Improving the reproducibility and the comparability of bond strength values
Verbesserung der Reproduzierbarkeit und Vergleichbarkeit von Werten für die Bindefestigkeit
One of the most popular test methods for the evaluation of thermally sprayed coatings and substrate pre-treatment is the bond strength test in accordance to the standard EN 582 (in Europe) or ASTM C633-79 (in the U.S.). An interlaboratory test, carried out in 2003, has shown that bond strength tests of samples that were joined by different institutions in accordance to DIN EN 582 lead to bond strength values that varied by the factor 2, even if the same adhesive was used. The test not only made clear that the adhesives used to join the loading block to the substrate block but also many other parameters have a tremendous influence on the results of the bond strength tests. It was also clarified that the DIN standard needs to be supplemented in order to improve the comparability and the reproducibility of the bond strength test results. The first aim of this work was to identify the influencing parameters by carrying out Failure Mode and Effect Analyses (FMEA) together with namable institutions. Based on these results, a work instruction based on the DIN standard will be composed in order to avoid its weak spots. Later, a second interlaboratory test will be carried out to evaluate the quality of the work instruction.