A Review on the Surface Treatment and Biocompatibility of titanium based Alloys Fabricated by Selective Laser Melting

In recent decades, pure titanium and its alloys, have been extensively employed in the medical field for the fabrication of orthopedic and dental implants, bone fixation plates and screws, as well as cardiac valve components. These materials have attracted considerable attention due to their favorable mechanical properties, including adequate strength and relatively low elastic modulus, which contribute to improved compatibility with bone tissue. Nevertheless, despite these advantages, titanium and its alloys face several critical limitations. Compared to alloys such as Co-Cr-Mo, they exhibit relatively low hardness, insufficient wear resistance, and suboptimal long-term biocompatibility. Furthermore, pure titanium and its alloys are generally considered bioinert. Once implanted, they tend to become encapsulated by a fibrous tissue layer, which may lead to the physical separation of the implant from the surrounding host tissue. This phenomenon negatively affects osseointegration and long-term implant stability. To address these issues, surface modification has been recognized as an essential strategy for enhancing the performance of titanium-based biomaterials. Through surface engineering, it is possible to convert bioinert titanium surfaces into bioactive interfaces, thereby promoting osseointegration and long-term integration with bone tissue. A wide range of techniques have been developed for the surface modification of titanium and its alloys, which can be broadly categorized into physical and chemical approaches. Physical techniques include thermal spraying, plasma spraying and ion implantation, all of which enhance the surface characteristics without altering the bulk properties of the material. Chemical techniques, on the other hand, involve methods such as sol-gel processing, acid and alkali treatments, and chemical vapor deposition (CVD), which are capable of creating bioactive surfaces or functional coatings tailored for specific biomedical applications. Selective Laser Melting (SLM) is an advanced additive manufacturing technique that enables the production of complex, high-precision titanium-based alloys with tailored microstructures and properties. This method allows for precise control over porosity, geometry, and surface characteristics, which are critical for biomedical applications such as implants. Titanium-based alloys produced via SLM exhibit excellent biocompatibility, corrosion resistance, and mechanical properties compatible with human bone, including a reduced elastic modulus to minimize stress shielding. Furthermore, the rapid solidification inherent in SLM enhances microstructural refinement, reduces the formation of undesirable phases, and allows for customized mechanical performance through post-processing heat treatments. The combination of design flexibility, mechanical performance, and biological compatibility makes SLM-fabricated titanium alloys a highly promising solution for next-generation biomedical implants. Overall, the advancement of surface modification technologies is considered one of the most promising pathways for overcoming the inherent limitations of titanium and its alloys produced by selective laser melting, thereby ensuring their reliability and long-term success in biomedical applications.

کلیدواژه ها:

titanium ، selective laser melting ، surface treatment ، biocompatibility ، additive manufacturing ، coating