Experimental and multiscale numerical investigation of wear mechanism and cutting performance of polycrystalline diamond tools in micro-end milling of titanium alloy Ti-6Al-4V

摘要

The present study reports on experiments and numerical simulations carried out to determine the wear and cutting performance of different polycrystalline diamond (PCD) tools in micro-end milling titanium alloy. The influence of tool geometrical parameters on wear resistance and machined surface precision was discussed. Furthermore, subsurface microstructure alteration was employed as an important index for evaluating the cutting performance of PCD tools. A dislocation dynamics-based multiscale framework, which is capable of promulgating the potential mechanism of above alteration, was adopted to quantitatively predict the evolution behavior of subsurface damages layer during micro-cutting process. The results demonstrated that the tool nose, flank and rake wear were of major wear forms and inappropriate tool structural changes can further accelerate tool failure. A PCD tool with rake angle of 5 degrees, clearance angle of 15 degrees, tool cutting edge radius of 20 mu m and PCD granularity of 10 mu m has highest cutting performance among the tested tools. Using this cutting tool, a surface roughness of Ra = 75 nm better than most previously reported value on titanium alloy Ti-6Al-4V was achieved. A mass of subsurface damages consisted of discrete dislocation configuration, parallel glide lines and persistent slip bands were found after machining. Particularly, small tool cutting edge radius, large rake as well as clearance angle contributed to reducing defects quantity and decreasing the thickness of subsurface damages layer.