ASTM C1326-08
(Test Method)Standard Test Method for Knoop Indentation Hardness of Advanced Ceramics
Standard Test Method for Knoop Indentation Hardness of Advanced Ceramics
SIGNIFICANCE AND USE
For advanced ceramics, Knoop indenters are used to create indentations. The surface projection of the long diagonal is measured with optical microscopes.
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.
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 load, and cracking is much less of a problem (1). 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 loads 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.
The Knoop indentation is shallower than Vickers indentations made at the same load. Knoop indents may be useful in evaluating coating hardnesses.
Knoop hardness is calculated from the ratio of the applied load 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 load to the area of contact of the four faces of the undeformed indenter.)
A full hardness characterization includes measurements over a broad range of indentation loads. Knoop hardness of ceramics usually decreases with increasing indentation size or indentation force (load). The trend is known as the indentation size effect (ISE). Hardness approaches a pla...
SCOPE
1.1 This test method covers the determination of the Knoop indentation hardness of advanced ceramics.
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 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 health practices and determine the applicability of regulatory limitations prior to use.
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Designation:C 1326–08
Standard Test Method for
1
Knoop Indentation Hardness of Advanced Ceramics
This standard is issued under the fixed designation C 1326; 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 2.3 ISO Standard:
ISO 9385 Glass and Glass Ceramics—Knoop Hardness
1.1 This test method covers the determination of the Knoop
4
Test
indentation hardness of advanced ceramics.
1.2 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Definition:
standard.
3.1.1 Knoop hardness number (HK), n—an expression of
1.3 This standard does not purport to address all of the
hardness obtained by dividing the force applied to the Knoop
safety concerns, if any, associated with its use. It is the
indenter by the projected area of the permanent impression
responsibility of the user of this standard to establish appro-
made by the indenter.
priate safety and health practices and determine the applica-
3.1.2 Knoop indenter, n—a rhombic-based pyramidal-
bility of regulatory limitations prior to use.
shaped diamond indenter with edge angles of 172° 308 and
2. Referenced Documents 130° 008.
2
2.1 ASTM Standards:
4. Summary of Test Method
C 730 Test Method for Knoop Indentation Hardness of
4.1 This test method describes an indentation hardness test
Glass
using a calibrated machine to force a pointed, rhombic base,
C 849 Test Method for Knoop Indentation Hardness of
pyramidal diamond indenter having specified face angles,
Ceramic Whitewares
under a predetermined load, into the surface of the material
E4 Practices for Force Verification of Testing Machines
under test and measures the surface projection of the long
E 177 Practice for Use of the Terms Precision and Bias in
diagonal of the resulting impression after removal of the load.
ASTM Test Methods
E 384 Test Method for Microindentation Hardness of Ma-
NOTE 1—A general description of the Knoop indentation hardness test
terials is given in Test Method E 384. The present test method differs from this
description only in areas required by the special nature of advanced
E 691 Practice for Conducting an Interlaboratory Study to
ceramics.
Determine the Precision of a Test Method
NOTE 2—This test method is similar to Test Methods C 730 and C 849,
IEEE/ASTM SI 10 Standard for Use of the International
but differs primarily in the choice of load and the rate of loading. In
System of Units (SI) (The Modern Metric System)
addition, the length correction factor for the resolution limits of optical
2.2 European Standard:
microscopes is not utilized.
CEN ENV 843-4 Advanced Technical Ceramics, Mono-
5. Significance and Use
lithic Ceramics, Mechanical Properties at RoomTempera-
ture, Part 4: Vickers, Knoop, and Rockwell Superficial
5.1 For advanced ceramics, Knoop indenters are used to
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Hardness Tests
create indentations.The surface projection of the long diagonal
is measured with optical microscopes.
5.2 The Knoop indentation hardness is one of many prop-
1
This test method is under the jurisdiction of ASTM Committee C28 on
erties that is used to characterize advanced ceramics.Attempts
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on
Mechanical Properties and Performance.
have been made to relate Knoop indentation hardness to other
Current edition approved Aug. 1, 2008. Published September 2008. Originally
hardness scales, but no generally accepted methods are avail-
approved in 1996. Last previous edition approved in 2003 as C 1326 – 03.
2 able. Such conversions are limited in scope and should be used
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contactASTM Customer Service at service@astm.org. ForAnnual Book ofASTM
Standards volume information, refer to the standard’s Document Summary page on
4
the ASTM website. Available from International Organization for Standardization (ISO), 1, ch. de
3
Available from European Committee for Standardization (CEN), 36 rue de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http://
Stassart, B-1050, Brussels, Belgium, http://www.cenorm.be. 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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C 1326–08
with caution, except for special cases where a reliable basis for indentation tip and the polished surface of some advanced
the conversion has been obtained by comparison tests. ceramics. This may be overcome by careful adjustment of the
5.3 For advanced ceramics,
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:C 1326–03 Designation:C 1326–08
Standard Test Method for
1
Knoop Indentation Hardness of Advanced Ceramics
This standard is issued under the fixed designation C 1326; 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.
1.2This 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 health practices and determine the applicability of regulatory
limitations prior to use.
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 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 health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
C 730 Test Method for Knoop Indentation Hardness of Glass
C 849 Test Method for Knoop Indentation Hardness of Ceramic Whitewares
E 4 Practices for Force Verification of Testing Machines
E 177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods E380Practice for Use of the International
System of Units (SI) (the Modernized Met-
ric System)
E 384 Test Method for Microhindentation Hardness of Materials
E 691Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method 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)
2.2 European Standard:
CEN ENV 843-4 Advanced Technical Ceramics, Monolithic Ceramics, Mechanical Properties at Room Temperature, Part 4:
3
Vickers, Knoop, and Rockwell Superficial Hardness Tests
2.3 ISO Standard:
4
ISO 9385 Glass and Glass Ceramics—Knoop Hardness Test
3. Terminology
3.1 Definition:
3.1.1 Knoop hardness number (HK), n—an expression of hardness obtained by dividing the force applied to the Knoop indenter
by the projected area of the permanent impression made by the indenter.
3.1.2 Knoop indenter, n—a rhombic-based pyramidal-shaped diamond indenter with edge angles of 172° 308 and 130° 008.
4. Summary of Test Method
4.1 This test method describes an indentation hardness test using a calibrated machine to force a pointed, rhombic base,
pyramidal diamond indenter having specified face angles, under a predetermined load, into the surface of the material under test
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 Oct.Aug. 1, 2003.2008. Published November 2003.September 2008. Originally approved in 1996. Last previous edition approved in 19992003
as C1326–99.C 1326 – 03.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from European Committee for Standardization, Brussels, Belgium.
3
Available from European Committee for Standardization (CEN), 36 rue de Stassart, B-1050, Brussels, Belgium, http://www.cenorm.be.
4
Available from International Standards Organization, Geneva, Switzerland.
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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C 1326–08
and measures the surface projection of the long diagonal of the resulting impression after removal of the load.
NOTE 1—A general description of the Knoop indentation hardness test is given in Test Method E 384. The present test method differs from this
description only in areas required by the special nature of advanced ceramics.
NOTE 2—This test method is similar to Test Methods C 730 and
...
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