Evaluating the effectiveness of various coating layers applied on k-grade cemented carbide cutting tools on machinability of titanium alloy Ti-6Al-4V in high speed end milling

Titanium alloys Ti-6Al-4V are widely used in many industrial and medical applications because of their superior qualities over many other alloys like aluminum and steel. Some of their properties like high strength to weight ratio, ability to maintain strength at elevated temperatures (around 500°C) and ability of corrosion resistance in severe environmental conditions has made them excellent to use in many aerospace and bio-medical industrial applications. But the properties which make them ideal for most practical applications severely hinders their machinability and therefore, the material is renowned as difficult to machine material. The low thermal conductivity of titanium alloys does not allow the generated heat to dissipate away quickly and thus results in chemical reaction with cutting tool materials at higher temperatures and due to which these alloys are still machined with un-coated carbide tools at very low cutting speeds and the advantage of machining at high speed machining regime for these alloys are still not seen. The high cost of super hard cutting tools and also possible chemical reaction with work material still does not allow industrialists to use these materials for machining of titanium alloy. On the other hand recent advances in deposition of coating material on carbide tools has attracted many researchers in finding their advantages and best optimal coating combination for enhancing machinability of titanium alloys with carbide tools. This study therefore is specifically aimed and designed in evaluating the effectiveness of different coating layers on k-grade cemented carbide cutting tool by studying their effect on cutting forces, tool stresses and heat distribution by using finite element numerical simulations at high speed cutting conditions. Finite element numerical simulations are widely employed in academic research field because it provides fast & reliable results and thus eliminates expensive experimentation costs which - therwise is always required. Three different type of coating materials has been used in this study and the results has shown that the k-grade cemented carbide cutting tool with multi-layer coating (Al₂O₃+TiAlN+TiN) has shown some advantages over uncoated and single layer coating (TiAlN) in terms of heat distribution, cutting forces and tool stresses at same cutting conditions due to higher hot strength and resistance to adhesion. It can be concluded from the study that multi-layer coated k-grade cemented carbide cutting tools can be used at slightly higher speeds than un-coated or single layer coated carbide tools and can give higher tool life as compared to single layer and un- coated carbide tools.