ASTM C is used for comparing adhesion or cohesion strengths of coatings of similar types of thermal spray materials. ASTM C ASTM C is a test method used in quality control, acceptance testing, developing thermal spray coatings and comparing adhesion or cohesion of adhesion thermal spray coating materials. The purpose of this standard is to aid in testing bond strength of thermal spray coatings. Bonding strength of thermal spray determines the adhesive strength between the coating and substrate. This is determined with a peel test. Cohesion strength of thermal spray is a measurement of tensile strength of the adhesive coating.

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The test is performed by applying a thermal spray coating to one face of a substrate fixture, bonding this coating to the face of a loading fixture, then applying a tensile force normal to the plane of the coating. Thermal spray coating materials include ceramics and metals. In some case a coating is formed of different spray materials. The substrate is generally a metal but may be a ceramic. ASTM C is mainly a quality control test but may be used to qualify thermal spray equipment.

It is useful for comparing adhesion or cohesion strengths of coatings of similar types of thermal spray materials. The results of the test should not be used to make absolute calculations relating to how much stress a part can withstand during use due to the shape differences between the part and the ASTM C test fixture.

In order to measure the bond strength, the thermal spray coating is applied to the substrate which is in the shape of a cylinder. The substrate with coating is then glued to another cylinder of equal diameter. The resulting assembly including a self aligning mechanism that ensures normal forces only are applied to the thermal spray coating when mounted in a testing machine.

The maximum force is recorded during the test and the bond strength is determined by dividing the maximum force by the cross-sectional area of the cylinder. The entire ASTM C specification should be reviewed prior to performing the test to ensure correct substrate surface preparation, application of coatings and test speeds.


ASTM C633 Thermal Spray Adhesion Testing

More B 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.



Nekasa This standard is subject to revision at any time by the responsible technical committee and must be reviewed every? Assuming a fracture value of 20 MPa psi the stress increase during testing with conventional tensile testers is more than MPapsi per second! The substrate fixture that spray coating is applied to is most commonly a cylinder made of the same metal that would be used as the substrate of the coating in its actual use. For certain fundamental investigations, it is suggested that very low cryogenic temperature be used.


ASTM C633 Thermal Spray Coatings Adhesion Test Equipment and Solutions



Download: ASTM C633.pdf


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