Influence of Cu and Sn on the microstructure and properties of antibacterial ferritic stainless steel

The influence of Cu and Sn on the microstructure, mechanical properties, corrosion resistance, and antibacterial properties of 430L ferritic stainless steel has been investigated by using Thermo-Calc calculations, EPMA (electron probe microanalysis), TEM (transmission electron microscopy), and XPS (X-ray photoelectron spectroscopy). Vichers hardness tests, potentiodynamic polarization, and antibacterial tests were also performed. For a copper content of 1.5 wt.%, the results showed that aging treatments at 600 degrees C, 700 degrees C and 800 degrees C are conducive for the precipitation of an e-Cu phase in the 430L ferritic stainless steel. It was also found that the e-Cu phase was composed of almost pure Cu (with a the content of 98.6-99.7 wt.%). Thermo-Calc calculations showed that there was only a very small amount of Fe, Cr, and Mn in thee-Cu phase. Moreover, the e-Cu phase was found to substantially coarsen with an extension of the aging time. The size of e-Cu phase increased from a few nanometers to hundreds of nanometers, and the number of e-Cu phase decreased gradually. Furthermore, the antibacterial rate of the 2(#) (430L - 1.5 wt.% Cu) and 3(#) steel (430L - 1.5% Cu - 0.4 wt.% Sn) samples increased significantly with an extension of the aging treatment time, and the antibacterial rate of the 3(#) steel was higher than that of the 2(#) steel sample. The antibacterial rate reached as high as 91.60% and 97.37%, respectively, for an aging time of 79,200 s.