Abstract
With the growth of Additive Manufacturing (AM) or 3D printing, the need for long lasting metal components for high-stress applications is becoming increasingly crucial. One of the biggest limitations is the low fatigue life of AM components due to a variety of factors including build orientation, surface roughness, and internal defects. To address the low fatigue behavior of metal AM components, there is an increase in interest in performing surface treatments such as machining or polishing on additive manufactured components. With AM’s unique potential to produce complex shapes, the ability to perform conventional surface processes on printed parts becomes difficult and limited. Preliminary effects of tool-less post processing techniques on fatigue life titanium Ti6Al4V specimens has been explored in this study with specimens undergoing hot isostatic pressing (HIP), in addition to a surface treatment process including cavitation peen, laser peen, shot peen or cavitation abrasive surface finishing. Uniaxial high cycle fatigue testing has been performed on untreated, HIP, and HIP + surface treated cylindrical electron beam melting (EBM) specimens. The location of crack initiation has been determined under high magnification and the location of internal defects are evaluated using micro-Computer Tomography (μCT). The location of crack initiation in all specimens was attributed to the sharp voids due to the rough surface or the subsurface defects which remained after post processing. The shot peen and polished titanium specimens exhibited the greatest increase in fatigue life due to the improvement in roughness and introduction of high compressive stresses.
