ASTM C1327-99
(Test Method)Standard Test Method for Vickers Indentation Hardness of Advanced Ceramics
Standard Test Method for Vickers Indentation Hardness of Advanced Ceramics
SCOPE
1.1 This test method covers the determination of the Vickers indentation hardness of advanced ceramics.
1.2 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.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: C 1327 – 99
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Method for
Vickers Indentation Hardness of Advanced Ceramics
This standard is issued under the fixed designation C 1327; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope indenter by the surface area of the permanent impression made
by the indenter.
1.1 This test method covers the determination of the Vickers
3.1.2 Vickers indenter, n—a square-based pyramidal-shaped
indentation hardness of advanced ceramics.
diamond indenter with face angles of 136° 008.
1.2 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 This test method describes an indentation hardness test
priate safety and health practices and determine the applica-
using a calibrated machine to force a pointed, square base,
bility of regulatory limitations prior to use.
pyramidal diamond indenter having specified face angles,
2. Referenced Documents under a predetermined load, into the surface of the material
under test and to measure the surface-projected diagonals of
2.1 ASTM Standards:
the resulting impression after removal of the load.
E 4 Practices for Force Verification of Testing Machines
E 177 Practice for Use of the Terms Precision and Bias in
NOTE 1—A general description of the Vickers indentation hardness test
ASTM Test Methods is given in Test Method E 384. The present method is very similar, has
most of the same requirements, and differs only in areas required by the
E 380 Practice for Use of the International System of Units
special nature of advanced ceramics. This test method also has many
(SI) (the Modernized Metric System)
elements in common with standards ENV 843-4 and JIS R 1610, which
E 384 Test Method for Microhardness of Materials
are also for advanced ceramics.
E 691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
5. Significance and Use
2.2 European Standard:
5.1 For advanced ceramics, Vickers indenters are used to
CEN ENV 843-4 Advanced Technical Ceramics, Mono-
create indentations whose surface-projected diagonals are mea-
lithic Ceramics, Mechanical Properties at Room Tempera-
sured with optical microscopes. The Vickers indenter creates a
ture, Part 4: Vickers, Knoop and Rockwell Superficial
square impression from which two surface-projected diagonal
Hardness
lengths are measured. Vickers hardness is calculated from the
2.3 Japanese Standard:
ratio of the applied load to the area of contact of the four faces
JIS R 1610 Testing Method for Vickers Hardness of High
of the undeformed indenter. (In contrast, Knoop indenters are
Performance Ceramics
also used to measure hardness, but Knoop hardness is calcu-
2.4 ISO Standard:
lated from the ratio of the applied load to the projected area on
ISO 6507/2 Metallic Materials—Hardness test—Vickers
the specimen surface.)
test—Part 2: HV0.2 to less than HV5
5.2 Vickers indentation hardness is one of many properties
that is used to characterize advanced ceramics. Attempts have
3. Terminology
been made to relate Vickers indentation hardness to other
3.1 Definition:
hardness scales, but no generally accepted methods are avail-
3.1.1 Vickers hardness number (HV), n—an expression of
able. Such conversions are limited in scope and should be used
hardness obtained by dividing the force applied to a Vickers
with caution, except for special cases where a reliable basis for
the conversion has been obtained by comparison tests.
5.3 Vickers indentation diagonal lengths are approximately
This test method is under the jurisdiction of ASTM Committee C-28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on
2.8 times shorter than the long diagonal of Knoop indentations,
Properties and Performance.
and the indentation depth is approximately 1.5 times deeper
Current edition approved Jan. 10, 1999. Published April 1999. Originally
than Knoop indentations made at the same load.
published as C 1327 – 96. Last previous edition C 1327 – 96.
Annual Book of ASTM Standards, Vol 03.01. 5.4 Vickers indentations are influenced less by specimen
Annual Book of ASTM Standards, Vol 14.02.
surface flatness, parallelism, and surface finish than Knoop
Available from European Committee for Standardization, Brussels, Belgium.
indentations, but these parameters must be considered none-
Available from Japanese Standards Association, Tokyo, Japan.
theless.
