1、Automated Installation for Modification Surface Propertiesof Details and Units of the Metallurgical Equipmentby the Electron Beam FacingS.I. Belyuk, A.G. Rau, I.V. Osipov*, N.G. Rempe*Institute of Strength Physics and Materials Science, 2/1 Akademicheskii Ave.,Tomsk, Russia*Tomsk State University of
2、 Control Systems and Radioelectronics, 40 Lenin Ave., Tomsk, Russia, Abstract : The electron-beam facing installation is designed for the production of coatings on the surface of metal articles. The coatings have protective, wear-resistive,and heat-resistive properties.The installation is capable of
3、 creating coatings on large-area surface with high efficiency.The technological process is automated.There are two plasma-cathode e-guns in the facing installation. This makes it possible to increase the facing efficiency and productivity. The guns are placed in a vacuum chamber on a two-rectilinear
4、 manipulator and can operate simultaneously.This installation is used in metallurgy for creating wear-resistant coatings on aerial and oxygen lances, on crystallizers of continuous casting of steel, on rolls, etc.1. IntroductionElectron-beam facing in vacuum 1,2 allows coatings with unique propertie
5、s to be produced. With this method of coating deposition there is no adhesion problem. The materials which can be treated by this method and the coatings which can be produced on their surfaces are widely diversified. The high repeatability of results in combination with the adaptable control of the
6、 technological process make it possible to produce coatings of required structure and preassigned properties.We have developed an installation intended for deposition of heat and aerial blast-furnace lances with the purpose of increasing their operational durability and also for restoration of vario
7、us machine parts and metallurgical equipment. It can also be used for welding various metals and alloys, including high-melting ones.The installation makes it possible to produce mono-and multilayer coatings of various purposes (hardening, wear-resistant, heat-resistant, temperature-resistant, etc.)
8、 depending on the composition of the facing powder on the surface of articles made of any metals, steels, and cast iron.With this installation it is possible to deposit coatings on plane surfaces of workpieces of length up to 2100 mm, width up to 900 mm, and thickness up to 200 mm and on bodies of r
9、evolution of diameter up to 1200 mm and length up to 2100 mm.The technological process of coating deposition is full-automatic.2. Electron-beam facingThe principle of electron-beam facing is shown in Fig. 1. The electron beam creates a molten metal pool on the surface of the workpiece. The powder wh
10、ose particles form a coating with required properties on the surface is supplied to the molten metal by a dispenser. The workpiece is moved inside the vacuum chamber relative to the (immobile) e-gun and dispenser or the e-gun with the dispenser are moved relative to the (immobile) workpiece.Fig.1.Th
11、e technology of multipass electron-beam facing is based on the phenomenon of freezing a powder into a melt pool. In every subsequent pass, a new portion of the powder is frozen and the previous portion is melted. The powder supplied to the pool speeds up the crystallization of the melt, thus promoti
12、ng the formation of a fine grain structure and moderating the residual stresses in the deposited coating. The required thickness of the deposited layer is obtained by varying the rate of powder supply or by increasing the number of passes.The process of facing is characterized by the following param
13、eters: the accelerating voltage, the electron beam current, the distance from the focusing system to the surface of the workpiece, the electron beam scanning diameter and length, the velocity of motion of the workpiece, and the rate of powder supply.3.Electron gunsThe facing process is accompanied b
14、y intense ejection of vapors and gases from the facing zone. The refore, to produce an electron beam, plasma-cathode guns are used 3, 4. These guns do not contain hot electrodes or components which would be heated in operation, and this makes them insensitive to reactive and high-melting vapors of t
15、he materials under treatment. They are capable of operating under the conditions of facing not taking special measures for protection of the emitter.Figure 2Figure 3The electron emission in the guns occurs from the plasma of a hollow cathode low-voltage reflected discharge 4. The electrons outgoing
16、from the plasma get in a high-voltage electric field where they are accelerated, collected in a beam, and focused by the magnetic field of the focusing system. The electron emission current from the plasma is controlled by varying the discharge current.In the design of the guns, metal used whose hermeticity and mechanical strength are provided by electron-beam weding.The gun housings are of in-chamber construction.The design o
