The expansion of wind energy leads to ever bigger and more efficient wind turbines. As wind turbines grow, so do the bearings mounted inside of them. The steels used to make these bearings need to fulfill high standards for hardness and toughness alike. Since the hardenability of conventionally used quenched and tempered steels does not suffice for future sizes, new alloying concepts need to be investigated. This work is part of a larger project and aims to validate proposed material-concepts. The criteria, the materials must meet, are a surface hardness in excess of 58 HRC whilst achieving 42 HRC and a Charpy-V-notch energy of 27 J at -40°C in the core. Samples for two material-concepts proposed by Buderus Edelstahl (9966 MOD and 300M MOD) were created using a vacuum-induction-melting-process (VIM-process) and tested for the defined criteria. The steel grade 7228, which is currently used for bearings in wind turbines, was used as reference material. Heat treatment parameters were defined and the sample material as well as the reference material were investigated at different tempering stages, using hardness measurements, tensile tests and Charpy-V-notch-tests. Additionally metallographic investigations and a Jominy end-quench test were carried out. The set criteria were met by the material-concept 9966 MOD, reaching a maximum hardness of 58.2 HRC and a Charpy-V-notch energy greater than 27 J at -40°C for two tempering temperatures. Moreover 9966 MOD met the required grain size of the prior austenite and the metallurgical cleanliness required for bearing-steels. The second material-concept 300M MOD showed high hardness and tempering resistance, but could not reach the required Charpy-V-notch energy. In both concepts the addition of Vanadium was omitted to raise the toughness of the material. The wanted effect was only achieved for 9966 MOD. The reference material 7228 had the second highest hardness and tempering resistance after 300M MOD, but could not meet the required toughness.