|
3777 |
|
Wednesday, May 21, 2014, Hall F 11:10 AM Cold Gas Spraying 1 |
|
Cold spraying of Cu-Al-bronze for cavitation protection in marine environments |
|
Sebastian Krebs* / Helmut-Schmidt University, University of the Federal Armed Forces Hamburg, Dep. of Materials Engineering, Germany Oliver Wirth / Helmut-Schmidt University, University of the Federal Armed Forces, Germany Frank Gärtner/ Helmut-Schmidt University, University of the Federal Armed Forces, Germany Thomas Klassen/ Helmut-Schmidt University, University of the Federal Armed Forces, Germany |
|
Travelling at higher speeds, modern ships face severe rudder cavitation-erosion, high corrosion rates, and erosive wear by dispersed sediments. At present, respective measures to cope with these problems include fluid dynamically optimized rudders, cavitation-resistant coatings on basis of synthetic materials and weld cladded coatings on steel basis. Ship Propeller are fabricated from expensive bulk Cu-Al-bronzes, established to withstand corrosion and cavitation. These bronzes could also enhance rudder life times, if deposited as coatings in satisfactory quality with bulk-like properties. The present study investigates cold spray coating formation characteristics of CuAl10Fe5Ni5 bronze powders with size distributions of 25-45 µm and 45-63 µm. Based on calculations of the impact conditions and the critical conditions for bonding, the range of optimum spray parameters was preselected in terms of the general coating quality parameter ·. Systematic variation of · in the range of about 1.4 to 1.7 was achieved by adjusting process gas temperatures between 600°C to 800°C and process gas pressures between 4 to 6 MPa. Single particle impact morphologies were investigated by scanning electron microscopy and categorized regarding impact and deformation behavior. The selected parameter regime yields deposition efficiencies of 50 78 %. Analysis of coating microstructures revealed that for the higher parameter sets, porosities of less than 1 % can be obtained. Results concerning coating performance indicate that the cavitation resistance of cold sprayed bronze coatings correlates with their mechanical strength. These first results demonstrate that cold-sprayed bronze coatings have a high potential for rudder protection and may evolve towards a competitive or even superior alternative to existing anti-cavitation procedures. |