Stainless steel（SS） is not recommended to be used in hospital environments for work surfaces and door furniture due to the lack of antibacterial properties.To this end,a novel SS surface modified layer with both a quick bacterial killing rate and relatively thick has been obtained by plasma surface alloying with Cu.The microstructure,elements distribution and phase identification were analyzed by SEM,GDS,XRD and XPS.A spread plate method was adopted for evaluation of antibacterial property of specimens against Escherichia coli（E.coli） and Staphylococcus aureus（S.aureus）.The experimental results demonstrate that the surface modified layer with the thickness of about 26 μm is uniform and dense.The layer is mainly composed of a mixture of pure Cu,expanded austenite phase and a few Fe3O4 phase.The Cu modified layer exhibits excellent antibacterial effects against E.coli and S.aureus within 1 h.No viable E.coli and S.aureus was found after 3 h（100% killed）.The modified layer is relatively thick,hence it is expected that the Cu modified SS will have a durable antibacterial function
ZHANG Xiang-yu HUANG Xiao-bo JIANG Li MA Yong FAN Ai-lan TANG Bin
By using double glow plasma surface metallurgy technique, the molybdenum （Mo） surface- modified layer on titanium （Ti） was obtained. The corresponding cross-section morphology, phase formation, and element concentration were investigated by optical microscopy, X-ray diffraction （XRD）, and glow discharge optical emission spectroscopy （GDOES）, respectively. The experimental results indicate that the Mo modified layer is composed of a 1.7 μm pure Mo deposition layer and a 14.3μm Mo diffusion layer. Along the sample thickness direction, nanoindentation tests were performed on the cross-section of the Mo diffusion layer and the Ti substrate （for the comparison purpose） by Hysitron TI900 TriboIndenter. The 2D and 3D residual indentation profiles of the Mo diffusion layer were obtained by scanning probe microscopy （SPM）. The elastic modulus and hardness values of every indent were acquired and analyzed. According to the load-displacement curves, the plastic deformation degrees of the Mo diffusion layer and the Ti substrate were analyzed. It is indicated that the Mo diffusion layer possesses high strength-toughness.
Cu modified layer was prepared on the surface of AISI304 stainless steel by plasma surface alloying technique. The effects of processing parameters on the thickness, surface topography, microstructure and chemical composition of Cu modified layer were characterized using glow discharge optical emission spectroscopy （GDOES）, scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The experimental results show that the surface modified layer is a duplex layer （deposited ＋ diffused layer） with thickness of about 26 ktm under the optimum process parameters. The modified layer is mainly composed of a mixture of Cu and expanded austenite phase. The ball-on-disk results show that the modified layer possesses low friction coefficients （0.25） and excellent wear resistance （wear volume 0.005 x 109 um3）. The Cu modified layer is very effective in killing the bacteria S. aureus. Meanwhile, no viable S. aureus is found after 3 h （100% killed） by contact with the Cu alloyed surface.
