RU2366756C1 - Method of application of coating on interrupting aluminium contacts of electric commutating devices - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to electric apparatus building and to systems of electric power supply, particularly to methods of application of coating on interrupting aluminium contacts of electric commutating devices. The method consists in ion-plasma sputtering of chromium copper on a treated contact at reference voltage on it of 90-120 V and at multiple changes of voltage during sputtering up to 1000-1200 V and back to a reference one and at frequency 1-2 times per each micrometer of sputtered coating thickness. At voltage 1000-1200 V duration of sputtering is 0.2-0.4 from time of coating sputtering of a micron thickness. Chromium copper alloyed with yttrium at amount of 0.2-0.6 wt % is used for sputtering.

EFFECT: increased operation life of aluminium current conducting parts of electric commutating devices.

1 dwg, 2 tbl, 1 ex

Description

The invention relates to electrical equipment and power supply systems and can be used for surface treatment of contact joints, in particular explosive aluminum contacts of electrical switching devices.

A known method of producing electrical contacts and welding electrodes from a mixture containing from 20 to 90% of a refractory metal component (tungsten, molybdenum, tungsten carbide, molybdenum carbide), from 0.1 to 1.0% yttrium and the rest, including the formation of powder molding from a refractory metal component, its sintering, after which it will contain interconnected (through) pores, filling these pores with a copper-yttrium alloy by percolation (infiltration) or impregnation (impregnation). The infiltration process is carried out by placing a solid copper-yttrium alloy on a base of refractory metal in contact with its pores and heating in a reducing atmosphere or vacuum to the melting temperature of copper. The melting copper-yttrium alloy is absorbed by the pores of the refractory metal base due to capillary attraction. One of the options of this method is mixing the powder of copper-yttrium alloy and powder of refractory metal together, compressing the mixture and then sintering it at a temperature either near or below the melting temperature of copper. Moreover, in both versions of the method, a copper-yttrium alloy can be formed either before introduction into the refractory metal matrix, or it can be formed during the infiltration procedure (US No. 3272603, CL 29-191, 1966).

The disadvantage of this method is the impossibility of using it to protect the surface of aluminum contacts, since the operations used in it involve the production of electrodes that are homogeneous in composition and material properties throughout the electrode volume.

Closest to the claimed is a method of obtaining a coating for electrical contact, which consists in ion-plasma sputtering of a coating of a double copper-chromium alloy with a content of 0.4-1.0% chromium according to a regime that provides multiple stepwise voltage changes from 90-120 to 1000 -1200 V and vice versa, the frequency of voltage changes being 1-2 times per micrometer of the coating thickness, and the duration of spraying at 1000-1200 V is 0.2-0.4 of the time of coating spraying with a thickness of 1 micrometer (SU No. 1628564, C. C23C 14/54, 1989).

The disadvantage of this method is that the resulting coating, when applied to rupture aluminum contacts of electrical switching devices operating when an electric discharge occurs during repeated switching (relays, starters, regulators), does not protect the contact working surfaces from electrical discharge erosion.

The objective of the invention is to increase the wear resistance of the surface of explosive aluminum contacts of electrical switching devices.

The technical result is to increase the service life of aluminum conductive parts of electrical switching devices.

The task and the specified technical result are achieved by the fact that in the method of coating rupture aluminum contacts of electrical switching devices, including ion-plasma deposition of chromium bronze on the contact being processed at a reference voltage of 90-120 V on it, multiple voltage changes during deposition up to 1000- 1200 V and back to the reference one with a frequency of 1-2 times per micrometer of the thickness of the sprayed coating and with a duration of spraying at a voltage of 1000-1200 V equal to 0.2-0.4 of the spraying time I micron thickness, according to the invention is sprayed chromium bronze doped yttrium in an amount of 0.2-0.6% by weight.

The use of an ion-plasma coating of chrome-plated bronze doped with yttrium on aluminum conductive parts can reduce the number of bridges formed by increasing the melting temperature of the contact surface material, as well as reduce the burn-out of the surface of aluminum parts in microarc zones due to the higher oxidation resistance of the doped chromium bronze.

The content of the alloying element is due to the following. A decrease in the yttrium content of less than 0.2% of the mass does not lead to an increase in heat resistance, therefore, the electroerosion resistance of the coating, and an increase in the yttrium content of more than 0.6% of the mass leads to a loss of plasticity of the coating, which reduces its fatigue resistance.

