1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 14627:2012Fine ceramics (advancedceramics, advanced technicalceramics) Test methodfor fracture resistance ofsilicon nitride materials forrolling bearing balls at roomtempe
2、rature by indentationfracture (IF) methodBS ISO 14627:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 14627:2012.The UK participation in its preparation was entrusted to TechnicalCommittee RPI/13, Advanced technical ceramics.A list of organizations represe
3、nted on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 708
4、08 4ICS 81.060.30Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2012.Amendments issued since publicationDate Text affectedBS ISO 14627:2012 ISO 2012Fine c
5、eramics (advanced ceramics, advanced technical ceramics) Test method for fracture resistance of silicon nitride materials for rolling bearing balls at room temperature by indentation fracture (IF) methodCramiques techniques Mthode dessai de rsistance la rupture des matriaux nitrure de silicium pour
6、billes de roulement billes temprature ambiante par la mthode de rupture par indentationINTERNATIONAL STANDARDISO14627First edition2012-07-15Reference numberISO 14627:2012(E)BS ISO 14627:2012ISO 14627:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unle
7、ss otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO co
8、pyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 14627:2012ISO 14627:2012(E) ISO 2012 All rights reserved iiiContents PageForeword iv1 Scope 12 Normative references . 13 Terms and definition
9、s . 14 Principle . 25 Apparatus 25.1 Testing machine . 25.2 Indenter 25.3 Verification by standard reference materials . 36 Test specimens 36.1 General . 36.2 Thickness 36.3 Surface finish . 37 Procedure 37.1 Specimen placement 37.2 Specimen leveling . 37.3 Clean the indenter . 37.4 Application of t
10、est load 37.5 Acceptability of indentations . 47.6 Number of indentations . 47.7 Measurement of indentation size 57.8 Measurement of crack size . 58 Calculation 59 Test report . 6Bibliography . 8BS ISO 14627:2012ISO 14627:2012(E)ForewordISO (the International Organization for Standardization) is a w
11、orldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented
12、on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted
13、 in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standar
14、d requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 14627 was prepared by Tec
15、hnical Committee ISO/TC 206, Fine ceramics.iv ISO 2012 All rights reservedBS ISO 14627:2012INTERNATIONAL STANDARD ISO 14627:2012(E)Fine ceramics (advanced ceramics, advanced technical ceramics) Test method for fracture resistance of silicon nitride materials for rolling bearing balls at room tempera
16、ture by indentation fracture (IF) method1 ScopeThis International Standard describes a test method that covers the determination of fracture resistance of silicon nitride bearing balls at room temperature by the indentation fracture (IF) method, as specified in ISO 26602.This International Standard
17、is intended for use with monolithic silicon nitride ceramics for bearing balls. It does not include other ceramic materials.This International Standard is for material comparison and quality assurance.Indentation fracture resistance, KI, IFRas defined in this International Standard is not to be equa
18、ted to fracture toughness determined using other test methods such as KIscand KIpb.NOTE KI, IFRis an estimate of a materials resistance to cracking as introduced by an indenter and has correlations with wear resistance and rolling contact fatigue performance as well as machining processes used for s
19、ilicon nitride materials since these properties are governed by the resistance to crack extension in localized damage areas. By contrast, fracture toughness, KIscand KIpbare intrinsic properties of a material and are relevant to macroscopic and catastrophic fracture events with long cracks, rather t
20、han those phenomena caused by microscopic and successive damage accumulation associated with short cracks.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the
21、 latest edition of the referenced document (including any amendments) applies.ISO 4287:1997, Geometrical Product Specifications (GPS) Surface texture: Profile method Terms, definitions and surface texture parametersISO 6507-2:2005, Metallic materials Vickers hardness test Part 2: Verification and ca
