Volume 59, Issue 10

The round robin test investigated the reliability users can expect for AlSi10Mg additive manufactured specimens by laser powder bed fusion through examining powder quality, process parameter, microstructure defects, strength and fatigue. Besides for one outlier, expected static material properties could be found. Optical microstructure inspection was beneficial to determine true porosity and porosity types to explain the occurring scatter in properties. Fractographic analyses reveal that the fatigue crack propagation starts at the rough as-built surface for all specimens. Statistical analysis of the scatter in fatigue using statistical derived safety factors concludes that at a stress of 36.87 MPa the fatigue limit of 10 7 cycles could be reached for all specimen with a survival probability of 99.999 %.

Defined micro-leaks have been used as reference leaks in non-destructive testing for many years, for example in the adjustment, calibration and functional testing of helium leak detectors. Test leaks are also used in non-destructive testing training to teach the staff how to detect these “invisible” leaks. The traditional production of test specimens with defined leakage, however, is timecon suming and expensive. In addition, these specimens are susceptible to impacts and can break easily. A new approach for producing robust specimens with defined leakage is gas dynamic cold spraying, or cold spraying, where a very small opening is closed using an open-pore metal powder filling. This manufacturing process is particularly suitable for industrial purposes due to the good controllability of the production process. Unlike traditionally manufactured glass bodies, the specimens produced in this way are less susceptible to mechanical impacts. The present study is concerned with the metallographic examination of porous coatings to create defined leaks using cold spraying.

Molten salt containing systems gain in importance for sustainable energy use and production. For research and development, interactions of molten salts with potential container materials are of major interest. This article introduces preparation procedures to display an intact metal and salt microstructure and their interface using light optical microscopy and scanning electron microscopy. The exemplary material combination is the ternary salt mixture NaCl-KCl-MgCl 2 and the low alloyed steel 1.4901 (T92) with a maximum service temperature of 550 °C. These are potential elements/materials for use in latent heat thermal energy storages.

Linear Friction Welding (LFW) is a rarely used joining technology. To test the suitability of this solid-state process for hot cracking-sensitive nickel base superalloys, tests were performed using conventionally and directionally cast slabs of Alloy 247. Since LFW does not involve melting of the weld flanks, there were some expectations that this special welding technique could overcome the poor weldability of Alloy 247. However, all tested specimens failed by liquation cracking (LC) within the Weld Center Zone (WCZ) at the directionally cast side.