1、Designation: C633 13Standard Test Method forAdhesion or Cohesion Strength of Thermal Spray Coatings1This standard is issued under the fixed designation C633; 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 () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 This test method covers the determination of
3、the degreeof adhesion (bonding strength) of a coating to a substrate or thecohesion strength of the coating in a tension normal to thesurface. The test consists of coating one face of a substratefixture, bonding this coating to the face of a loading fixture, andsubjecting this assembly of coating an
4、d fixtures to a tensileload normal to the plane of the coating. It is adapted particu-larly for testing coatings applied by thermal spray, which isdefined to include the combustion flame, plasma arc, two-wirearc, high-velocity oxygen fuel, and detonation processes forspraying feedstock, which may be
5、 in the form of, wire, rod, orpowder.NOTE 1Thermal spray coating materials include ceramics, such asmetal oxides or carbides, and metals. In some cases, a coating is formedof different spray materials, such as an oxide layer sprayed onto a sprayedmetal-bonding layer. The substrate generally is a met
6、al, but may be aceramic, such as an oxide or graphite.1.2 Usually this test method is performed at ambient tem-perature. Higher temperature testing is restricted by the needfor a suitable adhesive bonding agent. For certain fundamentalinvestigations, it is suggested that very low (cryogenic) tem-per
7、ature be used.1.3 This test method is limited to testing thermal spraycoatings that can be applied in thickness greater than 0.015 in.(0.38 mm). The limitation is imposed because an adhesivebonding agent is used in the test. Those bonding agentsestablished so far for this method tend to penetrate th
8、ermalspray coatings and may invalidate results unless the coatingsare thick enough to prevent penetration through the coating.Further development may establish that thin layers of certaintypes of especially dense coatings may be tested satisfactorily.Alternatively, new adhesive bonding agents that w
9、ould allowreduction of the minimum thickness limitation may becomeavailable.1.4 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This
10、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 and health limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E4 Practices for Force Verification of
11、 Testing Machines3. Significance and Use3.1 This test method is recommended for quality control,acceptance testing; or it may help to develop or qualify athermal spray operators equipment and procedure or to aid indeveloping thermal spray coatings with improved adhesion andintegrity.3.2 This test me
12、thod is useful for comparing adhesion orcohesion strengths of coatings of similar types of thermal spraymaterials. The test should not be considered to provide anintrinsic value for direct use in making calculations, such as todetermine if a coating will withstand specific environmentalstresses. Bec
13、ause of residual stresses in thermal spray coatings,actual strength depends upon the shape of the particular coatedpart.Also, in use, a coating may be stressed in a more complexmanner than is practical for a standard test.4. Apparatus4.1 A tension testing machine shall conform to the require-ments o
14、f Practices E4. The loads used in determining theadhesion or tensile strength shall be within the loading range ofthe testing machine, as defined in Practices E4. Permissiblevariation shall be less than 1.0 %. It shall be possible to applyincreasing tensile load at a constant rate of cross-head trav
15、elbetween 0.030 in./min (0.013 mm/s) and 0.050 in./min (0.0211This test method is under the jurisdiction ofASTM Committee B08 on Metallicand Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 onMaterials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved
16、Dec. 1, 2013. Published December 2013. Originallyapproved in 1969. Last previous edition approved in 2008 as C633 01(2008). DOI:10.1520/C0633-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
17、volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1mm/s). The machine shall include a load-indicating device thatregisters the maximum load applied befor
18、e rupture occurs.4.2 Self-aligning devices, for applying the tensile load to theassembly of the coating and fixtures, shall not permit eccentricload or bending moment to the specimen. Self-alignment isoften provided by the manufacturer as an integral part of thetesting machine.An alternative, satisf
19、actory apparatus is shownin Fig. 1, which also shows methods of connecting theself-aligning apparatus to an assembled test specimen.5. Material5.1 Adhesive Bonding AgentA suitable adhesive bondingagent shall be agreed between the purchaser and manufacturerof the coating and shall meet the following
20、requirements.35.1.1 The bonding agent shall be capable of bonding thecoating to the loading fixture with a tensile strength that is atleast as great as the minimum required adhesion and cohesionstrength of the coating.5.1.2 The bonding agent shall be sufficiently viscous not topenetrate through a 0.
