1、Designation:B93114Standard Test Method forMetallographically Estimating the Observed Case Depth ofFerrous Powder Metallurgy(PM)Parts1This standard is issued under the fixed designation B931;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revi
2、sion,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 Ametallographic method is described for estimating theobserved case depth of ferrous powder metallurgy(PM
3、)parts.This method may be used for all types of hardened cases wherethere is a discernible difference between the microstructure ofthe hardened surface and that of the interior of the part.1.2 With the exception of the values for grit size for whichthe U.S.standard designation is the industry standa
4、rd,thevalues stated in SI units are to be regarded as standard.1.3 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-b
5、ility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B243 Terminology of Powder MetallurgyE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE407 Practice for Microetching Metals and Alloys3.Terminology3.1 DefinitionsDefinitions of powder metal
6、lurgy(PM)terms can be found in Terminology B243.Additional descrip-tive information is available in the Related Material section ofVol 02.05 of the Annual Book of ASTM Standards.3.2 The metallographically estimated observed case depth isdefined as the distance from the surface of the part to the poi
7、ntwhere,at a magnification of 100X,there is a discernibledifference in the microstucture of the material.4.Summary of Test Method4.1 The powder metallurgy part is sectioned and the surfaceprepared for metallographic evaluation.The metallographicspecimen is etched and the distance is measured from th
8、esurface of the part to the point at which a discernible differencein the microstructure of the material is observed.5.Significance and Use5.1 The engineering function of many PM parts may requirean exterior portion of the part to have a hardened layer.Wherecasehardeningproducesadistincttransitionin
9、themicrostructure,metallographic estimation of the observed casedepth may be used to check the depth to which the surface hasbeen hardened.6.Apparatus6.1 Equipment for the metallographic preparation of testspecimenssee Appendix X1.6.2 Metallographic Microscope,permitting observation andmeasurement a
10、t a magnification of 100.7.Reagents and Materials7.1 Etchantssuchas2to5%nital,nital/picralcombinations,or other suitable etchants.For more informationon suitable etchants refer to Practice E407.8.Test Specimens8.1 Cut a test specimen from the PM part,perpendicular tothe hardened surface at a specifi
11、ed location,being careful toavoid any cutting or grinding procedure that would affect theoriginal microstructure.8.2 Mounting of the test specimen is recommended forconvenience in surface preparation and edge retention.Edgeretention is important for proper measurement of the observedcase depth.9.Pro
12、cedure9.1 Grind and polish the test specimen using methods suchas those summarized in Appendix X1.9.2 Etch the specimen with etchants such as 2 to 5%nitalor nital/picral combinations.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is th
13、e direct responsibility of Subcom-mittee B09.05 on Structural Parts.Current edition approved Sept.1,2014.Published September 2014.Originallyapproved in 2003.Last previous edition approved in 2009 as B93109.DOI:10.1520/B0931-14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcont
14、act ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Consho
15、hocken,PA 19428-2959.United States1 9.2.1 Observed Case Depth:9.2.1.1 Examine the surface region of the part at a magni-fication of 100.9.2.1.2 Measure the distance from the surface of the part tothe point where there is a discernible difference in the micro-structure of the material.NOTE1The nature
16、 and amount of intermediate transformation prod-ucts will depend on the material being heat treated,its density,and thetype of surface hardening treatment being used.The sharpness of thechange in the microstructure at the point of transition will therefore vary.The microstructure expected at this transition point should be agreedbetween the producer and user of the part.Magnifications higher than100 may be used to check the microstructure of the part in the region ofthe transition zone.However,t