This standard is issued under the fixed designation C; the number 1 This test method is under the jurisdiction of ASTM Committee B08 on Metallic. ASTM C determines the bonding strength of thermal spray coatings. ASTM Standard C, “Standard Test Method for Adhesion or Cohesive Strength of Flame-Sprayed Coatings,” is widely used in industry and research for .
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The ASTM C satm standard was written to allow for coating adhesion in a tensile testing machine. Complicated universal link joints were required in order to achieve a pull force which was normal to the coating surface. The method works but is associated with a number of drawbacks: ASTM C testing standard is often specified as a default standard. Expensive equipment is then required to carry out this inflexible test method.
Why does the test cylinder have to be one inch diameter? What about the tensile increase rate?
ASTM C633 Adhesion or Cohesion Strength of Thermal Spray Coatings
These parameters were originally set because of the limitations of tensile testing machines. They were big machines with a measurably moving traverse to measure elongation.
The strain in a thin coating cannot be sensibly measured so tensile rate in millimeters per minute is not relevant. Assuming a fracture value of 20 MPa psi the stress increase during testing with conventional tensile testers is more than MPapsi per second!
ASTM C PDF DOWNLOAD
With The ASTM standard the rate of stress increase in the coating will depend on the thickness of the coating, which is another weakness of this standard: The stress increase should be the same regardless of coating thickness!
So instead of controlling the distance the the dolly is traveling during pull testing the machine should be able to control the materials pull stress increase measured in MPa or psi per second.
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ASTM C633 PDF DOWNLOAD
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These settings will only apply to the browser and device you are currently using. A 25mm diameter steel cylinder end is sprayed with the required coating.
Another cylinder with the same diameter is glued on axtm of this. After positioning this assembly into the tensile testing machine they were pulled apart.
Maximum pull stress is recorded. The Problems The method works but is associated with a number of drawbacks: To spray-coat a cylinder end is not necessarily a good representation of spraying another surface; If a coating adhesion on a particular substrate is to be investigated special test cylinders of the same material need to be made; The test procedure is slow and cumbersome; Not everybody has access to a tensile testing machine, and they can be very expensive to purchase The Solution The PAT adhesion tester has addressed all these problems.
With PAT there is a choice. How bad is it?