Date of this Version
T. Patil, 2018, Effect of Shot Peening on Stress Corrosion Behavior of Biodegradable Magnesium WE43.
Conventionally used metals for orthopedic devices made of titanium, stainless steel, and Co-Cr alloys are designed to be permanently implanted. However, long-term complications arise and a secondary implant removal surgery is often necessary. A mismatch in stiffness between the bone and implant results in stress shielding that negatively affects bone density. To overcome these problems, magnesium alloys (e.g., WE34) are favored due to a lower Young’s modulus (45 GPa) and biodegradability. The critical technical barrier with magnesium alloys is their high corrosion rate in physiological (salt-based) environments. One solution is to use surface treatments, such as shot peening (SP), to induce surface residual stresses and slow the degradation rate. The corrosion rate can be customized according to patient specific parameters, such as age and bone health, or application (i.e., pelvic fracture vs. spinal fracture) through SP process parameter manipulation (e.g., peening pressure). However, the effect of residual stresses from SP on stress corrosion behavior of magnesium alloys remains inconclusive. The purpose of this study is to evaluate the effect of shot peening with different peening pressures on the stress corrosion rate of WE43 using polarization tests. The results for this study indicate that the corrosion resistance of the alloy increased as the pressure of shot peening increased and is inversely proportional to the applied external load. A relation between the surface integrity and the stress-corrosion behavior of the shot peened samples has been found.
Advisors: Florin Bobaru and Michael Sealy