1、Designation: F2094/F2094M 141Standard Specification forSilicon Nitride Bearing Balls1This standard is issued under the fixed designation F2094/F2094M; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last revision. A num
2、ber in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTETable 4 was editorially corrected in November 2016.1. Scope1.1 This specification covers the establishment of the basicquality, physical/mechanic
3、al property, and test requirementsfor silicon nitride balls Classes I, II, and III to be used for ballbearings and specialty ball applications.1.2 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equiv
4、alents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.2. Referenced Documents2.1 Order of Precedence:2.1.1 In the event of a conflict between the text of thisdocument and the references herein, the
5、text of this documenttakes precedence. Nothing in this document, however, super-sedes applicable laws and regulations unless a specific exemp-tion has been obtained.2.2 ASTM Standards:2C1161 Test Method for Flexural Strength of AdvancedCeramics at Ambient TemperatureC1421 Test Methods for Determinat
6、ion of Fracture Tough-ness of Advanced Ceramics at Ambient Temperature2.3 ANSI Standard:ANSI/ASQC Z1.4 Sampling Procedures and Tables for In-spection by Attributes32.4 ABMA Standards:STD 10 Metal Balls42.5 ASME Standard:B 46.1 Surface Texture (Surface Roughness, Waviness, andLay)52.6 ISO Standards:4
7、505 HardmetalsMetallographic Determination of Poros-ity and Uncombined Carbon32.7 JIS Standards:R 1601 Testing Method for Flexural Strength (Modulus ofRupture) of High Performance Ceramics6R 1607 Testing Method for Fracture Toughness of HighPerformance Ceramics62.8 CEN Standards:EN 843-1 Advanced Te
8、chnical CeramicsMonolithicCeramicsMechanical Properties at Room Temperature,Part 1. Determination of Flexural Strength7ENV 843-5 Advanced Technical CeramicsMonolithicCeramicsMechanical Properties at Room Temperature,Part 5, Statistical Analysis73. Terminology3.1 Definitions of Terms Specific to This
9、 Standard:3.1.1 ball diameter variation, Vdws, nball diameter varia-tion is the difference between the largest and smallest diametermeasured on the same ball.3.1.2 ball gage, S, nprescribed small amount by which thelot mean diameter should differ from nominal diameter, thisamount being one of an est
10、ablished series of amounts. A ballgage, in combination with the ball grade and nominal balldiameter, should be considered as the most exact ball sizespecification to be used by a customer for ordering purposes.1This specification is under the jurisdiction ofASTM Committee F34 on RollingElement Beari
11、ngs and is the direct responsibility of Subcommittee F34.01 onRolling Element.Current edition approved March 15, 2014. Published March 2014. Originallyapproved in 2001. Last previous edition approved in 2013 as F2094/F2094M13.DOI: 10.1520/F2094_F2094M-14E01.2For referenced ASTM standards, visit the
12、ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Application for copies should be addressed to theAmerican National StandardsInstitute (ANSI), 25 W. 43
13、rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.4Application for copies should be addressed to the American Bearing Manufac-turers Association, 1200 19th Street NW, Suite 300, Washington, DC 20036-2401.5Application for copies should be addressed to the American Society ofMechanical Enginee
14、rs (ASME), ASME International Headquarters, Three ParkAve., New York, NY 10016-5990, http:/www.asme.org.6Application for copies should be addressed to the Japanese Standards Organi-zation (JSA), 4-1-24 Akasaka Minato-Ku, Tokyo, 107-8440, Japan, http:/www.jsa.or.jp.7Application for copies should be a
15、ddressed to the British Standards Institute(BSI), 389 Chiswick High Rd., London W4 4AL, U.K., http:/www.bsi-.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.3 ball gage deviation, S, ndifference between the lotmean diameter and th
16、e sum of the nominal diameter and theball gage.3.1.4 ball grade, G, nspecific combination of dimensionalform and surface roughness tolerances. A ball grade is desig-nated by a grade number followed by the letter “C” indicatingSilicon Nitride Ceramic.3.1.5 blank lot, nsingle group of same-sized ball
17、blanksprocessed together from one material lot through densification.3.1.6 ceramic second phase, nsintering additive basedphases, for example, yttria and alumina, which appear darkeror lighter than the silicon nitride matrix, but are not highlyreflective in nature when viewed under reflected light m
18、icros-copy and bright field illumination.3.1.7 color variation, nan area that appears lighter ordarker than the surrounding area under reflected light micros-copy but with no discernible physical discontinuity associatedwith it.3.1.7.1 DiscussionColor variation is often not visibleunder scanning ele
