Behavior of Forging Steels under Cyclic Loading — the Benefit of Air‐Hardening Martensites

The development of air‐hardening martensitic forging (LHD: luft härtend duktil) steels offers high material performance with a short and simple process route. In this study, five alloys (L1–L5), based on the existing LHD alloy concept but with different contents of aluminum, titanium, boron, and molybdenum, are cast at laboratory scale. The casted blocks are hot forged into semifinished products and cooled in air (uncontrolled). The tensile properties, the Charpy V‐notch impact energy, the cyclic material behavior, and the fatigue strength of the alloys L1–L5 are opposed to each other. Furthermore, the material properties are compared with the standard quench and tempered (Q+T) steel 42CrMo4 (reference material) and ranked against previously developed forging steels. The tensile properties and Charpy V‐notch impact energy are comparable with those of the reference material, whereas the new alloy concepts show a significantly higher cyclic yield strength and fatigue strength.