Fatigue properties of EBM as-built and chemically etched thin parts

EBM as-built fatigue samples were manufactured from both fresh and recycled powder. They were characterised by laboratory X-ray tomography in order to observe the porosity and surface state. Chemical etching was used and a clear improvement of the surface geometry was observed and quantified through a roughness reduction. Fatigue tests were performed on as-built and etched samples. The fatigue resistance obtained for as-built samples is lower than that of machined samples; powder recycling tends to also diminish the fatigue resistance whereas chemical etching improves it significantly. The study of the fracture surfaces coupled with the comparison of tomographic scans before and after failure shows that the crack leading to failure always initiate from a surface notch-like defect resulting from a lack of fusion.