| Abstract: | Aluminum as an alloying element in high-speed steel was investigated for the first time during the Second World War at the Montanuniversität Leoben. At this time there was an enormous consumption or rather a shortage of molybdenum and especially of tungsten worldwide. Tungsten was not only used for the high-speed steel production but was also very much needed for the war industry. Attempts were made in order to replace these alloying elements in high-speed steels with cheaper elements. It was found that a certain percentage of tungsten and molybdenum in high-speed steel can be replaced or substituted by an aluminium content of 0.3 up to 1.4 mass-% without any loss of cutting performance. However, no detailed metallurgical investigations were carried out to explain and clarify this behaviour of aluminium. The influence of aluminium in high-speed steels is highly controversial, due to the fact that aluminium compared to tungsten and molybdenum is not a carbide-forming element, but the special properties of high-speed steels are mainly gained by the presence of carbides. Despite several works in this field, there is no clear understanding of how aluminium can affect the properties of high-speed steel. In the present work, standard and modern examination methods, such as scanning electron microscope, energy dispersive X-ray spectroscopy, and atom probe tomography, were used to investigate the effect of aluminium on the primary and secondary hardening carbides in high-speed steels. The investigations were conducted on three high-speed steel grades with varying the aluminium content only. |
