1、Designation: B 934 04aStandard Test Method forEffective Case Depth of Ferrous Powder Metallurgy (P/M)Parts Using Microindentation Hardness Measurements1This standard is issued under the fixed designation B 934; the number immediately following the designation indicates the year oforiginal adoption o
2、r, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determinationof the effective case de
3、pth of powder metallurgy (P/M) 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
4、powder metallurgy materials, as described in TestMethod B 933 shall be followed.1.4 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 det
5、ermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B 243 Terminology of Powder MetallurgyB 933 Test Method for Microindentation Hardness of Pow-der Metallurgy (P/M) MaterialsE 384 Test Method for Microindentation Hardness of Ma-terials3. Termi
6、nology3.1 Definitions of powder metallurgy (P/M) terms can befound in Terminology B 243. 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
7、a part, extending inward fromthe 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
8、 to 50 HRC ismaintained, unless 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 hardnes
9、s falls below theequivalent of 50 HRC is defined as the effective case depth,unless otherwise specified.5. Significance and Use5.1 The engineering function of many P/M parts mayrequire an exterior portion of the part to have a specified casedepth and microindentation hardness. Measurement of effec-t
10、ive case depth is used to determine the depth to which themicroindentation hardness of the exterior portion of a part hasbeen increased 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 MethodE 384.
11、The type of hardness indenter and 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.7. Test Specimen7.1
12、 Cut a test specimen from the P/M part, perpendicular tothe hardened surface at a specified location, being careful toavoid any cutting or grinding procedure that would affect theoriginal microindentation hardness.7.2 Mounting of the test specimen is recommended forconvenience in surface preparation
13、, edge retention, and micro-indentation hardness measurement. Edge retention is importantfor proper depth measurement of the case.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.05 on St
14、ructural Parts.Current edition approved Oct. 1, 2004. Published October 2004. Originallyapproved in 2004. Last previous edition approved in 2004 as B 934 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS
15、TMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7.3 Grind and polish the test specimen using methodsrecommended in Appendix X2 of Test Me
16、thod B 933. 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 porosity is revealedthroughout the entire cross-secti
17、on 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. Careful etching is necessary asheavy etching obscures fe
18、atures 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 series of knownintervals from the surface of the test
19、 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 Fig. 1. Use acalibrated optical instrument, micromet
20、er 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 encountered upper bainite or fine pearlite in thema
21、rtensite 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 theequivalent of 50 HRC unless a different value is specifi
22、ed (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 B 933 shall be used for conversion to HRC.NOTE 1No compositional change occurs in induction hardened ma-terial
23、s 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 other than 50 HRC.NOTE 2For routine quality control t
24、esting, 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 surface of the part may be regarded as a straight
25、line 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 one will be greater. The two depthsselected shoul
26、d 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 versus depth from thesurface, draw a straight lin
27、e between the average microindentationhardness value at each of the two depths and read off the distance from thesurface of the part at which the specified microindentation hardness valueis reached. This is the effective case depth.NOTE 3An alternative method may be used for routine quality controlt
28、esting. 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. At least fivedeterminations of microindentation hardness shall be carried out at thedesired location
29、. 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 isspecified, measure the microindentation hardness at a distance from thesurface of the part that is le
30、ss than the specified maximum depth in orderFIG. 1 Minimum Spacing between IndentationsB 934 04a2to confirm that the part has been case hardened. At least five determina-tions of microindentation hardness shall be carried out at the desiredlocation. This average microindentation hardness should be e
31、qual 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 microindentation hardness shall be carried out at the desired l
32、ocation.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 depth is exceeded.9. Report9.1 The report shall inc
33、lude: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 shall be expressed as the loadin grams, for exa
34、mple, 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 of this test method is underreview by Subcommitt
35、ee B09.05 on Structural Parts.10.2 BiasNo bias can be defined since there is no standardcase-hardened material for which the effective case depth maybe measured.11. Keywords11.1 case depth; effective case depth; powder metallurgy;P/MFIG. 2 Schematic Plot of Microindentation Hardness versus Depth fro
36、m SurfaceB 934 04a3ASTM 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, and the riskof infringement
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39、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).B 934 04a4
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