The role of Ti in cavitation erosion and corrosion behaviours of NAB alloy in 3.5 % NaCl solution

Abstract

The influence of titanium on the cavitation erosion and corrosion behaviors of a NAB alloy in 3.5 % NaCl solution is investigated using tensile test, mass loss, SEM, Tafel plots, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS). The results show that the NAB alloy consists of the α phase, β phase and κ phase, in which titanium will enter the κ phase to form the titanium-rich κ phase. With the increment of titanium, the titanium-rich κ phase changes from mainly distributed at grain boundaries to more dispersed at grain boundaries and inside grains. In the case of high titanium content, the κ phase rich in titanium grows and produces an obvious segregation phenomenon, resulting in a decrease in the mechanical property and corrosion resistance of the substrate. The mass loss experiment shows that the mass loss caused by cavitation erosion decreases with increasing titanium content, and it increases with increasing titanium content when titanium content is over 0.478 %. The electrochemical experiments show that the corrosion resistance of NAB alloy in 3.5 % NaCl solution increases with increasing titanium content and reaches a maximum when titanium content is 0.478 %. The reason for the increased corrosion resistance of a NAB alloy containing titanium in 3.5 % NaCl solution is related to the appearance of TiO2 in the passive film automatically formed on a NAB alloy in air.