Powder metallurgy (PM) high speed steels have traditionally been used for tools but are gaining increased usage for demanding components such as rings in bearings and fuel injection. These components, but also many of the tools, are under cyclic load, sometimes several millions of cycles. For that reason, the fatigue resistance of PM-HSS (HSS) is one of the most important mechanical properties. Data and basic knowledge of fatigue resistance of PM-HSS is scarce in the open literature and this is today an obstacle for gaining more usage of PM-HSS in critical applications outside its traditional usage.
In this study we have looked at the influence from cleanliness, amount and size of non-metallic inclusions, and hardness on the tensile pull-pull fatigue resistance of PM-HSS. Results shows that high cleanliness can results in up to 50% higher fatigue strength. A novel part of the study includes the influence from voids typically surrounding non-metallic inclusions.