Improving the Wetting Behaviour of Steel Substrates by Use of Atmospheric Pressure Plasma

The need of dissimilar joints as well as protective, temperature- or wear-resistant coatings has been increasing in the last
decades. This trend can be observed in different areas of mechanical engineering. Coating or joining materials with different physical
properties is related to one significant criterion, which is known as the wetting behaviour of a substrate material. The surface free
energy level or the contact angle describes this criterion. APP (atmospheric pressure plasma) is a highly effective and adaptable
pre-process for improving the wetting behaviour of materials. In the scope of this work, the influence of three main APP
parameters—electrical current I, working distance a and translation velocity f—on the wettability of 1.0330 steel substrates was
investigated. Therefore, a DoE (design of experiments) based work plan was carried out. The experimental sequence is separated into
two parts. Firstly, the surface of the substrate is treated by APP. Secondly, the contact angles of the plasma-processed substrate are
measured in defined time steps. To calculate the surface free energy level out of the measured data, two different liquids were used.
This paper will show the time-dependent impact of APP on the wettability, the interaction of the main parameters, as well as the
surface condition of the steel substrate after APP.