In Vitro Corrosion Resistance and Antibacterial Performance of Novel Fe–xCu Biomedical Alloys Prepared by Selective Laser Melting

Abstract

Antibacterial Fe-xCu biomedical alloys are designed to have a satisfactory biodegradation rate compared with pure iron. Fe-xCu (x ¼ 0, 1.5, 2.3, 7.8, and 10.1 wt%) alloys are produced by selective laser melting (SLM). Alloying with Cu has a significant influence on the grain size, hardness, biodegradation rate, and antibacterial performance of SLMed Fe-xCu alloys. Increasing Cu content decreases the grain size and increases the hardness. SLMed Fe-1.5Cu, Fe-2.3Cu, and Fe-10.1Cu have degradation rates similar to that of pure iron, while the degradation rate of SLMed Fe-7.8Cu is almost 2.5 times faster. The SLMed Fe-2.3Cu, Fe-7.8Cu, and Fe-10.1Cu produce strong antibacterial performance. The mechanisms of degradation behavior and antibacterial performance are clarified. SLMed Fe-7.8Cu had appropriate mechanical properties, satisfactory degradation rates, strong antibacterial performance, and good cytocompatibility, and therefore is a novel type of antibacterial biomedical alloy with good potential for clinical application.

Study on a Novel Biodegradable and Antibacterial Fe-Based Alloy Prepared by Microwave Sintering

“…Cu and Fe have the standard potential of +0.34 V SHE [ 20 ] and −0.44 V SHE [ 5 ], respectively, which leads to the micro-galvanic corrosion effect between Cu-rich precipitation and Fe matrix in Fe-Cu alloy, increasing the corrosion rate. The release of Cu 2+ with corrosion progressing can produce the desired antibacterial effect, as was recently confirmed by Guo et al [ 21 ], who used selective laser melting to produce antibacterial Fe-xCu alloys having a satisfactory biodegradation rate compared to pure iron.…”

“…The corrosion potential ( E corr ) and corrosion current density ( i corr ) were evaluated by the Tafel extrapolation method [ 28 , 29 ]. The polarization curve of the microwave-sintered pure Fe had an obvious current platform in the anode region, as shown in Figure 4 a, which indicated that the pseudo-passivation film might be formed on the surface, affecting the corresponding degradation rate [ 21 ]. However, for the microwave-sintered Fe-8Cu samples, the anode branch current of polarization curve increased steadily with increasing potential.…”

“…Fe powders (particle size distribution of ≤70 μm) ( Figure 1 a) and Cu powders (particle size distribution of ≤50 μm) ( Figure 1 b) were used as raw materials, with purities of 99.9%, and were purchased from Changsha Tid Metal Materials Co. Ltd., Changsha, China. Based on previous process optimization [ 21 ], Fe powders were mixed with 8 wt.% Cu powders (designated as Fe-8Cu). Figure 1 c shows the morphology of the mixed Fe-8Cu powders, which were prepared by ball-milling (YXQM-0.4L, Changsha Miqi Instrument equipment Co. Ltd., Changsha, China) with a rotational speed of 300 rpm for 3 h. Ball to powder ratio was 5:1.…”

“…The corrosion rate, P i (mm/year), was evaluated from the corrosion current density, i corr (μA cm −2 ) using Equation (1) [ 21 ]. …”

“…Samples for the immersion tests were exposed for 30 d in the Hanks’ solution, which was refreshed every 24 h. After the immersion test, the surface corrosion products were removed by a solution with 2 g antimony oxide, 5 g stannous chloride and 100 mL hydrochloric acid. The degradation rate, P w (mm/year), was evaluated using Eqatuion (2) [ 21 ]. where W i was the initial sample mass (g) before immersion tests, and W f was the final sample mass (g) after immersion tests.…”