Optimizing Cavitation Resistance – An Approach By Cold Spraying Of Several Bronze Materials

Fast streaming fluid media cause cavitation-erosion in pumps, ship-propellers and rudders. For avoiding severe damages, materials with high resistance against plastic deformation and a high fatigue strength should be utilized. Bronzes fulfill these criteria, but as-cast bulk parts are rather costly. A promising alternative is cold-spray deposition of dense and oxide-free coatings onto exposed surfaces. To achieve high quality bronze coatings by cold-spraying, parameter optimization has to tackle the high hardness of the feedstock powder materials. Additionally, practical limits due to nozzle clogging have to be considered, which may occur at gas temperatures above 700 °C. The present study investigates possible solutions by systematic process parameter and feedstock material optimization, including variation of bronze compositions. Thus, dense coating microstructures and – in consequence - high hardness and good cavitation resistance have been obtained. Cold-spray coatings reach up to 8 times better cavitation resistance as compared to conventional shipbuilding steel (GL-A).