Preparation Of Surface Antibacterial Stainless Steel By Plasma Alloying Technology

Harmful bacteria can lead to the spread and infection of disease. While, antibacterial materials can effectively reduce the bacteria’s propagation. Stainless steel is one of the wide-used metal materials. To upgrade antibacterial properties of stainless steel has been a focus of intensive researches for a long time. Antibacterial stainless steel refers to such kind of stainless steel, which owns the antibacterial property through adding antibacterial agent, such as Ag, Cu and so forth.Although it is possible to introduce copper or silver into stainless steel via bulk alloying during material production, the complicated preparation procedure and the deterioration of bulk mechanical properties make it difficult to be used for practical applications. Thus, a plasma surface alloying technology with energy conservation and environment performance was used for preparing antibacterial stainless steel though plasma alloying with Cu-Ni alloy in this paper.The microstructure, elements distribution and phase identification of Cu-Ni-alloyed surfaces prepared under different gas pressure were analyzed using the scanning electron microscope, glow discharge spectrometer and X ray diffraction. The thickness of the alloyed layer prepared at45Pa is about6.5μm, and the Cu concentration on the alloyed surface is about2.5wt.%. The layer is mainly composed of expanded austenite phase.,A spread plate method was adopted for evaluation of antibacterial property of the Cu-Ni-alloyed surface prepared at45Pa against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) The Cu-Ni alloyed stainless steel exhibits excellent antibacterial effects, and over99.6%of S. aureus and over99.9%of E. coli coli are killed.The antibacterial mechanism of the alloyed surface was investigated by the X ray photoelectron spectroscopy. Results indicated that Cu ions released from the alloyed steel surface after being in contact with bacterial cause the cell wall damage, killing the bacteria.The electrochemical corrosion properties of the Cu-Ni-alloyed stainless steel and stainless steel substrate have been investigated in0.5mol/L NaCl solution. Compared with the substrate, the corrosion resistance of Cu-Ni alloyed sample is lower, which is related to the alloyed layer’surface status and the damage of the passive film of stainless steel.The tribological properties of the Cu-Ni alloyed stainless steel and stainless steel substrate were investigated by a pin-on-disc tribometer against GCrl5steel ball. The friction coefficient, wear volume and wear rate of the Cu-Ni alloyed stainless steel are lower than the substrate. The alloyed layer improves the wear risistance of stainless steel lightly.In this paper, the duplex treatment consisting of plasma surface alloyed with Cu followed by thermal diffusion under the bombardment of glow was also carried out on AISI304stainless steel in order to improve its antibacterial properties. Results indicated that the surface of the Cu-alloyed steel is uniform and dense. The Cu concentration on the alloyed surface reaches to5.7wt.%and the thickness of the alloyed layer is about2.7μm. The antibacterial rates gradually rise with increase of the contact time between the bacteria and the Cu-alloyed stainless stee. Contact with Cu-alloyed stainless stee after1h,80%of E.coli and73%of S.aureus are killed; after3h,96%of Escherichia coli and94%of Staphylococcus aureus are killed; after12h, more than99.9%of E.coli and S.aureus are killed.