Korrelation zwischen Ultra High Cycle Fatigue Ergebnissen und Reinheitsgraduntersuchungen mittels automatisiertem REM/EDX-Verfahren zur Bewertung schmelzmetallurgischer Verfahrensvarianten bei der Edelstahlerzeugung

Due to the large effort associated with the implementation of UHCF experiments, the development of alternative methods is very important. Therefore, in the present master thesis, a statistical evaluation method is used to predict the distribution of large non-metallic inclusions based on SEM/EDX results. The investigated steel grades are tool steels from Böhler Edelstahl GmbH & Co KG. The materials were manufactured by different production routes. Hot work tool steels, conventionally poured off, pressure electroslag and vacuum remelted, as well as a powder metallurgical produced cold work tool steel grades were compared to each other. In the statistical analysis of the SEM results, the 2D-distrubution distribution of the detected inclusions was transformed into a three-dimensional distribution. The failure inducing defects, found on the fracture surface of giga-cycle fatigue testing, were used to estimate the parameters for an extreme value distribution. This distribution is also transformed into 3D in order to determine the correlation between SEM/EDX-and UHCF tests results. Based on SEM results it is possible to determine the size distribution of non-metallic inclusions of high-purity steels. A significant influence of the production route and the consequent size spectrum of the inclusion on the correlation are observed