ASTM C1525-02
(Test Method)Standard Test Method for Determination of Thermal Shock Resistance for Advanced Ceramics by Water Quenching
Standard Test Method for Determination of Thermal Shock Resistance for Advanced Ceramics by Water Quenching
SCOPE
1.1 This test method describes the determination of the resistance of advanced ceramics to thermal shock by water quenching. The method builds on the experimental principle of rapid quenching of a test specimen at an elevated temperature in a water bath at room temperature. The effect of the thermal shock is assessed by measuring the reduction in flexural strength produced by rapid quenching of test specimens heated across a range of temperatures. For a quantitative measurement of thermal shock resistance, a critical temperature interval is determined by a reduction in the mean flexural strength of at least 30 %. The test method does not determine thermal stresses developed as a result of a steady state temperature differences within a ceramic body or of thermal expansion mismatch between joined bodies. Since the determination of the thermal shock resistance is performed by evaluating retained strength, the method is not suitable for ceramic components; however, test specimens cut from components may be used.
1.2 The test method is intended primarily for monolithic ceramics, but may also be applicable to certain composites such as whisker- or particulate-reinforced ceramic matrix composites that are macroscopically homogeneous.
1.3 Values expressed in this standard test method are in accordance with the International System of Units (SI) and Standard IEEE/ASTM SI 10.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C 1525 – 02
Standard Test Method for
Determination of Thermal Shock Resistance for Advanced
Ceramics by Water Quenching
This standard is issued under the fixed designation C 1525; 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 Estimating Weibull Parameters for Advanced Ceramics
C 1322 Practice for Fractography and Characterization of
1.1 This test method describes the determination of the
Fracture Origins in Advanced Ceramics
resistance of advanced ceramics to thermal shock by water
E 4 Practice for Force Verification of Testing Machines
quenching. The method builds on the experimental principle of
E 6 Terminology Relating to Methods of Mechanical Test-
rapid quenching of a test specimen at an elevated temperature
ing
in a water bath at room temperature. The effect of the thermal
E 616 Terminology Relating to Fracture Testing
shock is assessed by measuring the reduction in flexural
IEEE/ASTM SI 10 Standard for Use of the International
strength produced by rapid quenching of test specimens heated
System of Units (SI): The Modern Metric System
across a range of temperatures. For a quantitative measurement
2.2 European Standard:
of thermal shock resistance, a critical temperature interval is
EN 820-3 Advanced Technical Ceramics—Monolithic
determined by a reduction in the mean flexural strength of at
Ceramics—Thermomechanical Properties—Part 3: Deter-
least 30 %. The test method does not determine thermal
mination of Resistance to Thermal Shock by Water
stresses developed as a result of a steady state temperature
Quenching
differences within a ceramic body or of thermal expansion
mismatch between joined bodies. Since the determination of
3. Terminology
the thermal shock resistance is performed by evaluating
3.1 Definitions—The terms described in Terminologies
retained strength, the method is not suitable for ceramic
C 1145, E 6, and E 616 are applicable to this standard test
components; however, test specimens cut from components
method. Specific terms relevant to this test method are as
may be used.
follows:
1.2 The test method is intended primarily for monolithic
3.1.1 advanced ceramic, n—a highly engineered, high per-
ceramics, but may also be applicable to certain composites
formance, predominately non-metallic, inorganic, ceramic ma-
such as whisker- or particulate-reinforced ceramic matrix
terial having specific functional attributes. C 1145
composites that are macroscopically homogeneous.
3.1.2 critical temperature difference, DT , n—temperature
c
1.3 Values expressed in this standard test method are in
difference between the furnace and the ambient temperature
accordance with the International System of Units (SI) and
water bath that will cause a 30 % drop in the average flexural
Standard IEEE/ASTM SI 10.
strength.
1.4 This standard does not purport to address all of the
3.1.3 flexural strength, s , n—a measure of the ultimate
f
safety concerns, if any, associated with its use. It is the
strength of a specified beam specimen in bending determined at
responsibility of the user of this standard to establish appro-
a given stress rate in a particular environment.
priate safety and health practices and determine the applica-
3.1.4 fracture toughness, n—a generic term for measures of
bility of regulatory limitations prior to use.
resistance to extension of a crack. E 616
2. Referenced Documents 3.1.5 slow crack growth (SCG), n—subcritical crack growth
(extension) which may result from, but is not restricted to, such
2.1 ASTM Standards:
2 mechanisms as environmentally-assisted stress corrosion or
C 1145 Terminology of Advanced Ceramics
diffusive crack growth.
