Abstract
Wire arc additive manufacturing (WAAM) is gaining popularity among other additive manufacturing processes for the manufacture of large-scale components. The microstructural evolution of the solidification process in WAAM depends on the amount of heat input and the layering sequence. To examine the effect of layering sequences on the development of grain growth, microstructure, and mechanical properties, Inconel 825 alloy was deposited in various sequences for layering by WAAM using GMAW in this work. Several layering sequences were developed to prevent columnar grain production from oscillation beads and many passes in a single layer. The single direction of heat conduction promotes the growth of grains in that direction from bottom to top by linking grains at fusion boundaries. At the fusion border between the previously solidified bead and liquid metal, nucleation and epitaxial grain growth likely to develop. Hence, the transverse columnar grains are determined by the grain size of the previous layer. Traditional stacking sequence in one direction yields columnar grains, however zigzag layering sequence refined the grain growth. The zigzag layering sequence mostly disrupted the direction of heat conduction and grain development. The smaller size of fragmented grains improves the isotropic characteristics. The anisotropic behavior of additively manufactured deposits has been shown to depend on grain growth direction and size, which are affected by the layering sequence. Hardness and tensile strength of WAAM deposits with zig-zag layering sequence were found to be superior to standard layering sequence methods. Moreover, the zigzag layering sequence improves the resolution of deposited walls having a linear shape.
