RU2355521C2 - Contact point for electrospark alloying and method of its manufacturing - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to field of metal treatment by current effect, particularly to electrospark alloying. Electrode consists of at least two, connected to each other by butt ends, different electrodes of the same cross-section, each of them is implemented of alloying materials of the different composition, as compared with composition of material of electrodes contacting to it. Manufacturing method of electrode includes hot compaction of powder material in mould, consisting of matrix and puncheon, herewith into mould from the opposite side of matrix it is implemented the second puncheon, and in the capacity of puncheons there are used ready separated electrodes, which compiles manufactured electrode.

EFFECT: invention provides technology simplification of electrospark alloying and time saving of process during the plating of combined (wear-resistant and antifriction) alloying coating.

5 cl, 3 dwg, 1 ex

Description

The invention relates to the field of metal processing by the action of electric current, in particular to electrospark alloying (ESA), and can be used to impart special surface properties, for example, high wear resistance and / or antifriction, to mechanical engineering parts.

Known accepted as the closest analogue of the invention, the electrode for ESA, made of alloying material [1]. It is desirable to use hard alloys - transition metal carbides, in particular double cast tungsten carbide (WC · W ₂ C), which has become known as relit, as the material for the manufacture of such an electrode under conditions of imparting an alloying coating with increased wear resistance. However, the use of relit as the alloying electrode material is difficult due to its high porosity and brittleness, which, firstly, creates unstable parameters of the ESA process, and secondly, often leads to the destruction of the electrode during ESA. In addition, since, according to the strength conditions, the relay electrode is of relatively short length, it has a low material utilization factor (CMM), due to the fact that up to 25% of the electrode material is used to fix it in the electrode holder of the EIL installation. On the other hand, when forming a combined coating, in addition to the wear resistance of the antifriction properties, it is necessary to study it with graphite, which leads to a loss of time for replacing the relay electrode with a graphite electrode.

The achieved result of the invention is to simplify the ESA technology and reduce the time of the technological process when applying a combined alloying coating.

This is ensured by the fact that the electrode for spark spark alloying made of an alloying material according to the invention is composed of at least two individual electrodes of the same cross section fastened together by the ends, each of which is made of an alloying material of a different composition compared to the material of one contacting with it or two electrodes.

Moreover, according to the invention, in particular, the electrode can be composed of two separate electrodes, one of which is made of transition metal carbide, and the other of graphite. The electrode can also be made of three separate electrodes, one of which is made of transition metal carbide, and the other two are made of graphite, and graphite electrodes are located on both sides of the transition metal carbide electrode.

A known method of manufacturing an electrode for spark alloying, comprising hot pressing of the powder material in a mold consisting of a matrix and a punch [2]. This method is usually used for the manufacture of a single electrode from any one material. The manufacture of a composite electrode in this way does not allow for clear boundaries between the compositions of the materials of the contacting individual electrodes, which is unacceptable according to the conditions of the ESA process when applying a combined alloying coating.

The achieved result of the invention is to improve the quality of the composite alloying electrode in its manufacture using hot pressing.

This result is ensured by the fact that in the manufacture of an electrode for spark alloying by a method comprising hot pressing of powder material in a mold consisting of a matrix and a punch, according to the invention, a second punch is introduced from the opposite side of the matrix into the mold, and ready-made punches are used individual electrodes of the manufactured composite electrode. At the same time, it becomes possible to create a composite electrode having a carbide part in the form of a separate electrode, for example, from carbides Cr ₃ C ₂ or WC · W ₂ C (relite) and a graphite part in the form of a separate graphite electrode inserted into the electrode holder to increase the CMM of the carbide electrode. In addition, the composite electrode allows to ensure the stability of the parameters of the formation of the coating layer on parts of conductive materials and the possibility of forming combined coatings without changing the electrode in the modes:

- carbide material + graphite;

- graphite + carbide material;

- graphite + carbide material + graphite.

1 shows a composite electrode according to the invention, having carbide and graphite parts in the form of two separate electrodes; figure 2 is the same, with two graphite and one carbide separate electrodes; figure 3 - mold for the manufacture of a composite electrode according to the invention.

