Fatigue life and strength of 316L sintered steel of varying porosity

Despite the popularity of porous sintered materials, there is still insufficient information to provide a description of the phenomena occurring in these materials over the course of typical mechanical processes. The research results published until now are incomplete, particularly with regard to materials of high porosities. Materials of this type are of particular important in e.g. reconstructive medicine due to their excellent lubricating properties. The material tested was 316L austenitic steel of porosities p = 26%, p = 33% and p = 41%, obtained by powder metallurgy. The monotonic and fatigue characteristics of the tested material were determined. The results of monotonic tests were compared to the results obtained for solid 316L steel. Uniaxial cyclic tension-compression tests were conducted by controlling the amplitude of total strain. Analysis of test results and microscopy investigation of fractures made it possible to identify the process of fatigue damage growth. A completely different nature of fracture mechanism was observed for different loading cases. The results of these studies constitute the physical basis for modeling damage accumulation in inhomogeneous materials, particularly in porous sintered metals. Moreover, they make it possible to determine numerical dependencies for predicting the fatigue life of sintered materials with varying porosities.