Materials scientific challenges of a circular economy of high-alloy tool steels

Compared to other steel groups, high-alloy tool steels are particularly associated with a high energy and resource intensity. Cold-work and high-speed steels, in particular, can reach macro-hardnesses of up to 70 HRC. The steels, in their hardened and tempered condition providing them with relevant performance characteristics, are therefore processed in grinding processes accompanied by considerable metal removal rates to manufacture products for numerous applications. In line with a circular economy and aiming at minimizing the loss of high-quality and partially critical raw materials, it therefore makes sense to directly utilize the waste materials generated during grinding using powder metallurgical (PM) methods. This work highlights existing material scientific challenges and their impact on directly recycled tools on the example of the manufacture of cutting tools made from PM high-speed steel HS 12-0-5-5. The focus is on the accompanying metallographic investigations based on which correlations can be established between the grinding process, the introduction of impurities, powder metallurgical recycling, and the performance properties. It is shown that the processing of waste materials is of central importance and that circular economy must start at an earlier stage in the production process chain.