Available from International Standards Organization, Geneva, Switzerland.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 1327
5.5 Vickers indentations are much more likely to cause (as in Ref (4)) are not permitted. The tip offset shall be not
cracks in advanced ceramics than Knoop indentations. The more than 0.5 μm in length.
cracks may influence the measured hardness by fundamentally 7.2.2 Fig. 1 shows the indenter. The depth of the indentation
altering the deformation processes that contribute to the is ⁄7 the length of the diagonal. The indenter has an angle
formation of an impression, and they may impair or preclude between opposite faces of 136° 0 min (630 min).
measurement of the diagonal lengths due to excessive damage 7.2.3 The diamond should be examined periodically; and if
at the indentation tips or sides. it is loose in the mounting material, chipped, or cracked, it shall
5.6 A full hardness characterization includes measurements be replaced.
over a broad range of indentation loads. A comprehensive
NOTE 2—This requirement is from Test Method E 384 and is especially
characterization of this type is recommended but is beyond the
pertinent to Vickers indenters used for advanced ceramics. Vickers
scope of this test method, which measures hardness at a single,
indenters are often used at high loads in advanced ceramics in order to
designated load. create cracks. Such usage can lead to indenter damage. The diamond
indenter can be examined with a scanning electron microscope, or indents
6. Interferences can be made into soft copper to help determine if a chip or crack is present.
6.1 Cracking from the indentation tips can interfere with 7.3 Measuring Microscope:
determination of tip location and thus the diagonal length
7.3.1 The measurement system shall be constructed so that
measurements. the length of the diagonals can be determined with errors not
6.2 Cracking or spalling around the Vickers impression may
exceeding6 0.0005 mm.
occur and alter the shape and clarity of the indentation,
NOTE 3—Stage micrometres with uncertainties less than this should be
especially for coarse-grained ceramics whereby grains may
used to establish calibration constants for the microscope. See Test
cleave and dislodge. The cracking may occur in a time-
Method E 384. Ordinary stage micrometres, which are intended for
dependent manner (minutes or hours) after the impression is
determining the approximate magnification of photographs, may be too
made. coarsely ruled or may not have the required accuracy and precision.
6.3 Porosity (either on or just below the surface) may
7.3.2 The numerical aperture (NA) of the objective lens
interfere with measuring Vickers hardness, especially if the
shall be between 0.65 and 0.90.
indentation falls directly onto a large pore or if the indentation
NOTE 4—The apparent length of a Vickers indentation will increase as
tip falls in a pore.
the resolving power and NA of a lens increases. The variation is much less
6.4 At higher magnifications in the optical microscope, it
than that observed in Knoop indentations, however (2), (5), (6). The range
may be difficult to obtain a sharp contrast between the
of NA specified by this test method corresponds to 40 to 1003 objective
indentation tip and the polished surface of some advanced
lenses. The higher power lenses may have higher resolution, but the
ceramics. This may be overcome by careful adjustment of the
contrast between the indentation tips and the polished surface may be less.
lighting as discussed in Test Method E 384.
7.3.3 A filter may be used to provide monochromatic
illumination. Green filters have proved to be useful.
7. Apparatus
8. Test Specimens
7.1 Testing Machines:
7.1.1 There are two general types of machines available for
8.1 The Vickers indentation hardness test is adaptable to a
making this test. One type is a self-contained unit built for this
wide variety of advanced ceramic specimens. In general, the
purpose, and the other type is an accessory available to existing
accuracy of the test will depend on the smoothness of the
microscopes. Usually, this second type is fitted on an inverted-
surface and, whenever possible, ground and polished speci-
stage microscope. Descriptions of the various machines are
mens should be used. The back of the specimen shall be fixed
available (1–3).
7.1.2 Design of the machine should be such that the loading
rate, dwell time, and applied load can be set within the limits
set forth in 10.5. It is an advantage to eliminate the human
element whenever possible by appropriate machine design.
The machine should be designed so that vibrations induced at
the beginning of a test will be damped out by the time the
indenter touches the sample.
7.1.3 The calibration of the balance beam should be checked
monthly or as needed. Indentations in standard reference
materials may also be used to check calibration when needed.
