Some Consideration on Double Layer Structure in Plasma Assisted Nitriding of Austenitic Stainless Steel

Low temperature plasma assisted nit riding treatments of 316 stainless steel produce a complex layer constituted by tow different metastable f.c.c. solid solution denoted ( γ N1 and γ N2 ). About the formation of these double layers, different hypothesis was proposed in the literature. For verifying these hypotheses, the effects of differentes conditions such as nit riding temperature, cleaning and nit riding duration and cooling state have been studied. The results show that γ N2 sub layer produce during the ion bombardment cleaning procedure, before the nit riding treatment. Also the formation of the γ N2 layer is not connected to the cooling state of the sample after nit riding treatment

Electrodeposition and corrosion behavior of Zn−Ni−Mn alloy coatings deposited from alkaline solution

The potentiostatic electrodeposition of Zn−Ni−Mn was carried out in an alkaline solution with the addition of Mn salt. The effects of electrolyte Mn2+ concentration and deposition potential on the surface morphology, phase structure and corrosion behavior of coatings were studied. The results of corrosion polarization showed that the presence of higher Mn content in Zn−Ni−Mn coatings could lead to the formation of a good passive layer with a 7-fold increase in Rp of coating and a significant decrease in the corrosion current density compared to those of Zn−Ni coating. The XRD and the XPS analyses from the surface of Zn−Ni−Mn after corrosion test showed that the passive layer was composed of zinc hydroxide chloride, zinc oxide, zinc hydroxide carbonate, and manganese oxides

A promising perspective in improving corrosion and wear resistance of plain steel through electrodeposition of thick Ni–Mo–W ternary alloy

In this study, thick Ni–Mo–W ternary alloy coatings (∼24 μm) with 13–27 wt% Mo and 4–11 wt% W were electrodeposited from an alkaline citrate-ammonia bath using direct current. The effect of current density (20–100 mA/cm2) on the composition, current efficiency, morphology, structure, surface topography, tribological behavior, and corrosion resistance of coatings was investigated. The findings revealed an advantageous induced co-deposition of Mo in an electrolyte containing equimolar Mo and W ions. While increasing the current density decreased the Mo content of the coatings, they always had more Mo than W. Increasing the current density, according to SEM and AFM observations, changed the smooth and nodular morphology of Ni–Mo–W coatings to a relatively rough and cauliflower shape. The microhardness of the produced nanocrystalline solid solution coatings was 3.8–4.9 times higher than that of the plain carbon steel substrate. While the hardest coating (793 Hv) deposited at 100 mA/cm2 had the best wear resistance with a volume loss value of 0.04 mm3, it had the worst corrosion resistance among the coatings with icorr = 4.4 μA/cm2. The least hard coating (607 Hv), deposited at 40 mA/cm2, with the highest wear volume loss value of 0.11 mm3, however, was the most corrosion resistant sample with icorr = 1.9 μA/cm2