ASTM C1326-13(2018)

Standard Test Method for Knoop Indentation Hardness of Advanced Ceramics

SIGNIFICANCE AND USE
5.1 For advanced ceramics, Knoop indenters are used to create indentations. The surface projection of the long diagonal is measured with optical microscopes.  
5.2 The Knoop indentation hardness is one of many properties that is used to characterize advanced ceramics. Attempts have been made to relate Knoop indentation hardness to other hardness scales, but no generally accepted methods are available. Such conversions are limited in scope and should be used with caution, except for special cases where a reliable basis for the conversion has been obtained by comparison tests.  
5.3 For advanced ceramics, the Knoop indentation is often preferred to the Vickers indentation since the Knoop long diagonal length is 2.8 times longer than the Vickers diagonal for the same force, and cracking is much less of a problem (1).5 On the other hand, the long slender tip of the Knoop indentation is more difficult to precisely discern, especially in materials with low contrast. The indentation forces chosen in this test method are designed to produce indentations as large as may be possible with conventional microhardness equipment, yet not so large as to cause cracking.  
5.4 The Knoop indentation is shallower than Vickers indentations made at the same force. Knoop indents may be useful in evaluating coating hardnesses.  
5.5 Knoop hardness is calculated from the ratio of the applied force divided by the projected indentation area on the specimen surface. It is assumed that the elastic springback of the narrow diagonal is negligible. (Vickers indenters are also used to measure hardness, but Vickers hardness is calculated from the ratio of applied force to the area of contact of the four faces of the undeformed indenter.)  
5.6 A full hardness characterization includes measurements over a broad range of indentation forces. Knoop hardness of ceramics usually decreases with increasing indentation size or indentation force such as that shown in Fig. 1.6 The trend is known as the in...
SCOPE
1.1 This test method covers the determination of the Knoop indentation hardness of advanced ceramics. In this test, a pointed, rhombic-based, pyramidal diamond indenter of prescribed shape is pressed into the surface of a ceramic with a predetermined force to produce a relatively small, permanent indentation. The surface projection of the long diagonal of the permanent indentation is measured using a light microscope. The length of the long diagonal and the applied force are used to calculate the Knoop hardness which represents the material’s resistance to penetration by the Knoop indenter.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 Units—When Knoop and Vickers 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 occasionally provided for information. This test method specifies that Knoop hardness be reported either in units of GPa or as a dimensionless Knoop hardness number.  
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.5 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.

General Information

• Status: Historical
• Publication Date: 31-Dec-2017
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: C28 - Advanced Ceramics
• Drafting Committee: C28.01 - Mechanical Properties and Performance

