Selection of optimal process parameters for wire arc additive manufacturing

Title: Selection of optimal process parameters for wire arc additive manufacturing

Authors: Mariacira Liberini, Antonello Astarita, Gianni Campatelli , Antonio Scippa , Filippo Montevecchi, Giuseppe Venturini , Massimo Durante , Luca Boccarusso , Fabrizio Memola Capece Minutolo , A. Squillace

Keywords: Wire arc additive manufacturing; ER70S-6 Steel; Microstructure; Vickers hardness.

Abstract: This paper is about the optimal selection of process parameters for Wire Arc Additive Manufacturing technology. In particular, the selection of the process parameters is based on the evolution of the microstructure and on the mechanical properties of the final samples obtained through the successive deposition weld beads of a ER70S-6 steel. The feed rate and the heat input during the deposition of the weld beads have been varied, in order to understand how the temperature reached by the samples can affect the final product mechanical characteristics. The final cooling has been carried in calm air at room temperature and between the deposition of a weld bead and the following one it has been imposed a pause of 60s. The tests on mechanical properties carried out have been a full experimental campaign that includes: macrographic observations, micrographic observations and Vickers microhardness. The analysis of these tests has highligthed that by varying the process parameters, the samples do not have substantial differences between them. Instead, a microstructure that evolves from pearlitic-ferritic grains until bainitic lamellae along the vertical direction of the samples has been observed by micrographic analysis.

Purpose: the purpose is to define the effect of process parameters on the final microstructure of the product obtained in order to choose the optimal setup. The process parameters varied within the tests has been chosen in order to vary both the heat input of the process and the heat flux in a specific product area.

Design/methodology/approach: The test samples were made by depositing successive layers of materials on a low carbon steel substrate. The filler material used is a standard filler for welding structural steels: ER70S-6 designation according AWS legislation. The test samples were made by superimposing 15 layers. A pause of 60s was imposed between each layer deposition, in order to enable a partial cooling of the deposited material. In the execution of the specimens it was maintained a distance of 10 mm between the torch and the work surface. All the samples are cooled in calm air at room temperature.

Findings: in all the samples have been noted three different zones: the lower zone characterized by a ferritic structure with thin strips of pearlite, the middle zones characterized by equiaxed grains of ferrite and the upper zone characterized by a lamellar structure typically bainitic.

Practical implications: it’s possible to obtain a structure ferrite/bainite according to the needs required by the final product.

Full reference : Procedia CIRP 62

Link  : www.sciencedirect.com/science/article/pii/S2212827117301968