Study On Sliding Friction And Corrosion Behaviors And Wear Particles Of Different Joint Materials Combinations

Artificial joint implants need to bear various cyclic loads and different forms of damage in the human body environment, such as fatigue, abrasion and corrosion. Wear particles reflect different wear information and mechanisms for the artificial joint implants. Therefore, it is of great significance to perform the research on friction and corrosion behaviors and wear particles of artificial joint implants.The sliding friction and corrosion experiments were carried out between Co Cr Mo pin or 316 L stainless steel pin and UHMWPE plate. The size characteristics and fractal characterization of UHMWPE wear particles were investigated. The following main conclusions were obtained:Firstly, friction coefficient decreased with the increasing of load and friction coefficient increased with the increasing of the sliding velocity in the same lubricants. It was different for friction coefficient in different lubricants. It was maximum in SBF and minimum in distilled water for Co Cr Mo/UHMWPE. It was maximum in normal saline and minimum in SBF for 316 L stainless steel /UHMWPE. The damage of wear surface increased with the increasing of load and sliding velocity for Co Cr Mo/UHMWPE and 316 L stainless steel/UHMWPE. Ploughing wear and fatigue wear caused by cyclic plastic deformation were the main wear mechanisms.Secondly, the potential, current density and dynamic corrosion current increased with the increasing of load in the friction and corrosion test for Co Cr Mo/UHMWPE and 316 L stainless steel/UHMWPE and the damage of wear surface also became more serious. The resistance of friction corrosion of Co Cr Mo/UHMWPE was better than that of 316 L stainless steel/UHMWPE. The friction coefficient in friction and corrosion test was larger than that of the friction test for two joint combinations, which deceased with the increasing of load. The wear mechanism of friction and corrosion was similar to the pure friction, which were mainly controlled by the ploughing wear and fatigue wear caused by cyclic plastic deformation.Thirdly, the distribution characteristics of wear particles size were similar with load and sliding speed changing in friction corrosion test. The size of particles was less than 40 microns. The mean size of UHMWPE wear particles was about 20 to 25 microns at 100 N normal load. The mean size of UHMWPE wear particles was about 5 to 10 microns at 80 N and 100 N normal load. There was some influence on the distribution characteristics of wear particles size for the properties of lubricants. The size of wear particles of Co Cr Mo/UHMWPE was smaller than those of 316 L stainless steel/UHMWPE under three lubricants.Finally, the morphology of wear particles included the typical forms and wear particle aggregation. Typical morphology of wear particles included larger tuberous and flake wear particles, pole-liked and needle wear particles with long size, granular wear particles with less 5 microns size and near roundness wear particles which less 1 microns. The granular aggregation mainly included flocculent wear particles. The size was different and most of them were nanoscale particles. The result of radar graph fractal showed that the fractal dimension decreased with the UHMWPE particles from long pole-liked to granular and spherical. The obvious regularity revealed that the contour curve of wear particle had independence in dimension.