ASTM C633-13(2017)
(Test Method)Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings
Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings
SIGNIFICANCE AND USE
3.1 This test method is recommended for quality control, acceptance testing; or it may help to develop or qualify a thermal spray operator's equipment and procedure or to aid in developing thermal spray coatings with improved adhesion and integrity.
3.2 This test method is useful for comparing adhesion or cohesion strengths of coatings of similar types of thermal spray materials. The test should not be considered to provide an intrinsic value for direct use in making calculations, such as to determine if a coating will withstand specific environmental stresses. Because of residual stresses in thermal spray coatings, actual strength depends upon the shape of the particular coated part. Also, in use, a coating may be stressed in a more complex manner than is practical for a standard test.
SCOPE
1.1 This test method covers the determination of the degree of adhesion (bonding strength) of a coating to a substrate or the cohesion strength of the coating in a tension normal to the surface. The test consists of coating one face of a substrate fixture, bonding this coating to the face of a loading fixture, and subjecting this assembly of coating and fixtures to a tensile load normal to the plane of the coating. It is adapted particularly for testing coatings applied by thermal spray, which is defined to include the combustion flame, plasma arc, two-wire arc, high-velocity oxygen fuel, and detonation processes for spraying feedstock, which may be in the form of, wire, rod, or powder.
Note 1: Thermal spray coating materials include ceramics, such as metal oxides or carbides, and metals. In some cases, a coating is formed of different spray materials, such as an oxide layer sprayed onto a sprayed metal-bonding layer. The substrate generally is a metal, but may be a ceramic, such as an oxide or graphite.
1.2 Usually this test method is performed at ambient temperature. Higher temperature testing is restricted by the need for a suitable adhesive bonding agent. For certain fundamental investigations, it is suggested that very low (cryogenic) temperature be used.
1.3 This test method is limited to testing thermal spray coatings that can be applied in thickness greater than 0.015 in. (0.38 mm). The limitation is imposed because an adhesive bonding agent is used in the test. Those bonding agents established so far for this method tend to penetrate thermal spray coatings and may invalidate results unless the coatings are thick enough to prevent penetration through the coating. Further development may establish that thin layers of certain types of especially dense coatings may be tested satisfactorily. Alternatively, new adhesive bonding agents that would allow reduction of the minimum thickness limitation may become available.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: C633 − 13 (Reapproved 2017)
Standard Test Method for
Adhesion or Cohesion Strength of Thermal Spray Coatings
This standard is issued under the fixed designation C633; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript 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. Scope 1.4 Thevaluesstatedininch-poundunitsaretoberegarded
as standard. The values given in parentheses are mathematical
1.1 This test method covers the determination of the degree
conversions to SI units that are provided for information only
ofadhesion(bondingstrength)ofacoatingtoasubstrateorthe
and are not considered standard.
cohesion strength of the coating in a tension normal to the
surface. The test consists of coating one face of a substrate 1.5 This standard does not purport to address all of the
fixture,bondingthiscoatingtothefaceofaloadingfixture,and safety concerns, if any, associated with its use. It is the
subjecting this assembly of coating and fixtures to a tensile responsibility of the user of this standard to establish appro-
load normal to the plane of the coating. It is adapted particu- priate safety and health limitations prior to use.
larly for testing coatings applied by thermal spray, which is
1.6 This international standard was developed in accor-
defined to include the combustion flame, plasma arc, two-wire
dance with internationally recognized principles on standard-
arc, high-velocity oxygen fuel, and detonation processes for
ization established in the Decision on Principles for the
spraying feedstock, which may be in the form of, wire, rod, or
Development of International Standards, Guides and Recom-
powder.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
NOTE 1—Thermal spray coating materials include ceramics, such as
metal oxides or carbides, and metals. In some cases, a coating is formed
2. Referenced Documents
ofdifferentspraymaterials,suchasanoxidelayersprayedontoasprayed
metal-bonding layer. The substrate generally is a metal, but may be a
2.1 ASTM Standards:
ceramic, such as an oxide or graphite.
E4Practices for Force Verification of Testing Machines
1.2 Usually this test method is performed at ambient tem-
3. Significance and Use
perature. Higher temperature testing is restricted by the need
for a suitable adhesive bonding agent. For certain fundamental 3.1 This test method is recommended for quality control,
investigations, it is suggested that very low (cryogenic) tem-
acceptance testing; or it may help to develop or qualify a
perature be used. thermal spray operator’s equipment and procedure or to aid in
developingthermalspraycoatingswithimprovedadhesionand
1.3 This test method is limited to testing thermal spray
integrity.
coatings that can be applied in thickness greater than 0.015 in.
