Effect of process parameters and orientation on the tensile and low cycle fatigue properties of low-carbon steel builds manufactured by directed energy deposition-gas metal arc process

Directed energy deposition-gas metal arc (DED-GMA) process has recently gained considerable attention due to its inherent capability to produce large metallic components, with moderate complexity, at substantially high deposition rate compared to other additive manufacturing techniques. The effect of wire feed rate, energy input per unit length and orientation on the tensile and low cycle fatigue behaviour of multi-layer builds of low-carbon steel ER70S-6 is systematically studied in the present work. In addition, a detailed microstructural characterization is also carried out for better understanding of the microstructural evolution during deposition and its influence on the mechanical behaviour of the build. In general, insignificant variation of the tensile properties of DED-GMA specimens at different orientations signifies an overall isotropic behaviour. The vertically oriented samples, printed at highest energy input, show superior fatigue life. The number of cycles to failure, for the vertically oriented samples, at highest wire feed rate of 10 m/min and deposition travel speed of 1 m/min, are found to be around 718, 450 and 366 at strain amplitudes of ± 0.6, ± 0.8 and ± 1.0%, respectively. It is envisaged that the control of energy input by adjusting wire feed rate and deposition travel speed is crucial to improve the tensile and fatigue properties of the build.