Additive Manufacturing of Hot Work Tool Steel by Laser Powder Bed Fusion Utilizing Powder Mixtures Including Grinding Chips: Assessing Chemical Homogeneity and Achievable Hardness

Additive manufacturing offers potential benefits in tooling, such as reduced lead times and improved service life. However, carbon martensitic tool steels are prone to cold cracking during additive manufacturing. This can be mitigated by adjusting alloying compositions to stabilize ductile austenite during manufacturing, which can later be transformed to martensite through heat treatment. In situ alloying is a rapid process for this, in which powder mixtures are processed, thereby avoiding the elaborate gas atomization of prealloyed melts. However, this promotes chemical inhomogeneities, particularly with high‐melting refractory metal powders. In this study, two powder mixtures are prepared to produce chemically homogeneous tool steel samples containing refractory elements Mo and W. In the first mixture, these are provided by adding commercial high‐speed steel powder. In the second mixture, high‐speed steel grinding chips, a waste material typically disposed by landfill or combustion, are used. Both mixtures are processed using single‐ and double‐laser exposure. The chemical homogeneity and tempering behavior of the samples are compared to prealloyed references. Double‐laser exposure achieves sufficient densification and chemical homogenization, resulting in similar hardness compared to the references. However, excessively long chips are demixed during powder application, altering the global composition of samples made with recycled chips.