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Pyrex Journal of Engineering and Manufacturing Technology

November 2014 Vol. 1(1), pp. 001-010

Copyright 2014 Pyrex Journals




Review Paper


An Overview of Machinability of Titanium Alloys


*Venkateswara and Kesava

Department of Mechanical Engineering, Andhra University, Visakhapatnam, India.

Corresponding Author E-mail: venkyip254@gmail.com

Accepted 8th November, 2014.



Abstract


Lots of research and advances have been made in understanding the behavior of engineering materials when machining at higher cutting conditions. The improvements achieved from research and development activities in this area have particularly enhanced the machining of difficult-to-cut titanium alloys that have traditionally exhibited low machinability due to the poor thermal conductivity, high strength at elevated temperature, resistance to wear and chemical degradation, etc. These alloys are used widely where the strength-to-weight ratio and corrosion resistance are of the utmost importance. Even though there have been great advances in the development of cutting tool materials which have significantly improved the machinability of a large number of metallic materials, including cast irons, steels and some high temperature alloys such as nickel-based alloys, no equivalent development has been made for cutting titanium alloys due primarily to their abnormal characteristics. A good understanding of the cutting tool materials, cutting conditions and functionality of the machined component will lead to efficient and economical machining of titanium base super alloys. This paper reviews the main problems associated with the machining of titanium as well as tool wear, the mechanisms responsible for tool failure. Steep increase in productivity, hence lower manufacturing cost, without adverse effect on the surface finish and surface integrity of the machined component. It was found that the straight tungsten carbide (WC/Co) cutting tools continues to maintain their superiority in almost all machining processes of titanium alloys, whilst CVD coated carbides and ceramics have not replaced cemented carbides due to their reactivity with titanium and their relatively low fracture toughness as well as the poor thermal conductivity of most ceramics. Cubic Nitride Boron (CBN) tools are also generally used for machining harder alloys such as titanium and nickel alloys. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. An attempt has been made to discuss special machining methods, such as Rotary cutting, High pressure, coolant delivery, Cryogenic cooling, Minimum Quantity Lubrication and the use of ledge tools, which have shown some success in the machining of titanium alloys.

Keywords: Titanium alloys, Machinability, High temperature alloys, Rotary cutting, High pressure, coolant delivery, Cryogenic cooling, Minimum quantity lubrication, Hot machining, Carbide tools.

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