Corrosion behaviour of Duplex PVD Coatings in Comparison to Duplex Coatings based on Electroplated base Coatings and PVD Top Coatings

摘要

Hard, wear resistant PVD coatings, such as CrN, increase the performance and durability of mechanical components by reducing the mechanical wear rate or lowering the friction behavior. In general the PVD coatings outperform standard electroplated coatings such as hexavalent Chromium. On the other hand, several electroplated materials show a much more favorable corrosion protection of the base materials compared to the typical PVD hard coatings. As of today, there have been multiple examples of a duplex treatment of an electroplated base layer with a PVD hard coating on top. This is to achieve both good wear and corrosion resistance in demanding applications. These solutions tend to be expensive. In this study different base layers from different vacuum based technologies like Arc PVD, Sputtering PVD, PECVD were deposited at different thicknesses on mild steel. The neutral salt spray test (NSS) as well as DC polarization test were performed in order to determine the corrosion protection of these vacuum deposited materials. The adhesion of coating with substrate was measured and compared using Mercedes Benz Rockwell indentation test and scratch test. State of the art Electro-less Nickel plating was used as the base line coating. In the final phase of the project, the most promising base layer was combined with a CrN PVD top coating. This is compared to the referenced electro-less Ni base layer with CrN on top.