1、Designation: B934 10Standard Test Method forEffective Case Depth of Ferrous Powder Metallurgy (PM)Parts Using Microindentation Hardness Measurements1This standard is issued under the fixed designation B934; the number immediately following the designation indicates the year oforiginal adoption or, i
2、n 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 test method covers a procedure for determinationof the effective case depth
3、of powder metallurgy (PM) parts.1.2 A microindentation hardness traverse procedure is de-scribed to determine effective case depth. This test method maybe used to determine the effective case depth for all types ofhardened cases.1.3 The procedure for determining the microindentationhardness of powde
4、r metallurgy materials, as described in TestMethod B933 shall be followed.1.4 With the exception of the unit for density, for which thegrams per cubic centimeter unit is the long-standing industrypractice, the values in SI units are to be regarded as standard.1.5 This standard does not purport to ad
5、dress 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:2B243 Termino
6、logy of Powder MetallurgyB933 Test Method for Microindentation Hardness of Pow-der Metallurgy (PM) MaterialsE384 Test Method for Knoop and Vickers Hardness ofMaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions of powd
7、er metallurgy (PM) terms can befound in Terminology B243. Additional descriptive informa-tion is available in the Related Material section of Volume02.05 of the Annual Book of ASTM Standards.3.2 Definitions of Terms Specific to This Standard:3.2.1 case that portion of a part, extending inward fromth
8、e surface that has a microindentation hardness, after harden-ing, equal to or greater than a specified hardness.3.2.2 effective case depthperpendicular distance from thesurface of the hardened case to the furthest point where amicroindentation hardness value equivalent to 50 HRC ismaintained, unless
9、 otherwise specified.4. Summary of Test Method4.1 The powder metallurgy part is sectioned and the surfaceprepared for examination. Microindentation hardness measure-ments are taken at various depths below the part surface. Thedistance where the microindentation hardness falls below theequivalent of
10、50 HRC is defined as the effective case depth,unless otherwise specified.5. Significance and Use5.1 The engineering function of many PM parts may requirean exterior portion of the part to have a specified case depthand microindentation hardness. Measurement of effective casedepth is used to determin
11、e the depth to which the microinden-tation hardness of the exterior portion of a part has beenincreased over that of the interior of the part.6. Apparatus6.1 Knoop or Vickers Hardness Indenters, using 100 gf(0.9807 N) loads are recommended following Test MethodE384. The type of hardness indenter and
12、 load used shall beagreed upon between customer and producer.6.2 Calibrated Optical Instrument, Micrometer Stage,orother suitable means to measure the distance from the surfaceof the part to the center of the impression with a precision of0.025 mm.1This test method is under the jurisdiction of ASTM
13、Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.05 on Structural Parts.Current edition approved Dec. 1, 2010. Published March 2011. Originallyapproved in 2004. Last previous edition approved in 2009 as B934 09. DOI:10.1520/B0934-010.2For
14、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.1*A Summary of Changes section appears at the end of this standard
15、.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Test Specimen7.1 Cut a test specimen from the PM part, perpendicular tothe hardened surface at a specified location, being careful toavoid any cutting or grinding procedure that woul
16、d affect theoriginal microindentation hardness.7.2 Mounting of the test specimen is recommended forconvenience in surface preparation, edge retention, and micro-indentation hardness measurement. Edge retention is importantfor proper depth measurement of the case.7.3 Grind and polish the test specime
17、n using methodsrecommended in Appendix X2 of Test Method B933. The areato be traversed should be polished so the microindentationhardness impressions are unaffected, that is, the lighter theindenter load, the finer the finish necessary. Care should betaken to ensure that the true area fraction of po
18、rosity is revealedthroughout the entire cross-section of the specimen. It isessential in surface preparation to remove all smeared metaland to identify pores clearly so that they may be avoided duringtesting.7.4 The specimen should be lightly etched prior to micro-indentation hardness testing. Caref
19、ul etching is necessary asheavy etching obscures features and interferes with the mea-surement of the diagonals of the indentation.7.5 For heat treated steels, swabbing with or immersion in2 % nital for 4 to 7 s gives an appropriate structure.8. Procedure8.1 Measure microindentation hardness at a se
20、ries of knownintervals from the surface of the test specimen toward theinterior. Take a minimum of three acceptable microindentationhardness measurements at each depth. Space the indentationsso that adjacent tests do not interfere with each other. Theminimum spacing between tests is illustrated in F
21、ig. 1. Use acalibrated optical instrument, micrometer stage, or other suit-able means to measure the distance from the surface of the partto the center of the impression.8.2 Microindentation impressions should not be placed insoft regions such as copper or the center of nickel-rich regions.Randomly
22、encountered upper bainite or fine pearlite in themartensite should not be excluded as a measurement location.8.3 Plot microindentation hardness versus distance from thepart surface (see Fig. 2). The effective case depth shall be thedistance at which the microindentation hardness falls below theequiv
