The purpose of this study is to evaluate the corrosion fatigue properties of Ti-6Al-4V alloy with a unique textured surface created by selectively etching the surface. In contrast to surfaces created by sintering or plasma spraying, material is removed from the surface rather than added to it. Furthermore, the material does not require subsequent heat treatments which may affect the microstructure of the coating and the coating/substrate interface.
Ti-6Al-4V samples produced by three different processes were tested. These samples were: 1) etched, 2) plasma sprayed and 3) uncoated. Tapered cylindrical samples were tested in 37 °C Ringers' solution at 6 Hz with R=0.1 to a maximum of 107 cycles. Crack initiation sites were examined and characterized using scanning electron and light microscopy. An endurance limit of about 380 MPa was found for the etched samples whereas the plasma sprayed samples fractured in the order of 105 cycles at 242 MPa. All of the smooth samples went to run-out at 414 MPa except for one which fractured in 7.5 × 106 cycles. Fracture of the plasma sprayed samples initiated at multiple sites and was associated with delamination of the coating from the substrate. Fracture of the etched samples initiated at asperities on the surface of the sample.