Metallurgical Factors Influencing the Machinability of Inconel 718 John J. Schirra, Pratt & Whitney

Because of the large volume of Inconel 718 used by the aerospace and power generation industries and the high percentage of metal removed to machine complex component geometries; understanding and improving the machining characteristics of Inconel 718 would result in substantial cost savings. While progress has been made in developing improved tool materials and machining processes, a detailed understanding of the metallurgical factors influencing the machinability of Inconel 718 has not been generated. This paper presents work conducted by United Technologies Research Center and Pratt & Whitney Division establishing the relationship between the metallurgy and machinability of Inconel7 18. Factors such as fabrication technique (investment cast, cast + HIP and wrought), hardness, grain size and carbon content were all found to influence machinability. In addition to presenting the relationship between metallurgy and machinability of Inconel 718, suggestions are made in order to improve Inconel 718 machining characteristics and reduce fabrication costs. Superalloys 718,625,706 and Various Derivatives Edited by E.A. Loria The Minerals, Metals &Materials Society, 1994