
based entirely on comparison of the microstructures found with
the illustrations in Figs. 1, 3 and 4 of ADJB0276A
3
with due
consideration to the difference in field of view of the micro-
scope compared to the area of the illustrations. This can be
accomplished by scanning the specimen surface under the
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
Powders and Metal Powder Products and is the direct responsibility of Subcom-
mittee B09.06 on Cemented Carbides.
Current edition approved Dec. 1, 2005. Published December 2005. Originally
approved in 1954. Last previous edition approved in 2000 as B 276 – 91 (2000).
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
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
the ASTM website.
3
Available from ASTM International Headquarters. Order Adjunct No.
ADJB0276A.
1
*A Summary of Changes section appears at the end of this standard.
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Copyright by ASTM Int'l (all rights reserved);
Reproduction authorized per License Agreement with Monique Tyree (ASTMIHS Account); Tue Dec 20 13:30:11 EST 2005
Copyright ASTM International
Reproduced by IHS under license with ASTM
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