Due to the electrification of the power train, components such as the gearbox with the current alloy design reaching their load limits. Innovative automobile manufacturers are developing a more effective steel designs and more efficient production route for gear steel components to meet the increasing requirements on mechanical properties. This master thesis highlights this development by focusing on the thermo chemical heat treatment on two reference case hardening steels. The state of the art chapter sums up the conventional thermo chemical heat treatments consisting of carburizing, ageing and plasma nitriding, with a focus on the duplex heat treatment including all three. This work analyses the duplex heat treatment route which can exploit the full potential, defined by hardness and microstructure development of a case hardening steel concept. The state of the art chapter sums up the conventional thermo chemical heat treatments carburizing and plasma nitriding, with a focus on the duplex heat treatment including both. With a literature review, this thesis evaluates the potential of the alloying elements chromium, molybdenum and copper leading to precipitation hardening due to duplex heat treatment. The experimental interpretation of the heat treatment routes analyses the hardness measurements and microscopic microstructure characterization of the case and core region. This provides a conclusion about the generated hardening effects during tempering and nitriding. In addition, the cases region is analyzed with Glow Discharge Optical Emission Spectroscopy (GDOES) the retained austenite content is quantified with X-ray diffraction. The visible carbide and nitride precipitates are characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy. According to the experimental results, the aimed surface hardness of the examined steels was not achieved with this test matrix. An ageing time of 2 hours is too short to transform the retained austenite content or to initiate precipitation hardening effects. An aging time of 24 hours and longer can cause softening and over aging response. With the present results the tempering temperatures >400°C and a treatment time of 2 to 12 hours presumable leads to the intended precipitation hardening effects, considering there is enough molybdenum content in the alloy design to trigger an hardness increase. The low-carbon core also shows hardening effects due to the chromium content. The core hardness requirements are met even after nitriding for 30h at 520°C. The sequential nitriding application to carburizing and ageing achieves a hardness increase of approx. 30% during duplex heat treatment For meeting the given hardness requirements a reduction in carbon content in the case region potentially leads to an increase in hardness compared to the applied carburizing during the duplex heat treatment route. For meeting the hardness requirements set a reduction in carbon content in the case region potentially leads to an increase in hardness compared to the applied duplex heat treatment route.