ASTM B975-2018 Standard Test Method for Measurement of Internal Stress of Metallic Coatings by Split Strip Evaluation (Deposit Stress Analyzer Method).pdf

1、Designation: B975 15B975 18Standard Test Method forMeasurement of Internal Stress of Metallic Coatings by SplitStrip Evaluation (Deposit Stress Analyzer Method)1This standard is issued under the fixed designation B975; the number immediately following the designation indicates the year oforiginal ad

2、option or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe deposit stress analyzer method provides a rapid, accurate, and eco

3、nomical means for thedetermination of the internal tensile and compressive stress in metallic and nonmetallic coatings.Internal stress is expressed in pounds per square inch or megapascals. This procedure for measuringinternal stress offers the advantages of test specimens that are pre-calibrated by

4、 the manufacturer, asmall test specimen coating surface area, and rapid determination of the internal stress in the appliedcoating.1. Scope1.1 This test method for determining the internal tensile or compressive stress in applied coatings is quantitative. It is applicableto metallic layers that are

5、applied by the processes of electroplating or chemical deposition that exhibit internal tensile orcompressive stress values from 500200 to 145 000 psi (3.45(1.38 to 1000 MPa).1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values givenstate

6、din parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.eachsystem are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be usedindependently of the other, and values from t

7、he two systems shall not be combined.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theappl

8、icability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the

9、World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B636 Test Method for Measurement of Internal Stress of Plated Metallic Coatings with the Spiral ContractometerE177 Practice for Use of the Terms Precision and Bias in ASTM Test MethodsE691

10、 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 IEC Standard:3IEC 61010 Safety Requirements for Electrical Equipment for Measurement, Control, and Laboratory Use3. Terminology3.1 Definitions of Terms Specific to This Standard:1 This test method is und

11、er the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on TestMethods.Current edition approved Nov. 1, 2015Dec. 1, 2018. Published December 2015January 2019. Originally approved in 2015. Last previous edition approved in 2

12、015 asB975 15. DOI: 10.1520/B975-15.10.1520/B0975-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Availa

13、ble from International Electrotechnical Commission (IEC), 3, rue de Varemb, P.O. Box 131, 1211 Geneva 20, Switzerland, http:/www.iec.ch.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous vers

14、ion. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM Internation

15、al, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 average deposit thickness, naverage deposit thickness equals the deposit weight in grams divided by the specific gravityof the deposit in grams per cubic centimetre multiplied by the plated deposit surface

16、area per test strip (see Eq 3).3.1.2 constant K, nthis certifiable calibrated number is determined experimentally for each material lot of test stripsmanufactured to enable simple mathematical calculation of the internal deposit stress while factoring the influence of the percentelongation differenc

17、e between the deposit and the substrate without the use of complicated bent strip formulas. See Note 4 inSection 8.3.1.3 helix, nmetal strip approximately 0.01 to 0.013 in. (0.025 to 0.033 cm) thick formed as a helix approximately 0.9 in.0.9 in. (2.3 cm) in diameter and 0.61 in. 6.1 in. (15.5 cm) lo

18、ng with or without a polytetrafluoroethylene (PTFE) coating on theinside surface.3.1.4 in-site device, nthis device holds a test strip during the application of a coating.3.1.4.1 DiscussionAnodes are located external to the specimen holder.3.1.5 internal stress, nstress in a given layer of coating c

19、an result from foreign atoms or materials in the layer that stress thenatural structure of the deposit as the coating is being formed from sources independent of foreign atoms such as misfit dislocationsand the result of additional processing.3.1.5.1 DiscussionStress that develops in a given layer o

20、f material is measured as pounds per square inch or megapascals where 1 MPa = 145 psi.3.1.6 measuring stand, nthis stand supports the test strip above a logarithmic scale that enables determination of the totalnumber of increments spread between the test strip leg tips.3.1.7 modulus of elasticity, n

21、stress required to produce unit strain, which may be a change in length (Youngs modulus), atwist of shear (modulus of rigidity or modulus of torsion), or a change in volume (bulk modulus).3.1.7 on site specimen holder, nthis device holds a test strip during the application of a coating.3.1.7.1 Discu

22、ssionAnodes are located external to the specimen holder.3.1.8 power supply, nrectifier to supply amperage for plating.3.1.9 self-contained plating cell, nthis cell contains two anodes within the cell at an equal distance from the test strip that aresuspended in electrolyte for deposition to occur. A

23、 section for a heating coil and a pump for solution agitation is an option.3.1.10 test strip, nmetal strip formed from flat stock that receives the coating of material being evaluated for internal stress.4. Summary of Test Method4.1 The first attempt to measure stress values in applied coatings was

24、the bent strip method, wherein a coating of knownthickness was applied to a strip of flat stock material having a known modulus of elasticity, length, width, and thickness. In thetest, one end of the strip was held in a fixed position and one end could bend. The degree of bend experienced by the tes

25、t stripwas then measured. Equations were proposed by Stoney, Barklie, and Davies,Davies; Houssner, Balden, and Morse, Morse; andBrenner and Senderoff for this method of measurement to calculate the internal deposit stress that was sufficient to cause deflectionof the flat stock material.4.2 Later me

26、thods include the use of flat stock material formed into a helix that contracts or expands as a stressed coating isapplied to the base material (spiral contractometer as described in United States Patent 4,086,154) and a disk formed from flat stockmaterial that bows outward or inward as a stressed c

27、oating is applied to the base material (stress meter).4.3 The deposit stress analyzer method for determining the internal stress value of a given coatingplating uses bent striptechnology and the formulas devised for calculation of results applicable to this approach.Aspecific test piece comprises a

28、selectedmetallic material that exhibits spring-like properties with specified dimensions that define an end area split to give two legs (seeFig. 1). These test strips are coated with a resist, to prevent deposition,deposition on the front of one leg and the back side of theother leg and on both side

29、s above where the legs divide, leaving a space uncoated at the top for the purpose of making electricalcontact to the test piece during the plating process. As a test piece is plated, the legs bend to relieve the stress that is induced asdeposition occurs. Tensile stress bends the test strip legs wi

30、th the plated deposit on the outside, while compressive stress bendsthe test strip legs with the resist on the outside. See Fig. 2. Each test is performed at specific operating conditions that are usuallyselected to approximate the conditions for parts being processed in production mode.B975 1824.3.

