Materials' VickersHardnessandKnoopHardnessofMetallic StandardTestMethodsfor
This standard is issed under the fixed desigration E92; the number immediately following the designation indicates the year of originaladoption ot in the case of revision the year of last revision A number in parentheses indicates the year of last rcappeoval. A superscript
epsilon (e) indicates an editorial change since the last revision or reapproval.
This stand hr bem opprved for ase by agecier of te U.S. Deprmnr of Defense.
1. Scope*
continued mon usage force values in gf and kgf units areprovided for information and much of the discussion in thisstandard as well as the method of reporting the test results refers to these units.
1.1 These test methods cover the determination of theVickers hardness and Knoop hardness of metallic materials by the Vickers and Knoop indentation hardness principles. Thisstandad provides the requirements for Vickers and Knoophardness machines and the procedures for performing Vickers and Knoop hardness tests.
defined in terms of the test force in kilogram-force (kgf) and the surface Nor 1The Vickers and Knoop hardness numbers were originallyarea or prjted ara in mllmtres squed (mm²) Today the hars numbers are internationally defined in terms of SI units that is the testforce units are kilogram-force (kgf) and gram-force (gf). When Newton force in Newtons (N). However in practice the most monly usedunits of force are used the force must be divided by the conversion factor 9.80665 N/kgf.
1.2 This standard includes additional requirements in an-nexes:
Verification of Vickers and Knoop Hardness Testfing MachinesStandsrdization of Vickers and Knoop Indenters Vickers and Knoop Hardness Standardizing Machines Standardization of Vickers and Knoop Hardness Test BlocksCorection Faclors for Vickers Hardness Tests Made on Spherical and Cytindrical Surfaces
procedures are essentially identical for both the Vickers and 1.7The test principles tsting procedures and verificatintwo tests are the geometries of the respective indenters the Knoop hardness tests. The significant differences between themethod of calculation of the hardness numbers and thatVickers hardness may be used at higher force levels than Knoop hardness.
appendix which relates to the Vickers and Knoop hardness 1.3 This standard includes nonmandatory information in antests:
materials the test procedures described are applicable to other materials. Nore 2While Committee E28 is primarily concerned with metallicC1326 and C1327 for ceramic testing. Othermaterials may require special considerations for cxample see
Examples f Proceduresfor Detemining Vckers and Knoop Hardness Uncertainty Appendix X1
utilizing test forces ranging from 9.807 × 10-3 N to 1176.80 N 1.4 This test method covers Vickers hardness tests made(1 gf to 120 kgf) and Knoop hardness tests made utilizing test forces from 9.807 × 10? N to 19.613 N (1 gf to 2 kgf).
safery concerns jf any associated with its ase. Ir is the 1.8 This standard does not purport to address all of theresponsibility of the user of this standard o establish appro-biliry of regulatory limitations prior to use. priote sfety and health proctices and determine the applic-
1.5 Additional information on the procedures and guidancewhen testing in the microindentation force range (forces ≤ 1Microindentation Hardness of Materials. kgf) may be found in Test Method E384 Test Method for
dance with internationally recognized principles on standord- 1.9 This interncrional stcncdcrd was developed in accor-ization established in the Decision on Principles for the Development of International Standards Guides and Re-mendotions issued by the World Trade Organization TechunicalBarriers to Trade (TBT) Commintee.
were developed the force levels were specified in units of 1.6 UnirsWhen the Vickers and Knoop hardness testsgrams-force (gf) and kilograms-force (kgf). This standardspecifies the units of force and length in the Intermational System of Units (SI); that is force in Newtons (N) and length in mm or μm. However because of the historical precedent and
2. Referenced Documents
2.1 ASTM Srandards:2
-17
C1326 Test Method for Knoop Indentation Hardness ofAdvanced CeramicsC1327 Test Method for Vickers Indentation Hardness of Advanced CeramicsE3 Guide for Preparation of Metallographic Specimens E6 Terminology Relating to Methods of Mechanical TestingE29 Practice for Using Significant Digits in Test Data to E7 Terminology Relating to MetallographyE74 Practice of Calibration of Force-Measuring Instruments Determine Conformance with Specificationsfor Verifying the Force Indication of Testing MachinesE140 Hardness Conversion Tables for Metals Relationship Among Brinell Hardness Vickers Hardness RockwellHardness. Superficial Hardness Knoop Hardness Sclero- scope Hardness and Leeb HardnessE175 Terminology of Microscopy E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE384 Test Method for Microindentation Hardness of Mate- rialsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 ISO Standards:ISO 6507-1 Metallic Materials-Vickers hardness Test Part 1: Test MethodISO/IEC 17011 Conformity Assessment-General Require- ments for Accreditation Bodies Accrediting ConformityISO/IEC 17025 General Requirements for the Competence Assessment Bodiesof Testing and Calibration Laboratories
3.1.4 Vickers hardness mumber HV nthe calculated resultfrom a Vickers hardness test which is proportional to the testforce applied to the Vickers indenter divided by the surface area of the permanent indentation made by the indenter afterremoval of the test force.