(0.38 mm). The limitation is imposed because an adhesive 3.2 This test method is useful for comparing adhesion or
bonding agent is used in the test. Those bonding agents cohesionstrengthsofcoatingsofsimilartypesofthermalspray
established so far for this method tend to penetrate thermal materials. The test should not be considered to provide an
spray coatings and may invalidate results unless the coatings intrinsic value for direct use in making calculations, such as to
are thick enough to prevent penetration through the coating. determine if a coating will withstand specific environmental
Further development may establish that thin layers of certain stresses.Becauseofresidualstressesinthermalspraycoatings,
types of especially dense coatings may be tested satisfactorily. actualstrengthdependsupontheshapeoftheparticularcoated
Alternatively, new adhesive bonding agents that would allow
part.Also,inuse,acoatingmaybestressedinamorecomplex
reduction of the minimum thickness limitation may become manner than is practical for a standard test.
available.
4. Apparatus
4.1 Atension testing machine shall conform to the require-
ments of Practices E4. The loads used in determining the
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
and Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 on
Materials for Porcelain Enamel and Ceramic-Metal Systems. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2017. Published May 2017. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approvedin1969.Lastpreviouseditionapprovedin2013asC633–01(2013).DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/C0633-13R17. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C633 − 13 (2017)
adhesionortensilestrengthshallbewithintheloadingrangeof 5. Material
the testing machine, as defined in Practices E4. Permissible
5.1 Adhesive Bonding Agent—A suitable adhesive bonding
variation shall be less than 1.0%. It shall be possible to apply
agent shall be agreed between the purchaser and manufacturer
increasing tensile load at a constant rate of cross-head travel 3
of the coating and shall meet the following requirements.
between 0.030 in./min (0.013 mm/s) and 0.050 in./min (0.021
5.1.1 The bonding agent shall be capable of bonding the
mm/s).Themachineshallincludeaload-indicatingdevicethat
coating to the loading fixture with a tensile strength that is at
registers the maximum load applied before rupture occurs.
least as great as the minimum required adhesion and cohesion
4.2 Self-aligningdevices,forapplyingthetensileloadtothe strength of the coating.
assembly of the coating and fixtures, shall not permit eccentric 5.1.2 The bonding agent shall be sufficiently viscous not to
load or bending moment to the specimen. Self-alignment is penetrate through a 0.015-in. (0.38-mm) thickness of the
often provided by the manufacturer as an integral part of the
testingmachine.Analternative,satisfactoryapparatusisshown
in Fig. 1, which also shows methods of connecting the 3
Alistofsatisfactorybondingagentsisprovidedintheannexwhichfollowsthis
self-aligning apparatus to an assembled test specimen. standard.
Metric Equivalents
3 1 3 1 7 1 1
in. ⁄16 ⁄4 ⁄4 11 ⁄8 1 ⁄16 1 ⁄2 2 ⁄2
(mm) (4.8) (6.4) (19) (25.4) (29) (37) (38) (64)
FIG. 1 Self-Aligning Device
C633 − 13 (2017)
isthatadhesionstrengthgenerallydecreaseswithageoftheunusedagent.
coating. Certain commercial resins that cure or harden at room
If strength is lower than required, more adhesive bonding agent shall be
temperature by means of a curing agent have been proven
prepared and tested, or the agent shall be discarded and replaced.
satisfactory. If any other bonding agent is to be used, it shall
first be compared with a proven bonding agent using this test 6. Test Specimens
method with the desired thermal spray coating.
6.1 Substrate and Loading Fixtures— Each test specimen is
an assembly comprising a substrate fixture, to which the
NOTE 2—Thermal spray coatings may have an inherent porosity.
Excessive penetration of the adhesive bonding agent into this porosity coating is applied, and a loading fixture. The substrate and
may affect the results determined by this test method. Unless proved
loadingfixturesshalleachbecircular,solidcylindersofnoless
satisfactory by comparison testing, any agent requiring elevated tempera-
than 1.5 in. in length, or as agreed upon by the manufacturer
ture for curing should be avoided because viscosity may decrease at high
and customer.Asuggested detail for either fixture is shown in
temperature, allowing penetration.
Fig. 2. One end of each fixture shall be adapted for attachment
NOTE 3—When liquid epoxy bonding agents are used, there should be
a procedure in place to ensure relatively consistent thickness on every
to the self-aligning loading devices of the tension testing
sample.
machine. Both ends of each fixture shall have faces parallel to
5.1.3 The adhesion strength of the bonding agent shall be eachotherandnormaltotheloadingaxis.Thefacingdiameters
determined each time this test method is performed.This shall shallbenotlessthan0.9in.(23mm),normorethan1.0in.(25
mm). The diameters of the two fixtures shall be the same and
be done by using the bonding agent to attach a loading fixture
to a second loading fixture, in accordance with 6.5, except that shall be measured so that the error is no greater than 0.5%.
the coated substrate fixture of 6.5 is replaced with the second
NOTE 5—In Appendix X1, an alternative substrate and fixture arrange-
loading fixture.
ment is provided that has proved cost effective and simple.
6.1.1 Material for Substrate Fixture— The substrate fixture
NOTE4—Onereasonfortestingthebondingagenteachtimeistodetect
improper preparation of the agent if it is a two-part mix. Another reason shallbeconstructedofmetal,preferablymetalintendedforuse
1 31 1 5
U.S. 0.003 in. ⁄64 in. ⁄64 in. ⁄2 in. ⁄8 in.
Metric (0.08 mm) (0.39 mm) (12.3 mm) (12.7 mm) (15.9 mm)
U.S. ⁄4 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 Fixture
C633 − 13 (2017)
as the substrate for the coating. If no such substrate material is coating, using the adhesive bonding agent according to its
specified,thesubstratefixtureshallbeSAE1018or1020steel. manufacturer’sinstructions.Excessiveadhesiveshallbewiped
from the assembly with soft paper or cloth. The two fixtures
NOTE 6—If desired because of cost or ease of fabrication, it may be
shall be held together parallel and aligned until the bonding
suitable to attach or bond a layer of the specified substrate material to a
agentiscuredorhardened.Asuitableholdingdevicesuchasa
fixture formed ofanyconvenientmetal.Suchalayerofsubstrate material
need not be metal. The layer must be substantially thicker than the “V-block” shall be used for the purpose, except such a device
possible depth of effects on the substrate, such as recrystallization or
is not necessary if the surface of the coating has been ground
diffusionzones,thatmayresultfromapplyingthecoating.Alayergreater
or machined smooth.
than 0.1 in. (2.5 mm) thick should be sufficient.
6.6 Number of Test Specimens—The number of test speci-
6.1.2 Material for Loading Fixture—The loading fixture
mens chosen depends upon the purpose of the particular tests
shall be constructed of metal, but material is otherwise op-
under consideration. However, if specimens are to be used for
tional. It is usually convenient to make the loading fixture of
acceptancetests,notlessthanfivespecimensofatypeshallbe
thesamematerialasthesubstratefixture;thus,thefixturesmay
tested.
be interchangeable until a coating is applied to one.
7. Procedure
6.2 Coating Application—The front facing of the substrate
fixture shall be prepared in the manner required by the
7.1 Prepare the chosen number of substrate fixtures, and
specification for the coating. (Roughening by grit blasting or
apply a thermal spray coating to each. Finish the coating
surface grinding may be typical preparations.) The coating
surface if required.
shall be thermal sprayed onto this prepared surface.
7.2 Prepare the adhesive bonding agent. Attach cleaned
6.3 CoatingThickness—Thecoatingthicknessshallbemea-
loadingfixturestoallthecoatedsubstratefixturesatessentially
sured with a micrometer by measuring the total length of the
thesametime.Inaddition,prepareonesetofuncoatedfixtures
coating fixture before and after the coating is applied. (Care
formeasurementoftheadhesionstrengthofthebondingagent.
must be taken to avoid contaminating the prepared surface
7.3 Apply a tensile load to each test specimen at a constant
before coating.)The final coating thickness shall be more than
rate of cross-head travel between 0.030 in./min (0.013 mm/s)
0.015in.(0.38mm).Ifthecoatingistobegroundormachined,
and 0.050 in./min (0.021 mm/s) until rupture occurs. Record
the as-sprayed coating shall be approximately 0.005 in. (0.13
the maximum load applied.
mm) thicker to allow for removal of material. The coating
NOTE 7—Loading fixtures may be gravity or pressure devices. The
thickness shall not vary across the surface by more than 0.001
design of the loading fixtures should enable the correct alignment of the
in.(0.025mm).(Thisthicknessvariation,asmeasuredfromthe
specimen.
rear face, does not refer to the ordinary surface texture or
roughness typical of thermal spray coatings.) If, upon comple-
8. Calculation
tion of the thermal spraying, the coating thickness varies in
8.1 Calculatethedegreeofadhesionorcohesionstrengthas
excess of this limit, this shall be corrected by removing the
follows:
coatingandresprayingorbygrindingormachiningthecoating
Adhesionorcohesionstrength (1)
surface.