The electrode 1 for electrospark alloying, made of an alloying material, according to the invention is composed of at least two fixed electrodes 2 separate electrodes 3, 4, 5 of the same (in this case, circular) cross section 6. Each of the electrodes 3, 4, 5 made of alloying material of a different composition compared to the material of the electrodes in contact with it. According to the embodiment of FIG. 1, the electrode 1 is composed of two separate electrodes, 3, 4, the electrode 3 being made of transition metal carbide and the other made of graphite. In the embodiment of FIG. 2, the electrode 1 is composed of three separate electrodes 3, 4, 5, the electrode 3 being made of transition metal carbide, and the electrodes 4, 5 made of graphite. The latter are located on both sides of the transition metal carbide electrode 3. The length l of the composite electrode 1 consists of the length l _{to the} electrode 3 of the transition metal carbide and lengths l 4.5 _g of graphite electrodes. The length l _{to the} electrode 3 of the transition metal carbide is not more than four diameters d of this electrode. This ratio is selected from the condition of ensuring maximum strength and maximum and stable density of the carbide part of the composite electrode 1, as well as from the conditions of manufacturability in its production. The minimum diameter d of the composite electrode 1 must be at least 3 mm.

The mold for the manufacture of the composite electrode 1 (figure 3) contains a graphite matrix 7 and two punches 8 and 9, which are used as separate individual electrodes 3, 4 or 5 of the manufactured composite electrode. The diameter of the matrix corresponds to the diameter d of the manufactured electrode. For the convenience of technological operations, each punch in the initial state is equipped with a base 10.

An example of the manufacture of the composite electrode "MPG-7 graphite - relit (WC · W ₂ C) - MPG-7 graphite". The mold-forming surface of the matrix 7 is rubbed with hexagonal boron nitride powder to prevent particles of carbide material from sintering to the graphite walls. On one side of the matrix 7, a punch 8 of MPG-7 graphite is introduced. The matrix 7 with the punch 8 is installed on the base 10 of the latter, after which a small amount of cobalt or nickel powder is filled (0.010 ÷ 0.015 of the weight of the relyt 11 of the relic 11 measured in the cavity of the matrix 7). Then re-fill the powder of Nickel or cobalt in the same amount as before filling the measured weights of Relit. At the end of the backfill, an upper punch 9 of graphite of MPG-7 material is introduced into the cavity of the matrix 7, and the assembled matrix is placed in the heater of the electrode pressing device (shown). When the temperature reaches 1800-2000 ° C, shrinkage of the backfill begins, and the upper punch 9 is smoothly loaded using a press with the following parameters of the pressing mode:

- time to exit to mode 3-5 min - temperature of the beginning of pressing 2200 ± 30 ° C - the temperature of the end of pressing, 2550 ± 30 ° C - exposure at pressing temperature 20-40 s - pressing pressure 20 ± 2 MPa

At maximum load and a temperature of 2500 ± 30 ° C, make an exposure until the termination of shrinkage.

After that, the temperature is gradually reduced to 1500 ± 50 ° C, after which half the load is removed, and when the temperature reaches 800 ± 50 ° C, the load is completely removed. After cooling, the excess elements (bases 10) of the punches 8.9 are trimmed and the electrode 1 is removed from the matrix 7. In this case, the individual electrodes 3, 4, 5 of the composite electrode 1 are firmly connected by an intermediate eutectic zone 12 (Fig. 1, 2) of width b = (0.2 ÷ 1.0) d with clearly defined boundaries between the compositions of the individual electrodes.

Information sources

1. Application RU No. 99106787, B 23 H 1/04, 1997.03.20, 2001.08.22.

2. Application RU No. 2005125788, B 23 F 3/15, 2005.08.15, 2007.02.20.

Claims (5)

1. The electrode for electric spark alloying made of alloying material, characterized in that it consists of at least two bonded together the ends of the individual electrodes of the same cross section, each of which is made of alloying material of a different composition compared to the composition of the material in contact with it electrodes. 2. The electrode according to claim 1, characterized in that it is composed of two separate electrodes, one of which is made of transition metal carbide, and the other is made of graphite. 3. The electrode according to claim 1, characterized in that it is composed of three separate electrodes, one of which is made of transition metal carbide, and the other two are graphite, and graphite electrodes are located on both sides of the transition metal carbide electrode. 4. The electrode according to claim 2 or 3, characterized in that the length of the transition metal carbide electrode is not more than four diameters of this electrode. 5. A method of manufacturing an electrode for electrospark alloying, comprising hot pressing a powder material in a mold consisting of a matrix and a punch, characterized in that a second punch is introduced into the mold on the opposite side of the matrix, and finished individual electrodes are used as punches, which make up the manufactured electrode.

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