22、libration of testing machinesISO 6507-3:2005, Metallic materials Vickers hardness test Part 3: Calibration of reference blocksISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratoriesISO 17561:2002, Fine ceramics (advanced ceramics, advanced technical cerami
23、cs) Test method for elastic moduli of monolithic ceramics at room temperature by sonic resonanceISO 26602:2009, Fine ceramics (advanced ceramics, advanced technical ceramics) Silicon nitride materials for rolling bearing balls3 Terms and definitionsFor the purpose of this document, the following ter
24、ms and definitions apply. ISO 2012 All rights reserved 1BS ISO 14627:2012ISO 14627:2012(E)3.1fracture resistanceKI, IFRfracture resistance measured by the IF methodISO 26602:2009NOTE The indentation fracture resistance, KI, IFR, as used here is not to be equated to fast fracture toughness KIc. KI, I
25、FRis an estimate of a materials resistance to cracking as introduced by an indenter. KIcis considered to be an intrinsic property of a material and is independent of the test method.3.2preprocessed balldensified unit of material from a material lot before final shaping and finishingISO 26602:20094 P
26、rincipleThis International Standard is for material comparison, quality assurance of silicon nitride materials for rolling bearing balls as described in ISO 26602. The method determines the indentation fracture resistance value, KI, IFR, by forcing a Vickers indenter (diamond pyramid) into the surfa
27、ce of a test piece and measuring the lengths of both the diagonals and the associated cracks of the indentation that are left in the surface after removal of the indenter. See Figure 1.2a22a12c12c2Key2a is the diagonal length of the indent2c is the diagonal length of the crackFigure 1 Crack lengths
28、and diagonal sizes of the Vickers indentation5 Apparatus5.1 Testing machineThe testing machine shall be in accordance with ISO 6507-2.5.2 IndenterThe indenter shall meet the specification for the Vickers indenter. See the test method in ISO 6507-2. The diamond should be examined before the test, and
29、 if it is loose in the mounting material, chipped, or cracked, it shall be replaced.2 ISO 2012 All rights reservedBS ISO 14627:2012ISO 14627:2012(E)5.3 Verification by standard reference materialsThe reference materials which are in accordance with ISO 6507-3 shall be used to verify the testing mach
30、ine and their Vickers hardness shall not vary from the hardness of the material to be measured by more than 20 %.6 Test specimens6.1 GeneralThe ground and polished sections of the preprocessed balls or the finished products shall be used for the indentation fracture (IF) method. The surface finishin
31、g shall be done to avoid residual stress.6.2 ThicknessThe thickness of the specimen shall be large enough so that the crack lengths are not affected by variations in the thickness. As long as the thickness of the specimen is more than five times the crack length (2c), the test will not be affected.
32、In general, a specimen thickness of more than 3 mm is suitable.6.3 Surface finishSpecimens shall have a ground and polished surface so that the crack lengths can be measured accurately. The surface roughness, Ra, as defined in ISO 4287 shall be not more than 0,1 m. Any grinding-induced damage layer
33、at the surface shall be removed completely by polishing so that the crack lengths are not affected by any residual stress at the surface layer.NOTE If the specimen test area is insufficient to permit at least five valid indentations (see Figure 2) to be obtained using the spacing criterion given in
34、7.6, e.g. if bearing balls are employed, then it is permitted either to employ a larger test-piece from the same material lot, or several randomly selected bearing balls from the same lot.7 Procedure7.1 Specimen placementPlace the specimen on the stage of the machine so that the specimen will not ro
35、ck or shift during the measurement. The specimen surface shall be clean and free from any grease or film.7.2 Specimen levelingThe surface of the specimen being tested shall lie in a plane normal to the axis of the indenter.7.3 Clean the indenterThe indenter shall be cleaned prior to and during a tes
