Alternative Mechanical Milling routes for grain-refinement of conventional High-Speed Steel Powder for later consolidation by SPS

High-speed steel is the most superior tool steel in terms of wear resistance at high temperature. In order to further improve materials properties, conventional HSS-powder (< 76 μm) has been mechanically milled by a Planetary Ball Mill (medium kinetic system) and alternatively by a Simoloyer (high kinetic system) in order to reduce particle size and in particular the grain size of the powder material. Consolidation has been done by Spark Plasma Sintering in order to maintain a fine structure of the material. In the Planetary Ball Mill, 25 g of HSS-powder was milled for 720 ks (200h) and resulted in a particle size of < 15 μm at an average grain size of 10 nm. Similar results in the Simoloyer were achieved after 72 ks under higher powder load. The SPS-sintered parts were investigated by hardness, the characterization of the powder is given by XRD, SEM and laser diffraction.