Very high cycle fatigue properties of 2000 MPa ultrahigh-strength steels

The microstructure, mechanical properties and very high cycle fatigue (VHCF) properties of two 2000 MPa ultrahigh-strength martensitic steels were investigated. Results show that the newly developed steel possesses lower ultimate tensile strength but higher yield strength compared with the conventional steel, as well as a higher impact toughness and fracture toughness due to its better cleanliness and tempering at a higher temperature. Both steels experienced a typical VHCF fracture process. The newly developed steel had higher fatigue strength and longer fatigue life at the same stress amplitude compared with the conventional one, which could be related to its lower crack growth rate and better toughness.