To enable the development of novel Fe-C-B-Cr and Fe-C-B-Cr-Mo cold work tool steels, the microstructures and hardness-tempering behaviors of hypoeutectic laboratory melts are investigated. The results show that increasing Cr content enhances the thermodynamic stability of the ultrahard M 2 B borides. The formation of carboborides is suppressed by adjusting the B/(C þ B) ratio, Cr content, and austenitization temperature. A secondary hardenability at 500 C is achieved by Mo addition. In addition, Mo stabilizes the M 23 (C,B) 6 phase and at higher contents the M 3 B 2 boride. Based on these investigations, Fe0.4C1B-Cr alloys are designed which, inspired by the microstructure of the steel X153CrMoV12-1, feature a α 0 -Fe hardenable matrix but 15 vol% of eutectic M 2 B borides instead of M 7 C 3 for wear protection. The Fe0.4C1B-Cr steels are produced by casting and hot rolling as well as powder metallurgy and hot isostatic pressing. The (tribo-) mechanical properties are investigated and compared with X153CrMoV12-1. Fracture toughness, bending strength, wear resistance, and hardness of the novel Fe0.4C1B-Cr alloys are found to be similar or superior to the steel X153CrMoV12-1, at decreased material cost.