Experimental investigation on deposits of ER70S-6 wire on SiO2 substrate using non-transferred arc-based wire arc additive manufacturing

Abstract

Recent trends in additive manufacturing (AM) are to produce geometrically complex structures at minimal wastage of material, time and cost without sacrificing part quality and mechanical performance and to introduce ease in processing and part removal. Here, a non-transferred arc (NTA)-based wire arc additive manufacturing (WAAM) system has been developed to achieve the above objectives, where the arc is only generated between tungsten electrode and consumable filler wire. No electrical contact with the substrate facilitate deposits even on the non-conductive substrate surface, which helps to remove the final deposits easily. The influence of deposition parameters (welding current, voltage, wire feed speed (WFS) and travel speed) on response characteristics (bead uniformity, height deviation, droplet diameter, and droplet transfer frequency) is studied on a multi-performance level using grey relational analysis (GRA). Then, single- and multi-bead layer is fabricated over SiO2 substrate for ease in part removal after complete fabrication. WFS is referred to as a key deposition parameter that influences all deposition characteristics. It has been observed that NTA-based WAAM results in high bead uniformity with minimal spatter and low bead height difference between start and exit arc point. Complete ferrite microstructure with few pearlites is observed on the deposits with similar elemental composition on the top, bottom and interface surfaces. X-ray diffraction (XRD) study reveals ferrite diffraction planes ({110}, {200}, {211} and {220}) with no intermetallic formations on deposits. Also, compressive residual stress with less variation in crystallite size, stress, strain and microhardness among the top, bottom and lateral deposit surfaces indicates the fabricated part’s isotropic nature.