CoCrMo alloy has long been used as a pairing femoral head material for articular\njoint implant applications because of its biocompatibility and reliable tribological performance.\nHowever, friction and wear issues are still present for CoCrMo (metal)/CoCrMo (metal) or CoCrMo\n(metal)/ultrahigh molecular weight polyethylene (UHMWPE) (plastic) pairs in clinical observations.\nThe particulate wear debris generated from the worn surfaces of CoCrMo or UHMWPE can pose\na severe threat to human tissues, eventually resulting in the failure of implants and the need for\nrevision surgeries. As a result, a further improvement in tribological properties of this alloy is\nstill needed, and it is of great interest to both the implant manufacturers and clinical surgeons.\nIn this study, the surface of CoCrMo alloy was laser-treated by a fibre laser system in an open-air\ncondition (i.e., no gas chamber required). The CoCrMo surfaces before and after laser remelting were\nanalysed and characterised by a range of mechanical tests (i.e., surface roughness measurement and\nVickers micro-hardness test) and microstructural analysis (i.e., XRD phase detection). The tribological\nproperties were assessed by pin-on-disk tribometry and dynamic light scattering (DLS). Our results\nindicate that the laser-treated surfaces demonstrated a friction-reducing effect for all the tribopairs\n(i.e., CoCrMo against CoCrMo and CoCrMo against UHHMWPE) and enhanced wear resistance\nfor the CoCrMo/CoCrMo pair. Such beneficial effects are chiefly attributable to the presence of the\nlaser-formed hard coating on the surface. Laser remelting possesses several competitive advantages\nof being a clean, non-contact, fast, highly accurate and automated process compared to other surface\ncoating methods. The promising results of this study point to the possibility that laser remelting\ncan be a practical and effective surface modification technique to further improve the tribological\nperformance of CoCr-based orthopaedic implants.
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