What drives me - Kassel doctoral candidates and their topics

My dissertation deals with the bonding of stainless steels, or stainless steel. Basically, the metal has a great advantage: stainless steel does not rust. The surface is not particularly reactive because it is protected by the natural chromium oxide layer. But the disadvantage is that it is difficult to bond to stainless steel. This then becomes a problem in medical technology, for example.

Medical equipment is very expensive and requires extensive cleaning after each operation. During sterilization in an autoclave, the materials are exposed to heat, pressure and steam, which puts a lot of stress on them. For example, the adhesive in an endoscope bonds the stainless steel metal tube to the sapphire lens. The treatment in the autoclave can attack exactly this adhesive and the device will be damaged.

This is where my work comes in: How can the stainless steel be pretreated so that the bondings are more resistant to aging under hydrothermal stress? There are many factors that determine whether a bond will work or not. Bonding depends on temperature, humidity, pressure - all of which make bonding a very specialized process.

For my work, I treated the metal surface of my samples with a laser. This allowed me to create a surface texture that is very advantageous for bonding, as shown by the subsequent tensile shear test. In the tensile shear test, the bonded metal samples are pulled apart until they break, i.e., the bond comes off.

It is not yet known exactly how these microstructures work. In the past, it was thought that the surface simply had to be rough in order to bond. But chemical interactions can also occur at the atomic level. A lot of research still needs to be done here.

My dissertation arose from the LaserPROMISE project at the Department of Separating and Joining Manufacturing Processes. I came to adhesive bonding technology through my student job and then enjoyed working on the subject in greater depth.