Evaluation of surface quality in milling of WAAM-fabricated ER70S-6: influence of cutting speed and deposition direction

Abstract

Wire Arc Additive Manufacturing (WAAM) has emerged as a prominent metal additive manufacturing method, offering high deposition rates, design flexibility, and reduced material waste, making it attractive for aerospace and automotive applications. However, WAAM parts typically exhibit high surface roughness and limited dimensional accuracy in the as-deposited condition, compromising critical properties such as fatigue life and corrosion resistance. In this context, post-deposition machining becomes essential to achieve the desired surface and dimensional requirements. Thus, this work investigates the face milling of ER70S-6 steel parts manufactured via WAAM-CMT, evaluating the influence of cutting speed (10 and 40 m/min) and milling direction, parallel and perpendicular to the deposition path, on surface quality, assessed through roughness measurements, hardness testing, and confocal microscopy. Results showed roughness reductions of up to 95% and 86% in the parallel and perpendicular directions, respectively, compared to the as-deposited surface. Parallel milling consistently achieved Ra values at least 60% lower than perpendicular milling. Hardness increased under all conditions, reaching up to 19% perpendicularly at 40 m/min. This study provides novel insights into machining parameter optimization for WAAM steel, offering practical guidelines for post-processing of additively manufactured components.