The effect of surface treatment on the fatigue life of aluminium 2139-AM components manufactured additively by PBF-LB/M

Additively manufactured (AM) parts often exhibit a poor surface quality, which influences their fatigue life. Surface treatments suitable to the complex structures of AM parts aim to improve this behaviour. In this study, front wing attachments for a small race car are topology and aerodynamically optimized and manufactured out of aluminium 2139-AM by powder bed fusion using a laser (PBF-LB/M). The attachments are tested for their fatigue life under a realistic load case in the surface conditions as-built and trowalised. The surface of all samples is non-destructively characterised by confocal microscopy. The results show no significant effect of the surface treatment on the fatigue life due to incomplete removal of the process-related valleys. However, the surface roughness values R a , R z , S a and S v also show no correlation with the fatigue life of the individual components. Fractographic images reveal that the critical surface defects exhibit undercuts that are not discernible by confocal microscopy or are situated within the inaccessible interior of the hollow samples. Additionally, the crack-initiating defects are scattered throughout the component and can be located in areas of lower stress. In conclusion, the applied surface treatment of trowalising was found insufficient for increasing fatigue life of the investigated components but might be beneficial at improved initial print qualities. Furthermore, confocal microscopy measurements are recommended to be conducted on larger areas to account for the statistical distribution of defects.