ASTM B931-14

Standard Test Method for Metallographically Estimating the Observed Case Depth of Ferrous Powder Metallurgy (PM) Parts

SIGNIFICANCE AND USE
5.1 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 With the exception of the values for grit size for which the U.S. standard designation is the industry standard, the values stated in SI units are to be regarded as standard.  
1.3 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.

General Information

• Status: Historical
• Publication Date: 31-Aug-2014
• ICS: 77.160 - Powder metallurgy
• Technical Committee: B09 - Metal Powders and Metal Powder Products
• Drafting Committee: B09.05 - Structural Parts

Relations

• Replaces: ASTM B931-09 - Standard Test Method for Metallographically Estimating the Observed Case Depth of Ferrous Powder Metallurgy (P/M) Parts
• Effective Date: 01-Sep-2014

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: B931 − 14
Standard Test 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* 4. Summary of Test Method
1.1 Ametallographicmethodisdescribedforestimatingthe 4.1 Thepowdermetallurgypartissectionedandthesurface
observed case depth of ferrous powder metallurgy (PM) parts. prepared for metallographic evaluation. The metallographic
Thismethodmaybeusedforalltypesofhardenedcaseswhere specimen is etched and the distance is measured from the
there is a discernible difference between the microstructure of surfaceoftheparttothepointatwhichadiscernibledifference
the hardened surface and that of the interior of the part. in the microstructure of the material is observed.
1.2 With the exception of the values for grit size for which
5. Significance and Use
the U.S. standard designation is the industry standard, the
5.1 TheengineeringfunctionofmanyPMpartsmayrequire
values stated in SI units are to be regarded as standard.
an exterior portion of the part to have a hardened layer.Where
1.3 This standard does not purport to address all of the
case hardening produces a distinct transition in the
safety concerns, if any, associated with its use. It is the
microstructure,metallographicestimationoftheobservedcase
responsibility of the user of this standard to establish appro-
depth may be used to check the depth to which the surface has
priate safety and health practices and determine the applica-
been hardened.
bility of regulatory limitations prior to use.
6. Apparatus
2. Referenced Documents
6.1 Equipment for the metallographic preparation of test
2
2.1 ASTM Standards:
specimens—see Appendix X1.
B243Terminology of Powder Metallurgy
6.2 Metallographic Microscope, permitting observation and
E177Practice for Use of the Terms Precision and Bias in
measurement at a magnification of 100×.
ASTM Test Methods
E407Practice for Microetching Metals and Alloys
7. Reagents and Materials
7.1 Etchants such as 2 to 5 % nital, nital/picral
3. Terminology
combinations, or other suitable etchants. For more information
3.1 Definitions—Definitions of powder metallurgy (PM)
on suitable etchants refer to Practice E407.
terms can be found in Terminology B243. Additional descrip-
tive information is available in the Related Material section of
8. Test Specimens
Vol 02.05 of the Annual Book of ASTM Standards.
8.1 Cut a test specimen from the PM part, perpendicular to
3.2 Themetallographicallyestimatedobservedcasedepthis
the hardened surface at a specified location, being careful to
defined as the distance from the surface of the part to the point
avoid any cutting or grinding procedure that would affect the
where, at a magnification of 100X, there is a discernible
original microstructure.
difference in the microstucture of the material.
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
1
This test method is under the jurisdiction of ASTM Committee B09 on Metal
case depth.
Powders and Metal Powder Products and is the direct responsibility of Subcom-
mittee B09.05 on Structural Parts.
Current edition approved Sept. 1, 2014. Published September 2014. Originally 9. Procedure
approved in 2003. Last previous edition approved in 2009 as B931–09. DOI:
9.1 Grind and polish the test specimen using methods such
10.1520/B0931-14.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or as those summarized in Appendix X1.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
9.2 Etch the specimen with etchants such as 2 to 5% nital
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. or nital/picral combinations.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B931 − 14
9.2.1 Observed Case Depth:
Repeatability
Repeatability
A
Average Standard Devia-
9.2.1.1 Examine the surface region of the part at a magni-
Limit
tion
fication of 100×.
x¯s r
r
9.2.1.2 Measure the distance from the surface of the part to
Sprocket A 880 39.2 110
Sprocket B 560 42.3 120
the point where there is a discernible difference in the micro-
A
structure of the material. The average of the laboratories’ calculated averages.
N
...

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. 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 − 09 B931 − 14
Standard Test 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. 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 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 With the exception of the values for grit size for which the U.S. standard designation is the industry standard, the values
stated in SI units are to be regarded as standard.
1.3 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:
B243 Terminology of Powder Metallurgy
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E407 Practice for Microetching Metals and Alloys
3. Terminology
3.1 Definitions—Definitions of powder metallurgy (PM) terms can be found in Terminology B243. Additional descriptive
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 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.
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 100×.
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 Feb. 15, 2009Sept. 1, 2014. Published April 2009September 2014. Originally approved in 2003. Last previous edition approved in 20032009
as B931–03.–09. DOI: 10.1520/B0931-09.10.1520/B0931-14.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
B931 − 14
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 E407.
8. Test Specimens
8.1 Cut a test specimen from the PM part, perpendicular to the hardened surface at a specified location, being careful to 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.
...