Volume 52, Issue 4

Owing to its excellent mechanical and thermal properties, silicon nitride is an increasingly used tool material in the metallurgical industry. Some of its applications involve high thermal cycling loads, which may lead to tool failure. The failure of ceramic materials initiates from defects in the volume or on the surface of components and samples. Surface defects, often introduced during finishing, are considerably more harmful than defects in the volume. It was possible to heal surface defects by applying a specifically developed heat treatment – provided the defects are not too large. In water quenching experiments on samples and components, it could be proven that the strength increase induced by the heat treatment also results in an improved thermal shock resistance. Due to high processing costs and in some cases due to the components' geometry, enhancing the surface quality of components is not possible. The proposed heat treatment is an alternative to increase strength, thermal shock resistance (and thus the reliability and service life of silicon nitride components) which requires little effort.

The combination Scanning Electron Microscopy/Focused Ion Beam sectioning represents an established method for the three-dimensional characterization of material microstructures. This work examines whether this method of analysis is also applicable in case of a high resolution structure elucidation of bacterial cells in interaction with material surfaces. Here, the focus is on imaging the mechanism of bacteria cell damage induced by antibacterial copper materials.

Cracks were found in the roots of steam turbine blades of the third blade row (LA-2) of the low-pressure turbine during revision works in a coal-fired power plant. Metallographic examinations reveal pitting corrosion sites, branched cracks, and local plastic deformation at the root of the first load bearing flank radius. The fracture surface was analyzed using light microscopy and scanning electron microscopy (SEM). Finite element (FE) simulations were performed in order to qualitatively represent the stress peak positions on the blade root.