Towards near-permanent CoCrMo prosthesis surface by combining micro-texturing and low temperature plasma carburising

• An innovative duplex surface treatment (micro-texturing and S-phase) was developed.
• In-situ visualisation of lubricating films on real geometry head and cup.
• Lubricating film thickness was increased by surface texturing on CoCrMo head.
• Testing time-dependant performance of dimpled surface and its longevity.
• Study of frictional behaviour of MoP joints with different texture geometries.

An advanced surface engineering process combining micro-texture with a plasma carburising process was produced on CoCrMo femoral head, and their tribological properties were evaluated by the cutting-edge pendulum hip joint simulator coupled with thin film colorimetric interferometry. FESEM and GDOES showed that precipitation-free C S-phase with a uniform case depth of 10 μm was formed across the micro-textures after duplex treatment. Hip simulator tests showed that the friction coefficient was reduced by 20% for micro-metre sized texture, and the long-term tribological property of microtexture was enhanced by the C-supersaturated crystalline microstructure formed on the surface of duplex treated CoCrMo, thereby enhancing biotribological durability significantly. In-situ colorimetric interferometry confirmed that the maximum film thickness around texture area was 530 nm, indicating that the additional lubricant during sliding motion might provide exceptional bearing life.

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