1、Designation: G171 03 (Reapproved 2017)Standard Test Method forScratch Hardness of Materials Using a Diamond Stylus1This standard is issued under the fixed designation G171; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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 test method covers laboratory procedures for de-termining the scratch hardness of the surfaces of solid materi-
3、als. Within certain limitations, as described in this guide, thistest method is applicable to metals, ceramics, polymers, andcoated surfaces. The scratch hardness test, as described herein,is not intended to be used as a means to determine coatingadhesion, nor is it intended for use with other than
4、specifichemispherically-tipped, conical styli.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 may involve hazardous materials,operations, and equipment. This standard does not purport toaddress all of the s
5、afety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety, health, and environmental prac-tices and determine the applicability of regulatory limitationsprior to use.1.4 This international standard was developed in accor-danc
6、e with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Stan
7、dards:2G40 Terminology Relating to Wear and ErosionG117 Guide for Calculating and Reporting Measures ofPrecision Using Data from Interlaboratory Wear or Ero-sion Tests (Withdrawn 2016)33. Terminology3.1 DefinitionsFor definitions of terms applicable to thisstandard see Terminology G40.3.2 Definition
8、s of Terms Specific to This Standard:3.2.1 scratch hardness number, na quantity, expressed inunits of force per unit area, that characterizes the resistance ofa solid surface to penetration by a moving stylus of given tipradius under a constant normal force and speed; namely,HSP5kPw2where:HSP= scrat
9、ch hardness number,k = a geometrical constant,P = applied normal force, andw = scratch width.NOTE 1The constant k may be chosen to include conversion factorsfor expressing HSPin units of GPa. For HSPin GPa, P in grams-force, andw in m, k = 24.98.3.2.2 scratching force, nthe force that opposes relati
10、vemotion between a moving stylus and the surface that is beingscratched by that stylus, and which is perpendicular to thenormal force exerted by the stylus.3.2.3 stylus drag coeffcient, nin scratch testing, the di-mensionless ratio of the scratching force to the normal forceapplied to the stylus; na
11、mely,Dsc5FscrPwhere:Dsc= stylus drag coefficient,Fscr= scratching force, andP = normal force.4. Summary of Test Method4.1 This test involves producing a scratch in a solid surfaceby moving a diamond stylus of specified geometry along aspecified path under a constant normal force and with aconstant s
12、peed. The average width of the scratch is measured,and that value is used to compute the scratch hardness numberin units of pressure.4.2 As an option, the scratching force may be measuredduring this test and used to compute a stylus drag coefficient,1This test method is under the jurisdiction of AST
13、M Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.30 on AbrasiveWear.Current edition approved Nov. 1, 2017. Published December 2017. Originallyapproved in 2003. Last previous edition approved in 2009 as G171 03 (2009)2.DOI: 10.1520/G0171-03R17.2For referenced AS
14、TM standards, visit the 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.3The last approved version of this historical standard is referenced onwww.astm
15、.org.Copyright 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 standardization established in the Decision on Principles for theDevelopment of
16、International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1which is a dimensionless measure of the resistance of the testsurface to deformation by a tangentially-moving stylus.4.3 This test is usually conducted under unlubr
17、icated con-ditions and at room temperature; however, it is possible toconduct scratch hardness tests under lubricated and elevatedtemperature conditions. The provisions of this standard allowtesting under both conditions provided that requirements forvalid scratch hardness testing are met and that t
18、he testingconditions are fully reported.4.4 Effects of moisture in the air and other ambient atmo-spheric conditions may affect results depending on the sensi-tivity of the test material to the environment. If such effects areeither expected or observed during the course of testing,precautions to co
19、ntrol the surrounding atmosphere and todocument the relative humidity level should be taken andreported.5. Significance and Use5.1 This test method is intended to measure the resistance ofsolid surfaces to permanent deformation under the action of asingle point (stylus tip). It is a companion method
