Green Machining of Titanium Alloy Using Uncoated and Multilayer PVD-Coated Carbide Tools: Wear Mode, Wear Mechanism and Performance
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The preliminary result on looking at performance of the off-center ball end mill carbide tools: alloyed uncoated (W-Ti/Ta/Nb)C-Co (tool A) and multilayer PVD-coated (WC-Co)(TiCN/TiAlN/TiN) (tool B) with nominal diameter of 16 mm in end milling of titanium alloy Ti-6%Al-2%Sn-4%Zr-2%Mo-0.08%Si (Ti-6242S) under green machining is reported in this paper. Results of machining trial show that localised flank wear (VB3) is a dominant failure mode for both tools due to a concentrated of the coupled thermo-mechanical load at the tool leading edge. After machining for approximately 20 minutes, tools A and B start to reach VB3 ? 0.3 mm when used at cutting speed of 100 m/min and feed of 0.15 mm/tooth. Further examination using SEM/EDAX shows that flank wear, rake wear, plastic deformation and brittle fracture are all failure modes suffered by tools because of adhesion (attrition) and dissolution-diffusion wear mechanisms. In conclusion, tools A and B can be recommended for green milling of Ti-6242S and the best compromise between cutting speed and tool life is given by end milling at cutting speeds of 100- 125 m/min.