21、015-in. (0.38-mm) thickness of thecoating. Certain commercial resins that cure or harden at roomtemperature by means of a curing agent have been provensatisfactory. If any other bonding agent is to be used, it shallfirst be compared with a proven bonding agent using this testmethod with the desired
22、thermal spray coating.NOTE 2Thermal spray coatings may have an inherent porosity.Excessive penetration of the adhesive bonding agent into this porositymay affect the results determined by this test method. Unless provedsatisfactory by comparison testing, any agent requiring elevated tempera-ture for
23、 curing should be avoided because viscosity may decrease at hightemperature, allowing penetration.NOTE 3When liquid epoxy bonding agents are used, there should be3Alist of satisfactory bonding agents is provided in the annex which follows thisstandard.Metric Equivalentsin.3161434 1118 1716 112 212(m
24、m) (4.8) (6.4) (19) (25.4) (29) (37) (38) (64)FIG. 1 Self-Aligning DeviceC633 132a procedure in place to ensure relatively consistent thickness on everysample.5.1.3 The adhesion strength of the bonding agent shall bedetermined each time this test method is performed. This shallbe done by using the b
25、onding agent to attach a loading fixtureto a second loading fixture, in accordance with 6.5, except thatthe coated substrate fixture of 6.5 is replaced with the secondloading fixture.NOTE 4One reason for testing the bonding agent each time is to detectimproper preparation of the agent if it is a two
26、-part mix. Another reasonis that adhesion strength generally decreases with age of the unused agent.If strength is lower than required, more adhesive bonding agent shall beprepared and tested, or the agent shall be discarded and replaced.6. Test Specimens6.1 Substrate and Loading Fixtures Each test
27、specimen isan assembly comprising a substrate fixture, to which thecoating is applied, and a loading fixture. The substrate andloading fixtures shall each be circular, solid cylinders of no lessthan 1.5 in. in length, or as agreed upon by the manufacturerand customer. A suggested detail for either f
28、ixture is shown inFig. 2. One end of each fixture shall be adapted for attachmentto the self-aligning loading devices of the tension testingmachine. Both ends of each fixture shall have faces parallel toeach other and normal to the loading axis.The facing diametersshall be not less than 0.9 in. (23
29、mm), nor more than 1.0 in. (25mm). The diameters of the two fixtures shall be the same andshall be measured so that the error is no greater than 0.5 %.NOTE 5In Appendix X1, an alternative substrate and fixture arrange-ment is provided that has proved cost effective and simple.6.1.1 Material for Subs
30、trate Fixture The substrate fixtureshall be constructed of metal, preferably metal intended for useas the substrate for the coating. If no such substrate material isspecified, the substrate fixture shall be SAE 1018 or 1020 steel.NOTE 6If desired because of cost or ease of fabrication, it may besuit
31、able to attach or bond a layer of the specified substrate material to afixture formed of any convenient metal. Such a layer of substrate materialneed not be metal. The layer must be substantially thicker than thepossible depth of effects on the substrate, such as recrystallization ordiffusion zones,
32、 that may result from applying the coating.Alayer greaterthan 0.1 in. (2.5 mm) thick should be sufficient.6.1.2 Material for Loading FixtureThe loading fixtureshall be constructed of metal, but material is otherwise op-tional. It is usually convenient to make the loading fixture ofU.S. 0.003 in.164
33、in.3164 in.12 in.58 in.Metric (0.08 mm) (0.39 mm) (12.3 mm) (12.7 mm) (15.9 mm)U.S.34 in. 0.990 in. 1 in. 1.000 in. 1 ft. 24 in.Metric (19 mm) (25.15 mm) (25.4 mm) (25.4 mm) (0.3 m) (610 mm)FIG. 2 Substrate and Loading FixtureC633 133the same material as the substrate fixture; thus, the fixtures may
34、be interchangeable until a coating is applied to one.6.2 Coating ApplicationThe front facing of the substratefixture shall be prepared in the manner required by thespecification for the coating. (Roughening by grit blasting orsurface grinding may be typical preparations.) The coatingshall be thermal
35、 sprayed onto this prepared surface.6.3 Coating ThicknessThe coating thickness shall be mea-sured with a micrometer by measuring the total length of thecoating fixture before and after the coating is applied. (Caremust be taken to avoid contaminating the prepared surfacebefore coating.) The final co
