Under tribological conditions in aqueous medium, the contact of materials does involve some degradations of materials. Especially friction under small reciprocal displacement, i.e., fretting corrosion, is occurring; this topic has been highlighted since the 80′s regarding hip implants. Hip prosthesis is assembled from three parts: femoral stem, neck and head. Fretting corrosion or friction corrosion between metallic parts first involves some degradation of the oxides layers. This step is governed by mechanics and it is related to some few minutes. Afterwards the corrosion occurrs enhanced by mechanical degradation. As well focused some oxides and some metallic ions are related to biocompatibility issues. Some strategies are available in order to avoid metal against metal friction and/or fretting. Some hard coatings and some smooth coatings were investigated. The first one is diamond-like carbon (DLC), and the second is a polyetheretherketone (PEEK), polymeric one. The investigations were focused on fretting corrosion solicitations of Ti-6Al-4V vs. Ti-6Al-4V + coating. DLC as a coating delays the corrosion degradation. The PEEK coating does not promote any corrosion degradation of the metallic counter part and more generally any wear.
This work aims at studying the fretting biocorrosion response of newly developed Ti-6Al-4V/ZrO2 in simulated body fluid. Ti-6Al-4V alloy with different volume fractions of ZrO2 produced via powder metallurgy techniques were spark plasma sintered to produce Ti-6Al-4V composites with improved properties. The microstructures of the resulting spark plasma sintered composites were examined using a scanning electron microscope (SEM). Fretting corrosion tests were conducted for each material composition with a special device used for fretting corrosion investigations with a cylinder-on-flat configuration. The tests were done in foetal bovine serum maintained at ambient temperature. Open circuit potential, dissipated energy and coefficient of friction were monitored throughout the experiments. The results show that the microstructures produced after zirconia additions were very different from those observed in pure Ti-6Al-4V. The presence of zirconia promoted the formation of globular zirconia-rich agglomerates throughout the matrix, leading to more improved fretting biocorrosion properties of Ti-6Al-4V.
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