Materials aspects of hydro-abrasive wear in the dredging industry

A better understanding of the wear mechanism of materials is essential to selecting suitable materials to prolong service time and reduce costs. Wear resistance is not an intrinsic material property but a response to a system including multiples parameters determined by the material, the counter body, the load condition, and the environment. Wear is a common cause of materials degradation, as well as Corrosion. When mechanical wear and corrosion co-exist, they interact with each other and, often, enhance each other, resulting in faster material failure than the situation where only a single factor exists. This thesis presents the study of the interaction between corrosion and wear with the goal of obtaining a better understanding of the wear mechanism to guide the material selection. To study the wear mechanism, a pin on disc tribometer was employed to precisely control the load, rotational speed, and corrosion environment. A potentiostat was also used to provide well-defined corrosion environment (corrosion is quantified by the current and potential). By connecting the pin on disc with a potentiostat, a well-controlled mechanical and chemical (electrochemical) system was employed to perform wear experiments. Results show that the influence of corrosion on wear is found to be much more complex than simply enhancing, as proposed at the onset of my PhD research. The new findings in this thesis show that the influence of corrosion is highly dependent on the specific situation and the corresponding wear mechanism. Corrosion may increase wear rate when the process is governed by cyclic formation and removal of surface corrosion products. Corrosion may decrease wear rate when the process is governed by the galvanic micro coupling effect. Corrosion may not influence wear rate when the process is dominated by impacting.