Improved fatigue strength of AM Ti6Al4V by surface post-processing
Magnus Kahlin 1,2, Hans Ansell 1,2, Johan Moverare 2
1Saab AB, 2Linköping University
The fatigue strength of L-PBF and E-PBF Ti6Al4V with rough as-built surface is generally
dominated by the rough surface rather than by internal defects. Consequently, the surface
roughness needs to be improved before additively manufactured parts should be
introduced to critical structural aerospace applications. Additively manufactured Ti6Al4V
subjected to hot isostatic pressing and machining can achieve similar fatigue strength as
conventional wrought material.
However, parts that require machining of all surfaces will be limited to traditional
machining geometries without the beneﬁts of a freeform additively manufactured part. In
order to increase the fatigue strength while maintaining a complex design, L-PBF and E-PBF
Ti6Al4V were subjected to ﬁve surface post-processing methods: shot peening, laser shock
peening, centrifugal ﬁnishing, laser polishing or linishing.
The fatigue strength was increased with over 100% for both L-PBF and E-PBF material but
only shot peened or centrifugal ﬁnished L-PBF material achieved comparable fatigue
strength to conventional wrought material.
Moreover, the surface roughness alone was not found to be a suﬃcient indicator of fatigue
strength. The ﬁnal fatigue strength after post-processing depends instead of a combination
of surface roughness, residual stress, microstructure and remaining subsurface defects.
Open access papers available at International Journal of Fatigue: