ASTM C633-01
(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
This test method is recommended for quality control, acceptance testing; or it may help to develop or qualify a thermal spray operator’ equipment and procedure or to aid in developing thermal spray coatings with improved adhesion and integrity.
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 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.
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Designation: C 633 – 01
Standard Test Method for
1
Adhesion or Cohesion Strength of Thermal Spray Coatings
This standard is issued under the fixed designation C 633; 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 (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. Scope responsibility of the user of this standard to establish appro-
priate safety and health limitations prior to use.
1.1 This test method covers the determination of the degree
ofadhesion(bondingstrength)ofacoatingtoasubstrateorthe
2. Referenced Documents
cohesion strength of the coating in a tension normal to the
2.1 ASTM Standards:
surface. The test consists of coating one face of a substrate
2
E 4 Practices for Force Verification of Testing Machines
fixture,bondingthiscoatingtothefaceofaloadingfixture,and
subjecting this assembly of coating and fixtures to a tensile
3. Significance and Use
load normal to the plane of the coating. It is adapted particu-
3.1 This test method is recommended for quality control,
larly for testing coatings applied by thermal spray, which is
acceptance testing; or it may help to develop or qualify a
defined to include the combustion flame, plasma arc, two-wire
thermal spray operator’s equipment and procedure or to aid in
arc, high-velocity oxygen fuel, and detonation processes for
developingthermalspraycoatingswithimprovedadhesionand
spraying feedstock, which may be in the form of, wire, rod, or
integrity.
powder.
3.2 This test method is useful for comparing adhesion or
NOTE 1—Thermal spray coating materials include ceramics, such as
cohesionstrengthsofcoatingsofsimilartypesofthermalspray
metal oxides or carbides, and metals. In some cases, a coating is formed
materials. The test should not be considered to provide an
of different spray materials, such as an oxide layer sprayed onto a sprayed
intrinsic value for direct use in making calculations, such as to
metal-bonding layer. The substrate generally is a metal, but may be a
determine if a coating will withstand specific environmental
ceramic, such as an oxide or graphite.
stresses. Because of residual stresses in thermal spray coatings,
1.2 Usually this test method is performed at ambient tem-
actual strength depends upon the shape of the particular coated
perature. Higher temperature testing is restricted by the need
part.Also, in use, a coating may be stressed in a more complex
for a suitable adhesive bonding agent. For certain fundamental
manner than is practical for a standard test.
investigations, it is suggested that very low (cryogenic) tem-
perature be used.
4. Apparatus
1.3 This test method is limited to testing thermal spray
4.1 A tension testing machine shall conform to the require-
coatings that can be applied in thickness greater than 0.015 in.
ments of Practices E 4. The loads used in determining the
(0.38 mm). The limitation is imposed because an adhesive
adhesionortensilestrengthshallbewithintheloadingrangeof
bonding agent is used in the test. Those bonding agents
the testing machine, as defined in Practices E 4. Permissible
established so far for this method tend to penetrate thermal
variation shall be less than 1.0 %. It shall be possible to apply
spray coatings and may invalidate results unless the coatings
increasing tensile load at a constant rate of cross-head travel
are thick enough to prevent penetration through the coating.
between 0.030 in./min (0.013 mm/s) and 0.050 in./min (0.021
Further development may establish that thin layers of certain
mm/s).The machine shall include a load-indicating device that
types of especially dense coatings may be tested satisfactorily.
registers the maximum load applied before rupture occurs.
Alternatively, new adhesive bonding agents that would allow
4.2 Self-aligningdevices,forapplyingthetensileloadtothe
reduction of the minimum thickness limitation may become
assembly of the coating and fixtures, shall not permit eccentric
available.
load or bending moment to the specimen. Self-alignment is
1.4 This standard does not purport to address all of the
often provided by the manufacturer as an integral part of the
safety concerns, if any, associated with its use. It is the
testingmachine.Analternative,satisfactoryapparatusisshown
in Fig. 1, which also shows methods of connecting the
1
self-aligning apparatus to an assembled test specimen.
ThistestmethodisunderthejurisdictionofASTMCommitteeB08onMetallic
and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.12 on
Materials for Porcelain Enamel and Ceramic-Metal Systems.
Current edition approved March 10, 20
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