Korrosionsuntersuchungen an mittels PVD mit Zn und Zn/Mn beschichteten Stählen

Corrosion Studies of Steels Coated by means of PVD with Zn and Zn/Mn Alternative methods for hot dip‐ or electrogalvanic deposition of zinc coatings on steel are gas phase depositions (PVD). They posess high flexibility with respect to alloy composition, and are environmentally harmless. However, a PVD‐coated steel must have at least the same corrosion resistance than steels with “classical” surface finishing. Therefore, the corrosion behaviour of Zn‐coatings and Zn/Mn/system‐coatings deposited by electron beam evaporation without and with ion beam assistance (IBAD) on low alloy steel, was determined by means of salt spray test and electrochemical potential/time measurements. At first the influence of chemical and irradiation pre‐treatment and ion bombardment during deposition on the corrosion resistance of the coatings was investigated. Than the effect of the Zn‐layer thickness was determined in comparison with an 8μm thick electrogalvanized reference coating. Finally Zn/Mn‐alloys, Zn/Mn‐multilayers and Zn‐coatings with Mn‐ or Zn/Mn‐surface layers (top layers) were investigated. By means of optimised pre‐treatment and ion bombardment conditions one obtains, considering the layer thickness, PVD‐Zn coatings with corrosion resistance comparable with the reference layer. The best Mn‐containing coatings are Zn‐coatings with Mn‐toplayer. They surpass the corrosion resistance of the reference layer considerably. Additionally it could be shown that in tendency the potential/time measurements agree very well with the results of the salt spray test.     

Struktur der Randschicht nichtrostender Stähle nach Tieftemperatur‐Nitrierung – eine Mößbauerstudie

Case structure of stainless steel after low temperature nitriding – a Mössbauer study Due to the nitriding of stainless steel at temperatures between 300 °C and 400 °C cases of high hardness and nitrogen contents ranges between 8wt.% and 12 wt.% could be prepared. In the present work the nitriding was performed by gas and plasmanitriding. The phase generation was investigated by use of the Conversion‐Mössbauer‐specrtoscopy (CEMS and XCMS) and the X‐ray diffraction. The chemical composition was determined by GDOS and the hardness test using the Martens‐hardness under load. In spite of different principles of action no significant differences between the structure and properties of the gas and plasmanitrited samples could be observed within the bounds of the used test methods. Clear differences were found in the nitriding behaviour of different steels.