1、Designation: B276 05 (Reapproved 2015)Standard Test Method forApparent Porosity in Cemented Carbides1This standard is issued under the fixed designation B276; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method specifies procedures for th
3、e metallo-graphic determination of apparent porosity in cemented car-bides.NOTE 1The term “apparent porosity” is construed to mean allmicrostructures observed on a properly prepared, unetched surface,including structures resulting from uncombined carbon, non-metallicinclusions, etc., as well as true
4、, inherent porosity.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to
5、 use.2. Referenced Documents2.1 ASTM Standards:2B243 Terminology of Powder MetallurgyB665 Guide for Metallographic Sample Preparation of Ce-mented Tungsten Carbides2.2 ASTM Adjunct:3ADJB0276A Apparent Porosity (4 prints of 4 photomicro-graphs each)3. Terminology3.1 DefinitionsDefinition of powder me
6、tallurgy terms canbe found in Terminology B243.4. Significance and Use4.1 Cemented carbide materials may contain small voidsthat, depending on the application, may affect the performanceof the product. To assist users in specifying the maximumacceptable level of porosity, this test method illustrate
7、s a broadrange of porosity levels for each of three porosity types. Thistest method is not intended to be used as a specification, but thelevels shown here may be cited in specifications written byproducers and users of cemented carbides.5. Interferences5.1 Lack of adequate pressure on the specimen
8、duringpolishing may result in material being torn from the surface ofthe specimen. This condition may be erroneously interpreted asporosity.6. Apparatus6.1 A metallographic microscope permitting observationand measurement up to a magnification of 200.6.2 Equipment for the metallographic preparation
9、of testspecimens.7. Specimen Preparation7.1 Where possible, specimens should be metallographi-cally mounted in a plastic material, so that they can be polishedwithout rounding the edges. Larger specimens may be polishedwithout mounting. When the specimens are too large, theyshall be sectioned using
10、a diamond cut-off wheel or byfracturing (appropriate safety precautions shall be utilizedwhen fracturing a specimen). The area selected for examina-tion should represent, as nearly as possible, the entire crosssection.7.2 The specimen shall be prepared for metallographicexamination. A suitable proce
11、dure is described in PracticeB665.The surface to be examined shall be unetched and free ofgrinding and polishing marks.8. Procedure8.1 Pore size shall be defined as the maximum dimension ofthe pore. Make special reference to the presence of cracks andslits, as well as nonmetallic inclusions.8.2 Clas
12、sification of Type “A” and “C” apparent porosity isbased entirely on comparison of the microstructures found withthe illustrations in Figs. 1, 3 and 4 of ADJB0276A3with dueconsideration to the difference in field of view of the micro-scope compared to the area of the illustrations. This can be1This
13、test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved Oct. 1, 2015. Published October 2015. Originallyapproved in 1954. Last previous edition approve
14、d in 2010 as B276 91(2010). DOI:10.1520/B0276-05R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Availabl
15、e from ASTM International Headquarters. Order Adjunct No.ADJB0276A.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1accomplished by scanning the specimen surface under themicroscope at the appropriate magnification, and noting whichof
16、the illustrations most nearly represents the fields observed.Choose an area fully representative of the specimen surface forcomparison with the illustrations.NOTE 2The illustrations in Figs. 14 of ADJB0276A represent onlya portion of the field of view typically observed in modern microscopes.Typical
17、ly, the field of view of a microscope is 6.5 larger than the areain these figures. The exact relationship between the area observed at anygiven magnification in the microscope and the area of the illustrations canbe determined using the method in Annex A1.8.2.1 Classify pores 10 m as Type A (see Fig
18、. 1 ofADJB0276A and examine at a magnification of 200. Reportthe porosity level by reference to the appropriate illustrationwith consideration to the relationship of area between theillustration and that observed in the microscope, and designateas A02, A04, A06, or A08. If the level of Type A pores
19、is lessthan 50 % of that shown in the illustration for A02, thendesignate this as A00. If the porosity is not uniform over thearea of the test-piece section being examined, identify thelocation of the section, for example, as top, bottom, edge, rim(case), core, and so forth.8.2.2 Classify pores in t
20、he range from 10 to 25 m asType B (see Fig. 2 of ADJB0276A and examine at a magni-fication of 100.8.2.2.1 If the number of “B” pores appears to be less thanor equal to that represented by B02, with consideration to therelationship of area between the illustrations in Fig. 2 ofADJB0276A and that obse
21、rved in the microscope (see A1.3),count the number of “B” pores in a representative area (0.25cm2). Divide this count by the area examined (see A1.3)toobtain the number of “B” pores/cm2. If this number is less than70 pores/cm2, designate this as B00-#, where # is the numberof “B” pores/cm2so obtaine
22、d. If the number is greater than orequal to 70 pores/cm2, designate this as B02. If no “B” poresare observed, designate this as B00-0.8.2.2.2 If the number of “B” pores appears to be greater thanthat represented by B02, with consideration to the relationshipof area between the illustrations in Fig.
23、2 of ADJB0276A andthat observed in the microscope (see A1.4), classify the “B”porosity as B04, B06, or B08 with reference to the illustrationsin Fig. 2 of ADJB0276A. If the porosity is not uniform over thearea of the test-piece section being examined, identify thelocation of the section, for example
24、, as top, bottom, edge, rim(case), core, and so forth.8.2.3 Count and report pores larger than 25 m as thenumber of pores per cm2. Choose the size ranges as follows:25 to 75 m, 75 to 125 m, and over 125 m.8.2.4 Classify porosity resulting from uncombined carbonas Type C (see Figs. 3 and 4 of ADJB027
25、6A and examine at amagnification of 100 or 200. Report the porosity level byreference to the appropriate illustration with consideration tothe relationship of area between the illustrations in Figs. 3 and4ofADJB0276A and that observed in the microscope, anddesignate as C02, C04, C06, or C08. If the
26、porosity ofuncombined carbon is not uniform over the area of thetest-piece section being examined, identify the location of thesection, for example as top, bottom, edge, rim (case), core, andso forth. If no uncombined carbon is observed, designate this asC00.9. Report9.1 The report shall include the
27、 following:9.1.1 Reference to this test method,9.1.2 Complete identification of the test specimen,9.1.3 Results obtained, and9.1.4 Details of any occurrence that may have affected theresult.10. Precision and Bias10.1 A precision and bias statement cannot be made for thistest method.11. Keywords11.1
28、apparent porosity; cemented carbides; hardmetals; mi-crostructure; powder metallurgyANNEX(Mandatory Information)A1. DETERMINATION OF THE FIELD OF VIEW OF MICROSCOPEA1.1 Using a metallograph, view a stage micrometer.A1.2 Determine the diameter (D) of the field of view to aprecision of 0.002 cm.A1.3 C
29、alculate the area of the field of view using theformula:A 5 D/2!2(A1.1)where:A = area of field of view, cm2, andD = diameter of field of view, cm.A1.4 Determine the number of photomicrographs equiva-lent to the field of view of the microscope at the appropriatemagnification using the following:At 10
30、0:# photographs = A/0.00676 cm2using ADJB0276AAt 200:# photographs = A/0.0017cm2using ADJB0276AB276 05 (2015)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised
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