C 1161 Test Method for Flexural Strength of Advanced
2 3.1.6 thermal shock, n—a large and rapid temperature
Ceramics at Ambient Temperature
change, resulting in large temperature differences within or
C 1239 Practice for Reporting Uniaxial Strength Data and
across a body. C 1145
This test method is under the jurisdiction of ASTM Committee C28 on
Advanced Ceramics and is the direct responsibility of Subcommittee C28.01 on Annual Book of ASTM Standards, Vol 03.01
Properties and Performance. Annual Book of ASTM Standards, Vol 14.02.
Current edition approved April 10, 2002. Published July 2002. Available from CEN, 36, rue de Stassart, B-1050 Brussels, Belgium, ww-
Annual Book of ASTM Standards, Vol 15.01. w.cenorm.be.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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 1525
3.1.7 thermal shock resistance, n—the capability of material 6.4 The formulae presented in this test method apply strictly
to retain its mechanical properties after exposure to one or only to materials that do not exhibit R-curve behavior, but have
more thermal shocks. a single-valued fracture toughness. If the test material exhibit a
strong R-curve behavior, that is, increase in fracture toughness
4. Summary of Test Method
with increasing crack length, caution must be taken in inter-
4.1 This test method indicates the ability of an advanced preting the results.
ceramic product to withstand the stress generated by sudden
6.5 Test data for specimens of different geometries are not
changes in temperature (thermal shock). The thermal shock directly comparable because of the effect of geometry on heat
resistance is measured by determining the loss of strength (as
transfer and stress gradients. Quantitative comparisons of
compared to as-received specimens) for ceramic test specimens thermal shock resistance for different ceramic compositions
quickly cooled after a thermal exposure. A series of rectangular
should be done with equivalent test specimen geometries.
or cylindrical test specimen sets are heated across a range of
7. Apparatus
different temperatures and then quenched rapidly in a water
7.1 Test Apparatus:
bath. After quenching, the test specimens are tested in flexure,
7.1.1 The test method requires a thermal exposure/
and the average retained flexural strength is determined for
quenching system (consisting of a furnace, specimen handling
each set of specimens quenched from a given temperature. The
equipment, and a quench bath) and a testing apparatus suitable
“critical temperature difference” for thermal shock is estab-
for measuring the flexural strength of the test specimens.
lished from the temperature difference (exposure temperature
7.1.2 The test method requires a furnace capable of heating
minus the water quench temperature) that produces a 30 %
and maintaining a set of test specimens at the required
reduction in flexural strength compared to the average flexural
temperature to 6 5K(6 5°C). The temperature shall be
strength of the as-received test specimens.
measured with suitable thermocouples mounted in proximity to
5. Significance and Use
the specimen(s) in the furnace. Furnaces will usually have an
open atmosphere, because air exposure is common during the
5.1 The high temperature capabilities of advanced ceramics
transfer to the quench bath.
are a key performance benefit for many demanding engineering
applications. In many of those applications, advanced ceramics
NOTE 1—If air exposure is detrimental, a special furnace-quench
will have to perform across a broad temperature range with
system can be set up in which both the furnace and the quench unit are
exposure to sudden changes in temperature and heat flux. contained within an inert atmosphere container. A common design for
such a system consists of a tube furnace positioned vertically above the
Thermal shock resistance of the ceramic material is a critical
quench tank, so that the test specimen drops directly into the tank from the
factor in determining the durability of the component under
furnace.
transient thermal conditions.
7.1.3 The method requires a test specimen handling equip-
5.2 This test method is useful for material development,
ment designed so that the test specimen can be transferred from
quality assurance, characterization, and assessment of durabil-
the furnace to the quenching bath within 5 s.
ity. It has limited value for design data generation, because of
7.1.4 A water bath controlled to 293 6 2 K (20°C 6 2°C)
the limitations of the flexural test geometry in determining
fundamental tensile properties. is required. The water bath must have sufficient volume to
prevent the temperature in the bath from rising more than 5 K
5.3 Appendix X1 provides an introduction to thermal
stresses, thermal shock, and critical material/geometry factors. (5°C) after test specimen quenching. It is recommended that
the bath be large enough for the test specimens to have cooled
The appendix also contains a mathematical analysis of the
stresses developed by thermal expansion under steady state and sufficiently before reaching the bottom of the bath, or contain
a screen near the bottom to prevent the test specimens from
transient conditions, as determined by mechanical properties,
thermal characteristics, and heat transfer effects. resting directly on the bottom of the bath.
