Mechanical behavior of apatite-alumina coatings deposited by high-velocity oxy-fuel spray (SHVOF): Prosthesis application

Alumina–fluorapatite (Al₂O₃–Fap) composite coatings deposited on 316 L stainless steel by Suspension High-Velocity Oxy-Fuel (SHVOF) spraying were investigated as candidate surfaces for prosthetic applications. Compared with conventional atmospheric plasma spraying (APS), SHVOF processing is known to produce denser coatings with improved adhesion, which is of interest for load-bearing biomedical interfaces. In this study, low fluorapatite contents (0–1 wt%) were incorporated into an alumina matrix to explore their influence on coating mechanical behavior. The coatings were characterized in terms of surface roughness, adhesion strength, and elastic properties. The results indicate that the addition of fluorapatite modifies the coating morphology and leads to an increase in surface roughness (Ra from ∼1.7 to ∼3.1 μm), while maintaining adhesion values within the range reported for thermally sprayed bioceramic coatings. An increase in elastic modulus was also observed, from 59.7 GPa for pure alumina to 98.3 GPa for Al₂O₃–Fap (1 wt%), corresponding to an increase of approximately 64%, indicating a marked modification of the coating mechanical response. In parallel, a three-dimensional finite element (FE) model of a cylindrical 316 L implant inserted into cortical bone was developed using Abaqus/CAE to simulate the early stage of implantation. The model was used to evaluate von Mises stresses and contact pressures at the bone–implant interface. The simulations predict von Mises stresses of approximately 48 MPa and contact pressures ranging from 25 to 55 MPa during insertion, values consistent with those reported for cortical bone under similar conditions. However, these results depend on simplifying assumptions, including linear elastic and isotropic bone behavior and the absence of an explicit coating layer. Overall, this combined experimental–numerical approach provides quantitative insight into the effect of low fluorapatite additions on the mechanical performance of SHVOF-deposited alumina coatings. The results suggest that such coatings may contribute to improved mechanical compatibility at the implant interface, although further biological and in vivo investigations are required to confirm their clinical relevance.