Effect of hirtisation on the roughness and fatigue performance of porous titanium lattice structures
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Additive manufacturing (AM) has enabled the fabrication of extremely complex components such as porous metallic lattices, which have applications in aerospace, automotive, and in particular biomedical devices. The fatigue resistance of these materials is currently an important limitation however, due to manufacturing defects such as semi-fused particles and weld lines. Here Hirtisation^ is used for post-processing of Ti-6Al-4V lattices, reducing the strut surface roughness (Sa) from 12 to 6 μm, removing all visible semi-fused particles. The evenness of this treatment in lattices with ρ /ρ_s up to 18.3 finding no evidence of reduced effectiveness on internal surfaces. After normalising to quasi-static mechanical properties to account for material losses during hirtisation (34-37 properties show a marked improvement due to the reduction in surface roughness. Normalised high cycle fatigue strength (σ_f,10^6/σ_y) increased from around 0.1 to 0.16-0.21 after hirtisation, an average increase of 80 surrounding bone is crucial, the σ_f/E ratio is a key metric. After hirtisation the σ_f/E ratio increased by 90 stiffness matched implant materials with greater fatigue strength. This work demonstrates that hirtisation is an effective method for improving the surface roughness of porous lattice materials, thereby enhancing their fatigue performance.
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