This investigation studies the effect of the shot-blasting treatment on the cyclic deformation behavior of a commercially pure titanium, with two microstructures: equiaxed and acicular. The fatigue tests were carried out in artificial saliva medium at 37° C. Cyclic deformation tests have been carried out up to fracture, and the fatigue crack nucleation and propagation have been analyzed. The results show that the shot-blasting treatment improves the fatigue life in the mi-crostructures studied, and that the equiaxed was better in mechanical properties than the acicular. The cause of this improvement in the mechanical properties is due to the compressive stress on the material surface for the shot-blasted specimens. Hardness tests were carried out to determine the value of these internal stresses.
The design of an oral implantable device always has to take into consideration the cyclic loading during the life in-service of the implant. Therefore, the fatigue endurance of the materials used will play a very important role when trying to estimate the long-term performance of the device. Thus, the assessment of the fatigue behavior of implantable alloys takes on an added significance. Wrought cobalt-chromium, titanium, and Ti-6Al-4V alloys show both a similar fatigue endurance when evaluated by means of rotary bending fatigue tests (about 550 MPa), 1 and when tested in corrosion fatigue in torsion. 2 A relevant aspect is that the elastic modulus of titanium (110 GPa) is about half that of stainless steel (200 GPa) and that of cobalt-chromium-molybdenum alloys (235 GPa). This is a very important point to be taken into account when considering the load transfer into the bone when a joint prosthesis or an osteosynthesis device is to be designed.
Table 1 summarizes the fatigue endurance for some of the alloys previously discussed. The fatigue strength limit is reduced in all cases when the material is tested in saline solution in relation to tests performed in air. Also, both in air or in saline solution, titanium shows the highest fatigue strength limit.
Titanium and titanium alloys can be strengthened and their mechanical properties may be varied by controlling their composition and by means of thermomechanical processing techniques. 3–8 Recent approaches in the development of new titanium alloys have been to produce new alloys without vanadium to avoid possible toxic effects of this metal. 9 This has led to the alloys Ti-5Al-2.5Fe 8–9 and the recently developed Corona 5 (Ti-4.5Al-5 Mo-1.5Cr).
Titanium and titanium alloys are resistant to general corrosion, pitting, and crevice corrosion, which may occur in other alloys as a result of the aggressive attack of body fluids. 10–12 Osseointegration of the implant is meant to be achieved by bone ingrowth into the roughness of the titanium surface. 13–20 In this paper, the influence of the shot-blasting treatment on the fatigue and fracture properties has been studied.