MILLING OF TITANIUM ALLOY USING DIRECTED THROUGH SPINDLE COOLANT

摘要

This study investigates machining performance during milling of Ti6AI4V at speeds of 152 to 610 m/min using directed through spindle coolant (TSC). Cutting tests were performed for rough milling, finish face milling, and finish peripheral milling using 25.4 mm indexable endmills. Four TSC configurations, in which the stream location, diameter and angle were varied, were tested at 150 psi. Cutting tool geometry (rake and clearance angle), nose radius, and edge preparation were also varied during the experiments to determine their effect on tool life. Polycrystalline diamond (PCD), diamond coated carbide (DCC), and two micrograin C2 carbide (grain size <1μm) inserts were used. The dominant failure mechanism for all tool materials was flank wear near the depth of cut unless the insert experienced excess mechanical (feed per tooth, f_t > 0.038 mm) or thermal (excessive cooling) shock, whereby, chipping of the rake face would result. For rough milling at 152 m/min under low-pressure (150 psi) TSC, the tool life for carbide averaged 3.8 times that of flood coolant. For peripheral finish milling under high-pressure (600 psi) TSC, PCD doubled the tool life of carbide at 229 m/min and reached speeds of 610 m/min with reasonable tool life. At 229 m/min, carbide tooling performed the best under 300 psi peripheral finishing but failed due to chipping at 600 psi. DCC failed prematurely due to chipping in all cases.