PERFORMANCE EVALUATION OF UNCOATED AND COATED CARBIDEudTOOLS WHEN END MILLING OF TITANIUM ALLOY USINGudRESPONSE SURFACE METHODOLOGY

摘要

Titanium alloys are being constituted in modern aerospace structure, marine,automotive and chemical industry due to their strength-to-weight ratio, excellent corrosion and fracture resistance and low modulus of elasticity. However, titanium and its alloys are considered very difficult-to-machine material due to its highly chemical reactivity and tendency to weld to the cutting tool. These result in edgeudchipping and rapid tool failure. Although in the past, many studies had been carried out to predict the tool performance during end milling operation in terms of primaryudmachining parameters, the effect of tool geometry was not taken into consideration. Therefore, an effort has been made in this research to evaluate the influence of tooludgeometry (radial rake angle), feed and cutting speed when end milling titanium alloy, Ti-6Al-4V. Machining trials were performed under flood condition with a constantudaxial and radial depth of cut. The cutting tools used were uncoated solid carbide tools grade K30 and coated with a physical vapor deposition (PVD) TiAlN and Supernitride. Tool performance of the above mentioned tools were investigated under various cutting conditions, while the surface roughness of the milled parts and cutting forces were measured. The performance of cutting tools was described using response surface methodology. It was found that, the cutting speed, feed rate and radial rake angle have a significant effect on various responses investigated such as tool life, surface roughness and cutting forces. The developed mathematical models were validated statistically using analysis of variances (ANOVA), which can be used for predicting the optimum cutting conditions within the limits of the factors investigated. In general, coated solid carbide tools performed better than the uncoated tools when end milling Ti-6Al-4V.