Enhancing manufacturing and post-processing properties of WAAM ER110 HSLA steel: in situ hot forging + post-deposited heat treatment effects on surface quality and specific cutting energy

Abstract

This work focuses on the influence of post-deposited heat treatments (PDHT) on the properties and machinability of high-strength low-alloy steel (HSLA) samples, produced by WAAM and the forged (HF-WAAM) variant. An adequate combination of deposition parameters was established, and the manufactured specimens were 3D scanned to evaluate the surface quality. Effects of normalizing and quenching & tempering (Q&T) heat treatments on the microstructure were assessed through optical microscopy and SEM, and the influence on the material hardness and electrical conductivity was evaluated. Orthogonal cutting experiments were conducted to determine the specific cutting energy (SCE), a crucial indicator of the cutting performance and machinability characteristics of the work material. The results revealed a significant SCE decrease when cutting the WAAM and HF-WAAM samples subjected to PDHT, with 8% and 38% decreases for pot-normalization, and 22% and 27% reductions after Q&T, compared to the as-built condition. No significant differences were registered when machining between the WAAM and HF-WAAM variants. HF-WAAM samples after PDHT show superior hardness, without compromising the cutting energy consumption. However, the geometrical features, namely the significant increase of the surface waviness of the hot-forged parts (≈70%) must be considered, being a critical factor to avoid possible undesirable machining effects.