ASTM B276-05(2010)
(Test Method)Standard Test Method for Apparent Porosity in Cemented Carbides
Standard Test Method for Apparent Porosity in Cemented Carbides
SIGNIFICANCE AND USE
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.
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 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(Reapproved 2010)
Standard Test Method for
Apparent Porosity in Cemented Carbides
This standard is issued under the fixed designation B276; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) 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* acceptablelevelofporosity,thistestmethodillustratesabroad
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 A metallographic microscope permitting observation
and measurement up to a magnification of 200×.
2. Referenced Documents
6.2 Equipment for the metallographic preparation of test
2.1 ASTM Standards:
specimens.
B243Terminology of Powder Metallurgy
B665Guide for Metallographic Sample Preparation of Ce-
7. Specimen Preparation
mented Tungsten Carbides
7.1 Where possible, specimens should be metallographi-
2.2 ASTM Adjunct:
callymountedinaplasticmaterial,sothattheycanbepolished
ADJB0276AApparent Porosity (4 prints of 4 photomicro-
withoutroundingtheedges.Largerspecimensmaybepolished
graphs each)
without mounting. When the specimens are too large, they
3. Terminology shall be sectioned using a diamond cut-off wheel or by
fracturing (appropriate safety precautions shall be utilized
3.1 Definitions—Definition of powder metallurgy terms can
when fracturing a specimen). The area selected for examina-
be found in Terminology B243.
tion should represent, as nearly as possible, the entire cross
section.
4. Significance and Use
7.2 The specimen shall be prepared for metallographic
4.1 Cemented carbide materials may contain small voids
examination. A suitable procedure is described in Practice
that, depending on the application, may affect the performance
B665.Thesurfacetobeexaminedshallbeunetchedandfreeof
of the product. To assist users in specifying the maximum
grinding and polishing marks.
8. Procedure
This test method is under the jurisdiction of ASTM Committee B09 on Metal
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
8.1 Poresizeshallbedefinedasthemaximumdimensionof
tee B09.06 on Cemented Carbides.
the pore. Make special reference to the presence of cracks and
Current edition approved Sept. 1, 2010. Published October 2010. Originally
approved in 1954. Last previous edition approved in 2005 as B276–91(2005)e1.
slits, as well as nonmetallic inclusions.
DOI: 10.1520/B0276-05R10.
8.2 Classification of Type “A” and “C” apparent porosity is
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
basedentirelyoncomparisonofthemicrostructuresfoundwith
Standards volume information, refer to the standard’s Document Summary page on 3
the illustrations in Figs. 1, 3 and 4 of ADJB0276A with due
the ASTM website.
consideration to the difference in field of view of the micro-
Available from ASTM International Headquarters. Order Adjunct No.
ADJB0276A. scope compared to the area of the illustrations. This can be
*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
B276 − 05 (2010)
accomplished by scanning the specimen surface under the of area between the illustrations in Fig. 2 of ADJB0276A and
microscope at the appropriate magnification, and noting which that observed in the microscope (see A1.4), classify the “B”
of the illustrations most nearly represents the fields observed. porosityasB04,B06,orB08withreferencetotheillustrations
Chooseanareafullyrepresentativeofthespecimensurfacefor inFig.2ofADJB0276A.Iftheporosityisnotuniformoverthe
comparison with the illustrations. area of the test-piece section being examined, identify the
location of the section, for example, as top, bottom, edge, rim
NOTE 2—The illustrations in Figs. 1–4 of ADJB0276A represent only
(case), core, and so forth.
a portion of the field of view typically observed in modern microscopes.
8.2.3 Count and report pores larger than 25 µm as the
Typically, the field of view of a microscope is ~6.5× larger than the area
in these figures. The exact relationship between the area observed at any
number of pores per cm . Choose the size ranges as follows:
givenmagnificationinthemicroscopeandtheareaoftheillustrationscan
>25 to ≤75 µm, >75 to ≤125 µm, and over 125 µm.
be determined using the method in Annex A1.
8.2.4 Classify porosity resulting from uncombined carbon
8.2.1 Classify pores ≤10 µm as Type A (see Fig. 1 of
as Type C (see Figs. 3 and 4 of ADJB0276A and examine at a
ADJB0276A and examine at a magnification of 200×. Report
magnification of 100 or 200×. Report the porosity level by
the porosity level by reference to the appropriate illustrati
...
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