31、1 The internal deposit stress is calculated based on the total number of increments deflection observed from tip to tip afterplating. This value is determined as the test strip is suspended above a measuring stand. See Fig. 3. Results are calculated by useof a simple deposit stress analyzer formula

32、expressed in pounds per square inch. See Eq 2 and Eq 3.5. Significance and Use5.1 Internal stress in applied coatings exhibits potential to cause a breakdown of resistance to corrosion and erosion as a resultof the formation of fractures from micro-cracking and macro-cracking within the applied coat

33、ing. This phenomenon can also causeblistering, peeling, reduction of fatigue strength, and loss. The resulting stress can be tensile in nature, causing the deposit tocontract, or compressive in nature, causing the deposit to expand.FIG. 1 Test Strip Parameters1 in. = 2.54 cmFIG. 2 Deposit Stress Ana

34、lyzer Measuring StandCompressive and Tensile Stressed Test StripsB975 1835.2 To maintain quality assurance by the bent strip method, it is necessary to monitor production processes for acceptable levelsof internal deposit stress in applied coatings. Note that the highest value of the internal deposi

35、t stress as obtained on astress-versus-coating-thicknessstress-versus-plating-thickness curve is usually the truest value of the internal deposit stress. Mostlow values are false. Initial values tend to be lower than the actual value because of the effect of stock material edge burrs andthe resistan

36、ce of the stock material to bending. Excessive deposit thickness causes lower-than-true valuesvalue since the coatingoverpowers and changes the initial modulus of elasticity of the test piece, which becomes more difficult to bend as the coatingcontinues to build upon it. This phenomenon can be corre

37、cted considerably by use of a formula that compensates for modulus ofelasticity differences between the deposit and the substrate materials, but it does remain a factor. See Eq 2.6. Apparatus6.1 Deposit Stress Analyzer Measuring StandThis stand has a scale over which a test strip is suspended to det

38、ermine theincrements of spread as the value of U between the test strip leg tips caused by the induced deposit stress. See Fig. 24. See Eq1 and Eq 2.6.2 On site In-site Plating Device for In-TankIn-tank or Laboratory Bench Plating (External Anodes)This device does nothold a plating bath. It is a 10.

39、875 in. (2.22 cm) diameter, cylindrical tube that is designed with an adjustable bracket to enableplacement of the cell in a working tank as a permanently mounted fixture. It is also amenable to laboratory studies where smallsolution volumes are advantageous. See Fig. 43. This device supports a sing

40、le test strip during the deposition process. Toelectroplate a test strip, the existing tank anodes may be used for the test if they are of similar composition and size and are locatedequally distant and parallel to the device open ports. Using a rectifier that is separate from the power supply used

41、to plate the parts,connect the positive outletlead to each of the two selected tank anodes, and the negative outletlead to the top of the test strip atthe crossbar that extends over the top of the device. The bottom of the device is sufficiently closed to prevent the test strip fromdropping through.

42、 It is critical that the test strip legs do not pass through the side openings as a test strip is placed inside the device.Adjust the test strip into position against the bottom of the device and approximately 4 in. (10 cm) below the solution level. A 0-1to 0-2 amp output constant amperage, amperage

43、 and constant voltage power supply is recommended to control the amperageaccurately. The negative lead from a power supply is then connected to the test strip at the crossbar located at the top of the device.When using deposition conditions similar to work that is processed in the work tank, the str

44、ess measurement result will representthe condition of the work being processed. The device may also be used on a laboratory table in a container for a plating bath assmall as 400 mL in which two small nickel anodes are positioned each across from a celldevice side opening. See Fig. 43. Thisbecomes h

45、elpful and economical when the plating solution is undergoing laboratory studies in regard to additions of multipleadditives, particularly if precious metals are involved. In-tank deposit stress testing yields similar results to those determined ona laboratory bench setup when the test parameters ar

46、e similar. However, the deposit stress will vary over a given part, particularlyover parts that are electroformed where the low-current density area deposits usually exhibit the highest deposit stress. In suchcases, the determined deposit stress becomes an approximate average value that serves as a

47、quality control procedure.FIG. 3 In-site 1 Plating DeviceB975 1846.3 Cells for In-TankIn-tank Plating or Laboratory Bench Plating (Internal Anodes)When agitation and solution temperatureare not needed for tests, a test plating cell that includes two anodes of similar size and composition at an equal

48、 distance from thetest piece is recommended. When solution agitation and elevated bath temperature are required, a two-section cell could be usedwhere one side has a pump and heater. Cells with open low side ports would permit immersion into a working bath allowing thecell to fill as it is being low

49、ered. The test strip mustshall have its own power supply. In these cells, a test strip is suspended at thecenter of the cell by clipping it its top end to a stainless steel cross support bar. Two anodes 238 238 18 1/8 in. (5 5 in. (6 6 0.3 cm) are positioned along the end of the cell walls where anode pockets are attached. These cells can be designed to behung directly in a working tank or they could be used in a laboratory setup.6.4 AnodesWhen using the deposit stress analyzer method to evaluate the internal deposit stress by electroplating a