Today, biomaterials and bioceramics are of great importance due to their biocompatibility compared to other materials, which are widely used in medical engineering applications to replace soft and hard tissue, screws and fracture plates, and replace joints. The challenges in orthopedic implants have led to the production of implants that behave both biologically and tribologically. Titanium implants have special medical applications due to their lightness and resistance to corrosion in biological environments, as well as their density close to the bones of the body. However, it is difficult to create a bond between titanium and bone, and this is a challenge that many researches such as coating the surface of the alloy are being done to solve it. For this purpose, in this research, hydroxyapatite is a suitable option for coating on the titanium substrate due to its bioactivity and proper bonding with bone tissue and proper ossification. However, hydroxyapatite will not provide the desired durability and stability of metal implants due to insufficient adhesion between the coating and the titanium substrate. One of the ways to improve the properties of hydroxyapatite as a bioceramic is to prepare composite materials based on hydroxyapatite. This research aims to enhance the performance of orthopedic implant coatings by comparing a multi-component bioceramic coating with a traditional single-component coating. Specifically, the study examines a tri-component coating made of hydroxyapatite, titania, and alumina (HA-TiO₂-Al₂O₃) applied to Ti6Al4V alloy substrates via plasma spraying for use in orthopedic implants, alongside a conventional hydroxyapatite (HA) coating. To prepare the tri-component coating, the HA-TiO₂-Al₂O₃ powders were mixed in weight ratios of 80%, 15%, and 5% respectively, and then milled for homogenization. Both the tri-component and single-component HA coatings were applied using the plasma spray technique. The coatings were subjected to a variety of analyses, including X-ray diffraction, surface roughness eva‎luation, microhardness testing, wettability analysis, adhesion strength measurement, bioactivity testing, and cytotoxicity assessment. The results demonstrated that the tri-component coating had a denser structure with fewer unmelted particles compared to the single-component HA coating. The addition of alumina reduced surface roughness from 5.58 µm to 1.55 µm, decreased the water contact angle from 85.92° to 61.28°, increased hardness from 278.5 HV0.5 to 470.2 HV, and improved adhesion strength from 1.09 MPa to 5.95 MPa. Also, the results of the bioactivity test showed that after 14 days of immersion in the body simulation solution, a dense layer of hydroxyapatite was formed, which confirmed the bioactivity of hydroxyapatite-titania-alumina ternary coatings compared to the single-component coating. The results of the culture of 63MG cells after five days showed that the three-component hydroxyapatite-titania-alumina coating had relatively higher viability (85.07% of control) than the one-component hydroxyapatite coating (80.33% of control). These enhancements significantly improved the tribological and biological properties of the coatings, making them more suitable for orthopedic implant applications.

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مصطفي ميلاني

مهران نحوي , عليرضا علافچيان