6.4 Grinding or Machining the Coating Surface—The sur-
5maximumload/cross 2sectionalarea
face of the coating may be finished by grinding or machining
when the thickness variation is excessive. If the thickness
9. Interpretation of Results
variation is not excessive, it shall be optional to finish the
9.1 Any interpretation of results depends on the purpose of
surfaceofthecoatingasausefulandconvenientaidinholding
using this test method and on the description of failure. The
the fixtures together parallel and aligned as required for the
adhesion or cohesion strength value measured represents the
next step. No specific grinding or machining procedure can be
weakest part of the system, whether in the coating or at an
recommended, as this depends on the type of coating material.
interface.Alow-power microscope with a magnification range
Usually manufacturers of the coatings have recommendations
up to 100× is suggested for determining location of failure
published or available. Only a rough grinding or machining
(also termed as the “locus” of failure).
stepisneeded,toprovideafinalcoatingthicknessthatdoesnot
9.2 Theadhesionstrengthofthecoatingisgiveniffailureis
varybymorethan0.001in.(0.025mm).Removalrateshallbe
entirely at the coating-substrate interface.
insufficient to damage the coating or bond. A recommended
method is to use a surface grinder with a magnetic chuck,
9.3 The cohesion strength of the coating is given if rupture
positioning the rear face of the coated fixture on this magnetic
isonlywithinthecoating.Failureinthebondingagentmaybe
chuck. No other treatment, such as grit blasting, shall be done
a satisfactory result for a quality control assurance test or for a
to the surf
...
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 version. Because
it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: C633 − 13 C633 − 13 (Reapproved 2017)
Standard Test Method for
Adhesion or Cohesion Strength of Thermal Spray Coatings
This standard is issued under the fixed designation C633; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript 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. Scope
1.1 This test method covers the determination of the degree of adhesion (bonding strength) of a coating to a substrate or the
cohesion strength of the coating in a tension normal to the surface. The test consists of coating one face of a substrate fixture,
bonding this coating to the face of a loading fixture, and subjecting this assembly of coating and fixtures to a tensile load normal
to the plane of the coating. It is adapted particularly for testing coatings applied by thermal spray, which is defined to include the
combustion flame, plasma arc, two-wire arc, high-velocity oxygen fuel, and detonation processes for spraying feedstock, which
may be in the form of, wire, rod, or powder.
NOTE 1—Thermal spray coating materials include ceramics, such as metal oxides or carbides, and metals. In some cases, a coating is formed of different
spray materials, such as an oxide layer sprayed onto a sprayed metal-bonding layer. The substrate generally is a metal, but may be a ceramic, such as
an oxide or graphite.
1.2 Usually this test method is performed at ambient temperature. Higher temperature testing is restricted by the need for a
suitable adhesive bonding agent. For certain fundamental investigations, it is suggested that very low (cryogenic) temperature be
used.
1.3 This test method is limited to testing thermal spray coatings that can be applied in thickness greater than 0.015 in. (0.38
mm). The limitation is imposed because an adhesive bonding agent is used in the test. Those bonding agents established so far for
this method tend to penetrate thermal spray coatings and may invalidate results unless the coatings are thick enough to prevent
penetration through the coating. Further development may establish that thin layers of certain types of especially dense coatings
may be tested satisfactorily. Alternatively, new adhesive bonding agents that would allow reduction of the minimum thickness
limitation may become available.
1.4 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E4 Practices for Force Verification of Testing Machines
3. Significance and Use
3.1 This test method is recommended for quality control, acceptance testing; or it may help to develop or qualify a thermal spray
operator’s equipment and procedure or to aid in developing thermal spray coatings with improved adhesion and integrity.
This test method is under the jurisdiction of ASTM Committee B08 on Metallic and Inorganic Coatings and is the direct responsibility of Subcommittee B08.12 on
Materials for Porcelain Enamel and Ceramic-Metal Systems.
