| Orthopedic implants are used as medical devices that are surgically implemented into the body and designed to replace a missing joint, a bone or to support a damaged structure. Even though orthopedic implants have excellent outcomes such as restoring mobility and increasing the quality of lives, the failure of these implants occasionally takes place. This thesis examines a process called "superfinishing" as an alternative surface modification method for use on orthopedic implants that may yield better patient outcomes. It is believed that superfinishing may improve desired properties such as bending stress, fatigue strength, resistance to bacteria adhesion, wear resistance, chemical inertness, low coefficient of friction, and similar or better adhesion characteristics than stainless steels/titanium. The focus of this thesis is to show improvement in bending strength. In this study, specimens were superfinished in two different types of abrasives: aluminum oxide (Al3O 2) and silicon carbide (SiC). The results demonstrated that roughness value of stainless steel rods in Al2O3 powder/walnut shell mix decreased to 0.156mum from 0.221mum and roughness value of stainless steel rods in SC powder/walnut shell mix decreased to 0.100mum from 0.184mum which is 36-44% decrease in roughness value. The experiment indicated that roughness value of these rods becomes stable after 21 minutes of superfinishing process but the maximum average load results were collected after 9 minutes of superfinishing process. This study showed that the longer superfinishing process does not necessarily increase the bending strength. This study also showed that the bending strength of superfinished Ti-6Al-4V rods was increased by 3.81% with SiC abrasives. In addition, bending strength of superfinished 316L rods were increased by 3.35% in Al3O2 abrasives and by 6.49% in SiC abrasives after 9 minutes of superfinishing process. Residual stresses should be studied as the future work to grasp the effects of superfinishing process. |
