Anisotropy of the tensile properties in austenitic stainless steel obtained by wire-feed electron beam additive growth

Abstract

Currently, new approaches to the production of metal structures of different sizes are actively developing. These approaches are based on the technologies of additive manufacturing or 3D printing methods, which assume consistent layer-by-layer growth (printing) of parts of structures with a shape and size that are as close as possible to the desired parameters. During these processes, each subsequent layer is formed by fusing the material to preceding layers. Thus, the methods of additive growth are based on heating a part of the material to the melting temperature. Therefore, in the process of printing, the billets experience multiple heating and cooling cycles. As a result, different parts of the billets have different thermal histories and could possess different mechanical properties. In this paper, the anisotropy of the tensile mechanical properties of the billet of austenitic Fe-18Cr-9Ni-0.08C steel produced by wire-feed electron-beam printing was investigated. It was experimentally shown that, after additive growth, the samples of austenitic steel, which were cut from different parts of the steel billet and differently oriented with respect to the growth direction possessed significant anisotropy of mechanical properties under uniaxial tension: yield strength varies in the range from 250 to 310 MPa, and elongation to failure ranges from 48 to 65%. According to microstructural analysis, this behavior is associated with heterogeneity of the elemental composition, macroscopic heterogeneity of the dendritic structure of ferrite in austenite (layering), heterogeneity of the phase composition and residual stresses in the steel billet obtained by the additive wire-feed growth.