To ensure the accuracy of the bonding strength test results of high-temperature resistant coatings, the following key aspects can be addressed:
1、 Sample preparation process
Strictly follow standard specifications: Process the specimens according to relevant national standards, industry standards (such as ISO, ASTM and other international or domestic authoritative standards for the preparation of coating bonding strength test specimens) to ensure accurate and consistent shape and size of the specimens. For example, in the preparation of tensile test specimens, strict control should be exercised over dimensional parameters such as length, diameter, or length width to avoid uneven stress distribution caused by size differences, which may affect the test results.
Ensure uniform sample quality: In the selection of substrate materials, it is necessary to ensure that the material is uniform and free of internal defects. If the substrate itself has problems such as pores and inclusions, it will interfere with the true manifestation of coating bonding strength. At the same time, the preparation process of the coating should also be strictly implemented to ensure uniform coating thickness and smooth surface. For example, when using the spraying process, precise control of spraying parameters such as spraying distance, spraying speed, feeding speed, etc. should be carried out to make the density and bonding state of the coating similar, reducing testing errors caused by uneven coating quality.
Proper handling of sample surface: It is crucial to perform standardized pre-treatment on the substrate surface before coating. By using appropriate cleaning techniques such as ultrasonic cleaning to remove oil stains, sandblasting to increase roughness, etc., it is ensured that the substrate surface is clean, the roughness meets the requirements, and there are no impurities such as oxide layers. This can provide a good and consistent bonding foundation between the coating and the substrate, avoiding the impact of surface treatment differences on the comparability of test results.
2、 Testing equipment and environment
Select appropriate and calibrated equipment: Based on different testing methods (such as using high-precision tensile testing machines for tensile testing and precise scratch testing instruments for scratch testing), choose professional equipment that meets testing requirements and has a sufficiently high level of accuracy. And it is necessary to regularly calibrate the equipment to ensure accurate measurement of key components such as force sensors and displacement sensors. For example, the force value display error of the tensile testing machine should be controlled within a very small range to ensure the authenticity and reliability of the measured tension and other data, thereby ensuring the accuracy of the combined strength calculation results.
Control the testing environment conditions: maintain a relatively stable temperature and humidity environment, as changes in temperature and humidity may affect the performance of the sample and the operational stability of the equipment. For example, in some high-precision scratch tests, fluctuations in ambient temperature may alter the mechanical properties such as brittleness of the coating, thereby affecting the damage of the coating during the scratch process and the corresponding critical load value. It is generally recommended to control the temperature of the testing environment within the standard room temperature range (such as 20 ℃± 5 ℃) and the humidity within an appropriate range (such as 40% -60%).
3、 Test operation process
Standardized operating procedures: Operators must strictly follow the established testing methods and procedures for testing. During the tensile test, the specimen must be installed correctly to ensure uniform force distribution during the loading process and avoid situations such as eccentric loading; When conducting scratch tests, it is important to accurately set parameters such as scratch speed, length, and loading rate to ensure consistent testing conditions and reduce the impact of human error on the results.
Reasonably set testing parameters: Based on the characteristics of the coating and substrate materials, as well as the requirements of the testing method, scientifically and reasonably determine the testing parameters. For example, in the combination of thermal shock testing and observation method, it is necessary to accurately set the temperature range, temperature rise and fall rate, cycle times and other parameters of thermal shock, so that it can truly simulate the thermal stress situation faced by the coating under actual high-temperature environment. Only in this way can the observed phenomena such as coating peeling and cracking accurately reflect the actual level of bonding strength.
4、 Data processing and analysis stage
Multiple repeated tests and taking the average: For samples with the same coating and substrate combination, multiple (generally no less than 3) repeated tests should be conducted, as a single test may be affected by accidental factors. Taking the average after multiple tests can effectively reduce random errors and make the results more representative and accurate. For example, in a shear test, multiple shear tests are conducted on a group of samples, and the average of the shear bond strength values obtained each time is taken as the final test result.
Proper data statistics and analysis: Use the correct statistical methods to analyze the test data, eliminate abnormal data (such as excessively high or low values that deviate significantly from other data, which may be due to sample preparation defects or testing operation errors), calculate the uncertainty of the measurement results, clearly understand the reliability of the results, and ensure that the final bond strength test results are scientific, accurate, and rigorous.

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