36、t series. A cotton swab with ethanol, methanol or isopropanol may be used. Indenting into soft copper also may help remove debris.7.4 Application of test loadIndentations shall be made using a Vickers indenter under the following conditions: Load 196,1 N Dwell Time 15 s ISO 2012 All rights reserved
37、3BS ISO 14627:2012ISO 14627:2012(E)If indentations made at the test load of 196,1 N lead to no acceptable indentations (see Figure 2), use a lower test load of 98,07 N. The test load employed shall be described in the test report to show the precision of measurements.NOTE 1 KI, IFRmeasured at a load
38、 of 98,07 N may be slightly smaller than that obtained at 196,1 N, especially for those silicon nitrides with self-reinforced microstructures which produce rising R-curve behavior. Also, the accuracy of the measurement of crack length may become worse when the indentation size gets smaller at the te
39、st load of 98,07 N.NOTE 2 If the thickness of the tiny ball specimen is not more than five times the crack length (2c), or the specimen test area is insufficient for a single indentation to satisfy the spacing criterion given in 7.6 (see Figure 3), a test load lower than 98,07 N is permitted by mutu
40、al agreement between the customer and vendor.7.5 Acceptability of indentationsOnly indentations whose four primary cracks emanate straight and radially from each corner shall be accepted. Indentations with badly asymmetrical, split or forked cracks or with gross chipping shall be rejected. If the di
41、fference between the horizontal crack length and the vertical one is more than 10 % of the mean value of the horizontal and vertical ones, the result shall be rejected.2c12c26cl1 10cKey1 edge of test piece2 indentations2c is the diagonal length of the crackl1is the distance between centres of indent
42、ationsl2is the distance from the centre of indentation to the edge of sampleFigure 3 Closest permitted spacing between indentations and from indentation to the test piece edge for Vickers indentations7.7 Measurement of indentation sizeMeasure both diagonals of each hardness impression as “2a” values
43、 to within 2 m within 10 min after unloading, e.g. with an optical microscope attached to the hardness tester, a metallurgical microscope or a traveling microscope.7.8 Measurement of crack sizeEnlarge the indentation by at least 100x using an optical microscope attached to the hardness tester, a met
44、allurgical microscope or a traveling microscope, and measure visible tip-to-tip crack lengths associated with the hardness impression as “2c” values to within 10 m within 10 min after unloading. Crack observations with higher total magnification, e.g. not less than 200x by using a Charge Coupled Dev
45、ice (CCD) camera or a traveling microscope, are preferred to minimize measuring errors.NOTE The achievable precision of crack size measurement depends upon the microstructure of material, the surface finish and the magnification of a microscope. Reading crack lengths of indentations in bearing-grade
46、 silicon nitrides with a total magnification of 100x will enable the precision suggested in 7.8 to be achieved by well-trained operators. The calculated indentation fracture resistance, KI, IFR, is sensitive to the precision of the crack length measurements, as is obvious from Equation (3) in 8.3. T
47、hus, employing higher magnification greater than 100x is preferable to ensure the validity of the test results.The magnification employed shall be described in the test report to show the precision of the measurements.8 Calculation8.1 For each indentation, calculate the mean values of 2a and 2c.2222
48、222212 12aaaccc=+=+and (1)8.2 For each indentation, calculate the Vickers hardness value as follows: ISO 2012 All rights reserved 5BS ISO 14627:2012ISO 14627:2012(E)HVPa= 0,001854()22(2)where:HV is the Vickers hardness, in gigapascals (GPa);P is the applied load, in newtons (N);a is the mean half-le
49、ngth diagonal value, in millimetres (mm).8.3 For each indentation, calculate the indentation fracture resistance by Niiharas method as follows:KEHVPcI,IFR=0 0009780415,(3)where:KI, IFRis the indentation fracture resistance, in megapascals square root metre (MPam1/2);E is the elastic modulus, in gigapascals (GPa);HV is the Vickers hardness, in gigapascals (GPa);P is the applied load, in newtons (N);c is the mean half-crack length, in millimetres (mm).NOTE It is proven that at loads of 98,07 N and
