ASTM C1212-98(2004)
(Practice)Standard Practice for Fabricating Ceramic Reference Specimens Containing Seeded Voids
Standard Practice for Fabricating Ceramic Reference Specimens Containing Seeded Voids
SIGNIFICANCE AND USE
This practice describes a method of fabricating known discontinuities in a ceramic specimen. Such specimens are needed and used in nondestructive examination to demonstrate sensitivity and resolution and to assist in establishing proper examination parameters.
SCOPE
1.1 This practice describes procedures for fabricating both green and sintered test bars of silicon carbide and silicon nitride containing both internal and surface voids at prescribed locations.
1.2 The values stated in SI units are to be regarded as the 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:C1212–98 (Reapproved 2004)
Standard Practice for
Fabricating Ceramic Reference Specimens Containing
Seeded Voids
This standard is issued under the fixed designation C1212; 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 4. Significance and Use
1.1 This practice describes procedures for fabricating both 4.1 This practice describes a method of fabricating known
green and sintered test bars of silicon carbide and silicon discontinuities in a ceramic specimen. Such specimens are
nitride containing both internal and surface voids at prescribed needed and used in nondestructive examination to demonstrate
locations. sensitivity and resolution and to assist in establishing proper
1.2 The values stated in SI units are to be regarded as the examination parameters.
standard.
5. Apparatus
1.3 This standard does not purport to address all of the
5.1 Aeroduster, moisture-free.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- 5.2 Die, capable of exerting a pressure of up to 120 MPa,
that will not contaminate the compacted material.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use. 5.3 Optical Magnifier, capable of providing 10 to 30X
magnification.
2. Referenced Documents
5.4 Tubing, latex, thin-wall, capable of withstanding iso-
2.1 ASTM Standards: press.
B311 Test Method for Density of Powder Metallurgy (PM) 5.5 Carver Press or similiar type of appartus capable of
Materials Containing Less Than Two Percent Porosity exerting the necessary pressure to consolidate the sample.
C373 Test Method for Water Absorption, Bulk Density, 5.6 Cold Isostatic Press, capable of maintaining 500 MPa.
Apparent Porosity, andApparent Specific Gravity of Fired 5.7 Vacuum Oven or Furnace which can maintain a tem-
Whiteware Products perature of 525°C.
5.8 Imaging Equipment with the capability of producing a
3. Terminology
hard copy output of the image (that is, 35mm camera, CCD
3.1 Definitions of Terms Specific to This Standard:
camera outputted to a video printer, a stereo microscope with 4
3.1.1 green specimen—a ceramic specimen formed as origi- X 5 instamatic film, etc.).
nally compacted prior to high-temperature densification.
5.9 Sintering Furnaces capable of reaching temperatures of
3.1.2 internal void—a cavity in a specimen with no connec- 1400–2200°C. Depending on the ceramic system chosen, the
tion to the external surface.
furnace may be required to operate in a vacuum and/or under
3.1.3 seeded voids—intentionally placed discontinuities at inert gas atmospheres at pressures as high as 200 MPa.
prescribed locations in reference specimens.
5.10 Commercial or similar device capable of measuring
3.1.4 sintered specimen—formed ceramic specimen after within .01 mg. Measuring densities according to Archimedes
firing to densify and remove solvents or binders.
principle requires the use of a sample holder suspended in
3.1.5 surface void—a pit or cavity connected to the external water attached to the scale.
surface of a specimen.
6. Materials
6.1 Silicon Carbide or Silicon Nitride Powders, of appro-
This practice is under the jurisdiction of ASTM Committee C28 on Advanced
priate purity and particle size, prepared with sintering aids and
Ceramics and is the direct responsibility of Subcommittee C28.03 on Physical
binder representative of the product to be inspected and in a
Properties and Non-Destructive Evaluation.
Current edition approved May 1, 2004. Published June 2004. Originally
manner appropriate for dry pressing with granule size less than
approved in 1992. Last previous edition approved in 1998 as C1212–98. DOI:
100-mesh.
10.1520/C1212-98R04.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
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C1212–98 (2004)
6.2 Styrene Divinyl Benzene Spheres, with diameters as 7.2.1.2 Sinter green samples under suitable conditions to
necessary. Other material with low vaporization temperatures achieve full densification. Nominal sintering conditions for
may be substituted, but pressing characteristics and final void silicon nitride are 1700–1900°C for1hinan inert atmosphere
sizes may be different. at 0–200 MPa; for silicon carbide, sintering temperatures of
2000–2200°C for 0.5 h under vacuumare commonlyused.The
7. Fabrication of Surface Voids sintering aids used will dictate the firing conditions. Measure
the bulk density using eitherTest Method B311 orTest Method
7.1 Green Specimens:
C373 or from volume and weight measurements.
7.1.1 The test piece geometry must be appropriate for the
7.2.2 Void Measurement—See 7.1.3.
size and geometry limits of the NDE test method. If the
7.3 Surface Void Characteristics (for Both Green and Sin-
purpose of the test is to determine if the NDE method is
tered Specimens):
suitable for the detection of voids in a particular part/sample,
7.3.1 Surface voids produced by this procedure are not
ideally the test sample should be identitcal to the part/sample.
spheroidal in shape. The final dimensions are a function of the
If this is not feasible due to fabrication or testing limitations,
compressibility of the seeded spheres and the compressibility
thetestsampleshouldbesimilartothepart/sampleinchemical
and sintering characteristics of the powders that comprise the
composition, density, and thickness (the thickness of the test
bulk material.
sample should be the same as the thickness in the area of the
7.3.2 Silicon Nitride Test Bars—Made from 100-mesh pow-
part/sample being examined.
der containing yttria and silica sintering additives: The lateral
7.1.2 Procedure:
surface dimensions of voids smaller than 100 µm are up to
7.1.2.1 Prepare the test specimen bars by pouring ceramic
10 % greater than the diameter of the seeded styrene divinyl
powder into a die in an amount sufficient to make a specimen
benzene spheres. Surface dimensions of larger voids are
of the desired thickness. Level the surface and press at a
approximately equal to the seeded sphere diameter. The depth-
nominal pressure of 60 MPa.
to-width ratio increases from 0.6 to 0.8 as the seeded sphere
7.1.2.2 Remove the ram to expose the specimen. Clean the
size increases from 50 to 115 µm.
specimen of all particles that are not flush with the top surface;
7.3.3 Silicon Carbide Test Bars—Made from 100-mesh
this can generally be performed with a moisture-free aero-
alpha silicon carbide powder; in green specimens, the lateral
duster.
surface void dimensions are approximately 25 % greater than
7.1.2.3 Place large spheres in the desired location on the
the diameter of seeded divinyl benzene spheres, while in
specimen surface. Small microspheres may be moved to the
sintered specimens they are approximately 10 % greater. The
desired position with a single
...
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