P. M. Reinders, P. Kaestner, G. Bräuer, Technische Universität Braunschweig, Braunschweig, Germany
Austenitic steels are known for their high corrosion resistance but at the same time have low wear resistance and high interfacial contact resistance (ICR), which limits their application e. g. as bipolar plates in Proton Exchange Membrane Fuel Cells (PEMFC). Plasma diffusion treatment, specially the well-known plasma nitriding, improves the hardness and interfacial contact resistance but mostly worse the corrosion behavior in PEMFC environment.
Aim of this study is to evaluate the less known plasma carburizing as a suitable process for functionalization austenitic stainless steels. For this purpose, a number of processes were executed under specific variation of temperature ranging from 360 °C to 450 °C and duration of 10 to 16 h. The samples were analyzed using x-ray diffractometer, x-ray photoelectron spectroscopy, SEM, Vickers microindentation, potentiodynamic polarization and ICR measurements.
It could be shown that the corrosion current density (1.78 μA·cm^-2) of the treated samples are an order of magnitude lower than those of the reference (17.38 μA·cm^-2). The ICR was also reduced from > 1000 mΩ·cm^-2 down to 31 mΩ·cm^-2. After corrosion, even lower values around 15 mΩ·cm^-2 were achieved. The targets according to DOE ( < 1 μA·cm^-2 and < 10 mΩ·cm^-2) were almost achieved. A comparison to the plasma nitrided samples was also performed and shows the high potential of plasma carburizing.