ASTM E92-23

Standard Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials

SIGNIFICANCE AND USE
4.1 Vickers and Knoop hardness tests have been found to be very useful for materials evaluation, quality control of manufacturing processes and research and development efforts. Hardness, although empirical in nature, can be correlated to tensile strength for many metals, and is an indicator of wear resistance and ductility.  
4.2 Microindentation hardness tests extend testing to materials that are too thin or too small for macroindentation hardness tests. Microindentation hardness tests also allow specific phases or constituents and regions or gradients too small for macroindentation hardness testing to be evaluated. Recommendations for microindentation testing can be found in Test Method E384.  
4.3 Because the Vickers and Knoop hardness will reveal hardness variations that may exist within a material, a single test value may not be representative of the bulk hardness.  
4.4 The Vickers indenter usually produces essentially the same hardness number at all test forces when testing homogeneous material, except for tests using very low forces (below 25 gf) or for indentations with diagonals smaller than about 25 µm (see Test Method E384). For isotropic materials, the two diagonals of a Vickers indentation are equal in length.  
4.5 The Knoop indenter usually produces similar hardness numbers over a wide range of test forces, but the numbers tend to rise as the test force is decreased. This rise in hardness number with lower test forces is often more significant when testing higher hardness materials, and is increasingly more significant when using test forces below 50 gf (see Test Method E384).  
4.6 The elongated four-sided rhombohedral shape of the Knoop indenter, where the length of the long diagonal is 7.114 times greater than the short diagonal, produces narrower and shallower indentations than the square-based pyramid Vickers indenter under identical test conditions. Hence, the Knoop hardness test is very useful for evaluating hardness gradients since Knoo...
SCOPE
1.1 These test methods cover the determination of the Vickers hardness and Knoop hardness of metallic materials by the Vickers and Knoop indentation hardness principles. This standard provides the requirements for Vickers and Knoop hardness machines and the procedures for performing Vickers and Knoop hardness tests.  
1.2 This standard includes additional requirements in annexes:    
Verification of Vickers and Knoop Hardness Testing Machines  
Annex A1  
Vickers and Knoop Hardness Standardizing Machines  
Annex A2  
Standardization of Vickers and Knoop Indenters  
Annex A3  
Standardization of Vickers and Knoop Hardness Test Blocks  
Annex A4  
Correction Factors for Vickers Hardness Tests Made on Spherical and Cylindrical Surfaces  
Annex A5  
1.3 This standard includes nonmandatory information in an appendix which relates to the Vickers and Knoop hardness tests:    
Examples of Procedures for Determining Vickers and Knoop Hardness Uncertainty  
Appendix X1  
1.4 This test method covers Vickers hardness tests made utilizing test forces ranging from 9.807 × 10-3 N to 1176.80 N (1 gf to 120 kgf), and Knoop hardness tests made utilizing test forces from 9.807 × 10-3 N to 19.613 N (1 gf to 2 kgf).  
1.5 Additional information on the procedures and guidance when testing in the microindentation force range (forces ≤ 1 kgf) may be found in Test Method E384, Test Method for Microindentation Hardness of Materials.  
1.6 Units—When the Vickers and Knoop hardness tests were developed, the force levels were specified in units of grams-force (gf) and kilograms-force (kgf). This standard specifies the units of force and length in the International System of Units (SI); that is, force in Newtons (N) and length in mm or µm. However, because of the historical precedent and continued common usage, force values in gf and kgf units are provided for information and much of the discussion in this standard as well as the...

General Information

• Status: Published
• Publication Date: 30-Jun-2023
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.06 - Indentation Hardness Testing

