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Dual hardening steels are a group of metals, which reach their material properties through a combination of strengthening via carbides and intermetallic precipitates. Because of their combination of mechanical properties, dual hardening steels are a promising alloying concept for hot‐work applications. The applied materials for hot‐work applications have to meet certain requirements, such as high hardness, high thermal strength, thermal stability, and fracture toughness. In this paper, a dual hardening steel in different heat treatment conditions was tested under out‐of‐phase thermomechanical loading conditions. All tests were done under full reverse strain control and the minimum temperature was kept constant. In the thermomechanical fatigue tests, solution annealed samples reached higher lifetimes compared with aged specimens. The hardness measurements show that the starting procedure of the thermomechanical fatigue leads to an increase of the hardness approximate to the values of the specimens with the ageing heat treatment. Cyclic softening can be observed in the test with the highest maximum temperature of 600°C. An increase of the maximum temperature also causes a decrease of the lifetime.

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Hot-work tool steels are exposed to complex interacting cyclic thermal and mechanical loadings. Due to the combination of strengthening via carbides and intermetallic precipitates, dual hardening steels achieve well-balanced mechanical properties in terms of fatigue strength and fracture toughness. Therefore, dual hardening steels have a great potential for hot-work applications. Herein, out-of-phase thermomechanical fatigue tests are used to simulate the loading conditions experienced in hot-work tool steel applications on a laboratory scale. The testing is conducted on Fe-C-Cr-Mo-V and Fe-C-Cr-Mo-V-Ni-Al alloys to compare common 5% Cr and dual hardening hot-work tool steels. The resistance to thermomechanical fatigue is therefore correlated with single or dual hardening. Both alloys experience softening during the fatigue testing. Atom probe tomography investigations reveal coarsening of the secondary hardening precipitates for both alloys. However, the number density of surface cracks is greater for the 5% Cr hot-work tool steel. The dual hardening steel possesses higher resistance to softening and reaches a higher lifetime.

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