EXPERIMENTAL INVESTIGATION INTO WIRE ARC-BASED ADDITIVE MANUFACTURING OF STEEL COMPONENTS

Abstract

In recent years, welding based wire-arc additive manufacturing (WAAM) has been enthusiastically accepted to fabricate different parts of structural materials. In this study, a gas tungsten arc welding (GTAW) based WAAM setup was developed, and low-carbon alloy steel ER 70S-6 filler wire and SS 304 L were used to fabricate a geometry. Surface coating is further carried out to enhance the anticorrosive properties of WAAM products of mild steel and stainless steel. This study is divided into four parts. Development of experimental setup, Optimization of parameters, Mechanical characterization and Coating of the products built from the WAAM technique. To analyze the mechanical properties of the printed alloy, room temperature tensile test, hardness and Charpy toughness tests are produced. For ER70S-6 Wire produced products, the microstructure reveals a mostly homogeneous ferrite phase as a matrix and a small amount of pearlite phase at grain boundaries, except for the last build surface. Grain size was found to be doubled from middle build to last build surfaces. The bi-axial tensile test results show isotropic tensile properties in both directions. The observed morphological features of the fractured surfaces in both directions were found to be in good agreement with their tensile test results, confirming a higher ductility for the across the build samples. Large scatter was observed in the hardness tests concerning the building direction. A hydrophobic Zirconium nitride (ZrN) nanoflowers [ZrNNF] surface was successfully developed on mild steel (MS) substrate via an industrial PVD technique. The developed hierarchical surface was characterized using FE-SEM (field emission scanning electron microscopy), EDS (energy-dispersive X-ray spectroscopy), XPS (X-ray photoelectron spectroscopy) and AFM (atomic force microscopy). The electrochemical characteristics of ZrNNF coating were investigated using potentiodynamic and EIS measurements in saline media [3.5 wt. % NaCl solution]. The influence of hierarchical surface on corrosion parameters have also been examined. The experimental results reveal that the corrosion potential (Ecorr) of the coated substrate was shifted towards a more noble value (~ -55 mV) with a lower current density (Icorr) (0.0027 μA/cm2) as compared to the bare (10.9 μA/cm2) specimen. Similarly, EIS parameters also revealed a similar behavior of coated sample, resultant low corrosion rate than the bare sample. The anti-corrosion mechanism of the ZrNNF coating is also presented in detailed. Based on the presents results, the ZrNNF@MS coating shows excellent wetting and corrosion resistant properties under the saline environment. GTAW (gas tungsten arc welding) based WAAM approach was employed to fabricate a iv geometry by the filler wire of stainless steel (SS-304L) and subsequently covered with a hydrophobic dense and thick TiNNPs (Titanium nitride nanopyramids) film. Comprehensive characterizations of the uncoated and coated samples were performed in terms of morphology, composition, structure, wettability, tensile fracture and corrosion by FESEM, EDAX, XPS, XRD, contact angle (CA), and electrochemical work-station. The results indicated that the GTAW fabricated sample (WSS-304L) led to a significant change in the surface microstructure and roughness and to significantly improved wetting, corrosion durability and corrosion resistance of TiNNPs coating, while maintaining their mechanical properties. The corrosion behavior of the bare and coated substrate was studied using potentio-dynamic polarization measurements in order to correlate water repellency with corrosion resistance; however, the coated sample demonstrated active corrosion without passivation. This method is commonly used in the protection of various materials from active corrosion.