ASTM B294-17 Standard Test Method for Hardness Testing of Cemented Carbides.pdf

1、Designation: B294 17Standard Test Method forHardness Testing of Cemented Carbides1This standard is issued under the fixed designation B294; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in pare

2、ntheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the hardness testing of ce-mented carbides by use of a Rockwell hardness tester perform-ing tests in the Rockwell HRA scale

3、(regular scale, diamondindenter, 10 kgf (98.07 N) preliminary test force, and 60 kgf(588.4 N) total test force in the range of Rockwell 80 HRAandabove. Also covered are the procedures for the testing andselection of diamond indenters, the management and traceabil-ity of the four levels of standardiz

4、ed test blocks, and themaking and calibration of Primary, Secondary, and Workingstandardized test blocks.1.2 The Rockwell hardness tester is a convenient andreliable means of measuring the hardness of cemented car-bides. A hardness value is obtained easily, but it is subject toconsiderable error unl

5、ess certain precautions are observed.1.3 The latest version of Test Methods E18 shall be fol-lowed except where otherwise indicated in this test method.1.4 The values stated in SI units are to be regarded asstandard except that force and length values associated with theRockwell hardness testers wil

6、l comply with E18 with forcevalues specified as N (kgf) and indenter length values specifiedas mm.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, a

7、nd environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International

8、 Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE29 Practice for Using Significant Digits in Test Data toDetermine Conform

9、ance with Specifications2.2 ISO Standards:3ISO/IEC 17011 Conformity AssessmentGeneral Require-ments for Accreditation Bodies Accrediting ConformityAssessment BodiesISO/IEC 17025 General Requirements for the Competenceof Testing and Calibration Laboratories3. Significance and Use3.1 Rockwell hardness

10、 testing is one of the more importantmethods used to evaluate cemented carbides. For composi-tional groups of cemented carbides, hardness is an indication ofwear resistance and toughness. Lower hardness grades usuallyindicate less wear resistance but greater toughness. For aspecific grade of cemente

11、d carbide, hardness is an indication ofthe metallurgical quality of the material. In no case is Rockwellhardness testing the only test method to be considered inevaluating cemented carbides.4. Principles of Test Apparatus4.1 TesterAll hardness tests shall be performed using aRockwell hardness tester

12、 that meets the requirements definedin the latest version of Test Method E18 except whereotherwise indicated in this test method. Testers shall complywith the requirements of Annex A3 of this test method.4.2 ScaleAll tests shall be performed using the carbideRockwell HRA scale (a carbide diamond ind

13、enter, 10 kgf(98.07 N) preliminary force, and 60 kgf (588.4 N) total testforce.4.3 Effect of VibrationThe Rockwell hardness testershould be located in a vibration-free area in order to avoid1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products an

14、d is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved Nov. 1, 2017. Published February 2018. Originallyapproved in 1954. Last previous edition approved in 2010 as B294 10. DOI:10.1520/B0294-17.2For referenced ASTM standards, visit the ASTM website, www.

15、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.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ans

16、i.org.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardizatio

17、n established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1erroneous results. If this is not possible, the tester shall bemounted so as to minimize vibration

18、s, since vibrations tend tocause erratic readings.4.4 IndenterThe indenters used shall conform to therequirements defined in Annex A2 of this test method.4.5 AnvilsSelect an anvil suitable for the specimen to betested. The test piece should be supported rigidly, with the testsurface perpendicular to

19、 the line of travel of the indenter. Forthe best accuracy, flat test pieces should be tested on a flat spotanvil of approximately 6-mm diameter.The surface of the anvilthat contacts the sample should have a Rockwell hardness of atleast 58 HRC, and shall be polished smooth and be free of pitsand heav

20、y scratches that could affect the test results. Themounting surface of the anvil support and the mating surface ofthe anvil should be clean. Dust, dirt, grease, or scale should notbe allowed to accumulate on any part of the apparatus, as thiswill affect the results. Seat the anvil securely.4.6 Test

