1、Designation: C 633 01Standard Test Method forAdhesion or Cohesion Strength of Thermal Spray Coatings1This standard is issued under the fixed designation C 633; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. A number in parentheses indicates the year of last reapproval. Asuperscript 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. Scope1.1 This test method covers the determination of th
3、e 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 and
4、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 i
5、n 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 metal
6、, 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-perat
7、ure 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 ther
8、malspray 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 wou
9、ld allowreduction of the minimum thickness limitation may becomeavailable.1.4 This 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 us
10、e.2. Referenced Documents2.1 ASTM Standards:E 4 Practices for Force Verification of Testing Machines23. 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 inde
11、veloping thermal spray coatings with improved adhesion andintegrity.3.2 This test method 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,
12、 such as todetermine if a coating will withstand specific environmentalstresses. Because 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 standar
13、d test.4. Apparatus4.1 A tension testing machine shall conform to the require-ments of Practices E 4. The loads used in determining theadhesion or tensile strength shall be within the loading range ofthe testing machine, as defined in Practices E 4. Permissiblevariation shall be less than 1.0 %. It
14、shall be possible to applyincreasing tensile load at a constant rate of cross-head travelbetween 0.030 in./min (0.013 mm/s) and 0.050 in./min (0.021mm/s). The machine shall include a load-indicating device thatregisters the maximum load applied before rupture occurs.4.2 Self-aligning devices, for ap
15、plying 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, satisfactory apparatus is shownin Fig. 1, which also sh
16、ows methods of connecting theself-aligning apparatus to an assembled test specimen.5. Material5.1 Adhesive Bonding AgentA suitable adhesive bonding1This test method is under the jurisdiction of ASTM Committee B08 on Metallicand Inorganic Coatingsand is the direct responsibility of Subcommittee B08.1
17、2 onMaterials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved March 10, 2001. Published July 2001. Originallypublished as C 633 69. Last previous edition C 633 79 (1999).2Annual Book of ASTM Standards, Vol 03.01.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19
18、428-2959, United States.agent shall be agreed between the purchaser and manufacturerof the coating and shall meet the following 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
19、 adhesion and cohesionstrength of the coating.5.1.2 The bonding agent shall be sufficiently viscous not topenetrate through a 0.015-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
20、other bonding agent is to be used, it shallfirst be compared with a proven bonding agent using this testmethod with the desired thermal spray coating.NOTE 2Thermal spray coatings may have an inherent porosity.Excessive penetration of the adhesive bonding agent into this porositymay affect the result
21、s determined by this test method. Unless provedsatisfactory by comparison testing, any agent requiring elevated tempera-ture for curing should be avoided because viscosity may decrease at hightemperature, allowing penetration.NOTE 3When liquid epoxy bonding agents are used, there should bea procedur
22、e 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 bonding agent to attach a loading fixtureto a second loading fixture, in accordance with 6.5
23、, 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-part mix. Another reasonis that adhesion strength generally decreases with age of the unus
24、ed 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 FixturesEach test specimen isan assembly comprising a substrate fixture, to which the3A list of satisfactory b
25、onding agents is provided in the annex which follows thisstandard.Metric Equivalentsin.3161434 1118 1716 112 212(mm) (4.8) (6.4) (19) (25.4) (29) (37) (38) (64)FIG. 1 Self-Aligning DeviceC 6332coating is applied, and a loading fixture. The substrate andloading fixtures shall each be circular, solid
26、cylinders of no lessthan 1.5 in. in length, or as agreed upon by the manufacturerand customer. A suggested detail for either fixture 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
27、 shall have faces parallel toeach other and normal to the loading axis. The facing diametersshall be not less than 0.9 in. (23 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,
