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Input Sought from Testers of Thermal Spray Coatings for Cohesion

Thermal spray scientists and adhesion testers are sought to examine and suggest updates to ASTM C 633, Standard Test Method for Adhesion or Cohesive Strength of Flame-Sprayed Coatings. The test method is being revised by ASTM Committee B08 on Metallic and Inorganic Coatings to include new methodologies. Those interested should contact Chris Berndt, Ph.D., State University of New York, at the address that follows, and consult the Web site, “Measurement Technique, Analysis and Critique of the Tensile Adhesion Test (ASTM C 633) Method” at http://dol1.eng.sunysb.edu/Berndt/Berndt-NP34.

A wide range of feedback will be crucial for an effective revision. The thermal spray industry has experienced advancements in testing technique, increased applications, and new terminology since the test method was originally published in 1979.

“Technology has changed quite a bit, but it’s not only that,” said Berndt, vice president, Thermal Spray Society of ASM International. “It’s much more of a mature industry than what it was 25 years back. The whole ball game has really gone to a different league.

“Thermal spray is deep seated within the infrastructure of engineering in America,” he continued. “Thermal spray coatings that are tested with C 633 range from hydroxyapatite-coated onto prosthetic implants for orthopedic and dental devices, thermal-barrier coated turbine blades for aerospace or power-generating equipment, and coatings used in paper manufacturing.”

The following adjustments to Test Method C 633 have been proposed:
• Alter the title to reflect the generic technology of “thermal spray”;
• Define the fracture locus to provide a “common grounding” in terminology. This fracture locus needs to be reported for each fracture;
• For a multi-component system (e.g., a bond coat with a ceramic overlay), failure at the interface between two coatings is described as “internal adhesive”;
• Increase the minimum specimen length from 1 to 1.5 inches, “or as agreed upon by the manufacturer and customer”; and
• Change the specimen attachment system so that a pin coupling to the tensile testing device is permissible.
Input is actively being sought on these adjustments; all comments are highly invited.

An ASTM working group of thermal spray engineers, aerospace scientists, academicians, and corrosion specialists will be involved in the C 633 revision. As working group chair, Berndt is collecting input from all corners of industry through his association with ASM, the Steel Structures Painting Council, the National Association of Corrosion Engineers, and the American Welding Society.” I now feel that this important standard test method is undergoing a long overdue revision,” he concluded.

For further technical details, contact Chris Berndt, Ph.D., SUNY at Stony Brook, Dept. of Materials Science and Engineering, 306 Old Engineering, Stony Brook, NY (631/632-8507; 632/8525 or 8052). Committee B08 meets April 2-4, 2001, Phoenix, Ariz. For meeting information, contact Staff Manager Dan Schultz, ASTM (610/832-9716). //

Copyright 2000, ASTM