ASTM_B_578_-_87_2015.pdf

Designation:B57887(Reapproved 2015)Standard Test Method forMicrohardness of Electroplated Coatings1This standard is issued under the fixed designation B578;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.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers the determination of the hard-ness of metallic coatings upon various substrates.The mea-surements are made with the Knoop indenter under a test loadof 0.245 N(25 gf)or 0.981 N(100 gf).1.2 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:E384 Test Method for Knoop and Vickers Hardness ofMaterials23.Special Requirements3.1 In addition to the requirements listed herein,the testmethod shall be performed in accordance with Test MethodE384.3.1.1 The measurement shall be made on the cross sectionwith the long diagonal of the indentation parallel to thesubstrate using a Knoop indenter.NOTE1When a nondestructive test is necessary,the measurementmay be made normal to the surface provided that the whole of theindentation is clearly delineated in the field of the microscope at themagnification specified in Test Method E384,and the coating thickness isat least 0.7 that of the long diagonal.The outlines of the indentation mustbe sharp and undistorted by any mechanical effects resulting from thethinness of the coating such as“butterfly”fractures,etc.Values obtainedfrom measurements made normal to the electroplated surface may not beequivalent to those obtained on microsections and are not,therefore,reportable according to Section 6.3.1.2 The thickness of the coating shall be at least 38 m forsoft coatings such as gold,copper,and silver,and 25 m forhard coatings such as nickel,cobalt,iron,and hard gold.Thisis approximately equivalent to 0.6 times the length of the longKnoop diagonal.3.1.3 Make the indentation near the center of the crosssection of the coating.3.2 No single test load is applicable to all coatings.Use aload of 0.245 N for soft coatings(from 50 to 300 HK)and aload of 0.981 N for hard coatings(greater than 300 HK).3.2.1 A load of less than 0.245 N is not recommended.However,when the length of the diagonal is great enough at aload of 0.245 N,which may occur for very soft coatings suchas tin and indium,a lighter load or a lower magnification shallbe specified provided the requirements of 3.3 are met.Whentesting extremely hard coatings,a load greater than 0.981 Nmay be used provided this is specified in the purchase order.The Knoop hardness number decreases appreciably with loadsfrom 0.245 N to 0.981 N especially for the higher hardnessnumbers.3.3 Measure the length of the long diagonal to within 0.25m or 0.4%,whichever is larger,at the magnification specifiedin Test Method E384.3.4 When readings are taken in a direction parallel to thesubstrate,space them from each other by at least the length ofthe long diagonal.When two readings are taken in the directionof the short axis,separate them by at least the length of thediagonal perpendicular to the substrate(short diagonal).Insuch cases,the distance from the substrate and from the outersurface of the coating to an edge of the indentation shall be atleast the width of the short diagonal.3.5 If the electroplated coating is cracked,or if cracks or“butterfly”markings(see 7.2 of Test Method E384)appearwhen the indentation load is applied or removed,the hardnessmeasurement is invalid.4.Preparation of Test Specimen4.1 Overplate the specimen to a thickness of at least 12 mwith a metal of a contrasting color whose hardness approxi-mates that of the coating.1This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 onTest Methods.Current edition approved March 1,2015.Published April 2015.Originallyapproved in 1973.Last previous edition approved in 2009 as B578 87(2009).DOI:10.1520/B0578-87R15.2For 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 4.2 Cut out a section of the specimen approximately per-pendicular to the electroplated coating.4.3 Mount and polish the section as described in TestMethod E384.NOTE2Procedures 4.1 and 4.2 are interchangeable at the discretion ofthe