ASTM B797-93(1998)

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: B 797 – 93 (Reapproved 1998)
Standard Test Method for
Surface Finger Oxide Penetration Depth and Presence of
Interparticle Oxide Networks in Powder Forged (P/F) Steel
Parts
This standard is issued under the fixed designation B 797; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope magnification of 200 to 4003 to determine the presence of
interparticle oxide networks.
1.1 This test method covers a recognized metallographic
method for determining the maximum depth of surface finger
5. Significance and Use
oxide penetration and the concentration of subsurface interpar-
5.1 Presence of surface finger oxide penetration and inter-
ticle oxide networks in critical areas of powder forged steel
particle oxide networks are two of the properties used to
parts.
evaluate powder forged steel parts for proper processing.
1.2 This standard does not purport to address all of the
Maximum acceptable depths of penetration of surface finger
safety concerns, if any, associated with its use. It is the
oxide penetration and acceptable concentrations of subsurface
responsibility of the user of this standard to establish appro-
interparticle oxide networks depend on the component and its
priate safety and health practices and determine the applica-
service environment.
bility of regulatory limitations prior to use.
5.2 Results of tests may be used to qualify parts for
2. Referenced Document shipment.
2.1 ASTM Standards:
6. Apparatus
E 3 Methods of Preparation of Metallographic Specimens
6.1 Equipment for the metallographic preparation of test
3. Terminology specimens.
6.2 A metallographic microscope permitting observation
3.1 surface finger oxides—surface finger oxides are surface
and measurement up to a magnification of 400 diameters.
oxides that follow prior particle boundaries into a powder
forged part from the surface and cannot be removed by
7. Sampling
physical means such as rotary tumbling. Examples of surface
7.1 A metallographic specimen shall be removed from the
finger oxides are shown in Fig. 1.
powder forged part to cover each designated critical area.
3.2 interparticle oxide networks—interparticle oxide net-
Critical areas shall be defined by the applicable part drawing or
works are continuous or discontinuous oxides which follow
the purchaser order. Specimens shall be taken from the powder
prior particle boundaries in powder forged parts. Examples of
forged part in the condition in which it is to be supplied. The
interparticle oxide networks are shown in Fig. 2.
polished surface of the specimens shall be parallel to the
4. Summary of Test Method forging direction, that is, parallel to the direction of travel of
the forging punch.
4.1 A section representing both surface and subsurface
regions of a critical area is cut from the powder forged part and
8. Procedure
mounted for metallographic grinding and polishing.
8.1 Preparation of Specimens—In mounting the specimen
4.2 For surface finger oxide penetration, the polished and
for grinding and polishing, protection from rounding the edge
unetched sample is examined microscopically at a magnifica-
of the part is essential. In polishing the specimen it is important
tion of 4003. The maximum depth of penetration of surface
that a clean polish be obtained and that edge detail of the part
finger oxides is measured.
not be destroyed. Specimens shall be examined in the as-
4.3 For interparticle oxide network concentration, the pol-
polished condition, free of the effects of any prior etching (if
ished and unetched sample is examined microscopically at a
used). It is recommended that the procedures described in
Methods E 3 be followed. Automated grinding and polishing
This test method is under the jurisdiction of ASTM Committee B-9 on Metal
procedures are recommended.
Powders and Metal Powder Products and is the direct responsib
...