21、BlocksStandardized test blocks used to verify theperformance of the tester shall comply with the requirements inAnnex A1 of this test method.5. Test Specimens5.1 Size of SpecimensA minimum thickness of 1.6 mm isrecommended. With thinner specimens, breakage may occur,resulting in damage to the anvil,

22、 the indenter, or both. Speci-mens that have enough overhang to cause imbalance shall besupported properly. The 6-mm anvil will support flat testspecimens up to approximately 113 g and will also support thestandard test blocks recommended previously.5.2 Preparation of Test Specimens:5.2.1 The finish

23、 of the test surface is of major importance.The surface to be tested should be prepared to obtain aroughness of Ra 0.2 m.Acoarser finish will provide a widerrange of readings. Preparation shall be conducted in such a waythat alteration of the surface due to heat or cold-working isminimized. A 220-gr

24、it medium hardness resinoid bond dia-mond wheel, downfed 0.01 mm per pass with abundant flow ofcoolant, should provide the desired surface. The thickness ofthe layer removed from an as-sintered surface to be tested shallbe not less than 0.2 mm.5.2.2 The test and anvil surfaces of the test specimen s

25、hallbe parallel within 0.01 mm/mm in general practice, but within0.001 mm/mm when critical comparisons are being made. Thesurface in contact with the anvil shall be free of any irregularity(for example, a previous hardness indentation). Taper thatresults in the test surface not being normal to the a

26、xis of theindenter, or irregularity that causes instability during the test,will result in error.5.2.3 When determining the hardness of a test specimenwith a curved surface, the radius of curvature shall not be lessthan 15 mm. If less, then a flat surface at least 3 mm wide shallbe prepared on which

27、 to conduct the test, and there shall be anopposite flat surface such that the specimen conforms to therequirements of 5.2 and 5.3. If the test surface is curved or theopposite surface must be supported in a V-anvil, the repeat-ability and reproducibility limits of 8.2 and 8.3 may not apply.5.3 Prep

28、aration of Mounted CarbidesRemove mountedcarbides from the steel body by heating or some otherconvenient method. All braze metal or other bond materialshall be removed from both the test surface and the oppositeface. The specimen should then be prepared as described in 5.1and 5.2.6. Procedure6.1 Roc

29、kwell hardness tests should be carried out at anambient temperature within the limits of 10 to 35C. Users ofthe Rockwell hardness test are cautioned that the temperatureof the test material and the temperature of the hardness testermay affect test results. Consequently, users should ensure thatthe t

30、est temperature does not adversely affect the hardnessmeasurement.6.2 Procedures that are not described in this test methodshall conform to those of Test Method E18.6.3 Disregard the first two readings after an indenter or anvilhas been newly mounted.6.4 Test Cycle Time6.4.1 The application time for

31、 the additional test force(major load) shall be 2 to 6 s.6.4.2 The total test force (major load) shall be maintainedfor2to4s.NOTE 1On manual machines, the abrupt actuation of the total testforce (major load) application trip lever may affect the hardness valueobtained. In addition the abrupt actuati

32、on of the total test force (majorload) removal lever may significantly affect the hardness value obtained.6.5 The Rockwell HRAhardness value is read after the totaltest force (major load) has been removed and while thepreliminary test force (minor load) is still applied.6.6 Hardness should be read o

33、r estimated to at least thenearest 0.1 HRA. Calculations should be carried to twodecimal places.6.7 The distance between the centers of any two adjacentindentations, and the distance between the center of anyindentation and the edge of a test specimen, shall be at least 1.5mm.6.8 Make two trial dete

34、rminations of the hardness of the testspecimen. This action also reassures that the indenter is seatedproperly. Disregard the results and perform the following steps.6.8.1 Select a standardized test block that complies withAnnexA1 having a value closest to the trial hardness of the testspecimen. Det

35、ermine the Rockwell HRA hardness at threepoints on the block.6.8.2 If the arithmetic mean of the three determinationsdiffers from the certified hardness value of the standardized testblock by more than 60.5 HRA, check the diamond indenterand the testing equipment, and eliminate the cause of the erro