Current edition approved Dec. 1, 2013May 1, 2017. Published December 2013May 2017. Originally approved in 1969. Last previous edition approved in 20082013 as
C633 – 01(2008).(2013). DOI: 10.1520/C0633-13.10.1520/C0633-13R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C633 − 13 (2017)
3.2 This test method is useful for comparing adhesion or cohesion strengths of coatings of similar types of thermal spray
materials. The test should not be considered to provide an intrinsic value for direct use in making calculations, such as to determine
if a coating will withstand specific environmental stresses. Because of residual stresses in thermal spray coatings, actual strength
depends upon the shape of the particular coated part. Also, in use, a coating may be stressed in a more complex manner than is
practical for a standard test.
4. Apparatus
4.1 A tension testing machine shall conform to the requirements of Practices E4. The loads used in determining the adhesion
or tensile strength shall be within the loading range of the testing machine, as defined in Practices E4. Permissible variation shall
be less than 1.0 %. It shall be possible to apply increasing tensile load at a constant rate of cross-head travel between 0.030 in./min
(0.013 mm/s) and 0.050 in./min (0.021 mm/s). The machine shall include a load-indicating device that registers the maximum load
applied before rupture occurs.
4.2 Self-aligning devices, for applying the tensile load to the assembly of the coating and fixtures, shall not permit eccentric load
or bending moment to the specimen. Self-alignment is often provided by the manufacturer as an integral part of the testing
machine. An alternative, satisfactory apparatus is shown in Fig. 1, which also shows methods of connecting the self-aligning
apparatus to an assembled test specimen.
Metric Equivalents
3 1 3 1 7 1 1
in. ⁄16 ⁄4 ⁄4 1 1 ⁄8 1 ⁄16 1 ⁄2 2 ⁄2
(mm) (4.8) (6.4) (19) (25.4) (29) (37) (38) (64)
FIG. 1 Self-Aligning Device
C633 − 13 (2017)
5. Material
5.1 Adhesive Bonding Agent—A suitable adhesive bonding agent shall be agreed between the purchaser and manufacturer of the
coating and shall meet the following requirements.
5.1.1 The bonding agent shall be capable of bonding the coating to the loading fixture with a tensile strength that is at least as
great as the minimum required adhesion and cohesion strength of the coating.
5.1.2 The bonding agent shall be sufficiently viscous not to penetrate through a 0.015-in. (0.38-mm) thickness of the coating.
Certain commercial resins that cure or harden at room temperature by means of a curing agent have been proven satisfactory. If
any other bonding agent is to be used, it shall first be compared with a proven bonding agent using this test method with the desired
thermal spray coating.
NOTE 2—Thermal spray coatings may have an inherent porosity. Excessive penetration of the adhesive bonding agent into this porosity may affect the
results determined by this test method. Unless proved satisfactory by comparison testing, any agent requiring elevated temperature for curing should be
avoided because viscosity may decrease at high temperature, allowing penetration.
NOTE 3—When liquid epoxy bonding agents are used, there should be a procedure in place to ensure relatively consistent thickness on every sample.
5.1.3 The adhesion strength of the bonding agent shall be determined each time this test method is performed. This shall be done
by using the bonding agent to attach a loading fixture to a second loading fixture, in accordance with 6.5, except that the coated
substrate fixture of 6.5 is replaced with the second loading fixture.
NOTE 4—One reason for testing the bonding agent each time is to detect improper preparation of the agent if it is a two-part mix. Another reason is
that adhesion strength generally decreases with age of the unused agent. If strength is lower than required, more adhesive bonding agent shall be prepared
and tested, or the agent shall be discarded and replaced.
6. Test Specimens
6.1 Substrate and Loading Fixtures— Each test specimen is an assembly comprising a substrate fixture, to which the coating
is applied, and a loading fixture. The substrate and loading fixtures shall each be circular, solid cylinders of no less than 1.5 in.
in length, or as agreed upon by the manufacturer and customer. A suggested detail for either fixture is shown in Fig. 2. One end
of each fixture shall be adapted for attachment to the self-aligning loading devices of the tension testing machine. Both ends of
each fixture shall have faces parallel to each other and normal to the loading axis. The facing diameters shall be not less than 0.9
in. (23 mm), nor more than 1.0 in. (25 mm). The diameters of the two fixtures shall be the same and shall be measured so that
the error is no greater than 0.5 %.
NOTE 5—In Appendix X1, an alternative substrate and fixture arrangement is provided that has proved cost effective and simple.
