In case-hardened steel components, fine-grain stability is one of the most important properties of the microstructure, since a single coarse grain in a fine-grain matrix is often sufficient to cause premature failure of the component under appropriate loading. In order to better understand the influence of heat treatments on cold formed components, the case hardened microstructure of 16 different heat treatment combinations was investigated on the case hardening steel 20MnCr5 (1.7168). The process chain influences grain growth inhibiting precipitations, which in turn influence the fine grain stability. For this reason, aluminium nitrides in size ranges from approx. 15 to 250 nm were analysed in two samples using high-resolution scanning electron microscopy in both fine and coarse-grained areas. The respective areas examined had an average area of 1,250−2,000 μm 2 . The statistical analysis showed that within the samples no significant difference in morphology and density between aluminium nitrides in fine and coarse-grained areas could be found. On the other hand, more clusters appear in larger grains. Furthermore, a significant influence of the heat treatments on the aluminium nitrides could be detected.