In the present investigation, thin sheets of stabilized and unstabilized ferritic stainless steel were welded in butt joint configuration using irradiation of a 1070 $\mathrm{n}\mathrm{m}$ fiber-laser. Using optical microscopy, the microstructural evolution upon alternating heat input was characterized. In addition to that, hardness and tensile tests were carried out on the specimens. Detailed focus was given to the intergranular corrosion properties, which were investigated on basis of the Strauss test with different times of exposure to the corrosive environment. Following these tests, the mechanical properties of the joints were characterized using tensile tests. A combination of the latter with an inspection by $\mathsf{\mu }$-CT analysis allows for the proposition of an intergranular corrosion rate with regard to the degradation of the joint strength.

The intergranular corrosion susceptibility of ferritic stainless-steel weldments is strongly dependent on chromium carbide precipitation phenomena. Hence, stabilization is widely used to mitigate the aforementioned precipitation. In contrast, stabilization has proved ineffective to fully prevent intergranular corrosion due to segregation of unreacted chromium during solid-state heat-treatments. To analyze the precipitation behavior of 17 wt.-% chromium ferritic stainless steels during laser welding, sheets of unstabilized and titanium-stabilized ferritic stainless steels were welded in a butt joint configuration and characterized with special consideration of precipitation behavior by means of transmission electron microscopy. While unstabilized ferritic stainless steels exhibit pronounced chromium precipitate formation at grain boundaries, titanium-stabilization leads to titanium precipitates without adjacent chromium segregation. However, corrosion tests reveal three distinctive corrosion mechanisms within the investigated ferritic stainless steels based on their inherent precipitation behaviors. In light of the precipitation formation, it is evident that immersion in sulfuric acid media leads to the dissolution of either grain boundaries or the grain boundary vicinity. As a result, the residual mechanical strength of the joint is substantially degraded.

In the present investigation, commercially pure titanium is welded to AISI 316L stainless steel by intermixing niobium as filler material in a lap joint configuration. For this purpose, a pulsed Nd:YAG laser with various pulse durations and pulse peak powers is employed to obtain different mixing conditions for the materials. It will be demonstrated that, despite the implementation of the filler material, the weld seams are characterized by a high affinity for cracking, which in turn can be attributed to the formation of hard intermetallic compounds. Nevertheless, utilization of optimized process parameters can yield crack-free specimens in a reproducible manner through equable intermixing of otherwise critical alloy elements. Lap-shear forces of up to 140 N can be achieved with a single weld seam measuring 2.5 mm in length. By increasing the joint area with four adjacent weld seams, maximum loads up to 320 N are attained, thus exceeding the yield strength of the applied stainless steel. Considering the biocompatibility of the niobium filler material used, this work provides the foundation for this dissimilar material combination to be implemented in future medical technology applications.

The durability of adhesive bonds is not only affected by the quality of the bonding procedure but also by aging processes which influence the bond performance negatively on a long time scale. Especially the building industry, where safety related joints are increasingly boned with adhesives, demands new quality assurance methods. Therefore, appropriate monitoring techniques for developing cracks or critical stresses are essential. A new approach for in situ monitoring of transparent/opaque adhesives will be presented in this paper. Microcapsules, filled with special dyes, are embedded into adhesive systems. Upon breakage through cracks or exceedance of certain stress levels within the adhesive seam, the capsules release their liquid cores which leads to a detectable color change and, thus, enables non-destructive condition monitoring of the bond. In order to examine the feasibility of the approach, microcapsules are formed via interfacial polymerization. Microscopy techniques such as optical or scanning electron microscopy allow to study the capsule morphology, shape and dimensions (size and wall thickness) in dependence to the preparation procedure. Thereupon, the durability and release behavior are investigated with thermal analyses (differential scanning calorimetry and thermogravimetric analyses). Atomic force-based nanoindentation measurements give an insight into the size-dependency of mechanical properties like stiffness and burst forces. Finally, the principle of health monitoring is evaluated by dispersing the prepared capsules in the adhesive systems. Apart from the experimental examinations, numerical simulations of the crack propagation within the adhesive matrix are performed to demonstrate the effect of different microcapsule sizes and capsule walls on the fracture behavior. This preliminary study demonstrates the basic feasibility of the approach, but there is still a great need for investigations in order to employ the concept for industrial purposes.

Superhydrophobic paper has demonstrated significant potential for efficient water harvesting. Previous studies have indicated that the incorporation of pinning structures on superhydrophobic surfaces can enhance water collection efficiency. This study explores the feasibility of creating such pinning structures through femtosecond laser ablation of wax‐based superhydrophobic coatings. Static contact angle measurements and the roll‐off behavior of droplets on laser‐treated surfaces are conducted to evaluate the effects of laser ablation. Additionally, fogging tests are performed to assess the water collection performance, revealing an improvement of above 10% in comparison to unmodified superhydrophobic paper without localized pinning structures. Notably, the laser ablation process minimally affects the load‐bearing capacity of the paper, ensuring that its structural integrity is preserved. The ability to design laterally resolved pinning structures opens new possibilities for further optimization, such as the creation of flow paths, ultimately enhancing the overall efficiency of water harvesting systems.