Machining of titanium alloys for medical application: a review

Titanium alloys for their characteristics have acquired a prominent position in numerous industrial applications. Due to its properties, such as high resistance to corrosion, reduced density, high specific strength and low Young's modulus, titanium alloys became indispensable as a biomaterial with high use in medical devices, with special emphasis in the area of orthopaedics. Problems associated with its manufacturing by conventional machining processes, such as milling, turning and drilling are well known and studied. Its low thermal conductivity, high chemical reactivity, high hardness at high temperatures make it classified as difficult to machine material. Despite the already extensive knowledge about machining titanium alloys problems, and the constant technological development to overcome them, it is not yet possible to machine this material like other metals. This work is based on research and review papers from Scopus and Scholar from 2010 to 2020 and addresses the main issues related to the machining of titanium alloys used in medical devices manufacturing and current solutions adopted to solve them. From the research consulted it was possible to conclude that it is consensual that for milling, turning and helical milling cutting speed can reach up to 100m/min and up to 40m/min in drilling. As for feed rate, up to 0.1mm/tooth for milling and helical milling and up to 0.3mm/tooth for turning and 0.1mm/rev for drilling. Also, that Minimum Quantity Lubrication is a valid and efficient solution to mitigate titanium alloys machining problems.publishe

Cutting characteristics of binderless diamond tools in high-speed turning of Ti-6Al-4Vp: – Availability of single-crystal and nano-polycrystalline diamond

In this study, the tool performance of two types of binderless diamond tools – single-crystal diamond (SCD) and nano-polycrystalline diamond (NPD) – is investigated in the high-speed cutting of titanium alloy (Ti-6Al-4V) with a water-soluble coolant. The NPD tool allows for a larger cutting force than the SCD tool by dulling of the cutting edge, despite NPD being harder than SCD. This large cutting force and the very low thermal conductivity of NPD yield a high cutting temperature above 500°C, which promotes the adhesion of the workpiece to the tool face, thereby increasing tool wear. Based on the morphology of the tool edge without scratch marks and the elemental analysis by energy-dispersive X-ray spectroscopy (EDX) of both the flank face and the cutting chips, diffusiondissolution wear is determined to be the dominant mechanism in the diamond tool. A thin TiC layer seems to be formed in the boundary between the diamond tool and the titanium alloy at high temperatures; this is removed by the cutting chips