CoCrMo alloys have been used for biomedical implants for a number of years. One of the important parameters which influences durability of the coating and thus whole implant are parameters of surface texture, namely Ra and Rt, which are determined by standards ISO 7206-2:2011 and ISO 7207-2:2011. Three duplex surface systems were applied to improve mechanical properties. The combination of plasma nitriding and subsequent deposited thin films of the nACo 3 ®, DLC and ZrN were used as a duplex treatment. Plasma nitriding was implemented under these conditions: duration time 10 hours, the ratio of gases H 2 :N 2 =3:1, process temperature 450 °C, 500 °C and 550 °C. The surface texture parameters were measured on the polished surface of the CoCrMo alloy at first, then on the polished surface after plasma nitridation process and finally on the polished surface of deposited coating. It has been demonstrated that deposition of the selected coatings on the nitride surface influences the surface texture parameters Ra and Rt.
Hydroxyapatite (HA) is widely applied as bone graft material due to its osteoconductive potential and well-established biocompatibility. The high osteoconductive potential of the HA coating provides a potential structure for use as bone substitute in orthopedic, oral, and cranio-maxillofacial reconstructive surgery, and as dento-alveolar implants. The aim of this work is to present hydroxyapatite coatings which were prepared on CoCrMo as-cast alloy by electrochemical deposition technology in the mixed solution Ca(NO 3 ) 2 ·4H 2 O and NH 4 H 2 PO 4 . CoCrMo alloy complies with the ISO 5832-4 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. HA coating is used to ensure sufficient bioactivity, but application of hydroxyapatite in orthopedic implants suffers from its low fracture toughness and poor wear resistance. Carbon nanotube (CNT), with its high stiffness and mechanical strength, is an attractive reinforcement for HA to surmount these issues.
Given that CoCr alloys have excellent corrosion resistance and abrasion resistance, they have found their wide use as a material for replacing human joints, especially the knee and hip replacements (1, 2). CoCr alloys offer a wide range of positive mechanical properties such as high strength, hardness and elasticity. However, despite all the advantages in these alloys are occurring the following problems: corrosive processes that increase the level of metal ions in the local tissues, and systems (in blood) (3), adverse micro and nanotopography of surface, low biological activity, non-hydrophilic surface (2). New approaches are currently looking to reduce the amount of wear particles whilst maintaining the required biocompatibility of the material. The work is focused on the evaluation of surface structure CoCrMo alloy, which is used to produce joint replacements, after the deposition of hydroxyapatite by electrochemical method. The carbon nanotubes (CNT) were added to improve the mechanical properties of the deposited coating of hydroxyapatite.
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