Abstract
? 2021 Elsevier B.V.The intrinsic thermal distribution during the arc deposition can induce metastable microstructural characteristics and anisotropic properties. In this study, H13 buildups with different deposition structures were manufactured by cold metal transfer (CMT) technology. The defect distribution, phase constitution, and microstructural characteristics were investigated to explore the anisotropic mechanism of mechanical properties. The X-ray computed tomography results revealed that only microscopic globular pores were randomly retained within deposit. Compared to other structures, a minor amount of γ-Fe for single-layer single-track buildup was primarily attributed to the special thermal history. Equiaxed ferrite grains comprised dense needle-like martensites with homogeneous distribution. Martensitic growth orientation was roughly parallel to the adjacent ones inside individual ferrite grain, but exhibited no preferred crystallographic orientation. Anisotropy in mechanical properties was primarily determined by the effect of porosity and microstructures. The negligible anisotropy in micro-hardness and ultimate tensile strength was accounted for the non-directional martensitic growth direction inside different ferrite grains. The anisotropy in tensile plasticity could be attributed to microscopic pores underneath dimples during the tensile process. These findings reveal that CMT can fabricate crack-free buildups with homogeneous microstructures, resulting in insignificant anisotropic behavior in mechanical performances. The results of this study could provide a guidance for the arc deposition of large-sized martensitic steel parts.
NSTL
Elsevier