20、 to quasi-static hardness tests in which a stylus is pressed into a surfaceunder a certain normal load and the resultant depth or impres-sion size is used to compute a hardness number. Scratchhardness numbers, unlike quasi-static hardness numbers, in-volve a different combination of properties of th
21、e surfacebecause the indenter, in this case a diamond stylus, movestangentially along the surface. Therefore, the stress state underthe scratching stylus differs from that produced under aquasi-static indenter. Scratch hardness numbers are in principlea more appropriate measure of the damage resista
22、nce of amaterial to surface damage processes like two-body abrasionthan are quasi-static hardness numbers.5.2 This test method is applicable to a wide range ofmaterials. These include metals, alloys, and some polymers.The main criteria are that the scratching process produces ameasurable scratch in
23、the surface being tested without causingcatastrophic fracture, spallation, or extensive delamination ofsurface material. Severe damage to the test surface, such thatthe scratch width is not clearly identifiable or that the edges ofthe scratch are chipped or distorted, invalidates the use of thistest
24、 method to determine a scratch hardness number. Since thedegree and type of surface damage in a material may vary withapplied load, the applicability of this test to certain classes ofmaterials may be limited by the maximum load at which validscratch width measurements can be made.5.3 The resistance
25、 of a material to abrasion by a single pointmay be affected by its sensitivity to the strain rate of thedeformation process. Therefore, this test is conducted underlow stylus traversing speeds. Use of a slow scratching speedalso minimizes the possible effects of frictional heating.5.4 This test uses
26、 measurements of the residual scratchwidth after the stylus has been removed to compute the scratchhardness number. Therefore, it reflects the permanent deforma-tion resulting from scratching and not the instantaneous state ofcombined elastic and plastic deformation of the surface.6. Apparatus6.1 Ge
27、neral DescriptionThe apparatus consists of (1) therigid stylus mount and specimen holding fixture, (2) a means toapply a normal force while traversing the stylus along thesurface at constant speed, and (3) a means to measure the widthof the scratch. Optionally, the apparatus can be equipped witha se
28、nsor to detect the magnitude of the scratching force.6.1.1 StylusThe stylus shall be conical of apex angle 1206 5, and the cone shall terminate in a hemispherical tip of 200m (6 10 m) radius. The material of the tip shall be diamond.NOTE 2The smaller the tip radius, the higher the contact stress und
29、era given normal force. If a tip radius other than that indicated here is used,results shall indicate that a modified version of the standard was used, andthe size of the tip radius shall be reported (see also 10.1.1).6.1.2 ApparatusA means to traverse the specimen underthe stylus, or the stylus acr
30、oss the specimen, under constantspeed and normal force, shall be provided. Fixtures shall besufficiently rigid to withstand the normal, lateral, and tangentialforces associated with the scratching process without undueelastic or plastic deflection. The path of the stylus may be in astraight line or
31、an arc, as produced using a rotating table-typedevice.6.1.3 Scratch Width Measurement SystemA means formeasuring the width of the scratch shall be provided. This canconsist of any imaging system that is capable of magnifying thescratch such that its width can be accurately determined. Themeasuring s
32、ystem shall be capable of measuring the width ofthe scratch to a precision of at least 2 %. For example, therequired resolution for a measuring optical microscope neededfor an average 50 m-wide scratch shall be (0.02 50 m) =1.0 m or better. Reflecting-type, optical microscopes usingmonochromatic ill
33、umination or interference-contrast and hav-ing a measuring eyepiece are suitable for scratch measurement.Alternatively, photographic or video images may be used aslong as the magnifications are properly calibrated.6.1.4 Scratching Force (Optional)A load cell or similarforce-sensing device can be use
34、d to measure the scratchingforces generated during sliding. This standard does not specifya method for measuring the scratching force, only that thesensor shall be capable of being calibrated in the direction ofthe scratching force and in line with the contact point betweenthe stylus and surface.7.
