Surface Modifications of Biomedical Gum-Metal-Type Alloy by Nano Surface—Severe Plastic Deformation

Abstract

For developing performant metallic materials for medical implants, biomechanical adaptation is important for both the bulk material and the material’s surface. Therefore, a nano surface-severe plastic deformation (NS-SPD) treatment was applied on the surface of a gum-type alloy (Ti-Nb-Zr-Fe-O) with enhanced bulk mechanical biocompatibility. Six variants with different processing parameters were tested using small impact balls accelerated by compressed air. Before the NS-SPD treatment, the alloy was first subjected to thermomechanical processing to achieve a high compositional and structural homogeneity and proper mechanical properties of the core structure. A detailed microstructural analysis was performed on the thermomechanical-processed alloy and on the surface areas. The microstructural analysis (based on scanning electron microscopy electron backscatter diffraction and x-ray diffraction) reveals the influence of the NS-SPD treatment by formation of two different surface layers: an outer, very thin layer, approximately 10 μm in width, formed of titanium oxides as a consequence of surface oxidation during ball impacts in an air atmosphere, and one approximately 100 μm to 250 μm in width, representing a zone of high-density microstructural defects.