1、Designation: B934 10B934 15Standard 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 adoptio
2、n 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 test method covers a procedure for determination of the effective cas
3、e depth of powder metallurgy (PM) parts.1.2 Amicroindentation hardness traverse procedure is described to determine effective case depth.This test method may be usedto determine the effective case depth for all types of hardened cases.1.3 The procedure for determining the microindentation hardness o
4、f powder metallurgy materials, as described in Test MethodB933, shall be followed.1.4 With the exception of the unit for density, for which the grams 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 purp
5、ort to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B243
6、Terminology of Powder MetallurgyB933 Test Method for Microindentation Hardness of Powder Metallurgy (PM) MaterialsE384 Test Method for Knoop and Vickers Hardness of MaterialsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions
7、 of powder metallurgy (PM) terms can be found in Terminology B243. Additional descriptive information isavailable in the Related Material section of Volume 02.05 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 inwar
8、d from the surface that has a microindentation hardness, after hardening,equal to or greater than a specified hardness.3.2.2 effective case depthperpendicular distance from the surface of the hardened case to the furthest point where amicroindentation hardness value equivalent to 50 HRC is maintaine
9、d, unless otherwise specified.4. Summary of Test Method4.1 The powder metallurgy part is sectioned and the surface prepared for examination. Microindentation hardness measure-ments are taken at various depths below the part surface. The distance where the microindentation hardness falls below theequ
10、ivalent of 50 HRC is defined as the effective case depth, unless otherwise specified.1 This test method is under the jurisdiction ofASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee B09.05on Structural Parts.Current edition approved Dec. 1
11、, 2010Oct. 1, 2015. Published March 2011November 2015. Originally approved in 2004. Last previous edition approved in 20092010 asB934 09.B934 10. DOI: 10.1520/B0934-010.10.1520/B0934-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceast
12、m.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becaus
13、eit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears
14、 at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15. Significance and Use5.1 The engineering function of many PM parts may require an exterior portion of the part to have a specified case depth andmicroindent
15、ation hardness. Measurement of effective case depth is used to determine the depth to which the microindentationhardness of the exterior portion of a part has been 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 r
16、ecommended following Test Method E384. Thetype of hardness indenter and load used shall be agreed upon between customer and producer.6.2 Calibrated Optical Instrument, Micrometer Stage, or other suitable means to measure the distance from the surface of thepart to the center of the impression with a
17、 precision of 0.025 mm.7. Test Specimen7.1 Cut a test specimen from the PM part, perpendicular to the hardened surface at a specified location, being careful to avoidany cutting or grinding procedure that would affect the original microindentation hardness.7.2 Mounting of the test specimen is recomm
18、ended for convenience in surface preparation, edge retention, and microindentationhardness measurement. Edge retention is important for proper depth measurement of the case.7.3 Grind and polish the test specimen using methods recommended in Appendix X2 of Test Method B933. The area to betraversed sh
19、ould be polished so the microindentation hardness impressions are unaffected, that is, the lighter the indenter load, thefiner the finish necessary. Care should be taken to ensure that the true area fraction of porosity is revealed throughout the entirecross-section of the specimen. It is essential
20、in surface preparation to remove all smeared metal and to identify pores clearly sothat they may be avoided during testing.7.4 The specimen should be lightly etched prior to microindentation hardness testing. Careful etching is necessary as heavyetching obscures features and interferes with the meas
21、urement of the diagonals of the indentation.7.5 For heat treated steels, swabbing with or immersion in 2 % nital for 4 to 7 s gives an appropriate structure.8. Procedure8.1 Measure microindentation hardness at a series of known intervals from the surface of the test specimen toward the interior.Take
22、 a minimum of three acceptable microindentation hardness measurements at each depth. Space the indentations so thatadjacent tests do not interfere with each other. The minimum spacing between tests is illustrated in Fig. 1. Use a calibrated opticalinstrument, micrometer stage, or other suitable mean
23、s to measure the distance from the surface of the part to the center of theimpression.8.2 Microindentation impressions should not be placed in soft regions such as copper or the center of nickel-rich regions.Randomly encountered upper bainite or fine pearlite in the martensite should not be excluded
24、 as a measurement location.FIG. 1 Minimum Spacing between IndentationsB934 1528.3 Plot microindentation hardness versus distance from the part surface (see Fig. 2). The effective case depth shall be thedistance at which the microindentation hardness falls below the equivalent of 50 HRC unless a diff
