Wire and arc additive manufacturing (WAAM) stands out from other deposition techniques for being able to produce bigger parts and with higher deposition rates. However, due to the high thermal input, it is necessary to carefully select the deposition strategy and parameters to achieve good geometry, low defects and adequate mechanical properties. As a recent technology, different studies have been developed comprehending the deposition approach, aiming to achieve parts with specific characteristics, usually evaluating the geometry, microstructure and mechanical properties, such as yield and tensile strengths, residual stresses and microhardness; however, the last is usually presented by mean values, requiring more details to comprehend its behavior further. In this sense, this work aims to evaluate the microhardness variation on walls of ER70S-6 deposited by WAAM-CMT in detail, with different deposition strategies, unidirectional and bidirectional, and with and without interlayer temperature control. The wall’s geometry was also assessed in terms of height and width. The results showed that both bidirectional deposition and temperature control contributed to improving the wall’s geometry. Combining methods led to a 26% increase in the wall width and 9% in the height; combining both methods also led to a more homogeneous distribution of microhardness throughout the wall with less than 15 HV variation. For all the deposition strategies, the wall region influenced the microhardness, and relatively higher values were obtained on the upper region of the wall, followed by the central and lower regions.

Additive manufacturing (AM) stands out for its variable applications in terms of material, quality, and geometry. Wire Arc Additive Manufacturing (WAAM) is remarkable for producing large parts in reduced times when compared to other AM methods. The possibility of producing a part with a near-net shape not only enhances productivity but also reduces resources usage. However, parts produced by WAAM may need post-processing by machining to achieve functional surface requirements. Therefore, it is important that machining, even if minimized, does not lead to a significant environmental impact. In this sense, this work evaluates the effect of using compressed air, dry cut, and synthetic biodegradable cutting fluid at varying nozzle positions and flow rates on the surface quality of ER70S-6 steel produced by WAAM, after milling with TiAlN-coated carbide tools. To analyze the surface roughness, parameters Ra, Rq, and Rz were measured and microscopy was used to further evaluate the surfaces. The surface hardness was also evaluated. The results showed that a flow rate of 10 L/min promotes better surface quality, which can be further improved using compressed air, leading to a surface quality 50% better when compared to dry cutting. Dry cut was not suitable for machining ER70S-6 WAAM material as it resulted in rough surface texture with an Rz = 4.02 µm. Compressed air was the best overall condition evaluated, achieving a 36% Ra reduction compared to dry cutting, the second-lowest hardness deviation at 6.51%, and improved sustainability by eliminating the need for cutting fluid.

Advances in additive manufacturing (AM) have led to a growing demand for increasingly sophisticated post-processing methods. Thus, micro-machining may be required, demanding careful selection of cutting parameters. Therefore, this work contributes new literature on the micro milling of wire arc additive manufacturing (WAAM)-cold metal transfer (CMT) ER70S-6. For this, 400 µm diameter micro tools were used, and eight values of feed per tooth (fz) were evaluated. The results showed that values under 2.5 µm/tooth may not exceed the minimum chip thickness, resulting in increased roughness (Ra = 0.51 µm) and worsened surface texture. The fz of 5.0 µm/tooth is the most suitable to achieve smoother surfaces, resulting in Ra 0.39 µm. The fz of 20.0 µm/tooth was observed to be a good alternative associated with good results, lower burr formation, and high productivity. The results suggest that the minimum uncut chip thickness for WAAM-CMT ER70S-6 lies between 2.5 and 5.0 µm/tooth.

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