ASTM E384-2008a 260 Standard Test Method for Microindentation Hardness of Materials.pdf

1、Designation: E 384 08aStandard Test Method forMicroindentation Hardness of Materials1This standard is issued under the fixed designation E 384; 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

2、parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers determination of the microin-dentation

3、 hardness of materials, the verification of microinden-tation hardness testing machines, and the calibration of stan-dardized test blocks.1.2 This test method covers microindentation tests madewith Knoop and Vickers indenters under test forces in the rangefrom 9.8 3 10-3to9.8N(1to1000 gf ).1.3 This

4、test method includes an analysis of the possiblesources of errors that can occur during microindentation testingand how these factors affect the accuracy, repeatability, andreproducibility of test results.NOTE 1While Committee E04 is primarily concerned with metals, thetest procedures described are

5、applicable to other materials.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 determine the applica-bility of regulatory limitation

6、s prior to use.2. Referenced Documents2.1 ASTM Standards:2C 1326 Test Method for Knoop Indentation Hardness ofAdvanced CeramicsC 1327 Test Method for Vickers Indentation Hardness ofAdvanced CeramicsE3 Guide for Preparation of Metallographic SpecimensE7 Terminology Relating to MetallographyE 122 Prac

7、tice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteristicof a Lot or ProcessE 140 Hardness Conversion Tables for Metals RelationshipAmong Brinell Hardness, Vickers Hardness, RockwellHardness, Superficial Hardness, Knoop Hardness, andScleroscope HardnessE

8、 175 Terminology of MicroscopyE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE 766 Practice for Calibrating the Magnification of a Scan-ning Electron Microscope3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, see Termino

9、logy E7.3.2 Definitions of Terms Specific to This Standard:3.2.1 calibrating, vdetermining the values of the signifi-cant parameters by comparison with values indicated by areference instrument or by a set of reference standards.3.2.2 Knoop hardness number, HK, nan expression ofhardness obtained by

10、dividing the force applied to the Knoopindenter by the projected area of the permanent impressionmade by the indenter.3.2.3 Knoop indenter, na rhombic-based pyramidal-shaped diamond indenter with edge angles of /A = 172 308and / B = 130 08 (see Fig. 1).3.2.4 microindentation hardness test, na hardne

11、ss testusing a calibrated machine to force a diamond indenter ofspecific geometry into the surface of the material beingevaluated, in which the test forces range from 1 to 1000 gf (9.83 103to 9.8 N), and the indentation diagonal, or diagonals aremeasured with a light microscope after load removal; f

12、or anymicroindentation hardness test, it is assumed that the indenta-tion does not undergo elastic recovery after force removal.NOTE 2Use of the term microhardness should be avoided because itimplies that the hardness, rather than the force or the indentation size, isvery low.3.2.5 verifying, vcheck

13、ing or testing the instrument toassure conformance with the specification.3.2.6 Vickers hardness number, HV, nan expression ofhardness obtained by dividing the force applied to a Vickersindenter by the surface area of the permanent impression madeby the indenter.1This test method is under the jurisd

14、iction of ASTM Committee E04 onMetallography and is the direct responsibility of Subcommittee E04.05 on Micro-indentation Hardness Testing.Current edition approved March 15, 2008. Published April 2008. Originallyapproved in 1969. Last previous edition approved in 2008as E 384 08.2For referenced ASTM

15、 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM

16、 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2.7 Vickers indenter, na square-based pyramidal-shapeddiamond indenter with face angles of 136 (see Fig. 2).3.3 FormulaeThe formulae presented in 3.3.1-3.3.4 fforcalculating microindentation hardnes

17、s are based upon an idealtester. The measured value of the microindentation hardness ofa material is subjected to several sources of errors. Based on Eq1-9, variations in the applied force, geometrical variationsbetween diamond indenters, and human errors in measuringindentation lengths can affect t

18、he calculated material hardness.The amount of error each of these parameters has on thecalculated value of a microindentation measurement is dis-cussed in Section 10.3.3.1 For Knoop hardness tests, in practice, test loads are ingrams-force and indentation diagonals are in micrometers. TheKnoop hardn

19、ess number is calculated using the following:HK 5 1.000 3 1033 P/Ap! 5 1.000 3 1033 P/cp3 d2! (1)orHK 5 14229 3 P/d2(2)cp5tanS/B2D2 tanS/A2D(3)FIG. 1 Knoop IndenterFIG. 2 Vickers IndenterE 384 08a2where:P = force, gf,d = length of long diagonal, m,Ap= projected area of indentation, m2,/ A = included

