This work provides a fundamental understanding of sample preparation, characterization, and phase diagram generation with carbides of the high alloyed Fe-C-Cr-W-Mo system. For the method development, the quaternary systems Fe-10Cr-3W-CVar (X210CrWMoV1-2) and Fe-6W-5Mo-CVar (HS6-5-2) were studied, which are based on a cold work steel (Cr-W) and a high speed steel (W-Mo) alloy concept. These alloys are characterized by a high content of MC, M6C, M7C3 and M23C6 carbides. The literature research showed that the DTA/DSC method is widely used for the determination of the transformation temperatures. The method of choice is the scanning electron microscope to study the morphology of the carbides in SEM/BSE mode and to measure the elemental distribution in the carbides by SEM-EDX. In addition, the SEM/EBSD, TEM and XRD methods are used to confirm the different carbide types. The preparation of any alloy of the Fe-C-Cr-W-Mo system from Fe-cylinders with high purity metallic powders by induction melting followed by centrifugal casting was an important part of the method development. A following investigation with different annealing times showed that an extra diffusion annealing of at least 4h is necessary to reach a near equilibrium state. This can be avoided by "in-situ equilibration" with partial melting during the DSC measurement. All model alloys were investigated until melting by DSC measurements. Selected alloys were examined by SEM/BSE+EDX, and supplementary by XRD and SEM/EBSD. The combined investigations indicate good agreement between the methods, but also significant deviations from commercial thermodynamic databases, especially for the Fe-C-10Cr-3W system.