Study On Process And Properties Of Antibacterial Stailnless Steel By Plasma Permeating Technique

Antibacterial stainless steel is a new antibacterial material, which possesses high strength, corrosion resistance, antibacterial feature and so on.These are widely used in fields of medical apparatus, food processing, public health etc. Therefore, the stainless steel which possesses antibacterial feature becomes a new field of study hotspot in functional material.In this paper, using plasma surface alloying technique, the copperizing layer was prepared on the surface of 0Cr18Ni9 Austenitic stainless steel. The surface morphology, the layer microstructure were analyzed by a metallographic microscope and scanning electronic microscope （SEM）.The depth distribution of elements and the phase structure were analyzed by X-ray energy spectrum （EDS） and X-ray diffraction（XRD）.The micro-hardness distribution was measured by micro- hardness tester（HV-1000）. The abrasive wear resistance was investigated by using the wear tester （M200） under dry sliding wear conditions. The corrosion behaviors was investigated by using electro- chemical tests（P-268）under potentiodynamic conditions in several kinds of solutions. Finally, Antibacterial ability to Escherichia coli was evaluated by the film contact method.The results showed that:（1） The copperizing layer could be formed on the surface of 0Cr18Ni9 Austenitic stainless steel by the plasma surface alloying technology. The optimum technological parameters were as follows: limited vacuum 5Pa, working gas Ar, working pressure 20 Pa, source voltage 1000V, sample voltage 500V, holding temperature 950℃, holding time 3h.（2）Under the optimum technology, the surface of the copperizing layer is flatter and smoother. The copper content of the layer was decreasing gradually from the surface to the bottom. The metallurgical structure is even. The thickness of the copperizing layer was 33μm. The copper content is up to 3.5% in the surface. The white bonding is metal- lurgical between the layer and the substrate. The interfacial strength is high.The Chrom- ium migration are processed in the plasma surface alloying process.（3）The phases of the copperizing layer consist of Fe, Cu, Cu_xFe_1-x, CuO and Cu0.81Ni0.19.（4）The micro-hardness of the copperizing layer decreases gradually from the surface to the bottom.（5）Under the condition of the technique,the sputtering yield increases linearly with the increase of incident energy. But the energy was larger than 95 eV,the sputtering yield began to decrease. The mass diffusivity decreased with the increase of distance.（6）The result of the abrasive wear resistance showed that:With increasing of load, friction coefficient of the alloying layer shows a decreased state. Under the same load, the wear rate and the wear weight loss were less than untreated samples. In the wear process, rich horniness copper in the layer plays a role in reducing wear loss, rich flexible in the layer plays a role in supporting effect. Its wear mechanisms are adhesive wear and abrasive wear. The copperizing layer has good abrasion resistance.（7）The result of the corrosion property showed that:In 1mol/LHNO₃、3.5% NaCl solution, the corrosion resistance of the copperizing layer is slightly decrease with the untreated sample, but in 1mol/LNaOH solution, the corrosion resistance is slightly increase with the untreated sample. Copper-enriched phases distributed uniformly with small forms in the surface, which leads stainless steel not to form a continuous passive films. But the Cr contents on the surface of sample increase after plasma surface alloying process, the layer has identical corrosion resistance of the untreated sample.（8）The result of antibacterial test showed that: When the containing of copper achieve 2.5 percent, the copperizing layer exhibits antibacterial effect, and the rate of antibacterial can achieve 95.3 percent. The rate of antibacterial is increased with the increase of Cu content. When antibacterial action time achieves 18h, the copperizing layer exhibits antibacterial effect, and the rate of antibacterial can achieve 92.3 percent. With the prolongation of antibacterial action time, the sterilization function of antibacterial stainless steels increased remarkably. When the containing of copper achieve 3.5 percent, antibacterial action time achieves 36h, the rate of antibacterial can achieve 95.3 percent.（9）Antibacterial mechanism of the copperizing layer is that: Copper-enriched phases is precipitated in the copperizing layer, In the antibacterial test, Copper-enriched phases precipitates Cu ion. It can penetrate the cell wall, go deep into cells, combine with sulfido, and then the protein was congealed. Cu ion has a function of damaging syntheses activity, and then the cell loses its physiological function. Eventually,it makes a lot of interstitial fluid out and kills the bacterium.