Electron Beam Melting of Thermally Sprayed Layers – Overview

Abstract

Thermal spraying is one of the most common methods enabling the deposition of variously-purposed layers on surfaces of structural elements. However, in certain cases, the process of spraying itself is ineffective in terms of the stability and properties of protective layers. One of the possible solutions making it possible to reduce the porosity and improve the adhesion of surfaced layers involves their melting using the concentrated electron beam. The article contains an overview of reference publications concerning electron beam melting technologies.

Electron Beam Surface Hardening

“…The process involves the excitation and emission of electrons from the cathode, usually made of tungsten or a tungsten alloy. Electrons are first accelerated using very high voltage (even 300 kV) and, next deflected and directed to the working chamber using electromagnetic coils [10][11][12][13]. The design of the electron gun is presented in Figure 2.…”

“…Figure 3 presents exemplary electron beam scanning related to various oscillation frequencies. Figure 4 The primary advantages of electron beam hardening [10,12,13,[18][19][20] are the following: -metallurgical purity of the process (performed in vacuum), -precise computer-controlled deflection and focusing of the beam, -higher (in comparison with other technologies) heating rates (of up to 109 K/s), where the heating of the surface of an element is faster than its heat absorbability (resulting from the heat conductivity of a given material), -precise adjustment of process parameters, -high process repeatability, -easy automation, -high process precision, -high energy conversion efficiency (exceeding 90%). Exemplary applications of the electron beam surface hardening process are presented in Table 1.…”

Low-Alloy Steel Electron Beam Hardening

“…For this to be possible, the ratio of quenched to unquenched mass must be large enough to ensure that the heat is removed quickly enough. Hardening only the top layer of the component reduces deformation and the occurrence of stresses, in addition, it reduces energy consumption and thus the cost of manufacturing the component [1][2][3][4][5][6][7][8][9][10][11].…”