COMPARATIVE ANALYSIS OF POWER PARAMETERS AND SURFACE QUALITY WHEN CUTTING COARSE-GRAINED AND ULTRA-FINE-GRAINED TITANIUM ALLOYS

The study objective is to provide technological support and improve the surface quality of parts made of high strength ultra fine grained titanium alloy VT6 during milling, based on the selection of rational cutting modes. The problem is to establish the patterns of influence of cutting speed, feed, and depth on the components of the cutting force and surface roughness in order to substantiate the possibility of increasing treatment productivity while maintaining the structural stability of the material. A comparative study is conducted of the machinability (using the milling method) of samples of titanium alloy VT6 in a coarse grained (CG) state and samples in an ultrafine grained (UFG) state. The influence of milling modes on the surface roughness parameters Ra and the cutting force component Pz as key indicators of the quality and stability of the mechanical machining are examined. It is found out experimentally that using VT6 material in UFG state ensures a reduction in surface roughness (from 2.65 μm to 0.46 μm) at increased speed and feed during milling compared to VT6 with CG structure under identical conditions. An effect of reducing the cutting force component Pz is identified, which is explained by the earlier formation of shear and extreme localization of deformation in narrow shear zones. Rational technological parameters for milling UFG alloy VT6 are determined (cutting speed in m/min, feed in mm/tooth), ensuring the achievement of finishing machining parameters and maintaining the structural stability of the surface layer with a deformation depth of no more than 1 μm. The practical significance of the work is in substantiating the possibility of increasing the milling cutter’s minute feed by 7.6 times, which leads to a reduction in the main technological treatment time while ensuring the guaranteed quality of the machined surface of aircraft and medical products.