ASTM_B_946_-_11_2016.pdf

Designation:B94611(Reapproved 2016)Standard Test Method forSurface Finish of Powder Metallurgy(PM)Products1This standard is issued under the fixed designation B946;the number immediately following the designation indicates the 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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers measuring the surface finish ofpowder metallurgy(PM)products at all stages of manufactur-ing from green compact to fully hardened finished component.1.2 This test method provides the definition and schematicof some common surface finish parameters(Ra,Rt,and RzISO)1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:E691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 MPIF Standard:2MPIF Standard 58 Method for Determination of SurfaceFinish of Powder Metallurgy Products3.Significance and Use3.1 The surface finish of a component may be critical forcertain applications,affecting properties such as wearresistance,fatigue strength,and coefficient of friction.3.2 Surface finish may also be critical for componentassembly or system performance.Dimensional fit and matingsurface interaction may require certain surface finish require-ments to meet performance specifications.4.Interferences4.1 Because many conventional PM materials contain openporosity at the surface,special consideration should be takenwhen measuring surface finish.4.2 The use of a conical point stylus may result in inaccurateor inconsistent surface finish results because the sharper pointof the stylus may drop into open porosity on the surface of thecomponent.4.3 A chisel point stylus may be used for better accuracyand consistency.4.4 Because the direction of pressing may cause direction-ality in surface finish values,the direction of measurementshould be specified and reported.5.Apparatus5.1 Surface Finish Measuring Instrument.5.2 StylusChisel point,0.050 in.(1.27 mm)length and0.0004 in.6 30%(0.010 mm 6 30%)tip radius as shown inFig.1.To limit the possibility of the stylus dropping into opensurface porosity,a chisel point stylus is recommended.If acone stylus is used,filtering software shall also be used toremove the influence of open surface porosity.6.Sampling,Test Specimens,and Test Units6.1 The test surface shall be clean and free of any oil,dirt,debris,or foreign material.6.2 Sufficient surface area shall be available to permitmultiple traverses by the measuring instrument.6.3 The test surface shall be flat over a sufficient length(inaccordance with instrument instructions)to allow propermovement of the stylus.7.Procedure7.1 The PM parts manufacturer and purchaser shall agree onthe desired location and direction for surface finish measure-ment.7.2 Place the surface finish instrument in a position suitablefor measuring the test sample.7.3 Zero and verify the instrument over the surface finishrange expected for the test sample.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.05 on Structural Parts.Current edition approved April 1,2016.Published April 2016.Originallyapproved in 2006.Last previous edition approved in 2011 as B946 11.DOI:10.1520/B0946-11R16.2Available from Metal Powder Industries Federation(MPIF),105 College Rd.East,Princeton,NJ 08540,http:/www.mpif.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 7.4 Place the test sample under the stylus and then lower thestylus to the measuring position in accordance with theinstrument instructions.7.5 Measure the surface finish of the test surface.A mini-mum of three traverses at different locations is recommended.8.Report8.1 Report the surface finish to the nearest whole number inmicroinches(micrometres).Unless otherwise indicated,thesurface finish shall be Ra(average surface roughness)(see Fig.2).Depending on the type of instrument being used,othersurface finish measures may also be reported.NOTE1Rtis the maximum peak-to-valley height over the testedlength(absolute value between the highest and lowest peaks)as shown inFig.3.Rzis the ten-point height or the absolute value of the five highestpeaks and five lowest valleys over the evaluation length as shown in Fig.4.Rzis also known as the ISO ten-point height paramete