20、 longitudinal edge angle, 172 308,/ B = included transverse edge angle, 130 08 (see Fig. 1),andcp= indenter constant relating projected area of theindentation to the square of the length of the longdiagonal, ideally 0.07028.NOTE 3HK values for a 1-gf (9.8 3 103N) test are contained inAppendix X6. To

21、 obtain HK values when other test forces are employed,multiply the HK value from Table X6.1 for the d value by the actual testforce, g.3.3.2 The Knoop hardness, kgf/mm2is determined as fol-lows:HK 5 14.229 3 P1/d12(4)where:P1= force, kgf, andd1= length of long diagonal, mm.3.3.3 The Knoop hardness r

22、eported with units of GPa isdetermined as follows:HK 5 0.014229 3 P2/d22(5)where:P2= force, N, andd2= length of the long diagonal of the indentation, mm.3.3.4 For the Vickers hardness test, in practice, test loads arein grams-force and indentation diagonals are in micrometres.The Vickers hardness nu

23、mber is calculated as follows:HV 5 1.000 3 1033 P/As5 2.000 3 1033 P sina/2!/d2(6)orHV 5 1854.4 3 P/d2(7)where:P = force, gf,As= surface area of the indentation, m2,d = mean diagonal length of the indentation, m, anda = face angle of the indenter, 136 08 (see Fig. 2).NOTE 4HV numbers for a 1-gf (9.8

24、 3 103N) test load are containedin Appendix X6. To obtain HV values when other test forces areemployed, multiply the HV value from Table X6.2 for the d value by theactual test force, g.3.3.5 The Vickers hardness, kgf/mm2is determined as fol-lows:HV 5 1.8544 3 P1/d12(8)where:P1= force, kgf, andd1= me

25、an diagonal length of the indentations, mm.3.3.6 The Vickers hardness reported with units of GPa isdetermined as follows:HV 5 0.0018544 3 P2/d22(9)where:P2= force, N, andd2= mean diagonal length of the indentations, mm.4. Summary of Test Method4.1 In this test method, a hardness number is determined

26、based on the formation of a very small indentation by appli-cation of a relatively low force, in comparison to ordinaryindentation hardness tests.4.2 A Knoop or Vickers indenter, made from diamond ofspecific geometry is pressed into the test specimen surfaceunder an applied force in the range of 1 t

27、o 1000 gf using a testmachine specifically designed for such work.4.3 The size of the indentation is measured using a lightmicroscope equipped with a filar type eyepiece, or other typeof measuring device (see Terminology E 175).4.4 The Knoop hardness number is based upon the forcedivided by the proj

28、ected area of the indentation. The Vickershardness number is based upon the force divided by the surfacearea of the indentation.4.5 It is assumed that elastic recovery does not occur whenthe indenter is removed after the loading cycle, that is, it isassumed that the indentation retains the shape of

29、the indenterafter the force is removed. In Knoop testing, it is assumed thatthe ratio of the long diagonal to the short diagonal of theimpression is the same (see 7.1.4) as for the indenter.5. Significance and Use5.1 Hardness tests have been found to be very useful formaterials evaluation, quality c

30、ontrol of manufacturing pro-cesses and research and development efforts. Hardness, al-though empirical in nature, can be correlated to tensile strengthfor many metals, and is an indicator of wear resistance andductility.5.2 Microindentation tests extend hardness testing to mate-rials too thin or too

31、 small for macroindentation tests. Microin-dentation tests allow specific phases or constituents and regionsor gradients too small for macroindentation testing to beevaluated.5.3 Because the microindentation hardness will reveal hard-ness variations that may exist within a material, a single testval

32、ue may not be representative of the bulk hardness.6. Apparatus6.1 Test MachineThe test machine must support the testspecimen and control the movement of the indenter into thespecimen under a preselected test force, and should have a lightoptical microscope to select the desired test location and tom

33、easure the size of the indentation produced by the test. Theplane of the surface of the test specimen must be perpendicularto the axis of the indenter and the direction of the forceapplication. The plane of the test surface of test specimen mustbe level in order to obtain usable information.6.1.1 Fo

34、rce ApplicationThe test machine shall be capableof applying the following forces:6.1.1.1 The time from the initial application of the forceuntil the full test force is reached shall not exceed 10 s.6.1.1.2 The indenter shall contact the specimen at a velocitybetween 15 and 70 m/s.6.1.1.3 The full te

