ASTM C633 Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings
ASTM C633 defines a method of measuring the adhesion or cohesion of a thermal spray coating. This measures the adhesion of coatings to a substrate or the strength of the coating in the aerospace, automotive, and industrial coating markets. The test applies tensile loading perpendicular to the coated surface of the specimens, adhesive bonding agents, and a tensile testing machine. Test reports contain adhesion or cohesion strength values, observations of coating thickness, and failure modes. ASTM C633 aids manufacturers in assessing process quality, coating integrity, and thermal spray performance.
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IntroductiontoASTM C633
The ASTM C633 (Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings) provides a measure of the tensile bond between the thermal spray coating and the substrate. This standard addresses the adhesion of the thermal spray coat to the substrate (adhesion) or the internal strength of the coating itself (cohesion). ASTM C633 provides a process for coating system comparison and coating integrity determination. ASTM C633 applies to thermal spray coatings applied by plasma arc, combustion flame, wire arc, detonation, and high-velocity oxygen fuel (HVOF) methods.
Get Certified ASTM C633 Testing for Reliable Thermal Spray Coating Performance
Certification assists in confirming that thermal spray coatings possess the necessary adhesion and cohesion prior to entering industry. Testing certification guarantees the best bond strength, adhesion, and serviceability.
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Testing Procedures and Requirements
Technicians perform this test by gluing a coated substrate to a loading fixture and pulling the assembly apart until it fails. The operator makes a fixture for the substrate, then sprays thermal coatings onto one side. They then attach the coated specimen to a loading fixture with an appropriate adhesive. After that, the tensile testing machine pulls on the adhesive surface at right angles to it. The coating assembly keeps loading until failure. Finally, technicians determine the maximum tensile force and the failure mode.
Substrate Fixture
Preparing the substrate fixture and coating with thermal spray. Attach a coated fixture to a non-coated substrate.
Specimen Mounting
Technicians securely mount the specimen assembly in the universal testing machine using self-aligning fixtures. Then apply a tensile load perpendicular to the coating surface to reduce bending stresses.
Bond Strength Calculation
Operators calculate tensile adhesion (bond strength) by dividing the maximum failure load by the test specimen’s cross-sectional area. This usually comes out in MPa or psi.
Failure Mode Evaluation
Technicians determine the failure to be cohesive coating failure, adhesive failure, substrate failure, glue failure, or a failure in more than one mode. Failure analysis aids in identifying the actual performance of the thermal spray coating system.
ASTM C633 Tensile Testing Machine
Scope of ASTM C633
Tests adhesion and cohesion between coatings and between coating and substrate.
Evaluates the integrity and performance of coatings.
Coating qualification and quality control.
Works for plasma, flame, arc, HVOF, and detonation coatings.
Involvement in the development of the thermal spray process.
ASTM C633 Equipment and Sample Preparation
Specimen Details
Thermal spray-coated specimens of metallic or ceramic-based materials, including steel, stainless steel, aluminum alloys, nickel alloys, titanium alloys, graphite, and oxide ceramics. Coatings are ceramic, carbide, metal, cermet, or multilayer thermal spray systems.
Specimen Preparation
Technicians clean and roughen the surface of the substrate before the thermal spray coating. They uniformly apply the coating and adhere it to a loading fixture with a high-strength adhesive.
Specimen Dimensions
Coating thickness is maintained above 0.015 in (0.38 mm) to prevent adhesive penetration through the coating.
Use of ASTM C633 Test Standard
Analyzes the bond strength of thermal spray coating.
The coating quality assurance is supported.
Informs spray operators about their qualification requirements.
Help with coating material development.
Enhances the durability of the coating by evaluating it.
Why is adhesion strength important?
Adhesion strength is the bond between the coating and the substrate material. If the adhesion is weak, coating failure, cracking, and delamination can occur in service.
Why is cohesion strength critical?
Cohesion strength is the strength of the coating itself. Cohesion enhances the durability of the coating and resistance to mechanical stresses.
Common Challenges and Troubleshooting
Potential problems are insufficient drying of the adhesive, non-uniform coating thickness, the adhesive impregnating the coating, and misalignment of specimens. The following problems arise when testing the bond strength. Residual stresses in thermal spray coatings may also influence test results. Good specimen preparation, controlled coating, and calibrated equipment increase test accuracy and repeatability.
ASTM C633 Testing Technique, Process, and Data Collection
Technicians prepare and coat substrate fixtures in a thermal spray process. Then they adhere the coated surface to a loading fixture using adhesive. Following the test, the tensile testing machine pulls at the coating with a controlled tensile force, perpendicular to the coating plane. The coating assembly breaks at the weakest link or within the coating layer. Lastly, technicians measure the maximum load and determine adhesion or cohesion strength.
Analysis Results and Interpretation
ASTM C633 indicates the strength of adhesion or cohesion in megapascals (MPa) or pounds per square inch (psi). The high values observed show good coating bond and coating integrity. Low values indicate poor adhesion, weak cohesion, or poor coating application conditions.
Factors to Consider for ASTM C633 Testing
Speed: Efficient testing leads to faster coating qualification and inspection.
Expertise: Well-trained technicians prepare the coating and assess its bond strength.
Cost: Optimized testing procedures help reduce costs for coating development and quality control.
Rohit Dhembare is an Operations Associate at MaTestLab Inc. and holds a postgraduate degree in Organic Chemistry.
FAQ's
Where can I get the astm c633 tested?
You can share your astm c633 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm c633 test to various testing techniques.
How much do I need to pay for the astm c633 test?
Please contact us for a detailed quote for your astm c633 testing needs. Cost incurred to carry out different astm c633 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
How many samples are required for astm c633?
The required number of samples or specimens should comply with the procedure given in the astm c633 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
How much discount can I get on the astm c633 test?
MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
How many days will it take to complete the astm c633 test?
The turnaround time for astm c633 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
Where can I get the astm c633 tested?
You can share your astm c633 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm c633 test to various testing techniques.
MaTestLab Inc. offers accessible, quick, and affordable material testing, product testing, and failure analysis services. We support your on-demand testing and expert consultation needs with the help of our extensive network of material testing laboratories situated in the US and other parts of the world.
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