Failure Mechanisms in a Fatigue-Loaded High-Performance Powder Metallurgical Tool Steel

High-performance powder metallurgical (PM) produced tool steels are often subjected to fatigue loading. The lifetime of such components can be dominated by fatigue damage. Hence fatigue crack growth curves were determined for different heat treatments at positive and negative stress ratios. The fracture processes are analyzed by fractographic methods. Despite the brittleness of the investigated material the fatigue crack propagation behavior in the lower Paris regime is similar to the behavior of ductile alloys. The fatigue crack growth mechanisms in the upper Paris regime were examined by single overload experiments. On the basis of these investigations, a schematic model is proposed for the different fracture mechanisms in a fatigue-loaded PM tool steel for two different heat-treatment conditions.