Experimental and numerical investigation of thermal loads in Inocnel 718 machining

Inducing high thermal loads in machining of difficult-to-cut materials changes the mechanical properties of a machined surface/subsurface. In particular, a thermally affected layer leads to tensile residual stresses and microstructure changes. Nickel-based alloys are hard materials and frequently used in different industries. Since the generation of thermal loads in machining Inconel 718 is evident, in this paper an experimental and numerical investigation were performed to evaluate thermal loads and the depth of the affected layer in the machining of Inconel 718 superalloy. First, the effect of cutting parameters was studied on the average machined surface temperature by experimental tests. Then, the results of experiments were used to validate a 3D numerical model. Using the calibration strategy, the heat transfer coefficient at the chip-tool interface was found to be dependent on the cutting conditions. Next, the effect of the initial workpiece hardness and tool geometry, including tool nose radius and edge radius, was evaluated on thermal loads and the depth of the recrystallized layer. The critical strain criterion was used to estimate the depth of the recrystallized layer and then, the numerical results were compared with experimentally measured depth of the affected layer at different machining parameters.