25、erent value is specified (see Note1). Plot definition will dictate the required number of readings, particularly in the critical region of effective case depth. Theprocedure described in Appendix X1 of Test Method B933 shall be used for conversion to HRC.NOTE 1No compositional change occurs in induc
26、tion hardened materialsmaterials. The hardness of martensite is affected by the carbon content ofthe steel. Some lower-carbon steels will not reach the equivalent of 50 HRC when fully hardened. All concerned parties should agree upon the specifiedeffective case depth hardness if other than 50 HRC.NO
27、TE 2For routine quality control testing, where the effective case depth is reasonably well known, a somewhat simplified method of estimatingeffective case depth may be used. This method makes the assumption that the curve that represents microindentation hardness versus depth below thesurface of the
28、 part may be regarded as a straight line in the region of the effective case hardened depth. Microindentation hardness may be measured attwo depths from the surface selected, such that, on the basis of past experience, one will be less than the estimated effective case hardened depth andone will be
29、greater. The two depths selected should lie at about equal distances from the estimated effective case hardened depth. At least fivedeterminations of microindentation hardness shall be carried out at each of the selected depths below the part surface. On a plot of microindentationhardness versus dep
30、th from the surface, draw a straight line between the average microindentation hardness value at each of the two depths and read offthe distance from the surface of the part at which the specified microindentation hardness value is reached. This is the effective case depth.NOTE 3An alternative metho
31、d may be used for routine quality control testing. Where a minimum effective case depth is specified, measure themicroindentation hardness at a distance from the surface of the part that is equal to or greater than the specified minimum depth. At least fivedeterminations of microindentation hardness
32、 shall be carried out at the desired location. If the average microindentation hardness at this depth is equalto or greater than the effective case depth hardness, the part meets the specified requirement. Where a maximum effective case depth is specified, measurethe microindentation hardness at a d
33、istance from the surface of the part that is less than the specified maximum depth in order to confirm that the parthas been case hardened. At least five determinations of microindentation hardness shall be carried out at the desired location. This averagemicroindentation hardness should be equal to
34、 or greater than that specified for the effective case hardness. If it is, measure the microindentation hardnessat a distance from the surface of the part that is equal to the specified maximum depth. At least five determinations of microindentation hardness shallbe carried out at the desired locati
35、on. If the average microindentation hardness is less than the value specified for the effective case hardness, the maximumeffective case depth specification is met. If it is greater than or equal to the specified value, the maximum effective case depth is exceeded.9. Report9.1 The report shall inclu
36、de:9.1.1 The type of material and case measured (and when possible 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 and the load used,9.1.4 The load used in testing shall be expressed as the load in grams, for ex
37、ample, HV100 gf or HK 100 gf (preferred method),or the load in kilograms, for example, HV 0.1 or HK 0.1, and9.1.5 The effective case depth to the nearest 0.1 mm and the microindentation hardness specified.FIG. 2 Schematic Plot of Microindentation Hardness versus Depth from SurfaceB934 15310. Precisi
38、on and Bias10.1 PrecisionThe precision of this test method was developed as part of a Test Methods Assurance Program (TMAP)conducted by the Standards Committee of the Metal Powder Industries Federation (MPIF) and it is published here with thepermission of MPIF. The repeatability (r) and reproducibil
39、ity (R) measurements were determined (1993) according to PracticeE691. The test sample was prepared from FL-4605 (no graphite added) at 7.1 g/cm3 and then case-carburized to develop thedesired case/core relationship. The effective case depth was determined at 50 HRC after conversion from direct micr
40、oindentationhardness values by 7 participating laboratories.The mean case depth was 0.7 mm with a repeatability of 0.1 mm 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. Fo
41、r the sametest specimen, test results from two different laboratories should not be considered differentdifferent at the 95% confidence levelunless they differ by more than 0.5 mm.10.2 BiasNo bias can be defined since there is no standard case-hardened material for which the effective case depth may
42、 bemeasured.11. Keywords11.1 case depth; effective case depth; powder metallurgy; PMSUMMARY OF CHANGESCommittee B09 has identified the location of selected changes to this standard since the last issue(B934 09B934 10) that may impact the use of this standard.(1) AFig. 1 statement on units has been a
43、dded to the Scope.updated to match that in the current version of E384.(2) All instances of P/M have been changed to the currently approved 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 connec
44、tion 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 the responsib
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46、ideration 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 International, 100 B
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