ASTM_E_2109_-_01_2014.pdf

Designation:E210901(Reapproved 2014)Standard Test Methods forDetermining Area Percentage Porosity in Thermal SprayedCoatings1This standard is issued under the fixed designation E2109;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 These test methods cover procedures to perform poros-ity ratings on metallographic specimens of thermal sprayedcoatings(TSCs)prepared in accordance with Guide E1920 bydirect comparison to standard images and via the use ofautomatic image analysis equipment.1.2 These test methods deal only with recommended mea-suring methods and nothing in them should be construed asdefining or establishing limits of acceptability for any mea-sured value of porosity.1.3 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 determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to MetallographyE562 Test Method for Determining Volume Fraction bySystematic Manual Point CountE1245 Practice for Determining the Inclusion or Second-Phase Constituent Content of Metals by Automatic ImageAnalysisE1920 Guide for Metallographic Preparation of ThermalSprayed Coatings3.Terminology3.1 DefinitionsFor definitions of terms used in these testmethods refer to Terminology E7.3.2 Definitions of Terms Specific to This Standard:3.2.1 halo effectunwanted detection of the perimeter ofone phase(due to a shared gray value at the phase boundary)when setting the detection limits of another.3.2.2 linear detachment,na region within a TSC in whichtwo successively deposited splats of coating material have notmetallurgically bonded.3.2.3 porosity,ncavity type discontinuities(voids)orlinear detachments within a sprayed coating.3.2.4 splat,nan individual globule of thermal sprayedmaterial that has been deposited on a substrate.4.Significance and Use4.1 TSCs are susceptible to the formation of porosity due toa lack of fusion between sprayed particles or the expansion ofgases generated during the spraying process.The determina-tion of area percent porosity is important in order to monitorthe effect of variable spray parameters and the suitability of acoating for its intended purpose.Depending on application,some or none of this porosity may be tolerable.4.2 These test methods cover the determination of the areapercentage porosity of TSCs.Method A is a manual,directcomparison method utilizing the seven standard images inFigs.1-7 which depict typical distributions of porosity inTSCs.Method B is an automated technique requiring the use ofa computerized image analyzer.4.3 These methods quantify area percent porosity only onthe basis of light reflectivity from a metallographically pol-ished cross section.See Guide E1920 for recommendedmetallographic preparation procedures.4.4 The person using these test methods must be familiarwith the visual features of TSCs and be able to determinedifferences between inherent porosity and oxides.The indi-vidual must be aware of the possible types of artifacts that maybe created during sectioning and specimen preparation,forexample,pullouts and smearing,so that results are reportedonly on properly prepared specimens.Examples of properlyprepared specimens are shown in Figs.8-10.If there are doubtsas to the integrity of the specimen preparation it is suggestedthat other means be used to confirm microstructural features.This may include energy dispersive spectroscopy(EDS),1These test methods are under the jurisdiction of ASTM Committee E04 onMetallography and are the direct responsibility of Subcommittee E04.14 onQuantitative Metallography.Current edition approved May 1,2014.Published September 2014.Originallyapproved in 2000.Last previous edition approved in 2007 as E2109 01(2007).DOI:10.1520/E2109-01R14.2For 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 to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 wavelength dispersive spectroscopy(WDS)or cryogenic frac-ture of the coating followed by analysis of the fracturedsurfaces with a scanning electron microscope(SEM).5.Apparatus5.1 Test Method ATest Method A requires a reflected lightmetallurgical microscope,upright or inverted,equipped withsuitable objectives and capable of projecting an image onto aground glass viewing screen,video monitor or image recordingmedia,such as film or video prin