Heat Assisted Machining of Nickel Base Alloys: Experimental and Numerical Analysis

Abstract

Nickel base alloys are frequently used in aerospace industries, marine, biomedical application and other demanding industries due to their high strength, high hardness, resistant to corrosion and ability to withstand at elevated temperature. But machining of these materials in conventional way impairs severely their machinability due to certain inherent properties like low thermal conductivity, high chemical affinity and presence of hard particles in the microstructure etc. Therefore, tool life is reduced, due to the abrasion wear from the hard particles and high temperature of the tool-chip interface due to diffusion wear during machining of nickel base alloys.
In this work, hot machining is introduced for processing of nickel base alloys like Inconel 718, Inconel 625, and Monel 400. In this technique, heating on the workpiece is combined with conventional turning process was used to enhanced machinability of nickel base alloy without compromise quality and productive. The study revealed that the influence of the workpiece temperature on the workpiece surface enhanced machining performance in terms of better surface finish, MRR, and reduction of forces, wear compared to conventional turning process. The surface integrity has been studied in terms of surface roughness, and microhardness beneath the machined surface in hot machining operation. Finite element modeling was also employed to prediction of cutting force, temperature distribution, stress, in hot turning of Inconel 718. The finite element results were compared with the experimental value and close agreement was found. In any industries production of parts along with tool life, surface finish is the major concern. In order to optimize the machining of nickel base alloys, optimization technique was performed using desirability and principal component analysis. Finally, machinability comparison was made between three materials, in order to understand effect of machining parameters along with workpiece temperature. In the literature, no research studies were found on flame heat machining of nickel base alloys (Inconel 625, Inconel 718 and Monel 400). The research led to various contributions to finding in terms of experimental investigation, optimization and FEM modeling. The contribution of the thesis should be of interest who works in the areas of machining of hard materials.