ASTM B390-92(2000)
(Practice)Standard Practice for Evaluating Apparent Grain Size and Distribution of Cemented Tungsten Carbides
Standard Practice for Evaluating Apparent Grain Size and Distribution of Cemented Tungsten Carbides
SCOPE
1.1 This procedure for the visual comparison and classification of the apparent grain size and distribution of cemented tungsten carbides is limited to cemented tungsten carbides that contain approximately 6, 10, and 18% cobalt.
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: B 390 – 92 (Reapproved 2000)
Standard Practice for
Evaluating Apparent Grain Size and Distribution of
1
Cemented Tungsten Carbides
This standard is issued under the fixed designation B 390; 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.
1. Scope use the micrographs and the grain size chart as a guide in
developing their own specifications.
1.1 This procedure for the visual comparison and classifi-
cation of the apparent grain size and distribution of cemented
5. Specimen Preparation
tungsten carbides is limited to cemented tungsten carbides that
5.1 Specimens shall be prepared for metallographic exami-
contain approximately 6, 10, and 18 % cobalt.
nation in accordance with a procedure suitable for this type of
1.2 This standard does not purport to address all of the
cemented carbides.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
NOTE 1—A suitable procedure is described in Method B 657 and
priate safety and health practices and determine the applica- Practice B 665.
bility of regulatory limitations prior to use.
6. Procedure
2. Referenced Documents
6.1 Examine metallographically the entire surface of an
2.1 ASTM Standards: etched specimen at a magnification of 1500 diameters. Select a
representative area and make a comparison with the photomi-
B 657 Test Method for Metallographic Determination of
2
Microstructure in Cemented Carbides crographs in Fig. 1, Fig. 2, and Fig. 3.
6.2 The nominal analyses of the cemented tungsten carbide
B 665 Practice for Metallographic Sample Preparation of
2
Cemented Tungsten Carbides samples that were used to prepare the nine photomicrographs
shown in Fig. 1, Fig. 2, and Fig. 3 are as follows:
3. Terminology
6.2.1 Fig. 1—Tungsten carbide plus 6 % cobalt,
3.1 Definitions of Terms Specific to This Standard: 6.2.2 Fig. 2—Tungsten carbide plus 10 % cobalt, and
3.1.1 apparent grain size—the average diameter of a tung- 6.2.3 Fig. 3—Tungsten carbide plus 18 % cobalt.
sten carbide particle as measured on an etched metallographi- 6.3 The grain size for each of these specimens may be
cally polished surface of a specimen of sintered cemented designated as follows:
carbide. The apparent grain size is expressed in micrometres Type F—Fine grain,
and is generally reported as a range. Type M—Medium grain, and
Type C—Coarse grain.
4. Significance and Use
7. Evaluation
4.1 The apparent size and distribution of tungsten carbide
grains in cemented carbides affects the material’s wear resis- 7.1 The grain size rating of a cemented tungsten carbide
tance and fracture. For a given chemical composition, an specimen is accomplished by selecting the photomicrographs
increase in the average grain size will result in increased in Fig. 1, Fig. 2,or Fig. 3 that most nearly match the field
toughness and decreased wear resistance. This practice illus- observed on the specimen being evaluated (seeAppendix X1).
trates representative micro-structures for a wide range of 7.2 A range of numerical values for various concentrations
tungsten carbide-cobalt grades. This is not intended to be used of tungsten carbide particles, even though arbitrary, is sug-
as a specification for carbide grades; producers and users may gested in Table 1.
8. Report
1
8.1 After visual comparison of a specimen with the photo-
This practice is under the jurisdiction of ASTM Committee B09 on Metal
Powders and Metal Powder Products and is the direct responsibility of Subcom-
micrographs contained in this practice, the apparent grain size
mittee B09.06 on Cemented Carbides.
of a particular specimen shall be rated relative to one or more
Current edition approved Jan. 15, 1992. Published June 1992. Originally
of the photomicrographs. Cobalt contents should always be
published as B 390 – 62 T. Last previous editions B 390 –86.
2
Annual Book of ASTM Standards, Vol 02.05. specified. For example, a cemented tungsten carbide specimen
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B 390 – 92 (2000)
FIG. 2 Apparent Grain Size of Tungsten Carbide plus 10 % Cobalt
FIG. 1 Apparent Grain Size of Tungsten Carbide plus 6 % Cobalt
(15003)
(15003)
containing approximately 6 % cobalt, having a fine grain size
and a grain size distribution similar to the one shown in Fig.
10. Keywords
1(a) would be reported as Type 6-F. The “F” indicates a fine
10.1 apparent grain size; cemented carbides; cemented
grain size and the “6” identifies the cobalt co
...
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