3.1.4.1 DiscassionThe surface area of the permanent in-dentation made by the Vickers indenter is calculated basedprojected area of the indentation. partly on the measured mean length of the two diagonals of the
a Vickers square-based pyramidal diamond indenter having 3.1.5 Vickers hardness fest n-an indentation test in whichspecified face angles is forced under specified conditions intothe surface of the test material and after removal of the test force the lengths of the two diagonals of the projected area ofthe indentation are measured to calculate the Vickers hardness number.
3.2 Definitions of Terms Specific to This Standard:
known standard through verification or calibration. 3.2.1 standardization n-to bring in conformance to a
3.2.2 microindentation hardness test na hardness test normally in the Vickers or Knoop scales using test forces in the range of 9.807 × 103 to 9.807 N (1 to 1000 gf).
3.2.3 macroindention hardness test a hardness test using s tation tests include Vickers Rockwell and Brinell.
Norme 3Use of the term microhardness should be avoided because itimplies that the hardness rather than the force or the indentation size is very low.
Vickers) and the test force (kgf). 3.2.4 scale n-a specific bination of indenter (Knoop or
3. Terminology and Equations
terms used in this test method see Terminology E6 and 3.1 Definizions of Terms-For the standard definitions ofTerminology E7.
as using a Vickers indenter and a 10 kgf test force and HK 0.1 3.2.4.1 DiscaussionFor example HV 10 is a scale definedis a scale defined as using a Knoop indenter and a 100 gf testforce. See 5.10 for the proper reporing of the hardness level and scale.
from measurements of area or depth of the indentation made by 3.1.1 indentarion hardness nthe hardness as evaluatedspecified static loading conditions. forcing a specified indenter into the surface of a material under
3.2.5 as-found condition the state of the hardness ma-o supe uuue uu ue uoad o oad chine as reflected by the initial verification measurements maderepairs associated with an indirect verification.
3.1.2 Knoop hardness mamber; HK nthe calculated resultfrom a Knoop hardness test which is proportional to the test force applied to the Knoop indenter divided by the projectedarea of the permanent indentation made by the indenter after removal of the test force.
3.2.6 hardness machine na machine capable of perform-ing a Vickers or Knoop hardness test.
indentation made by the Knoop indenter is calculated based 3.1.2.1 DiscassionThe projected area of the permanentpartly on the measured length of the long diagonal of theprojected area of the indentation.
hardness machine used for general testing purposes. 3.2.7 hardness testing machine na Vickers or Knoop
3.2.8 hardness standardizing machine n-a Vickers orKnoop hardness machine used for the standardization of Vickers or Knoop hardness test blocks.
3.1.3 Knoop hardness Iesr nan indentation test in which aKnoop rhombic-based pyramidal diamond indenter having specified edge angles is forced under specified conditions intothe surface of the test material and after removal of the testthe indentation is measured to calculate the Knoop hardness force the length of the long diagonal of the projected area ofnumber.
3.2.8.1 DiscussionA hardness standardizing machine dif-fers from a hardness testing machine by having tighter toler- ances on certain parameters.
3.3 Equations:
ments d d -. d is calculated as: 3.3.1 The average d of a set of n diagonal length measure-
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where:
where:
4. Significance and Use
where each of the individual diagonal measurements d d2 . d is the mean of the two diagonal length measurements inthe case of a Vickers indentation or is the long diagonal length measurement in the case of a Knoop indentation.