7.2 Indenter:
7.2.1 The indenter shall meet the specifications for Vickers
indenters. See Test Method E 384. The four edges formed by
the four faces of the indenter shall be sharp. Chamfered edges
The boldface numbers in parentheses refer to the list of references at the end of
this test method. FIG. 1 Vickers Indenter
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
C 1327
so that the specimen cannot rock or shift during the test. 10.2.3 Leveling the specimen is facilitated if one has a
leveling device.
8.1.1 Thickness—As long as the specimen is over ten times
10.3 Magnitude of Test Load—A test load of 9.81 N (1 kgf)
as thick as the indentation depth, the test will not be affected.
is specified. If another load is used because of a special
In general, if specimens are at least 0.50 mm thick, the
requirement, or due to cracking problems at 9.81 N, then the
hardness will not be affected by variations in the thickness.
reporting procedure of 12.6 shall be used.
8.1.2 Surface Finish—Specimens should have a ground and
10.4 Clean the Indenter—The indenter shall be cleaned
polished surface. The roughness should be less than 0.1 μm
prior to and during a test series. A cotton swab with ethanol,
rms. However, if one is investigating a surface coating or
methanol, or isopropanol may be used. Indenting into soft
treatment, one cannot grind and polish the specimen.
copper also may help remove debris.
NOTE 5—This requirement is necessary to ensure that the surface is flat
NOTE 7—Ceramic powders or fragments from the ceramic test piece
and that the indentation is sharp. Residual stresses from polishing are of
can adhere to the diamond indenter.
less concern for most advanced ceramics than for glasses or metals.
References (7) and (8) report that surfaces prepared with 1 μm or finer
10.5 Application of Test Load:
diamond abrasive had no effect on measured ceramic hardness. Hardness
10.5.1 Start the machine smoothly. The rate of indenter
was only affected when the surface finish had an optically resolvable
motion prior to contact with the specimen shall be 0.015 to
amount of abrasive damage (7). (Extra caution may be appropriate during
0.070 mm/s. If the machine is loaded by an electrical system or
polishing of transformation toughening ceramics, such as some zirconias,
a dash-pot lever system, it should be mounted on shock
since the effect upon hardness is not known.)
absorbers which damp out all vibrations by the time the
9. Preparation of Apparatus
indenter touches the specimen.
9.1 Verification of Load—Most of the machines available
NOTE 8—This rate of loading is consistent with Test Method E 384.
for Vickers hardness testing use a loaded beam. This beam
10.5.2 The time of application of the full test load shall be
shall be tested for zero load. An indentation should not be
15s(62) unless otherwise specified. After the indenter has
visible with zero load, but the indenter should contact the
been in contact with the specimen from this required dwell
sample. Methods of verifying the load application are given in
time, raise it carefully off the specimen to avoid a vibration
Practices E 4.
impact.
9.2 Separate Verification of Load, Indenter, and Measuring
10.5.3 The operator shall not bump or inadvertently contact
Microscope—Procedures in Test Method E 384, Section 14,
the test machine or associated support (for example, the table)
may be followed.
during the period of indenter contact with the specimen.
9.3 Verification by Standard Reference Materials—Standard
10.6 Spacing of Indentations—Allow a distance of at least
reference blocks, SRM No. 2831, of tungsten carbide that are
four diagonal lengths between the centers of the indentations as
available from the National Institute of Standards and Tech-
illustrated in Fig. 2. If there is cracking from the indentations,
nology can be used to verify that an apparatus produces a
the spacing shall be increased to at least five times the length
Vickers hardness within6 5 % of the certified value.
of the cracks, as shown in Fig. 2.
10.7 Acceptability of Indentations:
10. Procedure
10.7.1 If there is excessive cracking from the indentation
10.1 Specimen Placement—Place the specimen on the stage tips and sides, or the indentation is asymmetric, the indent shall
be rejected for measurement. Fig. 3 provides guidance in this
of the machine so that the specimen will not rock or shift
during the measurement. The specimen surface shall be clean assessment. If this occurs on most indentations, a lower
indentation load (recommended 4.90 N) may be tried.
and free of any grease or film.
10.2 Specimen Leveling:
NOTE 9—If the indentations are s
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.