Cyclic stress–strain behavior and damage of tool steel AISI H11 under isothermal and thermal fatigue conditions

Isothermal and thermal fatigue is one of the most important factors controlling lifetime and damage of tools for hot metal forming processes. Rapid temperature alterations and the resulting inhomogeneous thermal stresses lead to cyclic plastic deformation, crack initiation and to crack propagation until final fracture of the components. In addition, characteristic residual stress states are formed due to inhomogeneous plastic deformations. In this paper results of isothermal and out-of-phase thermal fatigue tests of tool steel AISI H11 (German grade X38CrMoV5-1) in the temperature range 100 °C ≤ T ≤ 650 °C are presented. Stress amplitudes, plastic strain amplitudes and mean stresses were recorded as a function of the number of loading cycles. This allows a comprehensive assessment of the influence of loading parameters on the development of stresses, the formation of cracks and the lifetime of the material.