Surface Modification of Medium-Entropy Alloys

An orthopedic implant is a medical device designed to replace a bone, joint, or cartilage due to damage or deformity. Commonly used implants like Ti (110-120 GPa) and Co-Cr alloys (200-230 GPa) exhibit high elastic moduli, which can lead to ‘stress shielding’, which is a phenomenon that causes bone to weaken when the implant bears most of the load. In addition, the release of certain metallic ions from these materials can provoke adverse tissue reactions. To combat these drawbacks, medium-entropy alloys (MEAs) provide a variety of advantages in terms of lower elastic modulus (from a single-phase body-centered-cubic structure), improved corrosion resistance, and superior biocompatibility. The surface modification of implant surfaces is highly demanding in conferring bioactive properties to bioinert alloy surfaces. Among the various surface engineering approaches, the hydrothermal technique is highly advantageous in improving osseointegration. However, reports associated with the surface functionalization of MEAs are sparse in the literature. The present work explores the hydrothermal surface modification of Nb₃₀Ti₃₀Zr₃₀Cr₅Mo₅-based MEAs for implant application. This study delves deep into the structural aspects and surface characterization of these MEAs with particular emphasis on X-ray Photoelectron Spectroscopy (XPS) analysis for pertinent implant application. This work holds promising prospects in understanding MEA surfaces and how the obtained information can be used for developing futuristic bioimplant surfaces.