Tribocorrosion behaviour of hot pressed CoCrMo−Al₂O₃composites for biomedical applications

Abstract

Alumina/alumina wear couple can lower the wear rates and thus metallic ion releasing on load bearing metallic implant materials. However, the low fracture toughness of ceramics is still a major concern. Therefore, the present study aims to process and to triboelectrochemically characterise the 5 and 10 vol.-%Al 2 O 3 reinforced CoCrMo matrix composites. Corrosion and tribocorrosion behaviour of the composites were investigated in 8 g L 21 NaCl solution at body temperature. Corroded and worn surfaces were investigated by a field emission gun scanning electron microscope equipped with energy dispersive X-ray spectroscopy. After tribocorrosion experiments, wear rates were calculated using a profilometer. Results suggest that Al 2 O 3 particle addition decreased the tendency of CoCrMo alloy to corrosion under both static and tribocorrosion conditions. However, no significant influence on the corrosion and wear rates was observed in composites mainly due to increased porosity and insufficient matrix/ reinforcement bonding.

Synergism between corrosion and wear on CoCrMo−Al2O3 biocomposites in a physiological solution

“…Through the polarization curves it can be seen that the alloy and the composite exhibited similar polarization behavior. In the anodic domain, both materials presented a passivation plateau due to the formation of the passive oxide film as it has already been reported for hot pressed CoCrMo alloy [22,33,39]. Fig.…”

“…A recent study by some of the present authors [22] presented a first insight on the tribocorrosion behavior of CoCrMo À Al 2 O 3 composites in 8 g/l NaCl solution at body temperature and reported lower tendency to corrosion under sliding as compared to its base alloy. However, the composite materials did not exhibit an improvement on the wear rate mainly due to the insufficient bonding at the matrix/reinforcement interface.…”

“…6b) were recorded for both materials due to the mechanical damage of the passive film, leading to the formation of active sites on the worn area. Thus, under sliding, thermodynamic tendency for corrosion and corrosion kinetics were increased on both samples [22,30,31,33].…”

“…Microstructural and structural analysis of the hot pressed CoCrMo alloy was presented elsewhere indicating γ (fcc) phase as the matrix phase of the alloy and CrCo-σ phase as the secondary phase [22]. Fig.…”

“…Individual wear and corrosion behavior of MMCs have extensively been studied and it is known that improved wear resistance of MMCs is mainly linked to the direct strengthening effect of the particles occurring with the transferring of the load from matrix to the reinforcement, together with indirect strengthening mechanisms that is related to dislocation strengthening, Orowan strengthening and grain size refinement or modification of the matrix alloy with the effect of the reinforcement phase addition [11,12]. However, corrosion studies on MMCs showed that addition of the reinforcement phase may deteriorate the corrosion behavior through a galvanic coupling between the matrix and the reinforcement, selective or localized corrosion at the matrix/ reinforcement interface, or chemical degradation of the interphases and the reinforcement [13][14][15][16][17][18][19][20][21][22]. The literature on the tribocorrosion behavior of MMCs, on the other hand, is very limited as compared to the ones on the individual wear and corrosion studies.…”