Standard Test Method for Microindentation Hardness of ...

1 Designation: E 384 05a Standard Test Method for Microindentation Hardness of materials1 . This Standard is issued under the fixed designation E 384; 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 (e) indicates an editorial change since the last revision or reapproval. This Standard has been approved for use by agencies of the Department of Defense. 1. Scope E 691 Practice for Conducting an Interlaboratory Study to This test Method covers determination of the microin- Determine the Precision of a Test Method dentation Hardness of materials, the verification of microinden- E 766 Practice for Calibrating the Magnification of a Scan- tation Hardness testing machines, and the calibration of stan- ning Electron Microscope dardized test blocks.

2 3. Terminology This test Method covers Microindentation tests made with Knoop and Vickers indenters under test forces in the range Definitions For definitions of terms used in this test from 3 10-3 to N ( 1 to 1000 gf ). Method , see Terminology E 7. This test Method includes an analysis of the possible Definitions of Terms Specific to This Standard : sources of errors that can occur during Microindentation testing calibrating, v determining the values of the signifi- and how these factors affect the accuracy, repeatability, and cant parameters by comparison with values indicated by a reproducibility of test results. reference instrument or by a set of reference standards . Knoop Hardness number, HK, n an expression of NOTE 1 While Committee E04 is primarily concerned with metals, the Hardness obtained by dividing the force applied to the Knoop test procedures described are applicable to other materials.

3 Indenter by the projected area of the permanent impression This Standard does not purport to address all of the made by the indenter. safety concerns, if any, associated with its use. It is the Knoop indenter, n a rhombic-based pyramidal- responsibility of the user of this Standard to establish appro- shaped diamond indenter with edge angles of / A = 172 308. priate safety and health practices and determine the applica- and / B = 130 08 (see Fig. 1). bility of regulatory limitations prior to use. Microindentation Hardness test, n a Hardness test using a calibrated machine to force a diamond indenter of 2. Referenced Documents specific geometry into the surface of the material being ASTM standards : 2 evaluated, in which the test forces range from 1 to 1000 gf ( C 1326 Test Method for Knoop Indentation Hardness of 3 10 3 to N), and the indentation diagonal, or diagonals are Advanced Ceramics measured with a light microscope after load removal; for any C 1327 Test Method for Vickers Indentation Hardness of Microindentation Hardness test, it is assumed that the indenta- Advanced Ceramics tion does not undergo elastic recovery after force removal.

4 E 3 methods of Preparation of Metallographic Specimens NOTE 2 Use of the term microhardness should be avoided because it E 7 Terminology Relating to Metallography implies that the Hardness , rather than the force or the indentation size, is E 122 Practice for Choice of Sample Size to Estimate the very low. Average Quality for a Lot or Process E 140 Test Method for Hardness Conversion Tables for verifying, v checking or testing the instrument to Metals assure conformance with the specification. E 175 Terminology of Microscopy Vickers Hardness number, HV, n an expression of Hardness obtained by dividing the force applied to a Vickers indenter by the surface area of the permanent impression made 1. This test Method is under the jurisdiction of ASTM Committee E04 on by the indenter.

5 Metallography and is the direct responsibility of Subcommittee on Micro- Vickers indenter, n a square-based pyramidal-shaped Hardness . Current edition approved August 15, 2005. Published September 2005. Origi- diamond indenter with face angles of 136 (see Fig. 2). nally approved in 1969. Last previous edition approved in 2005 as E 384 05. Formulae The formulae presented in ffor 2. For referenced ASTM standards , visit the ASTM website, , or calculating Microindentation Hardness are based upon an ideal contact ASTM Customer Service at For Annual Book of ASTM tester. The measured value of the Microindentation Hardness of standards volume information, refer to the Standard 's Document Summary page on the ASTM website.

6 A material is subjected to several sources of errors. Based on Eq Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. 1. koopa group Tel: +9811 33366282. E 384 05a FIG. 1 Knoop Indenter FIG. 2 Vickers Indenter 1-9, variations in the applied force, geometrical variations HK 5 14229 3 P/d2 (2). between diamond indenters, and human errors in measuring indentation lengths can affect the calculated material Hardness . The amount of error each of these parameters has on the cp 5. tan S D. /B. 2. (3). calculated value of a Microindentation measurement is dis- cussed in Section 10. 2 tan S D. /A. 2. For Knoop Hardness tests , in practice, test loads are in grams-force and indentation diagonals are in micrometers.

7 The where: P = force, gf, Knoop Hardness number is calculated using the following: d = length of long diagonal, m, HK 5 3 103 3 ~P/Ap! 5 3 103 3 P/~cp 3 d2! (1) Ap = projected area of indentation, m2, or /A = included longitudinal edge angle, 172 308, 2. koopa group Tel: +9811 33366282. E 384 05a / B = included transverse edge angle, 130 08 (see Fig. 1), cation of a relatively low force, in comparison to ordinary and indentation Hardness tests . cp = indenter constant relating projected area of the A Knoop or Vickers indenter, made from diamond of indentation to the square of the length of the long specific geometry is pressed into the test specimen surface diagonal, ideally under an applied force in the range of 1 to 1000 gf using a test machine specifically designed for such work.

8 NOTE 3 HK values for a 1-gf ( 3 10 3 N) test are contained in The size of the indentation is measured using a light Appendix X6. To obtain HK values when other test forces are employed, multiply the HK value from Table for the d value by the actual test microscope equipped with a filar type eyepiece, or other type force, g. of measuring device (see Terminology E 175). The Knoop Hardness number is based upon the force The Knoop Hardness , kgf/mm2 is determined as fol- divided by the projected area of the indentation. The Vickers lows: Hardness number is based upon the force divided by the surface HK 5 3 P1/d12 (4) area of the indentation. It is assumed that elastic recovery does not occur when where: the indenter is removed after the loading cycle, that is, it is P1 = force, kgf, and assumed that the indentation retains the shape of the indenter d1 = length of long diagonal, mm.

9 After the force is removed. In Knoop testing, it is assumed that The Knoop Hardness reported with units of GPa is the ratio of the long diagonal to the short diagonal of the determined as follows: impression is the same (see ) as for the indenter. HK 5 3 P2/d22 (5). 5. Significance and Use where: Hardness tests have been found to be very useful for P2 = force, N, and materials evaluation, quality control of manufacturing pro- d2 = length of the long diagonal of the indentation, mm. cesses and research and development efforts. Hardness , al- For the Vickers Hardness test, in practice, test loads are though empirical in nature, can be correlated to tensile strength in grams-force and indentation diagonals are in micrometres.

10 For many metals, and is an indicator of wear resistance and The Vickers Hardness number is calculated as follows: ductility. HV 5 3 103 3 P/As 5 3 103 3 P sin~a/2!/d2 (6) Microindentation tests extend Hardness testing to mate- or rials too thin or too small for macroindentation tests . Microin- dentation tests allow specific phases or constituents and regions HV 5 3 P/d2 (7) or gradients too small for macroindentation testing to be where: evaluated. P = force, gf, Because the Microindentation Hardness will reveal hard- As = surface area of the indentation, m2, ness variations that may exist within a material, a single test d = mean diagonal length of the indentation, m, and value may not be representative of the bulk Hardness .