Comparison of Cutting Tool Performance in Machining of Titanium Alloys and Inconel 718 Super Alloy Navneet KHANNA 1 , Kuldip Singh SANGWAN 2 1 Mechanical Engineering Group, Birla Institute of Technology and Science, Pilani, India, khanna@bits-pilani.ac.in 2 Mechanical Engineering Group, Birla Institute of Technology and Science, Pilani, India, kss@bits-pilani.ac.in Abstract: The aim of the work is to critically compare the productivity and tool life enhancement by considering the interrelationships among microstructures, and tool-wear of Titanium alloys and Inconel 718 super alloy. Effects of different tool grades on machining of these alloys are conferred. Tool wear and surface integrity effects when machining these alloys by the geometrically defined tools are analyzed effectively. Different techniques for improving tool performance are discussed thoroughly. This comparison aims to supplement and synergize the existing vast knowledge of the machining of aerospace alloys. At the end, possible future work has been anticipated. Keywords: Cutting tool, Machining, Titanium alloys, Inconel 718, Surface integrity 1. Introduction Among advanced aerospace materials, two have been comprehensively studied: titanium alloy Ti6Al4V [1,12,13,15,16,19,20,21,30] and nickel-based superalloy Inconel 718[2,7,8,9,11,29]. Due to their remarkably high strength-to-weight ratio, excellent mechanical properties (especially high temperature performance), and superior corrosion resistance, Titanium alloys and Inconel 718 have received growing applications in making critical parts, components, and structures. For example, titanium alloy is used in landing gear beams, thrust fittings and fan casings whereas turbine casings, discs and shafts used in engine are made of Inconel 718. However, because of their high strength and low thermal conductivity, HSM of these two materials often cause several problems in modern manufacturing. Many researchers described incapability to improve cutting tool performance for machining of aerospace alloys by developing new coating materials very annoying. The available literature undoubtedly advances the fundamental understanding of various aspects of cutting tool performance in conventional and high speed machining processes. However, little literature is available presenting comparison of cutting tool performance in machining of Titanium alloys and Inconel 718.This paper also presents comparison of cutting tool performance in machining of newly developed Titanium alloys and Inconel 718 first time. For aerospace applications, the surface condition of the machined workpiece is of great concern because of its role in the functional life of the component under cyclic loading. Immense care is taken to ensure that there is no metallurgical damage to the component surface subsequent to the final finishing pass. This paper focuses only on the comparison of cutting tool performance in turning of titanium alloys and Inconel 718 under different cutting conditions. This comparison starts with a significant study of different titanium alloys and Inconel 718, cutting tool materials and their influence on tool life and surface integrity during machining, and then various tool performance enhancement techniques are highlighted. 2. Aeros pace Alloys Aeroengine alloys provide a serious challenge for cutting tool materials during machining due to their unique combinations of properties. Although these properties are desirable design requirements, they pose a greater challenge to manufacturing engineers due to the high temperatures and stresses generated during machining. The most common aerospace alloy Ti6Al4V, accounts for more than 50% of the titanium-alloy production. The titanium demand has been increased because of its large consumption in the aerospace sector. The outstanding strength-to-weight ratio of titanium alloys provides a decrease of aircraft weight and, consequently, a reduction in fuel consumption and emissions [3]. Some newly developed titanium alloys like Ti555.3 and TIMETAL®54M are rapidly used in some critical applications in aerospace industry. 2.1 TIMETAL 555(Ti555.3) TIMETAL 555 is a high-strength near-ȕ titanium alloy that was designed for advanced producibility and tremendous mechanical property combinations, including deep hardenability. The concept for the alloy was publicly introduced in 1997 as an enhanced version of the Russian alloy VT-22. Since then, TIMET has been manufacturing and evaluating TIMETAL 555 for a range of aerospace applications [4]. [5] reported that the Ti555.3 can be heat treated to high strengths, with minimum tensile strength values of above 1200MPa. This high tensile strength makes Ti555.3 a capable material for sophisticated structural and landing gear applications, compared with conventional titanium alloys. They found that Ti555.3 alloy has 20% of the globular residual alpha phase along with the beta–alpha Widmanstätten-transformed phase. They reported higher difficulties when machining Ti555.3 compared with the Ti6Al4V alloy because of the mechanical properties, especially the hardness and the tensile stress at elevated temperatures (400◦ C), the differences of structure with a variable quantity of the alpha phase, and the morphology of the transformed ȕ phase.