Influence of low heat input by CMT powered WAAM on attaining the microstructural and mechanical homogeneity of printed 304 SS cylindrical component

Abstract

Recently, several industries have been implementing the Cold Metal Transfer (CMT) powered Wire and Arc Additive Manufacturing (WAAM) technique because it fabricates large-scale products effectively. However, studies related to attaining uniformity in the microstructure and printing defects in the cylindrical components were lacking. So, the prime novelty is to examine the microstructural and mechanical homogeneity of the CMT-powered WAAM 304 austenitic stainless steel (SS) component. The X-ray diffraction (XRD) analysis substantiates the presence of austenite and ferrite phases all along the samples from the bottom to the top portion of the wall resulting in higher bond strength and uniformity in the microstructure. Optical Microscopy (OM) and the Scanning Electron Microscope (SEM) revealed the presence of dendritic microstructure with ferrite and austenite phases throughout the samples. The values connected to the dendritic formations are lower as a result of the reduced heat input by CMT, which leads to higher mechanical characteristics. The hardness values from the bottom to the top of the wall was 191 ± 10 HV, indicating uniformity and homogeneity in the microstructure. The tensile result showed a yield strength (σy) of 398 MPa and the ultimate tensile strength (σu) of 598 MPa and an elongation rate of 17 % in the building direction which proves the uniformity in the hardness values. Fracture morphology reveals the presence of microvoids and dimples, indicating lower ductility in the component. The Energy Dispersive Spectroscopy (EDS) also reveals the presence of higher Fe and Mn content, adding up to the successful fabrication of the cylindrical component.