1、Designation:B27605(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 revision.A nu
2、mber 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 the metallo-gr
3、aphic determination of apparent porosity in cemented car-bides.NOTE1The 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,inherent porosity.
4、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 use.2.Referenced Docum
5、ents2.1 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 metallurgy terms canbe found
6、 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 illustrates a broadrange of porosity leve
7、ls 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 duringpolishing may result in mate
8、rial 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 of testspecimens.7.Specimen Preparat
9、ion7.1 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 a diamond cut-off wheel or byfracturing(ap
10、propriate 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 procedure is described in PracticeB665.The surface t
11、o 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 Classification of Type“A”and“C”apparent porosity isbas
12、ed 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 test method is under the jurisdiction of ASTM Committee B
13、09 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 approved in 2010 as B276 91(2010).DOI:10.1520/B0276-05R15.2For refere
14、nced 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.3Available from ASTM International Headquarters.Order Adjunct No.ADJB0276A.Co
15、pyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 accomplished by scanning the specimen surface under themicroscope at the appropriate magnification,and noting whichof the illustrations most nearly represents the fields observed.Choose an are
16、a fully representative of the specimen surface forcomparison with the illustrations.NOTE2The illustrations in Figs.14 of ADJB0276A represent onlya portion of the field of view typically observed in modern microscopes.Typically,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 1