Методика определения режимов послойной электронно-лучевой наплавки проволоки для аддитивных технологий

Abstract

Electron beam wire feed deposition is a process that uses an electron beam as a power source and wire as raw material to fabricate metallic items in a vacuum chamber. This technology can be widely used for industrial applications due to its ability of using metal in a very efficient manner, making parts within a short period of time, and ensuring good quality of the produced items. The article presents elaboration of the calculation method for determining the operation modes of the electron beam technology for depositing the metal of wire made of Grade AISI 316L corrosion-resistant austenitic steel on a substrate made of the same material. The calculation method correlates the main process parameters, including the electronic beam current, the additive wire feed rate, and the electron beam gun translation speed, and the effects these parameters have on the geometry, microstructure, and mechanical properties of the obtained beads. The method assumes that the electron beam power is spent for heating and melting the wire and the substrate material. The production process thermal efficiency factor was introduced for taking into account the thermal losses. The item’s macrostructure was analyzed, as a result of which the thermal efficiency was estimated together with the effect the main process parameters have on its value. It was noted in an analysis of the weld beads’ microstructure that columnar crystals (dendrites) appear in the course of metal solidification. It has been found that the electron beam gun displacement speed (the deposition rate), a parameter affecting the molten metal cooling rate, is the key factor influencing the size of columnar grains. The hardness of the obtained beads was investigated, and the following conclusions have been drawn from those investigations. The deposited metal hardness decreases with increasing the bead height. The hardness of beads increases with the deposition rate, which is attributed to a higher melt crystallization rate and the formation of a more fine-grained structure. The growth of hardness toward the bead root is attributed to the fact that the temperature gradient in the root zone is higher than that at the bead top. It has also been found that the hardness value depends on the heat source parameters, the heat source traveling speed (the deposition rate), and the thermophysical properties of the material.