Knoop hardness machine at each hardness level under the 3.3.2 The repeatability R in the performance of a Vickers ornal measurements made on a standardized test block as part of particular verification conditions is determined from x diago-a performance verification. The repeatability is estimated as thepercent range of n diagonal measurements with respect to the measured average hardness value as:
= the longest diagonal length measurement made on thedn = the shortest diagonal length measurement made on standardized test block = the average (see 3.3.1) of the n diagonal length the standardized test block andmeasurements made on the standardized test block.
hardness machine at each hardness level relative to a standard- 3.3.3 The error E in the performance of a Vickers or Knoopized reference value is calculated as a percent error determinedS
d = the average (sce 3.3.1) of n diagonal length mea-surements made on a standardized test block as part of a perfommance verification andds = the certified diagonal length reported for the stan-12d J = absolute value (non-negative value without regard dardized test block.to its sign) of the difference between d and d
very useful for materials evaluation quality control of manu- 4.1 Vickers and Knoop hardness tests have been found to befacturing processes and research and development efforts. Hardness although empirical in nature can be correlated toresistance and ductility. tensile strength for many metals and is an indicator of wear
4.2 Microindentation hardness tests extend testing to mate-rials that are too thin or too small for macroindentation hardness tests. Microindentation hardness tests also allowspecific phases or constituents and regions or gradients tooRemendations for microindentation testing can be found in small for macroindentation hardness testing to be evaluated.Test Method E384.
hardness variations that may exist within a material a single 4.3 Because the Vickers and Knoop hardness will revealtest value may not be representative of the bulk hardness.
4.4 The Vickers indenter usually produces essentially thesame hardness number at all test forces when testing homoge-neous material except for tests using very low forces (below
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25 gf) or for indentations with diagonals smaller than about 25μm (see Test Method E384). For isotropic materials the twodiagonals of a Vickers indentation are equal in length.
4.5 The Knoop indenter usually produces similar hardnessnumbers over a wide range of test forces but the numbers tendto rise as the test force is decreased. This rise in hardness number with lower test forces is often more significant whentesting higher hardness materials and is increasingly more significant when using test forces below 50 gf (see Test MethodE384).
4.6 The elongated four-sided rhombohedral shape of theKnoop indenter where the length of the long diagonal is 7.114times greater than the short diagonal produces narrower and shallower indentations than the square-based pyramid Vickersindenter under identical test conditions. Hence the Knoop hardness test is very useful for evaluating hardness gradientsVickers indentations by orienting the Knoop indentations with since Knoop indentations can be made closer together thanthe short diagonals in the direction of the hardness gradient.
5. Principle of Test and Apparatus
5.1 Vickers and Knoop Hardness Test PrincipleThe gen-test consists of two steps. eral principle of the Vickers and Knoop indentation hardness
into contact with the test specimen in a direction normal to the 5.1.1 Step 1The applicable specified indenter is brought surface and the test force F is applied. The test force is held fora specified dwell time and then removed.
5.1.2 Step 2For the Vickers hardness test the lengths ofthe two diagonals are measured and the mean diagonal length is calculated which is used to derive the Vickers hardnessvalue. For the Knoop hardness test the length of the long diagonal is measured which is used to derive the Knoophardness value.
when the indenter is removed after the loading cycle. However 5.1.3 Most materials will exhibit some elastic recoveryfor the purposes of calculating the hardness results from the indentation diagonal lengths it is assumed that the indentationKnoop testing it is assumed that the ratio of the long diagonal retains the shape of the indenter after the force is removed. Into the short diagonal of the indentation is the same as for theindenter.
5.2 Testing Machine-The testing machine shall support thespecimen under a preselected test force and should have a light test specimen and control the movement of the indenter into theoptical microscope to select the desired test location and toplane of the surface of the test specimen should be perpendicu- measure the size of the indentation produced by the test. Theapplication. lar to the axis of the indenter which is the direction of the force
5.2.1 See the equipment manufacturer’s instruction manualfor a description of the machine’s characteristics limitations spd Suedo sanoodsu pre
5.3 Indenters:
5.3.1 Indenters for general Vickers or Knoop hardnesstesting shall ply with the requirements of a Class Bindenter or better in accordance with Annex A3.
TABLE 1 Standard Hardness Scales and Test Forces
5.3.2 Vickers IndenterThe ideal Vickers indenter (see Fig.A3.1) is a highly polished pointed square-based pyramidaldiamond with face angles of 136° 0”.
