• Kamdani, Kamaruddin

Abstract

Numerous studies on machinability of titanium and its alloys have been conducted inthe past few decades with the main objective of reducing cost of machining especiallyof aerospace alloys. Though classified as "difficult-to-cut" materials, titanium and itsalloys are attractive materials due to their unique high strength-weight ratio, which ismaintained up to elevated temperatures and their exceptional corrosion resistance. Inthis work, an experimental investigation of the influence of workpiece preheatingusing induction heating has been conducted for improvements of machinability oftitanium alloy Ti-6A1-4V ASTM B348. The inserts used were uncoated cementedcarbide filled into a 16 mm diameter end mill tool. The cutting speeds used in theseexperiments were 40, 80, 120 and 160 m/min; the depths of cut were 1 and 1.5 mmand the feed rates were 0.1 and 0.15 mm/rev. Thermo-couples were used in measuringthe surface temperature of work material during machining. The experiments of endmilling operation conducted on Vertical Machining Center (VMC) were designed tolook into the effect of preheating on chip serration and chatter, cutting force andtorque, tool wear and surface finish. A comparison of the above criteria for roomtemperature and preheated machining was made. The results show that preheatingmachining improves the machinability of titanium alloy. Increased plasticity of thework material during preheating reduces the frictional forces on the tool face and thefluctuation of cutting force and also contributes to improved damping capacity of thesystem. As a result preheated machining results in reduction in vibration amplitudes atresonance frequencies up to 67%. An increase in cutting force and torque mean valueleads to the formation of relatively thicker chips, which in turn leads to an increase inchip-tool contact length. The hottest spot on the tool is thus shifted away from thecutting edge leading to a more favourable temperature distribution in the tool. Morestable cutting, longer chip-tool contact length and favourable temperature distributionin the tool helps in reducing the dynamic stresses acting on the tool. This in turnreduces the enhances of micro and macro chipping of the tool. This leads to uniformand much lower tool wear up to three times reduction in flank wear has been achieved.Lower tools wear, helps in maintaining a sharp cutting edge at the nose section and theflank areas of the tool resulting in smoother surface roughness values during preheatedmachining.

Topics

• impedance spectroscopy
• surface
• corrosion
• experiment
• strength
• titanium
• titanium alloy
• plasticity