ASTM_B_657_-_11.pdf

Designation:B65711Standard 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 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 covers apparatus and procedures for themetallographic identification of microstructures in cementedcarbides.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.Precautions apply-ing 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 ofMicrostructure3.Terminology3.1 Definitions of Symbols:SymbolDefinition phasetungsten carbide phasebinder(for example,Co,Ni,Fe)phasecarbide of a cubic lattice(for example,TiC,TaC,NbC)that may contain other carbides(for example,WC)insolid solution-type phasesmultiple carbides of tungsten and 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 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 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 of-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-typeare colored orange to brown in the etched portion,and white tolight gray in the unetched portion.-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-phase.The other phases remainunetched.Etching by Technique 1 does not preclude subse-quent etching by Technique 2.Note and record the existence of-type phases and their distribution.7.3 Determine the presence of 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 phase.7.4 Determine the presence of phase in the same etchedspecimen as in 7.3.The phase appears gray,angular(idiomorphic),and straight-slided(see Fig.2).Examine theetched section and note and record the presence of phase.1This guide 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.1,2011.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 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,NY 10036.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.5 Identify the phase in the same etched specimen as 7.3and 7.4.This phase remains white and is usually thecontinuous,interstitial phase between the and grains.NOTE1This 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 Etching TechniquesNOTE1The 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 EtchantsConditions of EtchingObjectiveof Etching1Freshly prepared mixture of equal quantities of10%(mass mass)