Application of Nano-layers for the improvement of cavitation resistance

Feben Tereffe Huluka

Master's thesis

Application of nano-layers for the improvement of the cavitation resistance

Abstract:

Research on Nano layer coating application for the improvement of the resistance to cavitation erosion has been discussed. The coating was accomplished by Arc PVD method where the substrate was an aluminum alloy namely duralumin. A vibratory cavitation device at a constant amplitude was used to conduct the cavitation test on the coated and reference samples. The surface characterization during the incubation period was carried out with the help of a confocal microscope. The effect of roughness on the duration of the incubation period was analyzed and the failure mode was studied to examine the coating's behavior under cavitation. To better understand the response of the coatings to cavitation, further surface characterization was performed using SEM and Brinell hardness tester. This technique allows us to understand the failure mode of the coating and the influence of the different parameters that can affect the cavitation resistance. The influence of substrate hardness on the cavitation resistance was analyzed and discussed. The substrate's change in hardness is due to the coating process. For this reason, the influence of temperature and time during the application of the coating on the resistance to cavitation is discussed. All the data obtained from measurement were compared against a raw sample, which shows that the resistance of the coated samples all decreased. This is due to the change in the alloy's property during the coating process, which is explained in the chapter labeled discussion.

Abstract:

Research on Nano layer coating application for the improvement of the resistance to cavitation erosion has been discussed. The coating was accomplished by Arc PVD method where the substrate was an aluminum alloy namely duralumin. A vibratory cavitation device at a constant amplitude was used to conduct the cavitation test on the coated and reference samples. The surface characterization during the incubation period was carried out with the help of a confocal microscope. The effect of roughness on the duration of the incubation period was analyzed and the failure mode was studied to examine the coating's behavior under cavitation. To better understand the response of the coatings to cavitation, further surface characterization was performed using SEM and Brinell hardness tester. This technique allows us to understand the failure mode of the coating and the influence of the different parameters that can affect the cavitation resistance. The influence of substrate hardness on the cavitation resistance was analyzed and discussed. The substrate's change in hardness is due to the coating process. For this reason, the influence of temperature and time during the application of the coating on the resistance to cavitation is discussed. All the data obtained from measurement were compared against a raw sample, which shows that the resistance of the coated samples all decreased. This is due to the change in the alloy's property during the coating process, which is explained in the chapter labeled discussion.

Keywords

Cavitation, Coating, Incubation period, Arc PVD

Language used: English

Date on which the thesis was submitted / produced: 12. 6. 2020

Thesis defence

• Supervisor: Ing. Miloš Müller, Ph.D.

Technical University of Liberec

Faculty of Mechanical Engineering

Master programme / field:
Mechanical Engineering / Machines and Equipment Design