28、an alternative substrate and fixture arrange-ment is provided that has proved cost effective and simple.6.1.1 Material for Substrate FixtureThe substrate fixtureshall be constructed of metal, preferably metal intended for useas the substrate for the coating. If no such substrate material isspecified
29、, the substrate fixture shall be SAE 1018 or 1020 steel.NOTE 6If desired because of cost or ease of fabrication, it may besuitable 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
30、must be substantially thicker than thepossible depth of effects on the substrate, such as recrystallization ordiffusion zones, that may result from applying the coating. A layer greaterthan 0.1 in. (2.5 mm) thick should be sufficient.6.1.2 Material for Loading FixtureThe loading fixtureshall be cons
31、tructed of metal, but material is otherwise op-tional. It is usually convenient to make the loading fixture ofthe same material as the substrate fixture; thus, the fixtures maybe interchangeable until a coating is applied to one.6.2 Coating ApplicationThe front facing of the substratefixture shall b
32、e prepared in the manner required by thespecification for the coating. (Roughening by grit blasting orsurface grinding may be typical preparations.) The coatingshall be thermal sprayed onto this prepared surface.6.3 Coating ThicknessThe coating thickness shall bemeasured with a micrometer by measuri
33、ng the total length ofthe coating fixture before and after the coating is applied. (Caremust be taken to avoid contaminating the prepared surfacebefore coating.) The final coating thickness shall be more than0.015 in. (0.38 mm). If the coating is to be ground or machined,the as-sprayed coating shall
34、 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 thickness variation, as measured from theU.S. 0.003 in.164 in.3164 in.12 in.58 in.Metric (0.08 mm) (0.39 mm) (12.3 mm) (12.7 m
35、m) (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 FixtureC 6333rear face, does not refer to the ordinary surface texture orroughness typical of thermal spray coatings.) If, upon comple-tion of the t
36、hermal spraying, the coating thickness varies inexcess of this limit, this shall be corrected by removing thecoating and respraying 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
37、 thickness variation is excessive. If the thicknessvariation is not excessive, it shall be optional to finish thesurface of 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 be
38、recommended, as this depends on the type of coating material.Usually manufacturers of the coatings have recommendationspublished 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 shal
39、l beinsufficient to damage the coating or bond. A recommendedmethod is to use a surface grinder with a magnetic chuck,positioning 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 Fixture
40、sThe facing of the loadingfixture shall be free of oil, grease, or grinding or cutting fluids.The facing shall be mechanically 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
41、bonding agent according to itsmanufacturers instructions. Excessive adhesive shall be wipedfrom the assembly with soft paper or cloth. The two fixturesshall be held together parallel and aligned until the bondingagent is cured or hardened. A suitable holding device such as a“V-block” shall be used f
42、or the purpose, except such a deviceis not necessary if the surface of the coating has been groundor machined smooth.6.6 Number 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 foracceptanc
43、e tests, not less than five specimens of a type shall betested.7. Procedure7.1 Prepare the chosen number of substrate fixtures, 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 sub
44、strate fixtures at essentiallythe same time. In addition, prepare one set of uncoated fixturesfor measurement of the adhesion 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
45、 mm/s) until rupture occurs. Recordthe maximum load applied.NOTE 7Loading fixtures may be gravity or pressure devices. Thedesign 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 co
46、hesion strength5 maximum load/cross2sectional area(1)9. Interpretation of Results9.1 Any interpretation of results depends 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 t
47、he coating or at aninterface. A low-power microscope with a magnification rangeup to 1003 is suggested for determining location 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 cohesio
48、n 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 of
49、the coating.9.4 If failure occurs in a combination of these locations inone specimen, generally no interpretation of the initial causecan be provided. Fig. 3 diagrams the possible modes of failure.9.5 For a multicomponent system; for example, a bond coatwith a ceramic overlay, then failure at the interface betweentwo coatings is described as “internal adhesive.”FIG. 3 Nomenclature of Specimen Components and Classification of Failure LociiC 633410. Report10.1 The report shall include the following:10.1.1 Coating material or manufacturers designation tech-n
