1、Designation:B66508(Reapproved 2012)Standard Guide forMetallographic Sample Preparation of Cemented TungstenCarbides1This standard is issued under the fixed designation B665;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of
2、last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This guide prescribes a method for preparing cementedcarbides for metallographic examination.1.2 This standard does not pu
3、rport 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 Documents2.1 ASTM Standards:2B390
4、Practice for Evaluating Apparent Grain Size and Dis-tribution of Cemented Tungsten Carbides(Withdrawn2010)3B657 Guide for Metallographic Identification of Microstruc-ture in Cemented Carbides3.Significance and Use3.1 This sample preparation procedure may be used toprepare metallographic samples for
5、Test Method B657 andPractice B390.It does not include all variations of samplepreparation.4.Selection of Specimen4.1 Cemented tungsten carbides are very often in the formof relatively small pieces;it is possible to select and mount theentire piece in such manner as to permit examination of theentire
6、 cross section.When pieces are too large for this,however,they should be sectioned,using a diamond cutoffwheel,to allow viewing as much of a representative crosssection as possible.For micrographs,the area selected shouldrepresent,as nearly as possible,the entire cross section.5.Procedure5.1 There a
7、re several acceptable methods for preparingcemented tungsten carbide surfaces for microscopical exami-nation.Basically,they all use diamond wheels for grinding anddiamond powders for lapping.The grinding practices differ,toa minor degree,with respect to grit size of diamond.In allpractices,however,t
8、he final polish is produced by extremelyfine diamond powder lapping,and in all practices care must beexercised to retain the microstructure in its true form and toavoid pull-out of the softer matrix material(usually cobalt).While it is accepted that other procedures may be usedsuccessfully,this proc
9、edure has proved satisfactory in manylaboratories.5.1.1 MountingWhere possible,specimens should bemounted in a plastic material such as phenol-formaldehyde orpoly(methyl methacrylate)to facilitate polishing withoutrounding the edges.Larger specimens may be polished withoutmounting.When specimens are
10、 too large they may be sec-tioned using a diamond cut-off wheel or they may be fractured(appropriate safety precautions should be used when fracturingspecimens).The area selected for examination shouldrepresent,as nearly as possible,the entire cross section.5.1.2 Rough GrindingThe surface to be exam
11、ined may beground flat on a surface grinder with a resin-bonded diamondwheel(100 to 220 grit)operated at 5000 to 5500 surface feetper minute(25 to 28 m/s).After the surface is flat,severalclean-up passes are required;the maximum depth of cut shouldbe 0.0005 in.(13 m)per pass and copious amounts of c
12、oolantshould be used.5.1.3 PolishingPolishing in three steps using diamondpowder or paste on a synthetic short-napped cloth(the reverseside of photographic paper,or manila file folders may also beused).When automatic polishing equipment is used,a resin-bonded diamond disk may be substituted in the r
13、oughing lap.For manual polishing,speeds of 500 to 600 rpm should beused;automatic polishing generally requires speeds of 100 to200 rpm.1This guide is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Productsand is the direct responsibility of Subcommit-tee B09.06 on Ceme
14、nted Carbides.Current edition approved Oct.1,2012.Published October 2012.Originallyapproved in 1979.Last previous edition approved in 2008 as B66508.DOI:10.1520/B0665-08R12.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annua
15、l Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor
16、 Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.1.3.1 Roughing LapFor the roughing lap,use NISTGrade 20 diamond powder4(15 to 25 m)dispersed in lightspindle oil.Commercial diamond paste and thinner will pro-vide similar results.5.1.3.2 Second LapFor the second lap,use Grade 6diamond powder(4 to 8 m)or an equivalent paste.5.1.3.3 Finishing LapFor the finish lap,use Grade 1diamond powder(less than 2 m)or an equivalent paste.NOTE1Best results are obtained by applying considerabl
