1、Designation: B657 11Standard Guide forMetallographic Identification of Microstructure in CementedCarbides1This standard is issued under the fixed designation B657; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last re
2、vision. 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 covers apparatus and procedures for themetallographic identification of microstructures in cementedcarbides.1.2 T
3、his 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. Precautions apply-i
4、ng to use of hazardous laboratory chemicals should beobserved for chemicals specified in Table 1.2. Referenced Documents2.1 ASTM Standards:2B665 Guide for Metallographic Sample Preparation of Ce-mented Tungsten Carbides2.2 ISO Standard:3ISO 4499 HardmetalsMetallographic Determination ofMicrostructur
5、e3. Terminology3.1 Definitions of Symbols:Symbol Definitiona phase tungsten carbideb phase binder (for example, Co, Ni, Fe)g phase carbide of a cubic lattice (for example, TiC, TaC, NbC)that may contain other carbides (for example, WC) insolid solutionh-type phases multiple carbides of tungsten and
6、at least one metal of thebinder4. Significance and Use4.1 The microstructure of a cemented carbide affects thematerials mechanical and physical properties. This guide isnot intended to be used as a specification for carbide grades.Producers and users may use the microstructural information asa guide
7、 in developing their own specifications.5. Apparatus5.1 Metallographic Microscope capable of magnificationsup to 1500 times.5.2 Ordinary metallurgical laboratory equipment.5.3 Equipment for specimen preparation as outlined inGuide B665.6. Specimen Preparation6.1 A suitable procedure is described in
8、Guide B665.7. Procedure7.1 Examine the microstructure by gradual development ofthe phases by etching. Examples of suitable etching techniquesare given in Table 1. Examples of the appearance of someexpected phases, in fine, medium, and coarse grain sizes, aregiven in Fig. 1.7.2 Determine the presence
9、 of h-type phases by lightlyetching half the section with Technique 1 (see Table 1).Examine the entire section at low magnification and, ifnecessary, at magnifications up to 1500 times. Phases of h-typeare colored orange to brown in the etched portion, and white tolight gray in the unetched portion.
10、 g-Phase may also etchlightly and appear brownish in the etched portion, but will havea brown/gold color even in the unetched portion, therebydifferentiating it from h-phase. The other phases remainunetched. Etching by Technique 1 does not preclude subse-quent etching by Technique 2. Note and record
11、 the existence ofh-type phases and their distribution.7.3 Determine the presence of g phases by etching withTechnique 2 (Table 1). This phase appears light yellowishbrown and has a typically rounded shape (see Fig. 1). Examinethe etched section and note and record the existence of a gphase.7.4 Deter
12、mine the presence of a phase in the same etchedspecimen as in 7.3. The a phase appears gray, angular(idiomorphic), and straight-slided (see Fig. 2). Examine theetched section and note and record the presence of a phase.1This guide is under the jurisdiction of ASTM Committee B09 on MetalPowders and M
13、etal Powder Products and is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved Oct. 1, 2011. Published October 2011. Originallyapproved in 1979. Last previous edition approved in 2005 as B657 05. DOI:10.1520/B0657-11.2For referenced ASTM standards, visit
14、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 American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, N
15、Y 10036.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.5 Identify the b phase in the same etched specimen as 7.3and 7.4. This phase remains white and is usually the
16、 continu-ous, interstitial phase between the a and g grains.NOTE 1This procedure follows essentially ISO 4499.8. Report8.1 The report shall include complete identification of thespecimen and the phases present.9. Keywords9.1 cemented carbides; hardmetals; microstructure; powdermetallurgyTABLE 1 Etch
17、ing TechniquesNOTE 1The separate solutions of potassium hexacyanoferrate (III) and potassium or sodium hydroxide may be stored for a long time, but must befreshly mixed each day when used.EtchingTech-niqueComposition of Etchants Conditions of EtchingObjectiveof Etching1 Freshly prepared mixture of e
18、qual quantities of 10 %(mass/mass) aqueous solutions of K3Fe(CN)6(III)(potassium ferricyanide) and potassiumor sodium hydroxideEtch at approximately 20C for 2 to 10 s. Flush the test-piecesection with water immediately, without removing the oxide layer. Drythe surface carefully with acetone or alcoh
19、ol without wiping.Identification of hphase2 A Same as 1A Etch at approximately 20C for 2 to 4 min. Identification of a, b,and g phasesFIG. 1 g Phase Fine, All 8.5%Co, 5.9% TiC, 5.5% TaC, 2.4% NbC, balance WCB657 112FIG. 1 g Phase Medium (continued)FIG. 1 g Phase Coarse (continued), All 8.5%Co, 5.9%
20、TiC, 5.5% TaC, 2.4% NbC, balance WC (continued)B657 113FIG. 2 a Phase Fine, All 10% cobalt, balance WCFIG. 2 a Phase Medium (continued)B657 114SUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue (B657 05)that may impact the use of thi
21、s standard. (Approved October 2011.)(1) Replaced original micrographs with new digital imagescontaining micron bars.(2) The chemical composition of the pictured materials havebeen listed in the “Figure” headings.”ASTM International takes no position respecting the validity of any patent rights asser
22、ted 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, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by
23、the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receiv
24、e 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 you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM Intern
25、ational, 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 2 a Phase Coarse (continued), All 10% cobalt, balance WC (continued)B657 115