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: C1326 − 13 (Reapproved 2018)
Standard Test Method for
1
Knoop Indentation Hardness of Advanced Ceramics
This standard is issued under the fixed designation C1326; 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.
1. Scope 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This test method covers the determination of the Knoop
C730 Test Method for Knoop Indentation Hardness of Glass
indentation hardness of advanced ceramics. In this test, a
C849 Test Method for Knoop Indentation Hardness of Ce-
pointed, rhombic-based, pyramidal diamond indenter of pre-
ramic Whitewares
scribed shape is pressed into the surface of a ceramic with a
E4 Practices for Force Verification of Testing Machines
predetermined force to produce a relatively small, permanent
E177 Practice for Use of the Terms Precision and Bias in
indentation. The surface projection of the long diagonal of the
ASTM Test Methods
permanent indentation is measured using a light microscope.
E384 Test Method for Microindentation Hardness of Mate-
The length of the long diagonal and the applied force are used
rials
to calculate the Knoop hardness which represents the material’s
E691 Practice for Conducting an Interlaboratory Study to
resistance to penetration by the Knoop indenter.
Determine the Precision of a Test Method
1.2 The values stated in SI units are to be regarded as
IEEE/ASTM SI 10 Standard for Use of the International
standard. No other units of measurement are included in this
System of Units (SI) (The Modern Metric System)
standard. 3
2.2 European Standard:
CEN ENV 843-4 Advanced Technical Ceramics, Monolithic
1.3 Units—When Knoop and Vickers hardness tests were
Ceramics, Mechanical Properties at Room Temperature,
developed, the force levels were specified in units of grams-
Part 4: Vickers, Knoop, and Rockwell Superficial Hard-
force (gf) and kilograms-force (kgf). This standard specifies
ness Tests
the units of force and length in the International System of
4
2.3 ISO Standard:
Units (SI); that is, force in newtons (N) and length in mm or
ISO 9385 Glass and Glass Ceramics—Knoop Hardness Test
µm. However, because of the historical precedent and contin-
ued common usage, force values in gf and kgf units are
3. Terminology
occasionally provided for information. This test method speci-
3.1 Definitions:
fies that Knoop hardness be reported either in units of GPa or
3.1.1 Knoop hardness number (HK), n—an expression of
as a dimensionless Knoop hardness number.
hardness obtained by dividing the force applied to the Knoop
1.4 This standard does not purport to address all of the
indenter by the projected area of the permanent impression
safety concerns, if any, associated with its use. It is the
made by the indenter.
responsibility of the user of this standard to establish appro-
3.1.2 Knoop indenter, n—a rhombic-based pyramidal-
priate safety, health, and environmental practices and deter-
shaped diamond indenter with edge angles of 172° 30' and
mine the applicability of regulatory limitations prior to use.
130° 00'.
1.5 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
4.1 This test method describes an indentation hardness test
Development of International Standards, Guides and Recom-
using a calibrated machine to force a pointed, rhombic-based,
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
1
This test method is under the jurisdiction of ASTM Committee C28 on the ASTM website.
3
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on Available from European Committee for Standardization (CEN), 36 rue de
Mechanical Properties and Performance. Stassart, B-1050, Brussels, Belgium, http://www.cenorm.be.
4
Current edition approved Jan. 1, 2018. Published January 2018. Originally Available from International Organization for Standardization (ISO), 1, ch. de
approved in 1996. Last previous edition approved in 2013 as C1326 – 13. DOI: la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
10.1520/C1326-13R18. www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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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: C1326 − 13 C1326 − 13 (Reapproved 2018)
Standard Test Method for
1
Knoop Indentation Hardness of Advanced Ceramics
This standard is issued under the fixed designation C1326; 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.
1. Scope
1.1 This test method covers the determination of the Knoop indentation hardness of advanced ceramics. In this test, a pointed,
rhombic base, rhombic-based, pyramidal diamond indenter of prescribed shape is pressed into the surface of a ceramic with a
predetermined force to produce a relatively small, permanent indentation. The surface projection of the long diagonal of the
permanent indentation is measured using a light microscope. The length of the long diagonal and the applied force are used to
calculate the Knoop hardness which represents the material’s resistance to penetration by the Knoop indenter.
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 Units—When Knoop and Vickers 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 occasionally provided for information. This test method specifies that Knoop hardness be reported
either in units of GPa or as a dimensionless Knoop hardness number.
1.4 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2
2.1 ASTM Standards:
C730 Test Method for Knoop Indentation Hardness of Glass
C849 Test Method for Knoop Indentation Hardness of Ceramic Whitewares
E4 Practices for Force Verification of Testing Machines
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E384 Test Method for Microindentation Hardness of Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
IEEE/ASTM SI 10 Standard for Use of the International System of Units (SI) (The Modern Metric System)
3
2.2 European Standard:
CEN ENV 843-4 Advanced Technical Ceramics, Monolithic Ceramics, Mechanical Properties at Room Temperature, Part 4:
Vickers, Knoop, and Rockwell Superficial Hardness Tests
4
2.3 ISO Standard:
ISO 9385 Glass and Glass Ceramics—Knoop Hardness Test
3. Terminology
3.1 Definitions:
1
This test method is under the jurisdiction of ASTM Committee C28 on Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on Mechanical
Properties and Performance.
Current edition approved Aug. 1, 2013Jan. 1, 2018. Published October 2013January 2018. Originally approved in 1996. Last previous edition approved in 20082013 as
ε1
C1326 – 08C1326 – 13. . DOI: 10.1520/C1326-13.10.1520/C1326-13R18.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from European Committee for Standardization (CEN), 36 rue de Stassart, B-1050, Brussels, Belgium, http://www.cenorm.be.
4
Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://www.iso.ch.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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C1326 − 13 (2018)
3.1.1 Knoop hardness number (HK), n—an expression of hardness obtained by dividing the f
...