Marine wear and tribocorrosion

Abstract

As the use of marine systems grows and the requirements for seawater lubrication grows, the performance of key marine alloys used in propulsion, bearings and mechanical seals is under scrutiny. For example, the increased use and size of bulk carriers and ocean liners requires performance of propellers to be better understood and cavitation resistance needs to be predicted and improved. The growth in marine autonomous and renewable energy systems as well as aquaculture also places emphasise on greater understanding of marine alloy tribocorrosion performance. Therefore, this paper will review marine wear and tribocorrosion and focus on candidate or existing materials for the components must at risk of wear (i.e. propulsion and seawater handling systems) and the mitigating strategies used to limit effects of wear in aggressive ocean environments. It will look at recent research into the performance of cast nickel aluminium bronze, a propulsion material of choice, under cavitation erosion and sliding wear conditions in saline solutions. The mass loss and in-situ electrochemical measurements during cavitation erosion corrosion over time will be presented along with detailed reference to microstructural and compositional changes on the surface and subsurface. The influence of surface films and their stability will be explored. For sliding wear tests the temporal aspects of film removal and repair as a function of sliding frequency will be presented along with complimentary wear rates, friction and corrosion currents. Some initial results on coatings and bulk composite alternatives to NAB will also be presented. Research into solid particle erosion-corrosion will also be presented for NAB. The challenges in quantification of the interactions between mechanical and electrochemical processes present under marine tribocorrosion are discussed in detail.