بررسي خواص مكانيكي پوشش هيدروكسي آپاتيت بر روي بستره كبالت كروم موليبدن به روش پلاسما اسپري جهت كاربرد در ايمپلنتهاي زانو

Abstract With the increasing elderly population an‎d the growing preva‎lence of musculoskeletal disorders, the deman‎d for biomedical implants has significantly risen. Although metallic implants possess high mechanical strength, their bioinert surfaces may result in weak bonding with bone tissue. Therefore, the application of bioactive coatings such as hydroxyapatite to enhance the bone–implant interface has gained considerable importance. Due to its similarity to the mineral phase of bone, hydroxyapatite is biocompatible an‎d promotes cellular adhesion an‎d proliferation. However, achieving adequate coating adhesion an‎d mechanical stability remains challenging, an‎d plasma spraying is one of the most widely used techniques approved by the FDA for this purpose. In this study, the effects of different substrate roughness levels, the application of a titanium interlayer, an‎d post-deposition heat treatment on the microstructure, mechanical properties, an‎d biological performance of plasma-sprayed hydroxyapatite coatings were investigated. The substrates were prepared with three roughness ranges of 1–2, 5–7, an‎d 10–12 µm. The results showed that a roughness of 1–2 µm did not provide sufficient mechanical interlocking for the single-layer hydroxyapatite coating, leading to coating delamination. In contrast, a roughness of 5–7 µm resulted in the highest adhesion strength (44 MPa for the single-layer coating an‎d 41 MPa for the bilayer titanium–hydroxyapatite coating). Higher roughness values in the range of 10–12 µm reduced the adhesion strength to 35 MPa. The incorporation of a titanium interlayer improved the mechanical bonding of the coating to the substrate at 1–2 µm roughness an‎d prevented coating delamination. Structural analysis indicated that the use of a titanium interlayer increased the crystallinity of the coating from 63% to 75%. Heat treatment further enhanced the crystallinity of the single-layer coating to 87% an‎d significantly reduced porosity, although an increase in surface cracks due to the release of residual stresses was observed. Moreover, the hardness of the single-layer hydroxyapatite coating increased from 210 MPa to 584 MPa after heat treatment. Biological eva‎luation demonstrated that none of the coatings exhibited cytotoxicity, an‎d MG63 cell adhesion was confirmed on all samples. Overall, the findings indicate that plasma-sprayed hydroxyapatite coatings, particularly those prepared with an optimal substrate roughness an‎d a titanium interlayer, are suitable for biomedical applications.

رضا اميني نجف آبادي

عرفان عقيلي , مصطفي ميلاني

محمد خدائي , تقي اصفهاني