The method is as follows. Chromium bronze doped with yttrium in an amount of 0.2-0.6% of the mass is placed on the sprayed end surface of the cathode made of Ml copper. The cathode is placed in the cathode assembly of an electric arc evaporator of an ion-plasma spraying apparatus. The reference voltage is applied and the cathode surface is sprayed in vacuum at an arc current of 90-95 A to obtain a coating layer on the workpieces. After coating with a thickness of 0.3-0.5 microns, the voltage value is abruptly changed to 1000-1200 V, while the ion bombardment process is strengthened while the ion deposition process is reduced. High voltage is maintained for 0.2-0.4 of the time of supply of the reference voltage. During this time, a mechanothermal effect on the sprayed layer with its hardening occurs. After the indicated time, the high voltage is reduced to the reference one and the indicated cycle is repeated repeatedly so that the number of voltage surges is 1-2 for each micrometer of the thickness of the sprayed coating.

The invention is implemented in laboratory conditions on a modernized installation of ion-plasma spraying VU-1B. The alloys of chromium bronze BrX0.5 were alloyed by fusing it in induction furnaces with yttrium powder of the grade “Y _M -1” with a yttrium content of 98.74% and subsequent manufacture of alloys from the alloys, which were then fixed on the sprayed end surface of the copper cathode.

Example 1. To prepare the alloy with a yttrium content of 0.1% of the mass, weighed samples of BrX0.5 chromium bronze shavings in an amount of 799.19 g and yttrium powder 0.81 g. The mixture was mixed, loaded into a zirconium crucible and placed in an induction furnace with argon purge. The melting time was 30–40 min at a temperature of ~ 1600 ° C on the scale of an optical pyrometer. The obtained ingot was machined according to the dimensions of the cathode of the electric arc evaporator of the installation, a plate was cut from it, which was mechanically fixed on the end surface of the copper cathode made of Ml copper.

Other examples of the calculation of yttrium alloys are given in table 1.

Table 1 The content of components in the charge % Y content in the alloy 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 The mass of the powder Y _M -1 1,62 2.43 3.52 4.05 4.86 5.67 6.48 7.3 Weight of bronze shavings 798.38 797.57 796.48 795.95 795.14 794.33 793.52 792.7

Testing of the samples with the coatings was carried out on the original bench (Izmailov V.V., Novoselova M.V. To the development of methods for accelerated assessment of the electrical discharge erosion resistance of electrical contact materials. - Bulletin of the Tver State Technical University - Tver: TSTU, 2003, issue 3. - С .14-20; Izmailov V.V., Novoselova M.V. Method for assessing the electrical discharge erosion resistance of materials for electrical contacts. RU 2265862, class G01R 31/333, 2005).

A diagram of the working node of the stand is shown in the drawing. An electrode 1 made of a tungsten wire with a diameter of 1 mm is cyclically contacted with an aluminum sample 2, the surface of which is coated. The sample is placed in a brass sleeve 3, in which is fixed a pressure plate 4 having a central hole. The sleeve 3 is mounted on a micrometer screw 5, with which you can adjust both the distance between the contacts and the force in the contact. The presence of conductivity in the contact is recorded by a high-speed self-recording voltmeter.

The tests were carried out in the normal (not forced) mode. In this case, the switching frequency was adopted in accordance with GOST 24606.6-83 equal to 1 Hz, the distance between the contacts is 5 mm, the voltage is 220 V, the current strength was 1 and 5 A. The failure was assumed to be the absence of conductivity in the contact for ten consecutive switching operations.

The test results are shown in table 2.

table 2 Amperage The yttrium content in the coating material,% mass. 0 0.1 0.2 0.3 0.5 0.6 0.7 0.8 1A 22 thirty 54 63 87 116 32 25 5A 10 12 35 42 61 56 17 9 visible coating wear

Currently, the invention is at the stage of experimental laboratory testing.

Claims (1)

The method of coating rupture aluminum contacts of electrical switching devices, including ion-plasma deposition of chromium bronze on the contact being processed at a voltage reference of 90-120 V, multiple voltage changes during deposition to 1000-1200 V and back to the reference voltage with a frequency of 1-2 times for each micrometer of the thickness of the sprayed coating and with a duration of spraying at a voltage of 1000-1200 V equal to 0.2-0.4 of the time of spraying of the coating of micron thickness, characterized in that they spray chromium bronze, doped yttrium in an amount of 0.2-0.6 wt.%.

Images