Experimental Study On Surface Integrity Of Titanium Alloy Ti6Al4V By Ball End Milling

Titanium alloy,Ti6Al4V,has been widely used in aerospace,automotive,biomedical,and chemical industries due to its exceptional strength to weight ratio,high temperature performance,and corrosion resistance.However,machinability of Ti6Al4V is poor due to high strength at elevated temperatures,low modulus,and low thermal conductivity.Poor machinability of Ti6Al4V deteriorates the surface integrity of the machined surface.Poor surface integrity causes high machining cost,surface defects,and initiate cracks,and premature failure of the machined surface.Thus,it is indispensable to obtain better surface integrity when machining titanium alloy Ti6Al4V.Cutting parameters such as cutting speed,feed rate,and depth of cut have significant effect on the surface integrity when machining titanium alloy Ti6Al4V.Ball end milling is widely used in several sectors.However,it is difficult to control ball end milling effectively.Hence,this study investigates surface integrity of Ti6Al4V generated by ball end milling at different cutting speeds,feed rates,and depth of cuts.Surface roughness,microstructure,and microhardness of the milled surface are studied at different cutting speeds,feed rates,and depth of cuts.Hence,the study investigates to improve the machinability and surface integrity of Ti6Al4V using ball end milling and to determine suitable experimental parameters to achieve enhanced surface integrity.Cutting speeds selected for the study are 151 m/min,207 m/min,and301 m/min.Feed rates selected are 0.1 mm/tooth and 0.05 mm/tooth.Depth of cuts are 0.1 mm and 0.03 mm for the study.The cutting tool used in the study is a 12 mm cylindrical carbide ball end mill with 3 flutes,rake angle of 10o,and 30oaxial rake angle.Milling is conducted under dry condition.The range of average surface roughness R_a is 0.097?m to 0.256?m at cutting speed of 207 m/min and at cutting speed of 301 m/min respectively.The depth of deformation at cutting speed of 151 m/min,207 m/min,and 301 m/min are 5.5?m,9.7?m,and 12?m respectively.The depth of deformation for feed rate of 0.1 mm/tooth is 9.7?m and depth of deformation is 6.9?m at feed rate of 0.05 mm/tooth.The depth of deformation at 0.1 mm depth of cut is 9.7?m,whereas,the depth of deformation is 4?m at 0.03 mm depth of cut.At the depth of 50?m,microhardness is smaller than the microhardness of the bulk material at all cutting speeds.The results show that average surface roughness R_a decreases from the speed of 151 m/min to speed of 207 m/min and then increases from the speed of 207 m/min to speed of 301 m/min.The depth of deformation of subsurface increases with increase in the cutting speed,feed rate,and depth of cut.Therefore,cutting speed of 207 m/min,feed rate of 0.05 mm/tooth,and depth of cut of 0.03 mm are suitable to achieve better surface integrity in the study.