Method for electron-beam surfacing of multimodal-structure coatings

FIELD: electron-beam surfacing of flat and cylindrical surfaces, possibly manufacture of new parts and restoration of worn surfaces of parts operating at condition of intensified abrasive wear in combination with impact loads.

SUBSTANCE: in order to enlarge manufacturing possibilities of method, on surface of welded-on article melting zone by means of electron beam is created. Powder composition material for surfacing is fed to melting zone. Surfaced article is moved and powder material for surfacing is fed normally relative to motion direction of article. As coating is applied unfocused electron beam is used for acting upon surface of said coating without supply of material for surfacing. It provides separation of dispersed particles of strengthener from solid solution and formation of multimodal structure of surfacing along its whole thickness.

EFFECT: enlarged manufacturing possibilities of method.

1 dwg, 1 ex

 

The invention relates to welding, and in particular to methods of electron-beam welding of flat and cylindrical surfaces, and can be used for manufacturing new and restoring the surface of worn parts, working in conditions of intensive abrasive wear in combination with impact loads.

At the present time to increase the wear resistance of the working surfaces of parts of mechanisms and machines by their manufacturing and repair process, as fused powder mixtures are typically used hard and superhard composite materials such as Stellite, Carmit, the FTC [Gulyaev A.P.]. - M.: metallurgy 1986, 544 S.]. Data surfacing materials have found wide application in the mining industry, metallurgy, where there are no strict requirements on the quality of the structure welding. As a strengthening phase they contain 30...90% expensive carbides of titanium, tungsten, molybdenum, are very unevenly distributed over the volume of the deposited layer, especially when their content up to 30...50%. The main drawback of the composite cladding is fragile due to the high content of reinforcing particles, which limits their applications in heavy-duty friction with large contact loads, accompanied by the blow.

There is a method of electron-beam welding (RF Patent No. 2118243 from 1998.08.27, MKI UK 15/00), wherein on the surface of the fused product creates a zone of melting beam with linear sweep, clean the product move, and fusible powder material is fed into the gap between the lines of the beam sweep.

The disadvantage of this method is that it is applicable only for surfacing materials, not containing in its composition dispersed hardening phases. At low content of reinforcing particles is strong irregularity of their distribution surfaced in the material, resulting in reduced performance properties of the coatings. To increase the uniformity of distribution of the reinforcing phase it is necessary to increase the number of more than 40 vol.%, that limits the technological possibilities of the method and leads to increased fragility of the deposited coatings.

The closest way to the same destination to the claimed invention by a combination of traits is a method of electron-beam welding (RF Patent No. 2205094, from 2003.05.27, MKI UK 9/04, UK 15/00, UK 35/368), in which the protected surface metal products creates a zone of melting electron beam with a linear scan in the form of several parallel lines, facing material is fed to the zone melting, and the product is moved when the protected surface is pre-cleaned by melting electron beam without filing fused material the scan of the electron beam performs perpendicular to the direction of movement of the product, and as the fused material use of composite powders, or a mixture of heat-sensitive powders.

The disadvantage of this known method is that when forming the cladding of the composite powder of the refractory material particles partially (TiC) or fully (WC) dissolved in the liquid metal bath melt and rapid further crystallization and cooling do not have time to completely stand out from the solid solution. Any insoluble particles of concrete and partially segregated grains are unevenly distributed throughout the thickness of the hardened layer due to the significant difference in their densities with the density of the liquid metal bath melt. The formation of heterogeneous structures surfacing on the basis of αor γ- solid solution on its thickness contributes to uneven wear, failure to monitor and predict its performance, which ultimately leads to premature failure of the product.

The primary object of the present invention is the expansion of technological capabilities of the method of electron-beam welding and the improvement of physico-mechanical properties of fused products. In particular the improvement of wear resistance of low-alloy to positionnow surfacing and structural uniformity throughout the thickness of the hardened layer by creating a multimodal distribution of reinforcing particles in α or γsolid solution iron-based.

This object is achieved in that in the method of electron beam welding on the surface of the fused product creates a zone of melt electron beam fused powder composite material serves in the area of the melt, fuse product move, and fusible powder material serves perpendicular to the movement surfaced products. After coating on the additional passage is heat welding, which is an additional temperature effects defocused electron beam on the surface of the deposited coating without feeding the fused material. The current focus of the electron beam 10...20% less than the current focus, which is surfacing coating that provides the heating temperature of the coating 650 700...°S. This leads to the separation of dispersed particles of the hardener of the solid solution and formation of multimodal patterns surfacing throughout its thickness.

An example of a specific implementation.

The method of electron-beam welding is implemented on the basis of the welding electron-beam installation ELU-5, is additionally equipped with a powder feeder and the scanner beam. For surfacing, use the following powder materials, for example:

1. e - 20% Ni - 4% V - 4% Mo - 10% TiC;

2. Fe - 20% Mn - 4% V - 4% Mo - 1% - 15% WC;

3. steel R6M5 - 10% TiC;

4. steel R6M5-15% WC.

The mixture of the source powder is poured into a ceramic crucible and subjected to sintering in a vacuum at a temperature of 1050 1120...°C for 30 to 40 minutes. After cooling in the furnace resulting spectra are subjected to crushing and sieving into fractions. For welding use a fraction of composite powder 90...250 μm. Welding takes place by feeding the powder material from the powder feeder to the zone of melt generated by an electron beam with a linear scan, which is formed by using a scanner beam. After deposition of the coating on the additional pass is carried out, heat treatment, which is an additional temperature effect of the electron beam on the surface of the deposited coating. The current focus of the electron beam when the processing is put on 10...20% less than the current focus, which was conducted surfacing coating. The current of the electron beam is set such size that in his area the temperature was 650-700°S, which is controlled by a thermocouple on the sample-witnesses.

The drawing shows the microstructure of the coatings (Fe - 20% Ni - 4% V - 4% Mo - 10% TiC) and the distribution of the particles of the solid phase in size after welding (a, b) and subsequent aging (b, d). Acerage (a) shows the microstructure of the coating immediately after electron-beam welding. You can see the uneven distribution of carbide particles in the austenite matrix in the form of separate linear discharge. The average size of these particles is equal to 1.1 μm (see drawing). Heat treatment welding due to the additional temperature effects defocused electron beam leads to additional release of particles reinforcer (see drawing b). This contributes to the creation of a uniform multimodal distribution of particles of hardener in the solid solution (see drawing d). On the distribution of particles reinforcer dimensions (see drawing d) obvious three maxima in the distribution (d1=1.2 µm d2=2.5 μm, d3=4,1 μm), the average particle size of 1.8 μm. Thus formed multi-modal structure allows to increase the hardness of surfacing from 6 to 8.3 GPA, to reduce the variance of the distribution from 3.5 to 0.5 HPa, to reduce the wear material with 6×10-4to 3.7×10-4cm3per hour and keep it uniform throughout the thickness of the surfacing. The abrasive wear resistance was determined when worn about not gestazione abrasive particles (GOST 23.208-79). As the abrasive material was used quartz sand grain sizes 160...350 μm when the load on the sample 44±0,25 N.

The method of electron-beam welding, in which the surface of the product, the cat is the ROI napravlyayut floor, pre-cleaned by melting electron beam without the filing of fused material, then on the surface of the fused product creates a zone of melt electron beam surfaced product move, and fusible powder material is fed into the area of the melt in the feed direction perpendicular to the relative movement surfaced product, characterized in that the coating is formed in multiple passes, with the last pass perform defocused electron beam without filing surfaced material, providing the heating temperature of the coating 650-700°C.



 

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