A review on machining Ti–5Al–5V–5Mo–3Cr alloy using defined geometry tools

Due to its superior maximum strength/weight relation among titanium alloys and outstanding resistance to corrosion and fatigue, the Ti–5Al–5 V–5Mo–3Cr (Ti5553) alloy has been used in critical aerospace components, including landing gear parts and airframe structures for large modern aircraft. However, its high stress strength, low thermal conductivity, and ability to retain its mechanical properties at high temperatures contribute to its poor machinability. Several studies have indicated that Ti5553 alloy exhibits poorer machinability compared to Ti–6Al–4 V (Ti64), the most widely used titanium alloy at present. This paper presents a literature review of conventional machining of Ti5553, using tools with defined geometries and their performance using several materials for the tools, applying several coolant systems and heat-assisted machining. The Ti5553 performance was evaluated regarding tool wear, cutting efforts, chip morphology, and machined surface integrity. Notably, most researchers applied cutting speeds below 90 m/min and did not use cutting fluids. The best results achieved, in terms of tool wear, were applying high-pressure coolant (HPC) system, but cryogenic coolant can also be a good option. There are ongoing discussions regarding flank wear in Ti5553 machining, with tool wear predominantly influenced by adhesion and diffusion mechanism evidenced through crater wear. Ti5553 needs higher cutting efforts compared to the main titanium alloys, resulting in long, segmented chips with two well-defined shearing zones. Consequently, chip control through the cutting parameters is required. The machining parameters significantly impact the surface integrity and compressive residual stress after machining is required. Considering environmental considerations, future research trends emphasize the use of cryogenic and nanofluid cutting fluids, as well as the application of PCD tools and special carbide substrates and coatings.