19、ctron microscopy (SEM) examination.3.1.8 c-cracks, ncurved, constant radius cracks, the resultof ball-to-ball impact during finishing or subsequent handling.In extreme cases, the cracks can form a complete circle andmultiple concentric cracks can form.3.1.9 cracks, nirregular, narrow breaks in the s
20、urface ofthe ball typically having a visible width of less than 0.002mm0.00008 in.3.1.9.1 DiscussionMost cracks are formed after densifica-tion but occasionally may be present as material faults. Somecracks may not be visible with normal white light microscopyand may only show up under ultraviolet l
21、ight after processingwith a suitable fluorescent penetrant.3.1.10 cuts, nMechanically induced random, short, lineardepressions in the surface.3.1.11 deviation from spherical form, Rw, ngreatestradial distance in any radial plane between a sphere circum-scribed around the ball surface and any point o
22、n the ballsurface.3.1.12 finish lot, nsingle group of same-sized balls (whichmay be derived from multiple blank lots of the same materiallot) processed together through finishing.3.1.13 inclusion, nany discrete imhomogeneity in themicrostructure that is not intended to be included in thematerial.3.1
23、.13.1 DiscussionInclusions typically consist of foreignmaterial as a result of unintended external powder contamina-tion and resulting reaction product after sintering.3.1.14 lot diameter variation, Vdwl, ndifference betweenthe mean diameter of the largest ball and that of the smallestball in the lo
24、t.3.1.15 lot mean diameter, Dwml, narithmetic mean of themean diameter of the largest ball and that of the smallest ballin the lot.3.1.16 material lot, nsingle process lot of a blendedpowder (blended with additives), produced from a single lot ofsilicon nitride or silicon metal raw powder received f
25、rom amaterial supplier.3.1.16.1 DiscussionWhat constitutes a “single processlot” of blended powder can vary depending on the standardpractices of the vendor and the requirements of the customerand application. For example, for many customers/applications, combining multiple mill charges from one raw
26、material lot into a single material lot is acceptable while forothers, each mill charge would be considered a separatematerial lot. It is difficult, if not impossible, for a singledefinition of material lot to apply to all applications. Thematerial lot should be defined such that application-appropr
27、iatetraceability is maintained and adequate testing appropriate forthe intended application is performed to ensure that thechemistry and material properties of densified parts meetspecifications. The material lot requirements should be dis-cussed and agreed between the vendor and customer.3.1.17 mea
28、n diameter of a ball, Dwm, narithmetic meanof the largest and the smallest actual single diameters of theball.3.1.18 metallic phase, nmaterial phase that is highlyreflective when viewed by reflected light microscopy andbright field illumination.3.1.19 metallic smears, nmetallic material from lapping
29、or measuring equipment transferred onto the ball surface.3.1.20 nominal diameter, Dw, nsize ordered that is thebasis to which the nominal diameter tolerances apply. Thenominal diameter is specified in inches or millimeters (decimalform).3.1.21 nominal diameter tolerance, nmaximum allowabledeviation
30、from true specified nominal diameter for the indi-cated grade.3.1.22 pits, nvoids or cavities in the ball surface.3.1.22.1 DiscussionPits can be formed by severe materialpullout during ball finishing. Pits can also be a result ofbreakout of inclusions during finishing.3.1.23 porosity, nsmall, closel
31、y spaced voids permeating aregion of the ball surface or the whole ball.3.1.24 pressing defects, nthe result of cracks in the ballblanks prior to densification.3.1.24.1 DiscussionSome pressing defects heal more orless completely on densification resulting in a region ofmaterial with slightly differe
32、nt composition and optical char-acteristics than the rest of the ball. These are known as healedor partially healed pressing defects. Unhealed or open pressingdefects can have the appearance of cracks or fissures.3.1.25 raw material lot, nsingle process lot of raw siliconnitride or raw silicon metal
33、 powder received from a materialsupplier.3.1.26 scratches, nnarrow, linear, shallow abrasions onthe surface.3.1.27 scuffs, na dense concentration of small, parallelsuperficial scratches.F2094/F2094M 14123.1.28 single diameter of a ball, Dws, nthe distancebetween two parallel planes tangent to the su
34、rface of the ball.3.1.29 snowflakes, nregions of microporosity in the grainboundary phase that often display a dendritic appearance.3.1.29.1 DiscussionSnowflakes show up as white den-dritic features when viewed with oblique illumination or withultraviolet light after processing with a fluorescent pe
