Test method development for determination of the coatingquality of coated angled surfaces with acoustic cavitationmethod by using the sonotrode device

Common rail system is a high-tech fuel injection system used in today's diesel engines. Compared to the other injection systems, the common rail system has advantages in terms of performance, efficiency, noise generation and emissions. However, fuel system pressures have continued to increase from the past to the present, in order to achieve performance, efficiency and emission targets. Since increased fuel system pressure has a negative effect on the injector life, additional measures are taken in critical parts. In this study, it is aimed to develop a new test method by acoustic cavitation method for the determination of the coating quality of the valve piece which is one of the most exposed parts of the cavitation caused by the high pressure difference between the high pressure zone and the low pressure zone in the injector. In this study, since the existing coating quality tests of the valve piece such as HF (Haftung-Adhesion Test), Scratch test are inadequate, a new test method has been developed that can control homogeneity and minimizes the risk of evaluation by using acoustic cavitation which is a more suitable method considering the field conditions. In the first step, the cavitation cloud characteristics formed by the sonotrode device were investigated. In the second step, the tests were carried out at distance varies between the aluminum samples with a simple geometry and the sonotrode head. The cavitation cloud effects on the distance were examined. In the next step, the same tests were carried out with the valve piece and the optimum distance with the highest wear was determined. In the final stage, the limits for distinguishing coating quality were appointed. According to the test results, a new test method for the evaluation of the coating quality of the valve part which is one of the most critical parts of the common rail injector has been developed in accordance with the field conditions.