ASTM B276-05
(Test Method)Standard Test Method for Apparent Porosity in Cemented Carbides
Standard Test Method for Apparent Porosity in Cemented Carbides
SCOPE
1.1 This test method specifies procedures for the metallographic determination of apparent porosity in cemented carbides. 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.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:B276–05
Standard Test Method for
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Apparent Porosity in Cemented Carbides
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* range of porosity levels for each of three porosity types. This
testmethodisnotintendedtobeusedasaspecification,butthe
1.1 This test method specifies procedures for the metallo-
levels shown here may be cited in specifications written by
graphic determination of apparent porosity in cemented car-
producers and users of cemented carbides.
bides.
NOTE 1—The term “apparent porosity” is construed to mean all 5. Interferences
microstructures observed on a properly prepared, unetched surface,
5.1 Lack of adequate pressure on the specimen during
including structures resulting from uncombined carbon, non-metallic
polishing may result in material being torn from the surface of
inclusions, etc., as well as true, inherent porosity.
thespecimen.Thisconditionmaybeerroneouslyinterpretedas
1.2 This standard does not purport to address all of the
porosity.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 6. Apparatus
priate safety and health practices and determine the applica-
6.1 A metallographic microscope permitting observation
bility of regulatory limitations prior to use.
and measurement up to a magnification of 2003.
6.2 Equipment for the metallographic preparation of test
2. Referenced Documents
specimens.
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2.1 ASTM Standards:
B 243 Terminology of Powder Metallurgy
7. Specimen Preparation
B 665 Guide for Metallographic Sample Preparation of
7.1 Where possible, specimens should be metallographi-
Cemented Tungsten Carbides
callymountedinaplasticmaterial,sothattheycanbepolished
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2.2 ASTM Adjunct:
without rounding the edges. Larger specimens may be polished
ADJB0276A Apparent Porosity (4 prints of 4 photomicro-
without mounting. When the specimens are too large, they
graphs each)
shall be sectioned using a diamond cut-off wheel or by
fracturing (appropriate safety precautions shall be utilized
3. Terminology
when fracturing a specimen). The area selected for examina-
3.1 Definitions—Definition of powder metallurgy terms can
tion should represent, as nearly as possible, the entire cross
be found in Terminology B 243.
section.
7.2 The specimen shall be prepared for metallographic
4. Significance and Use
examination. A suitable procedure is described in Practice
4.1 Cemented carbide materials may contain small voids
B 665.Thesurfacetobeexaminedshallbeunetchedandfreeof
that, depending on the application, may affect the performance
grinding and polishing marks.
of the product. To assist users in specifying the maximum
acceptable level of porosity, this test method illustrates a broad
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
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This test method is under the jurisdiction of ASTM Committee B09 on Metal
slits, as well as nonmetallic inclusions.
Powders and Metal Powder Products and is the direct responsibility of Subcom-
mittee B09.06 on Cemented Carbides.
8.2 Classification of Type “A” and “C” apparent porosity is
Current edition approved Dec. 1, 2005. Published December 2005. Originally
basedentirelyoncomparisonofthemicrostructuresfoundwith
approved in 1954. Last previous edition approved in 2000 as B 276 – 91 (2000).
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2 the illustrations in Figs. 1, 3 and 4 of ADJB0276A with due
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 consideration to the difference in field of view of the micro-
Standards volume information, refer to the standard’s Document Summary page on
scope compared to the area of the illustrations. This can be
the ASTM website.
accomplished by scanning the specimen surface under the
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Available from ASTM International Headquarters. Order Adjunct No.
ADJB0276A.
*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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B276–05
microscope at the appropriate magnification, and noting which of area between the illustrations in Fig. 2 ofADJB0276A, and
of the illustrations most nearly represents the fields observed. that observed in the microscope (see A1.4), classify the “B”
Choose an area fu
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