Vickers Knoop Test fore Approximate Test force ApproximateHV 0.001 scale HK 0.001 scale^ 0.009807 (N) 0.001 (kgf) Test force (9)HV 0.015 HV 0.01 HK 0.015 HK 0.01 0.09807 0.1471 0.01 10 15 190/0AH HV 0.02 HV 0.025 HK 0.025 HK 0.02 0.1961 0.2451 0.02 0.025 20 25HV 0.1 HV 0.2 HK 0.05 HK 0.1 HK 0.2 0.4903 0.9807 1.961 0.06 0.1 200 100 50HV 0.3 HV 0.5 HK 0.3 HK 0.5 2.942 4.903 0.2 0.3 0.5 300 500 HV 1 HV 2 HK 2 HK 1 9.807 19.61 1 2 2000 1000HV 3 HV 5 HV 10 29.41 49.03 98.07 3 10 5HV 20 HV 30 294.1 196.1 20 30HV 50 HV 100 490.3 980.7 100 50HV 120 1177 120
as do doy A3.2) is a highly polished pointed rhombic-based pyramidal diamond. The included longitudinal edge angles are 172° 30°“001 pue
ing macroindentation test forces (over 1 kgf) with diamond indenters de apq mmryu op m msu pqs sn oL 3Npreviously used for microindentation testing. The diamond mount may not be strong enough to support the higher test forces and the diamond maynot be large enough to produce the larger indentation sizes.
a os e sn (76s) pns m 5.4 Measurement DeviceThe diagonals of the indentationwith a filar type eyepiece (see Terminology E175) or other type of measuring device. Additional guidance on measuringdevices may be found in Test Method E384.
capable of reporting the diagonal lengths to within the require- 5.4.1 The testing machine’s measuring device shall bements of 7.9.2.
Thhnltnn($ ooolN oos) sazis uogeuspu Jofue oug sonpoud o ufnous u p u u d n
5.4.2 The measuring device may be an integral part of theeb sese-s eao shighest quality image for measuring the indentation diagonal measuring microscope or measuring system. To obtain thethe measuring microscope should have adjustable illumination intensity adjustable alignment aperture and field diaphragms.
reported Vickers hardness number shall be converted to the Other units of force and length may be used; however theunits of kgf and mm as follows and given in Table 2.
5.8.1 Microindentation Vickers hardness is typically deter-mined using indentation test forces in grams-force (gf) andindentation diagonals measured in micrometres (μm). The Vickers hardness number in terms of gf and μm is calculatedas follows:
nal can be enlarged to greater than 25 % but less than 75 % of 5.4.3 Magnifications should be provided so that the diago-the field width. The device may be built with single or multiplemagnifying objectives.
ing devices and indenters used to perform Vickers and Knoop 5.5 Verjicarions-All testing machines indentation measur-hardness tests shall be verified periodically in accordance with Annex A1 prior to performing hardness tests.
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5.8.2 Macroindentation Vickers hardness is typically deter-mined using indentation test forces in kilograms-force (kgf) and indentation diagonals measured in millimetres (mm). TheVickers hardness number n terms of kgf and mm is calculated as follows:
5.6 Tesr Blocks-Test blocks meeting the requirements ofAnnex A4 shall be used to verify the testing machine in accordance with Annex A1.
5.7 Test ForcesThe standard hardness test forces are givenin Table 1. Other non-standard test forces may be used by special agreement.
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test forces in Newtons (N) and indentation diagonals measured 5.8.3 The Vickers hardness number in terms of indentationin millimetres (mm) is calculated as follows:
5.8 Calculaion of the Vickers Hardness NumberTheF in kgf divided by the surface area Ag of the indentation in Vickers hardness number is based on the indentation test forcemm²
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TABLE 2 Vickers and Knoop Formulae
Vickers hardness numberForce (F) unit kgf Diagonal (d) unit mm HV = 1.8544 × F/d Formulaof N um mm HV = 1854.4 × F/df HV = 0.1891 × F/dForce (F uni kgf Knoop hardness number Diagonal (d) unit mm HK = 14.229 × F/a Fomulaum mm HK=14229xF/ HK = 1.451 × F/df
The surface area (Ag) of the indentation is calculated as:
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where:
dv a = mean Vickers indentation diagonal length (mm). = face angle of the diamond indenter = 136° and
where:
where:
5.9 Calculation of the Knoop Hardness NumberTheKnoop hardness number is based on the indentation test force(kgf) divided by the projected area Az of the indentation (mm).
