Influence of Cutting Conditions on Surface and Sub-Surface Quality of High Speed Dry End Milling Ti-6Al-4V

Surface quality is one of the most critical restraints for determining cutting parameters and selecting of machining process in metal cutting process. In this study, the effects of cutting parameters and tool wear on the surface and sub-surface quality of high speed dry end milling Ti-6Al-4V were investigated. PVD Coated carbide tools were used under different high cutting speeds and feed rates. The quality of the machined surface and corresponding alteration on the sub-surface and entry/exit edges were characterized through scanning electron microscopy. The results showed that the better surface quality was obtained when machining at higher cutting speeds and feed rates. High speed dry end milling using the worn tool causes to plastic deformation of the alloy which is resulted in developing the lamellae on the surface and causing poor surface finish. Worn tools with the uniform tool wear land generated better surface quality compare to those with chipping and flaking on the tool edge surface. Tool wear is suggested as the other contributing factor in developing entry and exit edge damages. The results of sub-surface alteration measurement revealed that the worn tool enhanced the sub-surface alteration resulted in 45% increase in plastic deformation compare to the new tool.