CAVITATION AND ELECTROCHEMICAL CHARACTERISTICS IN SEAWATER BY WATER CAVITATION PEENING OF 5083-O Al ALLOY FOR SHIPS

摘要

Aluminum (Al) alloy ships are vulnerable to both damage from chlorine ions in seawater environments and cavitation-erosion due to fast relative motion of metal and liquid resulting from lightweight and high-speed vessels moving through seawater. These corrosive processes cause damage to the hulls of ships, resulting in large economic losses. Recently, cavitation peening technology to improve the durability of a material has been in development. The technology works by forming compressive residual stress on the surface layer of the material in order to improve fatigue strength and fatigue life. In this study, we performed a water cavitation peening (WCP) on a 5083-O Al alloy for ships by applying an ultrasonic piezoelectric effect and cavitation effect, as described in ASTM-G32. From these experiments, we determined an optimum WCP duration, 2.5 min, for sufficient cavitation resistance characteristics. This timing improved cavitation resistance by 48.68% compared to the untreated condition. A comprehensive comparison of all of results revealed that the optimum WCP duration was 3 min with respect to the point of cavitation and corrosion resistance.