35、Calibration7.1 The parts of the apparatus that require calibration are (1)the normal force application system, (2) stylus traverse speed,and optionally (3) the scratching force sensor.7.2 Loading SystemThe normal force applied to the styluswhile it is traversing the surface shall be calibrated in su
36、ch away that the normal force is known to within 1 %. Forexample, a normal force of 1 N shall be applied to within anaccuracy of 6 0.01 N. The means to calibrate the scratch testershall be determined by its individual design; however, themethod of normal force calibration shall be stated in the repo
37、rt.NOTE 3One method to calibrate the normal force on the stylus is touse a quasi-static system such as a button-type load cell placed under thestylus tip in the position where the test specimen is located.G171 03 (2017)27.3 Stylus Traverse SpeedThe speed of the stylus acrossthe surface s may be cali
38、brated in any suitable manner such astiming the period t required to produce a scratch of length L.Thus:s 5Lt(1)7.4 Scratching Force Sensor (Optional)The scratchingforce sensor shall be calibrated periodically in the direction ofthe scratching force, and as closely as possible in line with thepoint
39、of contact between the stylus and specimen. The intervalbetween calibrations shall be determined by the user to ensureaccurate readings of scratching force and compensate for anyelectronic signal drift.8. Procedure8.1 Specimen PreparationThe test specimen shall be pre-pared in such a way as to repre
40、sent the application of interestor polished to facilitate observation and measurement ofscratch width. A surface may be unsuitable for scratch testingif its roughness or porosity is such that the edges of the scratchare indistinct or jagged, or if the stylus cannot traverse thesurface without skippi
41、ng along it or catching in a pocket. In apolished condition, the surface should be as free as possiblefrom preparation artifacts such as grinding-induced cracks,gross grinding marks, and grain pull-out. Surface roughnessesof 0.02 to 0.05 m Ra(arithmetic average roughness) aretypical of polished surf
42、aces. Surfaces may be scratch tested inthe as-fabricated condition as long as the characteristics of thescratch do not display the types of artifacts described in thisparagraph.8.2 Specimen CleaningSince many different kinds ofmaterials can be scratch tested, one specific cleaning treatmentcannot be
43、 given. Specimens shall be cleaned in such a way thatthe surface is free from grit, grease, fingerprints, or othercontaminants. Metals and alloys may be cleaned in non-polarsolvents. Plastics may require alternative cleaning with eye-glass cleaner or similar. If contact with solvents or cleanerscoul
44、d result in changes to their properties, surfaces may betested as-received. The method of cleaning, if any, shall bedescribed in the report.8.3 Inspection of the StylusInspect the stylus tip with amicroscope or other topographic inspection method to ensurethat there are no defects (cracks, chips), w
45、ear or adheringmaterial left from manufacturing or resulting from a previoustest. Wiping the stylus with a soft cloth moistened with acetoneor other cleaning solvent is usually suitable.NOTE 4Oily residues on the stylus can lubricate the surface, reducethe scratch width, and increase the apparent sc
46、ratch hardness number.Chipped styli can increase the scratching force and produce striae thatextend along the entire bottom of the scratch.8.4 Normal ForceThe normal force shall be selected so asto produce a measurable groove in the surface, but it shall notbe so large as to cause fracture, spalling
47、, delamination, or otherform of gross surface damage.Aseries of scratches at differentnormal forces may be used to assess the resistance of the testmaterial to increasing localized stresses.8.5 Stroke Length and ShapeThe stroke length shall be atleast 5 mm. Strokes need not be linear, but may be in
48、the shapeof an arc, as in the case of turntable-type scratching apparatus.8.6 Scratching SpeedThe scratching speed shall be con-stant along the measured portion of the scratch, and in therange of 0.2 to 5.0 mm s-1.8.7 Conducting the TestEnsure that the instrument isleveled and that the stylus is nor
49、mal to the test surface whilescratching. Lower the stylus to apply the load on the specimensurface gently to avoid impact damage. Activate the traversingdrive to produce the scratch of desired length. Raise the stylusoff of the surface. Select another location at least 5 scratchwidths away from the previous scratch and produce anotherscratch parallel to the first. Repeat as necessary, but with aminimum of three (3) scratches per value of the normal force.Measure the scratch width as described in 8.8.8.8 Scratch Width MeasurementUsing a measuring m
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