Optimization of turning parameters for ultrafine grained Ti–Nb–Zr alloys using the Taguchi method

This study aimed to optimize turning parameters for Ti–Nb–Zr alloys in order to minimize surface roughness. Billets of two ultrafine-grained (UFG) titanium alloys, melt batches 92 and 94 of the Ti–Nb–Zr system, were investigated. To enhance mechanical properties, we produced a UFG structure by abc-pressing of billets followed by groove rolling. Experimental design employed the Taguchi method of orthogonal arrays, which enabled ranking of the technological parameters of the turning process according to their influence on the output characteristics. The experiment determined the optimal turning parameters for achieving minimal surface roughness in UFG titanium alloys. The lowest surface roughness was achieved at a feed rate of 0.07 mm/rev. The cutting speed was 60 m/min for alloy 94, which contained tin and tantalum as alloying elements, and 30 m/min for alloy 92, which contained neither tin nor tantalum. Cutting speed was found to exert the greatest influence on surface roughness. For the samples with the lowest surface roughness, the microhardness of the surface layer was measured. The average microhardness HV0.05 was 321 HV for alloy 92 and 252 HV for alloy 94. The microhardness of alloy 92 increased by 14.6% compared to its initial value of 280 HV. Thus, the turning parameters established in this study can be considered optimal for achieving minimal surface roughness in alloys 92 and 94 of the Ti–Nb–Zr system. The optimized turning parameters were applied in the fabrication of implants for osseointegration prosthetics. Future work will focus on determining the optimal combination of technological parameters for the thread-cutting process in the manufacture of biomedical implants from Ti–Nb–Zr alloys.