Constitutive modelling and machining behavior of wrought and FFF-produced stainless steels via direct and inverse parameter identification

Metal fused filament fabrication (MFFF) has gained attention as a cost-effective and safe additive manufacturing route for metallic components. However, sintered MFFF parts often require post-process machining to achieve the surface finish and dimensional accuracy needed for functional applications. The layer-wise deposition inherent to the MFFF process introduces a unique anisotropic microstructure and defect profile that fundamentally alters material removal mechanisms. The machining behavior of MFFF metals remains insufficiently understood, particularly the influence of raster orientation on cutting forces and chip formation. This study investigates the dynamic material response and machinability of MFFF-produced 17–4 PH and 316 L stainless steels across raster orientations of 0°, ±45°, and 90°. A combined framework including quasi-static tensile testing, high-strain-rate Split Hopkinson Pressure Bar experiments, and orthogonal cutting tests were used to derive Johnson-Cook (J-C) parameters. To reduce reliance on resource-intensive dynamic testing, an inverse parameter identification approach was used to estimate J-C constants from quasi-static tests and orthogonal cutting experiments. The calibrated models were coupled with Oxley’s machining theory to predict cutting forces, which were validated against experimental measurements. SEM analysis linked material resistance and chip formation to internal discontinuities and interlayer bonding, establishing a foundation for predictive modeling of MFFF components.