The Role of Porosity in Fatigue of PM Materials
In this paper it’s studied how density influences fatigue strength of two sintered steels; one standard, diffusion alloyed material and one sinter hardened pre alloyed chromium material. Fatigue testing on materials at different densities are performed and compared. Furthermore, extreme value statistics is applied to the pore structure to determine the size of the largest pore, and fracture mechanics is used to link fatigue strength to porosity. It’s found that there is a strong correlation between fatigue limit and largest pore size. For the sinter hardened material it’s found that a LEFM model can be used to predict fatigue crack initiation, whereas for the diffusion alloyed material with a complex microstructure initiation is a more complex interaction between porosity and the softer micro constituents.