Comparison of fatigue crack growth rate of selective laser sintered Rapid Steel via computational fracture mechanics

Abstract

The fatigue-crack growth behavior of materials manufactured by means of selective laser sintering was studied. In the process, specimens were prepared from metal powders (316 steel) into the desired shape by additive manufacturing technology, followed by sintering and infiltration in a suitable molten metal. The latter process was aimed at eliminating the inherent porosity associated with powder metallurgy. Porosity is known to adversely affect the fatigue-crack growth rate behavior of powder metallurgy components. Carefully conducted fatigue-crack growth rate tests (single-edge-notch four-point bending type) were carried out on RapidSteel (TM) and the results were compared with data of infiltrated low carbon steel in the literature. Finite element analysis was carried out as an intermediate step in order to validate the geometry factor calculations provided by empirical formulae. It was found that the fracture resistance of Rapid Steel was higher compared with low-carbon copper infiltrated steel tempered at 177 degrees C and 428 degrees C, and same as that tempered at 704 degrees C.