A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this techniq...A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.展开更多
A plasma electrolytic nitrocarburising （PEN/C） process was performed on stainless steel 316L to improve the surface properties for using as medical implants. A bath was optimised to reduce the required voltage to 15...A plasma electrolytic nitrocarburising （PEN/C） process was performed on stainless steel 316L to improve the surface properties for using as medical implants. A bath was optimised to reduce the required voltage to 150 volts. Aqueous urea-based solutions with 10% NH4Cl were prepared with slightly different amounts of Na2CO3 to optimise the electrolyte composition. The surface and the cross-section morphologies were studied by scanning electron microscopy. The microstructure and the chemical composition of samples were investigated by X-ray diffraction （XRD） and energy dispersive X-ray （EDX） techniques. The microstructure of the outer layer of the coatings was found to be a complex oxide containing Cr and Fe. The wear properties of the samples were examined by using a pin on disk wear test with Ringer＇s solution and were compared with their wear properties in the ambient atmosphere. The Ringe（s solution acted as a lubricant, reducing friction coefficient. Hardness and roughness were also studied. The bath with the composition of 10% NH4CI and 3% Na2CO3 exhibited the best tribological properties. The results showed that the tribological properties of treated samples were improved and the wear mechanism was abrasion of the pin.展开更多
文摘A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.
基金supported by the Research Committee of Shiraz University under grant No.88-GR-ENG-62,which is gratefully appreciated
文摘A plasma electrolytic nitrocarburising （PEN/C） process was performed on stainless steel 316L to improve the surface properties for using as medical implants. A bath was optimised to reduce the required voltage to 150 volts. Aqueous urea-based solutions with 10% NH4Cl were prepared with slightly different amounts of Na2CO3 to optimise the electrolyte composition. The surface and the cross-section morphologies were studied by scanning electron microscopy. The microstructure and the chemical composition of samples were investigated by X-ray diffraction （XRD） and energy dispersive X-ray （EDX） techniques. The microstructure of the outer layer of the coatings was found to be a complex oxide containing Cr and Fe. The wear properties of the samples were examined by using a pin on disk wear test with Ringer＇s solution and were compared with their wear properties in the ambient atmosphere. The Ringe（s solution acted as a lubricant, reducing friction coefficient. Hardness and roughness were also studied. The bath with the composition of 10% NH4CI and 3% Na2CO3 exhibited the best tribological properties. The results showed that the tribological properties of treated samples were improved and the wear mechanism was abrasion of the pin.