The projected area (Ap) of the indentation is calculated as:
dr Cp = Knoop indentation long diagonal length (mm) and = indenter constant relating the projected area of theindentation to the square of the length of the long diagonal ideally 0.07028 where:
A = the included longitudinal edge angle 172° 30' and B = included transverse edge angle 130° 0'.
Knoop hardness number shall be converted to the units of kgf Other units of force and length may be used however the and mm as follows and as given in Table 2.
tation test forces in grams-force (gf) and indentation long 5.9.1 Knoop hardness is typically determined using inden-number in terms of gf and μm is calculated as follows: diagonal measured in micrometres (μm). The Knoop hardness
test forces in kgf and the indentation long diagonal measured in 5.9.2 The Knoop hardness number in terms of indentationmm is calculated as follows:
5.9.3 The Knoop hardness number in terms of indentationmeasured in millimetres (mm) is calculated as follows: test forces in Newtons (N) and the indentation long diagonal
ues are not designated by a number alone because it is 5.10 Hardness NumberVickers and Knoop hardness val-necessary to indicate which force has been employed in making the test. The hardness numbers shall be followed by thesymbol HV for Vickers hardness or HK for Knoop hardness and be supplemented by a value representing the test force inkgf.
the hardness shall be supplemented with the actual total force 5.10.1 For nonstandard dwell times other than 10 to 15 s dwell time used in seconds separated by a “
5.10.2 The reported Vickers and Knoop hardness numbershall be reported rounded to three significant digits in accor-dance with Practice E29.
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5.10.3 Exampfles:
6. Test Piece
400 HK 0.5 = Knoop hardness of 400 detemined with a 500 gf (0.5 kgf)99.2 HV 0.1 = Vickers hardness of 99.2 determined with a 100 gf (0.1 kgf) indentstion test force. indenttintest foe725 HV 10 = Vickers hardness of 725 determined with a 10 kgf indentation test force.( ) 0 u =Z00 indentstion test force and a 22 s total force dwelltime.
Knoop test specimen. The specimen on which the indentation 6.1 There is no standard shape or size for a Vickers oris made should conform to the following:
the test should be performed on a flat specimen with a polished 6.2 PreparationFor optimum accuracy of measurement or otherwise suitably prepared surface. The quality of therequired surface finish can vary with the forces and magnifi- cations used. The lower the test force and the smaller theindentation size the more critical is the surface preparation. In all tests the preparation should be such that the indentationdefined when observed by the measuring system. Surface perimeter and the indentation tips in particular can be clearlypreparation remendations for low-force microindentation testing can be found in Test Method E384.
6.2.1 The test surface shall be free of any defects that coulddiagonals. It is well known that improper grinding and polish- affect the indentation or the subsequent measurement of theheating or cold work. Some materials are more sensitive to ing methods can alter test results either due to excessivepreparation-induced damage than others; therefore specialprecautions shall be taken during specimen preparation. Re- uoeedaad uds Suunp ponponu aseuep Kue aou
making an indentation. Etched surfaces can obscure the edge of 6.2.2 The specimen surface should not be etched beforethe indentation difficult. There may be microindentation testing the indentation making an accurate measurement of the size ofapplications where a light etch may be appropriate (see Test Method E384).
6.3 AligrmenTo obtain usable information from the test the specimen should be prepared or mounted so that the test surface is perpendicular to the axis of the indenter. This canreadily be acplished by surface grinding (or otherwisemachining) the opposite side of the specimen parallel with the side to be tested. Non-parallel test specimens can be testedusing clamping and leveling fixtures designed to align the test surface properly to the indenter.
6.4 Mouonted Tesr SpecimensIn many instances especiallyin microindentation testing it is necessary to mount the specimen for convenience in preparation and to maintain asharp edge when surface gradient tests are to be performed on the test specimen. When mounting is required the specimenosqdqavoid the use of polymeric mounting pounds that creep the specimen does not move during force application that is under the indenter force (see Test Method E384).
6.5 Thickness-The thickness of the specimen tested shallbe such that no bulge or other marking showing the effect ofthe test force appears on the side of the piece opposite the
