1、Designation: B 797 93 (Reapproved 2007)Standard Test Method forSurface Finger Oxide Penetration Depth and Presence ofInterparticle Oxide Networks in Powder Forged (P/F) SteelParts1This standard is issued under the fixed designation B 797; the number immediately following the designation indicates th
2、e year oforiginal adoption or, 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 metallographic method f
3、ordetermining the maximum depth of surface finger oxidepenetration and the concentration of subsurface interparticleoxide networks in critical areas of powder forged steel parts.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespons
4、ibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Document2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic Specimens3. Terminology3.1 Definitions of Terms Spec
5、ific to This Standard:3.1.1 surface finger oxidessurface finger oxides are sur-face oxides that follow prior particle boundaries into a powderforged part from the surface and cannot be removed byphysical means such as rotary tumbling. Examples of surfacefinger oxides are shown in Fig. 1.3.1.2 interp
6、article oxide networksinterparticle oxide net-works are continuous or discontinuous oxides that follow priorparticle boundaries in powder forged parts. Examples ofinterparticle oxide networks are shown in Fig. 2.4. Summary of Test Method4.1 A section representing both surface and subsurfaceregions o
7、f a critical area is cut from the powder forged part andmounted for metallographic grinding and polishing.4.2 For surface finger oxide penetration, the polished andunetched sample is examined microscopically at a magnifica-tion of 4003. The maximum depth of penetration of surfacefinger oxides is mea
8、sured.4.3 For interparticle oxide network concentration, the pol-ished and unetched sample is examined microscopically at amagnification of 200 to 4003 to determine the presence ofinterparticle oxide networks.5. Significance and Use5.1 The presence of surface finger oxide penetration andinterparticl
9、e oxide networks are two of the properties used toevaluate powder forged steel parts for proper processing.Maximum acceptable depths of penetration of surface fingeroxide penetration and acceptable concentrations of subsurfaceinterparticle oxide networks depend on the component and itsservice enviro
10、nment.5.2 Results of tests may be used to qualify parts forshipment.6. Apparatus6.1 Equipment for the metallographic preparation of testspecimens.6.2 A metallographic microscope permitting observationand measurement up to a magnification of 4003.7. Sampling7.1 A metallographic specimen shall be remo
11、ved from thepowder forged part to cover each designated critical area.Critical areas shall be defined by the applicable part drawing orthe purchaser order. Specimens shall be taken from the powderforged part in the condition in which it is to be supplied. Thepolished surface of the specimens shall b
12、e parallel to theforging direction, that is, parallel to the direction of travel ofthe forging punch.8. Procedure8.1 Preparation of SpecimensIn mounting the specimenfor grinding and polishing, protection from rounding the edgeof the part is essential. In polishing the specimen it is importantthat a
13、clean polish be obtained and that edge detail of the part1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.11 on Near Full Density Powder Metallurgy Materials.Current edition approved Marc
14、h 15, 2007. Published April 2007. Originallyapproved in 1988. Last previous edition approved in 2002 as B 797 93 (2002).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
15、 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.FIG. 1 Example of Surface Finger Oxide Penetration Extending Inward from the Powder Forged Part Surface (Shown more clearly at
16、high magnification.)B 797 93 (2007)2FIG. 2 Example of Interparticle Oxide Networks Within a Powder Forged Part (Shown more clearly at high magnification.)B 797 93 (2007)3not be destroyed. Specimens shall be examined in the as-polished condition, free of the effects of any prior etching (ifused). It
17、is recommended that the procedures described inMethods E3be followed. Automated grinding and polishingprocedures are recommended.8.2 Measurement of Surface Finger Oxide PenetrationDepthScan the perimeter of the metallographic specimen,initially at a magnification of 1003, and carefully examineeach d
18、esignated critical area at a higher magnification, forexample, 4003. Measure the maximum depth of penetration ofsurface finger oxides from the finished part surface in mi-crometers for each designated critical area.8.3 Measurement of Interparticle Oxide NetworkConcentrationScan the perimeter of the
19、metallographicspecimen at a magnification of 1003. Carefully examine eachdesignated critical area at a higher magnification, for example,200 to 4003. Record the presence of any interparticle oxidenetworks in the designated critical areas.9. Report9.1 The test report shall include the following infor
20、mation:9.1.1 Identification of the part and location of the testspecimen,9.1.2 The maximum depth of penetration of surface fingeroxides from the finished part surface in micrometers for eachdesignated critical area, and9.1.3 The presence or lack of interparticle oxide networks ineach designated crit
21、ical area. If interparticle oxide networks arepresent, if possible, prepare a photomicrograph for recordpurposes.10. Precision and Bias10.1 The precision and bias that can be expected throughuse of the test method for determining the maximum depth ofsurface finger oxide penetration is currently unde
22、r review bySubcommittee B09.11 on Near Full Density Powder Metal-lurgy Parts.10.2 The test method for interparticle oxide network con-centration is a “go-no go” test designed to give a qualitativeestimate. This method will be subject to sample preparationcare and to interpretation.11. Keywords11.1 i
23、nterparticle oxide networks; powder-forged (P/F) steelparts; surface finger oxidesASTM 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 v
24、alidity 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 responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your c
25、omments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments ha
26、ve 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 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 797 93 (2007)4