36、r.Repeat the determinations.6.8.3 If the arithmetic mean of the three determinationsdiffers from the certified hardness value of the standardized testblock by 60.5 HRA or less, record the difference, giving dueregard to the algebraic sign. This difference will be used tocorrect the arithmetic mean o

37、f the hardness of the testspecimens.B294 1726.8.4 Determine the Rockwell HRA hardness of the testspecimen, with determinations at three or more locationschosen at random, or as dictated by the purpose of the test.6.8.5 Calculate the arithmetic mean of the hardness deter-minations. Apply the correcti

38、on determined as in 6.8.3, givingdue regard to the algebraic sign.6.8.6 Report the corrected arithmetic mean of the hardnessdeterminations, rounded in accordance with Practice E294tothe nearest 0.1 HRA.7. Report7.1 Report the following information:7.1.1 All details necessary for identification of th

39、e testspecimen,7.1.2 The corrected mean hardness and the amount ofcorrection including the algebraic sign,7.1.3 The range of hardness determinations,7.1.4 The number of hardness determinations,7.1.5 The smallest division of readout or graduation of thehardness test machine and whether it is digital

40、or analog,7.1.6 The identification and original source of calibrationfor the standardized test blocks used,7.1.7 A reference to this test method, and7.1.8 Details of any deviations from this test method, ofoptional procedures used, and of any conditions and occur-rences that may have affected the re

41、sults.8. Precision and Bias58.1 The following statements regarding the repeatability andreproducibility of hardness (HRA) measurements of cementedcarbide test specimens shall apply only within the hardnessrange established for the indenter in accordance withA2.4.2.4 (5)orA2.4.2.4 (6).8.2 The repeata

42、bility limit (r) is 0.3 HRA. On the basis oftest error alone, the difference in absolute value of two testresults obtained in the same laboratory on the same testspecimen will be expected to exceed 0.3 HRA only approxi-mately 5 % of the time. The repeatability standard deviation(Sr) is 0.1 HRA.8.3 T

43、he reproducibility limit (R) between or among labora-tories is 0.4 HRA when each has calibrated its machine,indenter, and operator system with a standard test block thathas itself been calibrated to the same superior test block usedto calibrate the test blocks of the other laboratories. On thebasis

44、of test error alone, the difference in absolute value of thetest results obtained in different laboratories on the same testspecimen will be expected to exceed 0.4 HRA only approxi-mately 5 % of the time. The reproducibility standard deviation(SR) is 0.14 HRA.8.4 Neither the data of the interlaborat

45、ory study nor theo-retical considerations suggest a bias in this test procedure.8.5 If the test specimens are of a hardness substantiallyoutside the hardness ranges of the standard test blocks onwhich the indenter has been performance tested, and if inter-laboratory reproducibility is critical, the

46、same indenter andstandard test blocks should be used by each laboratory.9. Keywords9.1 cemented carbides; hardness; indenters; Rockwell hard-ness test; Scale HRA; test blocksANNEXES(Mandatory Information)A1. PREPARATION, CALIBRATION, AND CONTROL OF STANDARDIZED TEST BLOCKS USED IN THE PERFORMANCEOF

47、THE PROCEDURES OF THIS TEST METHODA1.1 Scope and Field of ApplicationA1.1.1 The Rockwell hardness levels of cemented carbidesare established by sets of Master test blocks that weredeveloped by the Cemented Carbide Producers Association(CCPA). This annex specifies how those Master blocks areutilized

48、to provide a traceable Rockwell hardness standard tothe user of this test method. It specifies the preparation andcalibration of Primary, Secondary, and Working standard testblocks that are traceable to the Master blocks.A1.1.2 Standardized test blocks complying with this annexare required for Rockw

49、ell hardness testing of cemented car-bides by the procedures defined in this test method.4When the second decimal place is less than 0.05, leave the first decimal placeunchanged. When the second decimal place is more than 0.05, increase the firstdecimal place by 0.1. When the second decimal place is exactly 5 and the firstdecimal place is odd, increase the first decimal by 0.1. If the first decimal place iseven, leave it unchanged.5The statements of repeatability and reproducibility in this section are based onan interlaboratory study conducted by the Cemented Carbide