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Nickel-based super alloys such as Inconel 718 are widely employed in extremely hostile applications owing to their superior thermo-mechanical properties. On the contrary, these latter lead the industries to adopt conservative process parameters (e.g. low cutting speed) resulting in lower production rates. The possibility to increase the cutting parameters could lead to higher material removal rates and drastic reduction of the machining time of the process. The aim of this study is to investigate the effects of extreme cutting parameters on the surface and subsurface alterations such as grain size and hardness changes by developing a finite element (FE) numerical model. The Zener-Hollomon and Hall-Petch equation were implemented to predict the grain size and micro hardness variations due to the cutting process. In addition, the depth of the affected layer due to machining was predicted using the critical strain equation. The obtained results proved the accuracy and reliability of the proposed FE model showing a good agreement between the simulated and the experimental results. [ABSTRACT FROM AUTHOR]

In the last few years, important step forwards have been made on Finite Element Simulation of machining operations. Wrought Ti6Al4 V alloy has been deeply investigated both numerically and experimentally due to its wide application in the industry. Recently, Additive Manufacturing technologies as the Electron Beam Melting and the Direct Melting Laser Sintering are more and more employed in the production of biomedical and aeronautical components made of Ti6Al4 V alloy. Fine acicular microstructures are generated by the application of additive manufacturing technologies, affecting the mechanical properties and the machinability. By the consequence, this peculiarity has to be considered in modelling the material behaviour. In this work, a numerical analysis of cylindrical external turning on Electron Beam Melted (EBM) Ti6Al4 V alloy is presented. A Johnson-Cook constitutive equation was implemented as a flow stress model and adapted with respect to the wrought Ti6Al4 V alloy. The model was calibrated and validated through the cutting forces and temperatures measurements acquired under dry and cryogenic lubricating conditions. [ABSTRACT FROM AUTHOR]

The main objective of this study is to implement a reliable FE model of the orthogonal machining of a Nickel based superalloy for the prediction of microstructural changes occurring during the process. A FE numerical model was properly calibrated using an iterative procedure based on the comparison between simulated and experimental results. A user subroutine was implemented in the FE code to simulate the dynamic recrystallization and consequently the grain refinement and hardness variation when orthogonal cutting of Nickel based superalloy is performed. Thus, Zener-Hollomon and Hall-Petch equations were implemented to predict the grain size and micro hardness, respectively. In addition, the depth of the affected layer was predicted using the critical strain equation. The obtained results proved the adequacy of the proposed model showing a good agreement between the simulated and the experimental results. [ABSTRACT FROM AUTHOR]