Design and production of high entropy refractory alloy for implants' application: mechanical properties, surface modification, bioactivity, and corrosion behavior

Abstract

Conventional implants perform satisfactorily in many cases. However, due to their inert characteristic, there is no satisfactory interaction with the body. The frequent causes are infections, inflammation, allergic, and necrosis responses, leading to device rejection. Three critical requirements must be considered for the correct interaction: 1) Minimize stress shielding, which is due to the incompatibility of Young's modulus (E) between the implant and the bone; 2) biocompatibility and the absence of toxic components, such as V, Al, Ni, Cu, etc.; and 3) adjustment of bioactivity and corrosion rates since there is a contradiction between anti-corrosion properties and good bioactivity for implanted materials. Thus, there is an urgent need to develop a new generation of orthopedic devices with a growing biological character that integrates easily into the body, promoting osseointegration and limiting rejection phenomena. Thus, to solve the issues above, two approaches will be proposed here: 1) Design and production of high entropy alloys (HEA) for this application. Titanium alloys have been widely used as biomaterials for body implants such as hip joints, dental implants, and medical devices due to their excellent corrosion resistance, high yield strength, and good ductility. However, many commercially used Ti-alloy implants exhibit a considerably high Young's modulus compared to human bones, and the resulting stress shielding effect leads to bone resorption. 1) Design and production of high entropy alloys (HEA) for this application. Titanium alloys have been widely used as biomaterials for body implants such as hip joints, dental implants, and medical devices due to their excellent corrosion resistance, high yield strength, and good ductility. However, many commercially used Ti-alloy implants exhibit a considerably high Young's modulus compared to human bones, and the resulting stress shielding effect leads to bone resorption. 2) The first approach can solve the stress-shielding and compatibility problems. However, as mentioned earlier, both bioactivity and corrosion rates must be adjusted. Thus, the most appropriate method for improving the biological performance of materials is modifying their surface to improve their interaction with the body. This can be done from nanotubes' growth by the electrolytic deposition process and by acidic surface treatments. Intermediate and subsequent processes such as surface preparation, chemical treatments, growth or deposition of other phases can increase the possibilities for modifying surfaces. The comparison between the alloy with modified surface and the unmodified alloy will attest to the efficiency of the surface modifications made in the bioactive behavior of the alloy. The proposal aims to use the facilities and expertise of researchers at the Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces, LEPMI, in close collaboration with the Science et Ingenierie des Matériaux et Procédés, SIMAP, which are Departments of University of Grenoble Alpes, Institut National Polytechnique de Grenoble, and also associated with Université Joseh Fourier. The research will cover the already historic and sustainable cooperation between these two departments. LEPMI, which has strong knowledge in electrochemistry and characterization and vast experience in surface modification, will receive the researcher, whom Prof. Virginie Roche will supervise. SIMAP, which has recognized experience in innovative alloy design and the study of its mechanical and tribological properties, will support the design and preparation of HEAs under the supervision of Prof. Yannick Champion. (AU)