Analysis of the effect of surface roughness on fatigue performance of powder bed fusion additive manufactured metals

• Published in: Theoretical and applied fracture mechanics Vol. 108; p. 102638
• Main Authors: Sanaei, Niloofar, Fatemi, Ali
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.08.2020; Elsevier BV
• Subjects: Defects; Fatigue cracks; Fatigue life; Fatigue limit; Machining; Metal additive manufacturing; Parameters; Performance evaluation; Post-processing; Powder beds; Process parameters; Rapid prototyping; S N diagrams; Surface cracks; Surface roughness; Surface roughness effects; Synergistic effect; Fatigue life; Surface roughness; Metal additive manufacturing; Process parameters; Defects
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2020.102638

•Fatigue limit increases with a decrease in surface roughness regardless of the microstructure.•Internal defects and microstructure cause scatter in fatigue limit versus surface roughness data.•Roughness affects fatigue strength more with smaller internal defects and coarser microstructure. An important advantage of AM is to create net-shaped components with no need for further surface machining since it is usually very difficult for complex geometries. The effect of surface roughness on fatigue performance of powder bed fusion additively manufactured metals was evaluated in this work. The intrinsic rough surface of metal AM parts that could act like existing surface cracks and significantly affect fatigue performance is investigated. The effect of processing and post-processing conditions on surface roughness of AM parts are reviewed and the effect of surface roughness on fatigue performance is analyzed. The synergistic effect of internal defects and surface roughness on fatigue performance is also evaluated. Arithmetic mean surface roughness parameter Ra is used here as a representation of surface roughness, since this parameter has been presented in most of the studies dealing with metal AM surface roughness. Surface roughness effect on fatigue performance is shown to be dominant even in the presence of relatively large internal defects and various microstructures. Ra decreases with an increase in power. This consequently increases fatigue limit, although scatter is observed due to the secondary effect of internal defects and microstructure. For similar microstructures, considering synergistic effect of Ra along with average critical internal defect size in combination with the stress amplitude, resulted in improved correlation of the S-N fatigue data.