The effect of additive manufacturing-induced anisotropy on tool wear when machining martensitic nitinol

Machining Nitinol (NiTi), one of the most exploited shape memory alloys in biomedical and aerospace fields, is challenging, with rapid cutting tool wear being a significant issue. This study evaluates how the anisotropy of martensitic NiTi, induced by laser powder bed fusion (LPBF), affects tool wear. NiTi samples were printed in two orientations, 0° and 90°, corresponding to vertical and horizontal directions relative to the building one. The printed samples were machined on a CNC lathe and flank wear was measured via SEM analysis. LPBF induced an anisotropic microstructure with different grain sizes, phase distributions, and mechanical properties, which, in turn, affected the material response to cutting. Tool wear analysis showed how the printing orientation influenced the interaction between the workpiece and tool, with the 0° samples causing higher tool wear than the 90°. This behavior was ascribed to the different morphology of the microstructure in the turned sections and a higher amount of austenitic phase characterizing the 0° samples than the 90° ones.