35、st force shall be applied for 10 to 15 sunless otherwise specified.E 384 08a36.1.1.4 For some applications it may be necessary to applythe test force for longer times. In these instances the tolerancefor the time of the applied force is 6 2s.6.1.2 Vibration ControlDuring the entire test cycle, thete

36、st machine should be protected from shock or vibration. Tominimize vibrations, the operator should avoid contacting themachine in any manner during the entire test cycle.6.2 Vickers IndenterThe Vickers indenter usually pro-duces a geometrically similar indentation at all test forces.Except for tests

37、 at very low forces that produce indentationswith diagonals smaller than about 25 m, the hardness numberwill be essentially the same as produced by Vickers machineswith test forces greater than 1 kgf, as long as the material beingtested is reasonably homogeneous. For isotropic materials, thetwo diag

38、onals of a Vickers indentation are equal in size.6.2.1 The ideal Vickers indenter is a highly polished,pointed, square-based pyramidal diamond with face angles of136 08. The effect that geometrical variations of these angleshave on the measured values of Vickers hardness are discussedin Section 10.6

39、.2.2 The four faces of the Vickers indenter shall be equallyinclined to the axis of the indenter (within 6 308) and shallmeet at a sharp point. The line of junction between oppositefaces (offset) shall be not more than 0.5 m in length as shownin Fig. 2.6.3 Knoop IndenterThe Knoop indenter does not p

40、roducea geometrically similar indentation as a function of test force.Consequently, the Knoop hardness will vary with test force.Due to its rhombic shape, the indentation depth is shallower fora Knoop indentation compared to a Vickers indentation underidentical test conditions. The two diagonals of

41、a Knoopindentation are markedly different. Ideally, the long diagonal is7.114 times longer than the short diagonal, but this ratio isinfluenced by elastic recovery. Thus, the Knoop indenter isvery useful for evaluating hardness gradients or thin coatings.6.3.1 The Knoop indenter is a highly polished

42、, pointed,rhombic-based, pyramidal diamond. The ideal included longi-tudinal edge angles are 172 308 and 130 08. The idealindenter constant, cp, is 0.07028. The effect that geometricalvariations of these angles have on the measured values ofKnoop hardness are discussed in Section 10.6.3.2 The four f

43、aces of the Knoop indenter shall be equallyinclined to the axis of the indenter (within 6 308) and shallmeet at a sharp point. The line of junction between oppositefaces (offset) shall be not more than 1.0 m in length forindentations greater than 20 m in length, as shown in Fig. 1.For shorter indent

44、ations the offset should be proportionatelyless.6.3.3 Indenters should be examined periodically and re-placed if they become worn, dulled, chipped, cracked orseparated from the mounting material.6.4 Measuring EquipmentThe test machines measuringdevice should report the diagonal lengths in 0.1 m incr

45、ementsfor indentations with diagonals from 1 to 200 m.NOTE 5This is the reported length and not the resolution of thesystem used for performing the measurements. As an example, if a lengthof 200 m corresponds to 300 filar units or pixels, the correspondingcalibration constant would be 200/300 = 0.66

46、666667. This value would beused to compute diagonal lengths, but the reported length would only bereported to the nearest 0.1 m.6.4.1 The optical portion of the measuring device shouldhave Khler illumination (see Appendix X1).6.4.2 To obtain maximum resolution, the measuring micro-scope should have

47、adjustable illumination intensity, adjustablealignment and aperture and field diaphragms.6.4.3 Magnifications should be provided so that the diago-nal can be enlarged to greater than 25 % but less than 75 % ofthe field width.7. Test Specimen7.1 For optimum accuracy of measurement, the test shouldbe

48、performed on a flat specimen with a polished or otherwisesuitably prepared surface. The surface must be free of anydefects that could affect the indentation or the subsequentmeasurement of the diagonals. Conducting tests on non-planarsurfaces is not recommended. Results will be affected even inthe c

49、ase of the Knoop test where the radius of curvature is inthe direction of the short diagonal.7.1.1 In all tests, the indentation perimeter, and the inden-tation tips in particular, must be clearly defined in the micro-scope field of view.7.1.2 The specimen surface should not be etched beforemaking an indentation. Etched surfaces can obscure the edge ofthe indentation, making an accurate measurement of the size ofthe indentation difficult. However, when determining the mi-croindentation hardness of an isolated phase or constituent, a