36、ating thickness shall be more than0.015 in. (0.38 mm). If the coating is to be ground or machined,the as-sprayed coating shall be approximately 0.005 in. (0.13mm) thicker to allow for removal of material. The coatingthickness shall not vary across the surface by more than 0.001in. (0.025 mm). (This
37、thickness variation, as measured from therear face, does not refer to the ordinary surface texture orroughness typical of thermal spray coatings.) If, upon comple-tion of the thermal spraying, the coating thickness varies inexcess of this limit, this shall be corrected by removing thecoating and res
38、praying or by grinding or machining the coatingsurface.6.4 Grinding or Machining the Coating SurfaceThe sur-face of the coating may be finished by grinding or machiningwhen the thickness variation is excessive. If the thicknessvariation is not excessive, it shall be optional to finish thesurface of
39、the coating as a useful and convenient aid in holdingthe fixtures together parallel and aligned as required for thenext step. No specific grinding or machining procedure can berecommended, as this depends on the type of coating material.Usually manufacturers of the coatings have recommendationspubli
40、shed or available. Only a rough grinding or machiningstep is needed, to provide a final coating thickness that does notvary by more than 0.001 in. (0.025 mm). Removal rate shall beinsufficient to damage the coating or bond. A recommendedmethod is to use a surface grinder with a magnetic chuck,positi
41、oning the rear face of the coated fixture on this magneticchuck. No other treatment, such as grit blasting, shall be doneto the surface of the coating.6.5 Attachment of FixturesThe facing of the loadingfixture shall be free of oil, grease, or grinding or cutting fluids.The facing shall be mechanical
42、ly cleaned by such means asmachining, grinding, light grit blasting, or rubbing with emorycloth. This facing shall be attached to the surface of thecoating, using the adhesive bonding agent according to itsmanufacturers instructions. Excessive adhesive shall be wipedfrom the assembly with soft paper
43、 or cloth. The two fixturesshall be held together parallel and aligned until the bondingagent is cured or hardened.Asuitable holding device such as a“V-block” shall be used for the purpose, except such a deviceis not necessary if the surface of the coating has been groundor machined smooth.6.6 Numbe
44、r of Test SpecimensThe number of test speci-mens chosen depends upon the purpose of the particular testsunder consideration. However, if specimens are to be used foracceptance tests, not less than five specimens of a type shall betested.7. Procedure7.1 Prepare the chosen number of substrate fixtures
45、, andapply a thermal spray coating to each. Finish the coatingsurface if required.7.2 Prepare the adhesive bonding agent. Attach cleanedloading fixtures to all the coated substrate fixtures at essentiallythe same time. In addition, prepare one set of uncoated fixturesfor measurement of the adhesion
46、strength of the bonding agent.7.3 Apply a tensile load to each test specimen at a constantrate of cross-head travel between 0.030 in./min (0.013 mm/s)and 0.050 in./min (0.021 mm/s) until rupture occurs. Recordthe maximum load applied.NOTE 7Loading fixtures may be gravity or pressure devices. Thedesi
47、gn of the loading fixtures should enable the correct alignment of thespecimen.8. Calculation8.1 Calculate the degree of adhesion or cohesion strength asfollows:Adhesion or cohesion strength (1)5 maximum load/cross 2 sectional area9. Interpretation of Results9.1 Any interpretation of results depends
48、on the purpose ofusing this test method and on the description of failure. Theadhesion or cohesion strength value measured represents theweakest part of the system, whether in the coating or at aninterface. A low-power microscope with a magnification rangeup to 100 is suggested for determining locat
49、ion of failure(also termed as the “locus” of failure).9.2 The adhesion strength of the coating is given if failure isentirely at the coating-substrate interface.9.3 The cohesion strength of the coating is given if ruptureis only within the coating. Failure in the bonding agent may bea satisfactory result for a quality control assurance test or for aqualification test, if the strength of the bonding agent is greaterthan the minimum required adhesion or cohesion strength ofthe coating.9.4 If failure occurs in a combination of these locations inone spec
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