1、Designation: G 171 03Standard Test Method forScratch Hardness of Materials Using a Diamond Stylus1This standard is issued under the fixed designation G 171; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This standard describes laboratory procedures for deter-mining the scratch hardness of the surfaces of solid materials.Within certa
3、in limitations, as described in this guide, this testmethod is applicable to metals, ceramics, polymers, and coatedsurfaces. The scratch hardness test, as described herein, is notintended to be used as a means to determine coating adhesion,nor is it intended for use with other than specifichemispher
4、ically-tipped, conical styli.1.2 This standard may involve hazardous materials, opera-tions, and equipment. This standard does not purport toaddress all of the safety concerns, if any, associated with itsuse. It is the responsibility of the user of this standard toestablish appropriate safety and he
5、alth practices and deter-mine the applicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:E 177 Practice for Use of the Terms Precision and Bias asApplied to Measurement of a Property of a Material2E 178 Practice for Dealing with Outlying Observations2G40 Termi
6、nology Relating to Wear and Erosion3G117 Guide for Calculating and Reporting Measures ofPrecision Using Data from Interlaboratory Wear or Ero-sion Tests33. Terminology3.1 DefinitionsFor definitions of terms applicable to thisstandard see Terminology G40.3.2 Definitions of Terms Specific to This Stan
7、dard: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= scratch hardness number,k = a geometr
8、ical 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 relativemotion between a moving stylus
9、 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, thedimensionless ratio of the scratching force to the normal forceapplied to the stylus; namely,Dsc5FscrPwhere:Dsc= stylus dr
10、ag 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 speed. The average width of the scr
11、atch 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,which is a dimensionless measure of the resistance of the testsurface to deformation
12、 by a tangentially-moving stylus.4.3 This test is usually conducted under unlubricated 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
13、 provided that requirements for1This test method is under the jurisdiction of ASTM Committee G02 on Wearand Erosion and is the direct responsibility of Subcommittee G02.30 on AbrasiveWear.Current edition approved Jan. 10, 2003. Published April 2003.2Annual Book of ASTM Standards, Vol 14.02.3Annual B
14、ook of ASTM Standards, Vol 03.02.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.valid scratch hardness testing are met and that the testingconditions are fully reported.4.4 Effects of moisture in the air and other ambient atmo-spher
15、ic 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 control the surrounding atmosphere and todocument the relative humidity level should be taken andreported
16、.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 to quasi-static hardness tests in which a stylus is pressed into a surfaceunder a certain normal load
17、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 the surfacebecause the indenter, in this case a diamond stylus, movestangentially along the surface. Ther
18、efore, 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 resistance of amaterial to surface damage processes like two-body abrasionthan are quasi-static hardness numbe
19、rs.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 the surface being tested without causingcatastrophic fracture, spallation, or extensive delamination of
20、surface 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 method to determine a scratch hardness number. Since thedegree and type of surface damage in a materia
21、l 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 of a material to abrasion by a single pointmay be affected by its sensitivity to the strain rate of th
22、edeformation 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 measurements of the residual scratchwidth after the stylus has been removed to compute the scratchhard
23、ness 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 General DescriptionThe apparatus consists of (1) therigid stylus mount and specimen holding fixture, (2)
24、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 sensor to detect the magnitude of the scratching force.6.1.1 StylusThe stylus shall be conical of apex an
25、gle 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 undera given normal force. If a tip radius other than that indicated here is used,results shall indicate t
26、hat 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 across the specimen, under constantspeed and normal force, shall be provided. Fixtures shall besufficientl
27、y 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 an arc, as produced using a rotating table-typedevice.6.1.3 Scratch Width Measurement SystemA means for
28、measuring 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 system shall be capable of measuring the width ofthe scratch to a precision of at least 2 %. For example
29、, therequired resolution for a measuring optical microscope neededfor an average 50 m-wide scratch shall be (0.02 3 50 m) =1.0 m or better. Reflecting-type, optical microscopes usingmonochromatic illumination or interference-contrast and hav-ing a measuring eyepiece are suitable for scratch measurem
30、ent.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 used to measure the scratchingforces generated during sliding. This standard does not specifya method fo
31、r 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. Calibration7.1 The parts of the apparatus that require calibration are (1)the normal force applicatio
32、n 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 such away that the normal force is known to within 1 %. Forexample, a normal force of 1 N shall be appl
33、ied 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 report.NOTE 3One method to calibrate the normal force on the stylus is touse a quasi-static system such a
34、s a button-type load cell placed under thestylus tip in the position where the test specimen is located.7.3 Stylus Traverse SpeedThe speed of the stylus acrossthe surface s may be calibrated in any suitable manner such astiming the period t required to produce a scratch of length L.Thus:s 5Lt(1)7.4
35、Scratching Force Sensor (Optional)The scratchingforce sensor shall be calibrated periodically in the direction ofG171032the scratching force, and as closely as possible in line with thepoint of contact between the stylus and specimen. The intervalbetween calibrations shall be determined by the user
36、to ensureaccurate readings of scratching force and compensate for anyelectronic signal drift.8. Procedure8.1 Specimen PreparationThe test specimen shall beprepared in such a way as to represent the application ofinterest or polished to facilitate observation and measurementof scratch width. A surfac
37、e may be unsuitable for scratchtesting if its roughness or porosity is such that the edges of thescratch are indistinct or jagged, or if the stylus cannot traversethe surface without skipping along it or catching in a pocket. Ina polished condition, the surface should be as free as possiblefrom prep
38、aration 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) are typicalof polished surfaces. Surfaces may be scratch tested in theas-fabricated condition as long as the characteristics of thescratch
39、 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 given. Specimens shall be cleaned in such a way thatthe surface is free from grit, grease, fingerprints, or ot
40、hercontaminants. 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 cleanerscould result in changes to their properties, surfaces may betested as-received. The method of cleaning, if any, sha
41、ll 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), wear or adheringmaterial left from manufacturing or resulting from a previoustest. Wiping the stylus with a soft
42、 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 scratch hardness number.Chipped styli can increase the scratching force and produce striae thatextend along the e
43、ntire 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, delamination, or otherform of gross surface damage. A series of scratches at differentnormal forces may be us
44、ed to assess the resistance of the testmaterial to increasing localized stresses. The selection of anormal force(s) for scratch testing of coatings is furtherdiscussed in 12.5.8.5 Stroke Length and ShapeThe stroke length shall be atleast 5 mm. Strokes need not be linear, but may be in the shapeof an
45、 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 normal to the tes
46、t 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 scrat
47、ch 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 mi-croscope or other calibrated magnifying or surface profilin
48、gsystem, measure the width of each scratch at three locationsspaced approximately equally along the length of the scratch.The width of the scratch shall be determined optically, asshown by the examples in Fig. 1. Owing to acceleration anddeceleration effects, scratch widths should not be measurednea
49、r the ends of the scratch.NOTE 5Other methods, such as surface profiling, may produce valuesdifferent from optical measurements. Therefore, to improve consistency,widths should be measured on enlarged images.8.8.1 Special Considerations in Optical ScratchMeasurementThe characteristics of the surfaces being tested,such as their roughness, color, degree of light diffusion, extentof plastic deformation, and reflectivity, will all affect the easeor difficulty in precisely locating scratch edges. In general,finer scratches present more difficulties in width m
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