Recently, the titanium, inconel and CFRP(Carbon fiber reinforced plastic) materials usage is rapidly increasing by developing of the high technology industrial field such as aerospace, automotive, bio-tech and etc. But, these materials has the properties of high hardness, rigidity and are difficult to cut. So, it is very difficult to apply processing with existing methods considering those mechanical and chemical characteristics. And, when we are machining these materials, the resulted product of these materials and existing method could be led to a bad characteristics such as low precision, low cutting property and a productivity. Hence, it is necessary to develop a machining technology for these materials, which are difficult to be machined and to study their characteristics while machining.
As the titanium alloy, which is considered as a light metal, and difficult to be machined, with the characteristics of highest specific strength, high rigidity, fracture resistance, thermal resistance and high temperature strength among practical metals, it is widely used in the industries of aerospace, chemistry and petrochemistry. The excellent mechanical properties of titanium alloy caused many problems in cutting work. Owing to the high temperature strength and low thermal conductivity, heat is concentrated on cutting tools during machining, and it causes high temperature at the interfaces between chip and the tool. High cutting heat promotes various phenomena related to heat and causes rapid tool wear. And the adhesion, which comes from the fusion and chemical reaction with tools at while titanium alloy machining, causes excessive chipping, rough machined surface and earlier fracture of tools.
Ti-6Al-4V ELI alloy, which is made by reducing the content of Fe and O₂ from Ti-6Al-4V to enhance toughness, fracture ductility and corrosion resistance, is being used in medical application as biomaterial and expands its application to various fields such as chemistry and automobile. However, the study of Ti-6Al-4V alloy occupies majority of titanium alloy study and few studies has been performed on the cutting work of ELI alloy.
In this study, turning works have been done with carbide, coated carbide and cermet tools to study the machining characteristics of Ti-6Al-4V ELI alloy, and the tool life, tool wear, surface roughness and cutting force related to the change in cutting speed and feed rate have been evaluated.
The main cause of the tool wear is due to the adhesion of the chip due to high cutting heat under machining process a Ti-6Al-4V ELI alloy. the Carbide tool was assured of the best for turning of Ti-6Al-4V ELI alloy. Surface roughness is influenced by the feed rate more than cutting speed. Superior surface roughness can be obtained at a slower feed rate.