Abstract

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Ti alloys, such as Ti6Al4V, are currently used in biomedical and dental implant applications. Ti alloys are used because they are stronger than commercially pure (CP) Ti due to the presence of alloying elements. However, toxicity of alloying elements during long-term use of implants is of concern. Another means of increasing the strength of materials is grain size refinement. In this study, ultrafine-grained (UFG, ~250 nm to 1 μm) CP Ti was produced by cryomilling followed by spark plasma sintering (SPS). Electrochemical impedance spectroscopy (EIS) and cell culture experiments were performed to compare the corrosion and biocompatibility properties of coarse grained (CG) Ti and UFG Ti. It was found that UFG Ti exhibited corrosion resistance comparable to CG Ti in Ringers solution. In addition, UFG Ti exhibited a reduced inflammatory response and enhanced cell adhesion compared to CG Ti. Investigation of surface roughness provided an explanation for enhanced cell adhesion.

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This study examines the influence of nano- and near-nano grains in bulk powder metal processing thus providing a baseline for understanding the potential of nanopowders for thermal spray application. Two light alloys (Al and Ti) and two tungsten carbide blends (WC-NiCrBSi and WC-CoCr) are cryomilled into nanocrystalline powders. The nanopowders are consolidated via hot isostatic pressing or spark plasma sintering and tested along with consolidated forms of virgin (micron scale) grains, shedding light on property improvements achieved through nanograined materials. HVOF coatings produced from nano- and micro-crystalline powders are tested as well, and the results are correlated with the improvements observed in the consolidated material forms.