23、alent of 50 HRC unless a different value is specified (seeNote 1). Plot definition will dictate the required number ofreadings, particularly in the critical region of effective casedepth. The procedure described in Appendix X1 of TestMethod B933 shall be used for conversion to HRC.NOTE 1No compositi
24、onal change occurs in induction hardened ma-terials The hardness of martensite is affected by the carbon content of thesteel. Some lower-carbon steels will not reach the equivalent of 50 HRCwhen fully hardened. All concerned parties should agree upon thespecified effective case depth hardness if oth
25、er than 50 HRC.NOTE 2For routine quality control testing, where the effective casedepth is reasonably well known, a somewhat simplified method ofestimating effective case depth may be used. This method makes theassumption that the curve that represents microindentation hardnessversus depth below the
26、 surface of the part may be regarded as a straightline in the region of the effective case hardened depth. Microindentationhardness may be measured at two depths from the surface selected, suchthat, on the basis of past experience, one will be less than the estimatedeffective case hardened depth and
27、 one will be greater. The two depthsselected should lie at about equal distances from the estimated effectivecase hardened depth. At least five determinations of microindentationhardness shall be carried out at each of the selected depths below the partsurface. On a plot of microindentation hardness
28、 versus depth from thesurface, draw a straight line between the average microindentationhardness value at each of the two depths and read off the distance from theFIG. 1 Minimum Spacing between IndentationsB934 102surface of the part at which the specified microindentation hardness valueis reached.
29、This is the effective case depth.NOTE 3An alternative method may be used for routine quality controltesting. Where a minimum effective case depth is specified, measure themicroindentation hardness at a distance from the surface of the part that isequal to or greater than the specified minimum depth.
30、 At least fivedeterminations of microindentation hardness shall be carried out at thedesired location. If the average microindentation hardness at this depth isequal to or greater than the effective case depth hardness, the part meetsthe specified requirement. Where a maximum effective case depth is
31、specified, measure the microindentation hardness at a distance from thesurface of the part that is less than the specified maximum depth in orderto confirm that the part has been case hardened. At least five determina-tions of microindentation hardness shall be carried out at the desiredlocation. Th
32、is average microindentation hardness should be equal to orgreater than that specified for the effective case hardness. If it is, measurethe microindentation hardness at a distance from the surface of the partthat is equal to the specified maximum depth. At least five determinationsof microindentatio
33、n hardness shall be carried out at the desired location.If the average microindentation hardness is less than the value specifiedfor the effective case hardness, the maximum effective case depthspecification is met. If it is greater than or equal to the specified value, themaximum effective case dep
34、th is exceeded.9. Report9.1 The report shall include:9.1.1 The type of material and case measured (and whenpossible the type of process used to produce the case),9.1.2 The location of the measurement,9.1.3 The type of microindentation hardness indenter andthe load used,9.1.4 The load used in testing
35、 shall be expressed as the loadin grams, for example, HV100 gf or HK 100 gf (preferredmethod), or the load in kilograms, for example, HV 0.1 or HK0.1, and9.1.5 The effective case depth to the nearest 0.1 mm and themicroindentation hardness specified.10. Precision and Bias10.1 PrecisionThe precision
36、of this test method wasdeveloped as part of a Test Methods Assurance Program(TMAP) conducted by the Standards Committee of the MetalPowder Industries Federation (MPIF) and it is published herewith the permission of MPIF. The repeatability (r) and repro-ducibility (R) measurements were determined (19
37、93) accord-ing to Practice E691. The test sample was prepared fromFL-4605 (no graphite added) at 7.1 g/cm3 and then case-carburized to develop the desired case/core relationship. Theeffective case depth was determined at 50 HRC after conver-sion from direct microindentation hardness values by 7 part
38、ici-pating laboratories.The mean case depth was 0.7 mm with a repeatability of 0.1mm and a reproducibility of 0.5 mm. Duplicate results from thesame laboratory should not be considered suspect at the 95%confidence level unless they differ by more than 0.1 mm. Forthe same test specimen, test results
39、from two different labora-tories should not be considered different8 at the 95% confi-dence level unless they differ by more than 0.5 mm.FIG. 2 Schematic Plot of Microindentation Hardness versus Depth from SurfaceB934 10310.2 BiasNo bias can be defined since there is no standardcase-hardened materia
40、l for which the effective case depth maybe measured.11. Keywords11.1 case depth; effective case depth; powder metallurgy;PMB934 104SUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue (B934 09)that may impact the use of this standard.(
41、1) A statement on units has been added to the Scope.(2) All instances of P/M have been changed to the currentlyapproved acronym PM.(3) A precision statement has been added in 10.1.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item m
42、entionedin 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 the responsible technical committ
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44、ing 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 International, 100 Barr Harbor Drive, P
45、O 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/).B934 105
