ASTM B931-09
(Test Method)Standard Test Method for Metallographically Estimating the Observed Case Depth of Ferrous Powder Metallurgy (P/M) Parts
Standard Test Method for Metallographically Estimating the Observed Case Depth of Ferrous Powder Metallurgy (P/M) Parts
SIGNIFICANCE AND USE
The engineering function of many PM parts may require an exterior portion of the part to have a hardened layer. Where case hardening produces a distinct transition in the microstructure, metallographic estimation of the observed case depth may be used to check the depth to which the surface has been hardened.
SCOPE
1.1 A metallographic method is described for estimating the observed case depth of ferrous powder metallurgy (PM) parts. This method may be used for all types of hardened cases where there is a discernible difference between the microstructure of the hardened surface and that of the interior of the part.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: B931 − 09
StandardTest Method for
Metallographically Estimating the Observed Case Depth of
1
Ferrous Powder Metallurgy (PM) Parts
This standard is issued under the fixed designation B931; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope surfaceoftheparttothepointatwhichadiscernibledifference
in the microstructure of the material is observed.
1.1 Ametallographicmethodisdescribedforestimatingthe
observed case depth of ferrous powder metallurgy (PM) parts.
5. Significance and Use
Thismethodmaybeusedforalltypesofhardenedcaseswhere
there is a discernible difference between the microstructure of 5.1 TheengineeringfunctionofmanyPMpartsmayrequire
the hardened surface and that of the interior of the part.
an exterior portion of the part to have a hardened layer.Where
case hardening produces a distinct transition in the
1.2 This standard does not purport to address all of the
microstructure,metallographicestimationoftheobservedcase
safety concerns, if any, associated with its use. It is the
depth may be used to check the depth to which the surface has
responsibility of the user of this standard to establish appro-
been hardened.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
6. Apparatus
2. Referenced Documents
6.1 Equipment for the metallographic preparation of test
2
specimens—see Appendix X1.
2.1 ASTM Standards:
B243Terminology of Powder Metallurgy
6.2 Metallographic Microscope, permitting observation and
E407Practice for Microetching Metals and Alloys
measurement at a magnification of 100×.
3. Terminology
7. Reagents and Materials
3.1 Definitions—Definitions of powder metallurgy (PM)
7.1 Etchants such as 2 to 5 % nital, nital/picral
terms can be found in Terminology B243.Additional descrip-
combinations, or other suitable etchants. For more information
tive information is available in the Related Material section of
on suitable etchants refer to Practice E407.
Vol 02.05 of the Annual Book of ASTM Standards.
3.2 Themetallographicallyestimatedobservedcasedepthis 8. Test Specimens
defined as the distance from the surface of the part to the point
8.1 Cut a test specimen from the PM part, perpendicular to
where, at a magnification of 100X, there is a discernible
the hardened surface at a specified location, being careful to
difference in the microstucture of the material.
avoid any cutting or grinding procedure that would affect the
original microstructure.
4. Summary of Test Method
8.2 Mounting of the test specimen is recommended for
4.1 Thepowdermetallurgypartissectionedandthesurface
convenience in surface preparation and edge retention. Edge
prepared for metallographic evaluation. The metallographic
retention is important for proper measurement of the observed
specimen is etched and the distance is measured from the
case depth.
9. Procedure
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
9.1 Grind and polish the test specimen using methods such
Powders and Metal Powder Productsand is the direct responsibility of Subcommit-
tee B09.05 on Structural Parts.
as those summarized in Appendix X1.
Current edition approved Feb. 15, 2009. Published April 2009. Originally
9.2 Etch the specimen with etchants such as 2 to 5% nital
approved in 2003. Last previous edition approved in 2003 as B931–03. DOI:
10.1520/B0931-09.
or nital/picral combinations.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
9.2.1 Observed Case Depth:
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
9.2.1.1 Examine the surface region of the part at a magni-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. fication of 100×.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
B931 − 09
9.2.1.2 Measure the distance from the surface of the part to 10.1.2 The type of etchant used,
the point where there is a discernible difference in the micro-
10.1.3 The location of the measurement, and
structure of the material.
10.1.4 The metallographically estimated observed case
NOTE 1—The nature and amount of intermediate transformation prod- depth to the nearest 0.1 mm.
ucts will depend on the material being heat treated, its density, and the
type of surface hardening treatment being used. The sharpness of the
11. Precision and Bias
change in the microstructure at the point of transition will therefore vary.
The microstructure expected at this
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation:B931–03 Designation:B931–09
Standard Test Method for
Metallographically Estimating the Observed Case Depth of
1
Ferrous Powder Metallurgy (P/M)(PM) Parts
This standard is issued under the fixed designation B 931; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Ametallographicmethodisdescribedforestimatingtheobservedcasedepthofferrouspowdermetallurgy(P/M)(PM)parts.
This method may be used for all types of hardened cases where there is a discernible difference between the microstructure of the
hardened surface and that of the interior of the part.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
B 243 Terminology of Powder Metallurgy
E 407 Practice for Microetching Metals and Alloys
3. Terminology
3.1 Definitions—Definitionsofpowdermetallurgy(P/M)(PM)termscanbefoundinTerminologyB 243.Additionaldescriptive
information is available in the Related Material section of Vol 02.05 of the Annual Book of ASTM Standards.
3.2 The metallographically estimated observed case depth is defined as the distance from the surface of the part to the point
where, at a magnification of 100X, there is a discernible difference in the microstucture of the material.
4. Summary of Test Method
4.1 The powder metallurgy part is sectioned and the surface prepared for metallographic evaluation. The metallographic
specimen is etched and the distance is measured from the surface of the part to the point at which a discernible difference in the
microstructure of the material is observed.
5. Significance and Use
5.1 The engineering function of many P/MPM parts may require an exterior portion of the part to have a hardened layer.Where
case hardening produces a distinct transition in the microstructure, metallographic estimation of the observed case depth may be
used to check the depth to which the surface has been hardened.
6. Apparatus
6.1 Equipment for the metallographic preparation of test specimens—see Appendix X1.
6.2 Metallographic Microscope, permitting observation and measurement at a magnification of 1003.
7. Reagents and Materials
7.1 Etchants such as 2 to 5 % nital, nital/picral combinations, or other suitable etchants. For more information on suitable
etchants refer to Practice E 407.
8. Test Specimens
8.1 Cut a test specimen from the P/MPM part, perpendicular to the hardened surface at a specified location, being careful to
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibility of Subcommittee
B09.05 on Structural Parts.
Current edition approved Oct. 1, 2003. Published October 2003.
Current edition approved Feb. 15, 2009. Published April 2009. Originally approved in 2003. Last previous edition approved in 2003 as B 931–03.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 02.05.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 ----------------------
B931–09
avoid any cutting or grinding procedure that would affect the original microstructure.
8.2 Mounting of the test specimen is recommended for convenience in surface preparation and edge retention. Edge retention
is important for proper measurement of the observed case depth.
9. Procedure
9.1 Grind and polish the test specimen using methods such as those summarized in Appendix X1.
9.2 Etch the specimen with etchants such as 2 to 5 % nital or nital/picral combinations.
9.2.1 Observed Case Depth:
9.2.1.1 Examine the surface region of the part at a magnification of 1003.
9.2.1.2 Measurethedistancefromthesurfaceoftheparttothepointwherethereisadiscernibledifferenceinthemicrostructure
of the material.
NOTE 1—The nature and amount of intermediate transformation products will depend on the material being heat treated, its density, a
...
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