1、Designation:C121298(Reapproved 2015)Standard Practice forFabricating Ceramic Reference Specimens ContainingSeeded Voids1This standard is issued under the fixed designation C1212;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the yea
2、r of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice describes procedures for fabricating bothgreen and sintered test bars of silicon carbide and siliconnitr
3、ide containing both internal and surface voids at prescribedlocations.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It i
4、s theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2B311 Test Method for Density of Powder Metallurgy(PM)Materials Containing Less Than
5、 Two Percent PorosityC373 Test Method for Water Absorption,Bulk Density,Apparent Porosity,andApparent Specific Gravity of FiredWhiteware Products,Ceramic Tiles,and Glass Tiles3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 green specimena ceramic specimen formed as origi-nally
6、compacted prior to high-temperature densification.3.1.2 internal voida cavity in a specimen with no connec-tion to the external surface.3.1.3 seeded voidsintentionally placed discontinuities atprescribed locations in reference specimens.3.1.4 sintered specimenformed ceramic specimen afterfiring to d
7、ensify and remove solvents or binders.3.1.5 surface voida pit or cavity connected to the externalsurface of a specimen.4.Significance and Use4.1 This practice describes a method of fabricating knowndiscontinuities in a ceramic specimen.Such specimens areneeded and used in nondestructive examination
8、to demonstratesensitivity and resolution and to assist in establishing properexamination parameters.5.Apparatus5.1 Aeroduster,moisture-free.5.2 Die,capable of exerting a pressure of up to 120 MPa,that will not contaminate the compacted material.5.3 Optical Magnifier,capable of providing 10 to 30Xmag
9、nification.5.4 Tubing,latex,thin-wall,capable of withstanding iso-press.5.5 Carver Press or similiar type of appartus capable ofexerting the necessary pressure to consolidate the sample.5.6 Cold Isostatic Press,capable of maintaining 500 MPa.5.7 Vacuum Oven or Furnace which can maintain a tem-peratu
10、re of 525C.5.8 Imaging Equipment with the capability of producing ahard copy output of the image(that is,35mm camera,CCDcamera outputted to a video printer,a stereo microscope with 4X 5 instamatic film,etc.).5.9 Sintering Furnaces capable of reaching temperatures of14002200C.Depending on the ceramic
11、 system chosen,thefurnace may be required to operate in a vacuum and/or underinert gas atmospheres at pressures as high as 200 MPa.5.10 Commercial or similar device capable of measuringwithin.01 mg.Measuring densities according to Archimedesprinciple requires the use of a sample holder suspended inw
12、ater attached to the scale.6.Materials6.1 Silicon Carbide or Silicon Nitride Powders,of appro-priate purity and particle size,prepared with sintering aids and1This practice is under the jurisdiction of ASTM Committee C28 on AdvancedCeramics and is the direct responsibility of Subcommittee C28.03 on
13、PhysicalProperties and Non-Destructive Evaluation.Current edition approved Jan.1,2015.Published April 2015.Originallyapproved in 1992.Last previous edition approved in 2010 as C121298(2010).DOI:10.1520/C1212-98R15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Cust
14、omer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 binder representative of the product to be
15、 inspected and in amanner appropriate for dry pressing with granule size less than100-mesh.6.2 Styrene Divinyl Benzene Spheres,with diameters asnecessary.Other material with low vaporization temperaturesmay be substituted,but pressing characteristics and final voidsizes may be different.7.Fabricatio
16、n of Surface Voids7.1 Green Specimens:7.1.1 The test piece geometry must be appropriate for thesize and geometry limits of the NDE test method.If thepurpose of the test is to determine if the NDE method issuitable for the detection of voids in a particular part/sample,ideally the test sample should be identitcal to the part/sample.If this is not feasible due to fabrication or testing limitations,the test sample should be similar to the part/sample in chemicalcomposition,density,and thickness(the
