A study of the wear performance in a hip simulator of a metal–metal Co–Cr alloy with different boron additions

There has been a widely renewed interest in the use of metal-on-metal bearings for hip arthroplasties due to the medium-term results using contemporary conventional hip replacements. However, the search for new hip joint designs is targeted at younger and more active patients to optimise the performance of the bearing couple. The aim of this study was to investigate the wear behaviour of a modified Co–Cr alloy with boron additions. For this purpose, as-cast Co–Cr cups and heads were mated with different boron additions (0, 0.3, 0.6 and 1 B wt%) and tested in 4×106 cycles using the three-axial FIME II hip joint simulator under variable load profiles, and foetal bovine serum solution was as the lubricant. The wear was measured gravimetrically throughout the test. In addition, the bearing couples were characterised with metallographic techniques, confocal microscopy, scanning electronic microscopy, energy dispersive spectroscopy and roughness and hardness tests. The results showed an increase of the hard phases and wear resistance as the boron increased. In tribological terms, the results of this study showed the potential of this novel alloy as alternative for total hip prostheses.