New Alloys and Service Performance on High Speed Crafts

This paper presents the test results of new propeller alloys developed by the authors to extend the service life of the propellers used on oceangoing hydrofoil craft. Comparative tests of high speed propellers cast with a new grade of corrosion resistant nitrided steel alloy as well as titanium alloys are summarized. These propellers have high specific strength and corrosion resistance in sea water. In addition, the design of these propellers was changed to have large skew to reduce the cavitation effects on the inclined propeller operation. Steel shafting with oxide coatings and graphite bearing compounds is introduced to avoid corrosion in sea water when titanium propellers are fitted. This approach resulted in the successful corrosion isolation of the titanium propellers from the shafting and hull. When these new propellers were installed they significantly increased the propeller service life on the oceangoing hydrofoil craft.