The Effect of Surface Treatment on the Fatigue Behavior of NiTi Alloys

NiTi alloys have been widely used as biomaterials especially for the realization of dental devices because of their biocompatibility and superelastic behavior. However, these tools can break frequently during clinical use. The susceptibility of these alloys to cyclic loadings in the presence of hydrogen can be one of major parameters in the degradation of fatigue properties. It is admitted that the state of surface is determining to know the influence of the hydrogen in the fatigue properties. In order to study the impact of some surface treatments and the effect of hydrogen on the fatigue behavior of NiTi alloys at high number of cycles, we propose to use the self-heating method. This methodology has the advantage of being faster and cheaper than traditional fatigue tests and allows to estimate the endurance limit of the material using empirical approach. In this case, the temperature variation is considered as a relevant parameter to predict the fatigue resistance of these alloys. The results of this study showed that after a surface electropolishing treatment, the hydrogen does not affect the fatigue properties of these alloys. However, after a mechanical polishing, the effect of hydrogen is more pronounced leading to a decrease in the fatigue life of NiTi alloys with a high increasing in temperature.