1、Designation: B 665 08Standard Guide forMetallographic Sample Preparation of Cemented TungstenCarbides1This standard is issued under the fixed designation B 665; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revis
2、ion. 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 purport
3、 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:2B 390
4、Practice for Evaluating Apparent Grain Size andDistribution of Cemented Tungsten CarbidesB 657 Guide for Metallographic Identification of Micro-structure in Cemented Carbides3. Significance and Use3.1 This sample preparation procedure may be used toprepare metallographic samples for Test Method B 65
5、7 andPractice B 390. 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 cross sect
6、ion. 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 are
7、 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, howe
8、ver, the 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,
9、this procedure 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
10、specimens are 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 should repre-sent, as nearly as possible, the entire cross section.5.1.2 Rough GrindingThe
11、surface to be examined 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 pas
12、s and copious amounts of coolantshould 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 di
13、sk may be substituted in the roughing lap.For manual polishing, speeds of 500 to 600 rpm should beused; automatic polishing generally requires speeds of 100 to200 rpm.5.1.3.1 Roughing LapFor the roughing lap, use NISTGrade 20 diamond powder3(15 to 25 m) dispersed in lightspindle oil. Commercial diam
14、ond 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.1This guide is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mitte
15、e B09.06 on Cemented Carbides.Current edition approved Nov. 1, 2008. Published December 2008. Originallyapproved in 1979. Last previous edition approved in 2003 as B 66503.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For An
16、nual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 1070, Gaithersburg, MD 20899-1070, http:/www.nist.gov.1*A Summary of Changes section appears at th
17、e end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.3.3 Finishing LapFor the finish lap, use Grade 1diamond powder (less than 2 m) or an equivalent paste.NOTE 1Best results are obtained by applying considerable
18、pressure tothe specimen in all lapping operations. Lack of adequate pressure willresult in pulling out the softer matrix material. It is also essential that thespecimen and operators hands be thoroughly cleaned between allgrinding or polishing steps; ultrasonic cleaning is recommended.6. Keywords6.1
19、 cemented carbides; cemented tungsten carbides;microstructureSUMMARY OF CHANGESCommittee B9 has identified the location of selected changes to this standard since the last issue (B 66503)that may impact the use of this standard.(1) Deleted Section 6 on Precision and Bias as this statement isnot appr
20、opriate for a Guide.(2) Added Summary of Changes.ASTM 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 that determination of the validity of any such patent rights
21、, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for re
22、vision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing yo
23、u shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).B665082
