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Determination Of The Fatigue Behavior Of Coatings By Means Of An Improved Impact Testing Evaluation Procedure


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C. David, K. G. Anthymidis, P. Agrianidis & D. N. Tsipas


Impact testing is an efficient experimental procedure that enables the determination of the fatigue resistance of mono- and multilayer coatings deposited on various substrates, which is not possible with the common testing methods previously available. In this paper an advanced impact tester, capable of assessing the fatigue failure resistance of coatings working under cyclic loading conditions, is presented. The fatigue failure of the tested coating was determined by means of scanning electron and optical microscopy. The test results were recorded in diagrams containing the impact load versus the number of successive impacts that the tested coating can withstand. Keywords: thin films and coatings, materials characterization, fatigue. 1 Introduction The impact test method has been introduced as a convenient experimental technique to evaluate the fatigue strength of coatings being exposed in alternate impact loads [1–4]. According to this method a coated specimen is cyclically loaded by a hard ball that repetitively impacts on the specimen surface. The superficially developed Hertzian pressure induces a complex stress filled within the coating, as well as, in the interfacial zone. Both these stress states are responsible for distinct failure modes, such as a cohesive or adhesive one. The


thin films and coatings, materials characterization, fatigue.