ASTM B276-91(2000)
(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.
1.2 This standard does not purport to address all of the safety problems, 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:B276–91(Reapproved2000)
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 acceptable level of porosity, this test method illustrates a broad
range of porosity levels for each of three porosity types. This
1.1 This test method specifies procedures for the metallo-
testmethodisnotintendedtobeusedasaspecification,butthe
graphic determination of apparent porosity in cemented car-
levels shown here may be cited in specifications written by
bides.
producers and users of cemented carbides.
NOTE 1—The term “apparent porosity” is construed to mean all
microstructures observed on a properly prepared, unetched surface,
5. Interferences
including structures resulting from uncombined carbon, non-metallic
5.1 Lack of adequate pressure on the specimen during
inclusions, etc., as well as true, inherent porosity.
polishing may result in material being torn from the surface of
1.2 This standard does not purport to address all of the
thespecimen.Thisconditionmaybeerroneouslyinterpretedas
safety concerns, if any, associated with its use. It is the
porosity.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
6. Apparatus
bility of regulatory limitations prior to use.
6.1 Ordinary laboratory apparatus.
6.2 A metallographic microscope permitting observation
2. Referenced Documents
and measurement up to a magnification of 200 diameters.
2.1 ASTM Standards:
6.3 Equipment for the metallographic preparation of test
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B 243 Terminology of Powder Metallurgy
specimens.
B 665 Practice for Metallographic Sample Preparation of
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Cemented Tungsten Carbides
7. Specimen Preparation
2.2 ASTM Adjunct:
7.1 Where possible, specimens should be metallographi-
ADJA0276 Apparent Porosity (5 prints of 5 photomicro-
callymountedinaplasticmaterial,sothattheycanbepolished
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graphs each)
without rounding the edges. Larger specimens may be polished
2.3 ISO Standard:
without mounting. When the specimens are too large, they
ISO 4505 Hardmetals—Metallographic Determination of
shall be sectioned using a diamond cut-off wheel or by
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Porosity and Uncombined Carbon
fracturing (appropriate safety precautions shall be utilized
when fracturing a specimen). The area selected for examina-
3. Terminology
tion shall represent, as nearly as possible, the entire cross
3.1 Definitions—Definition of powder metallurgy terms can
section.
be found in Terminology B 243.
7.2 The specimen shall be prepared for metallographic
examination.Thesurfacetobeexaminedshallbeunetchedand
4. Significance and Use
free of grinding and polishing marks.
4.1 Cemented carbide materials may contain small voids
NOTE 2—A suitable procedure is described in Practice B 665.
that, depending on the application, may affect the performance
of the product. To assist users in specifying the maximum
8. Procedure
8.1 Pore size shall be defined as the maximum dimension of
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This test method is under the jurisdiction of ASTM Committee B09 on Metal
the pore. Make special reference to the presence of cracks and
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
slits, as well as nonmetallic inclusions.
tee B09.06 on Cemented Carbides.
8.2 Classification of apparent porosity is based entirely on
Current edition approved Aug. 15, 1991. Published December 1991. Originally
comparison of the microstructures found with the photomicro-
published as B 276 – 54. Last previous edition B 276 – 86.
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Annual Book of ASTM Standards, Vol 02.05.
graphs in Figs. 1-5. This can be accomplished by scanning the
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Available from ASTM Headquarters. Request ADJA0276.
specimen surface under the microscope at the appropriate
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Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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B276
FIG. 1 Type AApparent Porosity (3 100)
magnification, and noting which of the photomicrographs most diameters. Report the porosity level by reference to the
nearly represents the fields observed. Choose an area fully appropriate photomicrograph, and designate asA02,A04,A06,
representative of the specimen surface for comparison with the or A08.
photomicrographs. 8.2.3 Classify pores in the range from 10 to 25 µm as
...
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