35、netrant.The individual micropores are often submicron in size and thesnowflakes can range in size from less than 10 m .00039 in.to over 1,000 m .039 in. in extreme cases.3.1.30 surface roughness Ra, nsurface irregularities withrelative small spacings, which usually include irregularitiesresulting fr
36、om the method of manufacture being used or otherinfluences, or both.3.1.31 unit container, ncontainer identified as containingballs from the same manufacture lot of the same composition,grade, and nominal diameter, and within the allowable diam-eter variation per unit container for the specified gra
37、de.4. Classification4.1 Silicon nitride materials for bearing and specialty ballapplications are specified according to the following materialclasses (see Appendix X1 for typical current applications):4.1.1 Class IHighest grade of material in terms of prop-erties and microstructure. Suitable for use
38、 in the most demand-ing applications. This group adds high reliability and durabilityfor extreme performance requirements.4.1.2 Class IIGeneral class of material for most bearingand specialty ball applications. This group addresses theconcerns of ball defects as is relative to fatigue life, levels o
39、ftorque, and noise.4.1.3 Class IIILower grade of material for low dutyapplications only. This group of applications primarily takesadvantage of silicon nitride material properties. For example:Light weight, chemical inertness, lubricant life extension dueto dissimilarity with race materials, and so
40、forth.5. Ordering Information5.1 Acquisition documents should specify the following:5.1.1 Title, number, and date of this specification.5.1.2 Class, grade, and size (see 4.1, 8.6, and 8.7).6. Material6.1 Unless otherwise specified, physical and mechanicalproperty requirements will apply to all mater
41、ial classes.6.2 To be classified as Class I, silicon nitride balls shall beproduced from either silicon nitride powder having the com-positional limits listed in Table 1 or from silicon metal powder,which after nitridation complies with the compositional limitslisted in Table 1.6.3 Composition is me
42、asured in weight percent. Testingshall be carried out by a facility qualified and approved by thesupplier. Specific equipment, tests, and/or methods are subjectto agreement between suppliers and their customers.6.4 Compounds may be added to promote densification andenhance product performance and qu
43、ality.6.5 Iron oxides may be added to promote densification withthe total iron content for the final product not to exceed 1.0weight %.6.6 Precautions should be taken to minimize contaminationby foreign materials during all stages of processing up to andincluding densification.6.7 A residual content
44、 of up to 2 % tungsten carbide frompowder processing is allowable.6.8 Final composition shall meet and be reported accordingto the specification of the individual supplier.6.9 Notification will be made upon process changes.6.10 Specific requirements such as specific material gradedesignation, physic
45、al/mechanical property requirements (forexample, density) or quality or testing requirements shall beestablished by specific application. The special requirementsshall be in addition to the general requirements established inthis specification.6.11 Typical mechanical properties will fall within the
46、rangelisted in Table 2. Individual requirements may have tighterranges. The vendor shall certify that the silicon nitride materialsupplied has physical and mechanical properties within therange given in Table 2. In the case of properties indicated by(+), the provision of the data is not mandatory.7.
47、 Physical Properties7.1 The following physical properties shall be measured, ata minimum, on each material lot.TABLE 1 Compositional Limits for Starting Silicon NitridePowders or Silicon Powder Converted to Silicon Nitride forClass I MaterialsAConstituents Limits (wt %)Silicon nitride 97.0 min.Free
48、silicon 0.3 max.Carbon 0.3 maxIron 0.5 max.AOther impurities or elements such as sodium, potassium, chlorine, etc. individu-ally shall not exceed 0.02 wt % max.TABLE 2 Typical Mechanical PropertiesAProperties Minimum MaximumDensity, g/cc lb/ft3 3.0 187 3.4 212Elastic modulus, GPa ksi 270 39 150 330
49、47 850Poissons ratio 0.23 0.29Thermal conductivity, W/m-KBtu/h-ft-F 20C (room temp.)20 11.5 38 21.9Specific heat, J/kg-K Btu/Ibm-F 650 0.167 800 0.191Coefficient of thermal expansion, 10-6/C(room temp. to 500C)2.3 3.4+ Resistivity, Ohm-m 10101016+ Compressive strength, MPa ksi 3000 435ASpecial material data should be obtained from individual suppliers.F2094/F2094M 14137.1.1 Average values for room temperature rupture strength(bend strength/modulus of rupture) for a m
