Growth kinetics and mechanical properties of boride layers formed at the surface of the ASTM F-75 biomedical alloy

Abstract

Abstract In this study, new data about the growth kinetics and indentation properties of cobalt boride layers formed on the surface of the ASTM F-75 biomedical alloy were estimated. The boron diffusion at the surface of the biomedical alloy was conducted using a powder-pack boriding process at temperatures of 1223–1273 K with different exposure times for each temperature. Two mathematical approaches were proposed to determine the boron diffusion coefficients of the CoB and Co2B layers in the range of boriding temperatures, in which the experimental results of the kinetics of the cobalt boride layers were compared with those estimated using diffusion models. Finally, the mechanical characterization of the cobalt boride layers was evaluated by indentation techniques with applied loads of 0.98 N and 50 mN, respectively. According to the nanoindentation tests, a maximum hardness value (30 GPa) and a maximum Young's modulus (380 GPa) were obtained near the surface region (5 μm) of the borided cobalt alloy.