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E92 − 23
Standard Test Methods for
Vickers Hardness and Knoop Hardness of Metallic
1
Materials
This standard is issued under the fixed designation E92; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
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. Scope* continued common usage, force values in gf and kgf units are
provided for information and much of the discussion in this
1.1 These test methods cover the determination of the
standard as well as the method of reporting the test results
Vickers hardness and Knoop hardness of metallic materials by
refers to these units.
the Vickers and Knoop indentation hardness principles. This
NOTE 1—The Vickers and Knoop hardness numbers were originally
standard provides the requirements for Vickers and Knoop
defined in terms of the test force in kilogram-force (kgf) and the surface
2
hardness machines and the procedures for performing Vickers
area or projected area in millimetres squared (mm ). Today, the hardness
and Knoop hardness tests. numbers are internationally defined in terms of SI units, that is, the test
force in Newtons (N). However, in practice, the most commonly used
1.2 This standard includes additional requirements in an-
force units are kilogram-force (kgf) and gram-force (gf). When Newton
nexes:
units of force are used, the force must be divided by the conversion factor
9.80665 N/kgf.
Verification of Vickers and Knoop Hardness Testing Machines Annex A1
Vickers and Knoop Hardness Standardizing Machines Annex A2
1.7 The test principles, testing procedures, and verification
Standardization of Vickers and Knoop Indenters Annex A3
procedures are essentially identical for both the Vickers and
Standardization of Vickers and Knoop Hardness Test Blocks Annex A4
Correction Factors for Vickers Hardness Tests Made on Annex A5
Knoop hardness tests. The significant differences between the
Spherical and Cylindrical Surfaces
two tests are the geometries of the respective indenters, the
1.3 This standard includes nonmandatory information in an
method of calculation of the hardness numbers, and that
appendix which relates to the Vickers and Knoop hardness
Vickers hardness may be used at higher force levels than
tests:
Knoop hardness.
NOTE 2—While Committee E28 is primarily concerned with metallic
Examples of Procedures for Determining Vickers and Appendix X1
Knoop Hardness Uncertainty materials, the test procedures described are applicable to other materials.
Other materials may require special considerations, for example see
1.4 This test method covers Vickers hardness tests made
C1326 and C1327 for ceramic testing.
-3
utilizing test forces ranging from 9.807 × 10 N to 1176.80 N
1.8 This standard does not purport to address all of the
(1 gf to 120 kgf), and Knoop hardness tests made utilizing test
-3 safety concerns, if any, associated with its use. It is the
forces from 9.807 × 10 N to 19.613 N (1 gf to 2 kgf).
responsibility of the user of this standard to establish appro-
1.5 Additional information on the procedures and guidance
priate safety, health, and environmental practices and deter-
when testing in the microindentation force range (forces ≤ 1
mine the applicability of regulatory limitations prior to use.
kgf) may be found in Test Method E384, Test Method for
1.9 This international standard was developed in accor-
Microindentation Hardness of Materials.
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
1.6 Units—When the Vickers and Knoop hardness tests
Development of International Standards, Guides and Recom-
were developed, the force levels were specified in units of
mendations issued by the World Trade Organization Technical
grams-force (gf) and kilograms-force (kgf). This standard
specifies the units of force and length in the International Barriers to Trade (TBT) Committee.
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
2.1 ASTM Standards:
1
These test methods are under the jurisdiction of ASTM Committee E28 on
Mechanical Testing and is the direct responsibility of Subcommittee E28.06 on
2
Indentation Hardness Testing. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2023. Published August 2023. Originally contact ASTM Cus
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E92 − 17 E92 − 23
Standard Test Methods for
Vickers Hardness and Knoop Hardness of Metallic
1
Materials
This standard is issued under the fixed designation E92; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
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. Scope*
1.1 These test methods cover the determination of the Vickers hardness and Knoop hardness of metallic materials by the Vickers
and Knoop indentation hardness principles. This standard provides the requirements for Vickers and Knoop hardness machines and
the procedures for performing Vickers and Knoop hardness tests.
1.2 This standard includes additional requirements in annexes:
Verification of Vickers and Knoop Hardness Testing Machines Annex A1
Vickers and Knoop Hardness Standardizing Machines Annex A2
Standardization of Vickers and Knoop Indenters Annex A3
Standardization of Vickers and Knoop Hardness Test Blocks Annex A4
Correction Factors for Vickers Hardness Tests Made on Annex A5
Spherical and Cylindrical Surfaces
1.3 This standard includes nonmandatory information in an appendix which relates to the Vickers and Knoop hardness tests:
Examples of Procedures for Determining Vickers and Appendix X1
Knoop Hardness Uncertainty
-3
1.4 This test method covers Vickers hardness tests made utilizing test forces ranging from 9.807 × 10 N to 1176.80 N (1 gf to
-3
120 kgf), and Knoop hardness tests made utilizing test forces from 9.807 × 10 N to 19.613 N (1 gf to 2 kgf).
1.5 Additional information on the procedures and guidance when testing in the microindentation force range (forces ≤ 1 kgf) may
be found in Test Method E384, Test Method for Microindentation Hardness of Materials.
1.6 Units—When the Vickers and Knoop hardness tests were developed, the force levels were specified in units of grams-force
(gf) and kilograms-force (kgf). This standard specifies the units of force and length in the International System of Units (SI); that
is, force in Newtons (N) and length in mm or μm. However, because of the historical precedent and continued common usage, force
values in gf and kgf units are provided for information and much of the discussion in this standard as well as the method of
reporting the test results refers to these units.
1
These test methods are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and is the direct responsibility of Subcommittee E28.06 on Indentation
Hardness Testing.
Current edition approved April 1, 2017July 1, 2023. Published May 2017August 2023. Originally approved in 1952. Last previous edition approved in 20162017 as
E92–16. DOI: 10.1520/E0092-17.–17. DOI: 10.1520/E0092-23.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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E92 − 23
NOTE 1—The Vickers and Knoop hardness numbers were originally defined in terms of the test force in kilogram-force (kgf) and the surface area or
2
projected area in millimetres squared (mm ). Today, the hardness numbers are internationally defined in terms of SI units, that is, the test force in Newtons
(N). However, in practice, the most commonly used force units are kilogram-force (kgf) and gram-force (gf). When Newton units of force are used, the
force must be divided by the conversion factor 9.80665 N/kgf.
1.7 The test principles, testing procedures, and verification procedures are essentially identical for both the Vickers and Knoop
hardness tests. The significant differences between the two tests are the geometries of the respective indenters, the method of
calculation of the hardness numbers, and that Vickers hardness may be used at higher force levels than Knoop hardness.
NOTE 2—While Committee E28 is primarily concerned with metallic materials, the test procedures described are applicable to other materials. Other
materials may require special considerations, for example see C1326 and C1327 for ceramic testing.
1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices a
...