7.1.5 Universal test machine used for strength testing in this
6. Interferences
test method shall conform to the requirements of Practice E 4.
6.1 Time-dependent phenomena such as stress corrosion or Specimens may be loaded in any suitable test machine pro-
slow crack growth may influence the strength tests. This might vided that uniform test rates, either using load-controlled or
especially be a problem if the test specimens are not properly displacement-controlled mode, can be maintained. The loads
dried before strength testing. used in determining flexural strength shall be accurate within
6.2 Surface preparation of test specimens can introduce 6 1.0 % at any load within the selected load rate and load
machining flaws which may have a pronounced effect on the range of the test machine as defined in Practice E 4.
measured flexural strength. The surface preparation may also 7.1.6 The configuration and mechanical properties of the
influence the cracking process due to the thermal shock test fixtures shall be in accordance with Test Method C 1161
procedure. It is especially important to consider surface con- for use with the standard four-point flexure specimens. If larger
ditions in comparing test specimens and components. test pieces (sizes A or C below) are employed, the test fixture
6.3 The results are given in terms of a temperature differ- shall be scaled accordingly. There are currently no standard
ence between furnace and quenching bath (DT). However, it is fixtures for testing cylindrical rods in flexure; however, the
important to notice that results may be different for the same fixtures to be used shall have the appropriate articulation. Test
DT but different absolute temperatures. It is therefore specified fixtures without appropriate articulation shall not be permitted;
in this test method to quench to room temperature. the articulation of the fixture shall meet the requirements
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 1525
specified in Test Method C 1161. 9.1.1 The maximum exposure target temperature of the
7.1.7 The method requires a 393 K (120°C) drying oven to furnace for the thermal shock test of a given advanced ceramic
remove moisture from test specimens before (if needed) and will be determined from the maximum performance tempera-
after quench testing. ture required for a specific application, specified in a compara-
tive thermal shock test, or cited in test literature.
8. Test Specimens
9.1.2 The initial exposure temperature can be determined
8.1 The ceramic test specimens shall be specifically pre-
from literature values, prior test experience, or from a 50 %
pared test pieces, prepared from bulk material or cut from
value of the maximum exposure temperature. Follow-on
components.
exposure/quench tests should be performed such that the
8.1.1 Specimen Size—Three specimen geometries are de-
critical temperature difference is determined within a 50 K
fined for use in this test method:
(50°C) interval.
8.1.1.1 Type A—Rods 10 6 1 mm in diameter, 120 mm
9.2 Clean the test specimens. Determine the thickness and
long.
width of each test specimen in accordance with Test Method
8.1.1.2 Type B—Bars 3 6 0.13 mm 3 4 6 0.13 mm in cross
C 1161.
section, minimum 45 mm long with chamfered edges, in
9.3 Dry the test specimens in an oven at 393 6 10 K (120
accordance with type B in Test Method C 1161.
6 10°C) for 2 h. Allow the specimens to cool to room
8.1.1.3 Type C—Bars 10 6 1mm 3 10 6 1 mm in cross
temperature in a dessicator. Select the specimens for quench
section, 120 mm long, with chamfered edges.
testing and store in the dessicator until furnace exposure.
NOTE 2—The test specimens of A and C type are intended to be large
9.4 Perform the initial flexural strength test on at least 10
enough to produce a materials ranking that is basically independent of
test specimens in accordance with Test Method C 1161 using
specimen size and appropriate for larger test specimens (1,2). Test
the appropriate test machine and fixture.
specimens of B type may require greater quenching temperature differ-
9.5 Determine the mean and standard deviation of the
ences in order to produce strength reduction. These test specimens may
strength of the as-received specimens.
not correctly rank the relative behavior of larger components. Only Type
B coincides with Type B in Test Method C 1161. 9.6 Place the first set (minimum five test specimens) of
NOTE 3—Under some circumstances the edges of prismatic test speci-
quench test specimens in the cold furnace and heat slowly
mens or the ends of cylindrical test specimens may be damaged by
[minimum 30 min to temperatures up to 873 K (600°C);
spallation during the quench test. These specimens should be discarded
minimum 60 min to temperature greater than 873 K (600°C)]
from the batch used for strength testing if the damage will interfere with
to the initial exposure temperature. Equilibrate at the exposure
the strength test. In any case such spallation must be noted in the report.
temperature for a period of 15 min and check/record the
Spallation problems can be alleviated by chamfering sharp edges.
exposure temperature. After equi
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