Bestimmung der Gefügeausbildung in Werkzeugstählen nach zyklisch thermischer Belastung

Tool steels have a wide range of applications due to their property combination of high wear and corrosion resistance combined with good toughness. The tool steels used for plastics processing have different microstructures due to the various alloying concepts and manufacturing processes. The required properties are set, for example, by high primary carbide contents, the precipitation of secondary hardness carbides (SHC), and sufficiently high free chromium contents in the matrix with the application of suitable heat treatments.

When tool steels are used as materials for plasticizing components of injection molding machines, cyclic thermal heating in the annealing temperature range can lead to microstructural changes that affect hardness and thus wear resistance.

In order to simulate such temperature stresses, samples of the selected steels were subjected to cyclic thermal loading in the dilatometer and examined with regard to hardness and microstructure. Scanning electronic methods were applied to describe the effect of the microstructural change of different tool steels on the hardness of the steels.

The results showed that the frequency of SHC found increased significantly after the repeated short-term thermal stress above the tempering temperature. In contrast, the size distribution of SHK hardly changed. In the future, the use of transmission electron microscopy, atomic probe tomography, and nanoindentation could provide even more accurate results.