6.1.1 Material for Substrate Fixture— The substrate fixture shall be constructed of metal, preferably metal intended for use as
the substrate for the coating. If no such substrate material is specified, the substrate fixture shall be SAE 1018 or 1020 steel.
NOTE 6—If desired because of cost or ease of fabrication, it may be suitable to attach or bond a layer of the specified substrate material to a fixture
formed of any convenient metal. Such a layer of substrate material need not be metal. The layer must be substantially thicker than the possible depth of
effects on the substrate, such as recrystallization or diffusion zones, that may result from applying the coating. A layer greater than 0.1 in. (2.5 mm) thick
should be sufficient.
6.1.2 Material for Loading Fixture—The loading fixture shall be constructed of metal, but material is otherwise optional. It is
usually convenient to make the loading fixture of the same material as the substrate fixture; thus, the fixtures may be
interchangeable until a coating is applied to one.
6.2 Coating Application—The front facing of the substrate fixture shall be prepared in the manner required by the specification
for the coating. (Roughening by grit blasting or surface grinding may be typical preparations.) The coating shall be thermal sprayed
onto this prepared surface.
6.3 Coating Thickness—The coating thickness shall be measured with a micrometer by measuring the total length of the coating
fixture before and after the coating is applied. (Care must be taken to avoid contaminating the prepared surface before coating.)
The final coating thickness shall be more than 0.015 in. (0.38 mm). If the coating is to be ground or machined, the as-sprayed
coating shall be approximately 0.005 in. (0.13 mm) thicker to allow for removal of material. The coating thickness shall not vary
across the surface by more than 0.001 in. (0.025 mm). (This thickness variation, as measured from the rear face, does not refer
to the ordinary surface texture or roughness typical of thermal spray coatings.) If, upon completion of the thermal spraying, the
coating thickness varies in excess of this limit, this shall be corrected by removing the coating and respraying or by grinding or
machining the coating surface.
6.4 Grinding or Machining the Coating Surface—The surface of the coating may be finished by grinding or machining when
the thickness variation is excessive. If the thickness variation is not excessive, it shall be optional to finish the surface of the coating
as a useful and convenient aid in holding the fixtures together parallel and aligned as required for the next step. No specific grinding
or machining procedure can be recommended, as this depends on the type of coating material. Usually manufacturers of the
coatings have recommendations published or available. Only a rough grinding or machining step is needed, to provide a final
A list of satisfactory bonding agents is provided in the annex which follows this standard.
C633 − 13 (2017)
1 31 1 5
U.S. 0.003 in. ⁄64 in. ⁄64 in. ⁄2 in. ⁄8 in.
Metric (0.08 mm) (0.39 mm) (12.3 mm) (12.7 mm) (15.9 mm)
U.S. ⁄4 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 Fixture
coating thickness that does not vary by more than 0.001 in. (0.025 mm). Removal rate shall be insufficient to damage the coating
or bond. A recommended method is to use a surface grinder with a magnetic chuck, positioning the rear face of the coated fixture
on this magnetic chuck. No other treatment, such as grit blasting, shall be done to the surface of the coating.
6.5 Attachment of Fixtures—The facing of the loading fixture shall be free of oil, grease, or grinding or cutting fluids. The facing
shall be mechanically cleaned by such means as machining, grinding, light grit blasting, or rubbing with emory cloth. This facing
shall be attached to the surface of the coating, using the adhesive bonding agent according to its manufacturer’s instructions.
Excessive adhesive shall be wiped from the assembly with soft paper or cloth. The two fixtures shall be held together parallel and
aligned until the bonding agent is cured or hardened. A suitable holding device such as a “V-block” shall be used for the purpose,
except such a device is not necessary if the surface of the coating has been ground or machined smooth.
6.6 Number of Test Specimens—The number of test specimens chosen depends upon the purpose of the particular tests under
consideration. However, if specimens are to be used for acceptance tests, not less than five specimens of a type shall be tested.
7. Procedure
7.1 Prepare the chosen number of substrate fixtures, and apply a thermal spray coating to each. Finish the coating surface if
required.
7.2 Prepare the adhesive bonding agent. Attach cleaned loading fixtures to all the coated substrate fixtures at essentially the same
time. In addition, prepare one set of uncoated fixtures for measurement of the adhesion strength of the bonding agent.
7.3 Apply a tensile load to each test specimen at a constant rate 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
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