RU2598737C2 - Method for treatment of friction bearing liners - Google Patents

Abstract

FIELD: electrophysics.

SUBSTANCE: invention relates to electrophysical and electrochemical treatment, in particular, to spark-erosion alloying of friction bearing liners. Method includes application on surface of liner an spark-erosion coating of soft material in form of copper, or tin bronze, or tin by spark-erosion alloying, that is carried out first with pulse energy 0.1-0.5 J, and then with pulse energy 0.01-0.05 J. On obtained coating a spark-erosion coating is applied from tin-antimony babbit, then spark-erosion alloying is carried out with a graphite electrode, first with pulse energy 0.2-0.4 J, and then with pulse energy 0.05-0.15 J.

EFFECT: invention enables to obtain on surface of friction bearing liners antifriction babbit coating, providing high quality of liners, their carrier and load capacity, as well as reliability and durability.

4 cl, 28 dwg, 2 tbl, 3 ex

Description

The invention relates to the field of electrophysical and electrochemical processing, in particular to electroerosive alloying, and can be used for surface treatment of liners of plain bearings.

A known method of electroerosive alloying (EEL) of a surface, that is, the process of transferring material to a surface to be treated by a spark electric discharge [N. Lazarenko. Electrospark alloying of metal surfaces. - M.: Mechanical Engineering, 1976].

The method has the following specific features:

- the anode material (alloying material) can form a coating layer on the cathode surface (alloyed surface) that is excessively tightly bonded to the surface, in this case, not only is there no interface between the deposited material and the base metal, but even diffusion of the anode elements into the cathode occurs;

- alloying can be carried out only in the indicated places, without protecting the rest of the surface of the part.

There is also known a method of pouring into chill molds on liners heated to 250 ° C, under pressure and at a temperature of 450-480 ° C of bearing materials from soft metals Sn, Pb, Cd, Sb, Zn, characterized by the presence of solid structural components in a plastic matrix and called babbitt [Garkunov D.N. "Tribotechnology". - M.: Mechanical Engineering, 1989, p. 120-122, 132-133].

A significant drawback of babbits is their low fatigue resistance, especially at temperatures above 100 ° C. With a decrease in the thickness of the bearing, the fatigue resistance increases, while the minimum thickness of the filling of babbit 0.25-0.4 mm is allowed.

Closest to the claimed invention is a method of processing the bearings of the bearings, which consists in tinning the bearings and pouring into the chill molds heated to 250 ° C under pressure and at a temperature of 450-480 ° C antifriction alloy of soft metals. Before pouring the antifriction alloy, an intermediate layer is applied to the surfaces to be filled by EDM alloying using a copper or tin bronze tool electrode at pulse energies of 0.01-0.5 J, followed by the formation of a strong diffusion layer of copper or tin bronze, while tinning copper forms a substitutional solid solution with tin, providing a guaranteed metallic bond [Ukrainian patent No. 64613 A, B23H 1/00, 3/00, 5/00, 2003] (Prototype).

Inserts of plain bearings processed by this method have insufficient reliability and durability due to bearing failure during failure of the babbitt.

The entire arsenal of methods for monitoring the filling of babbitt cannot give a full guarantee of the quality of the fill.

In addition, this method is quite time-consuming due to the processes of tinning and pouring.

The basis of the invention is the task of creating an improved method for processing plain bearing shells by forming an antifriction babbitt coating on the working surface of the liners by electroerosive alloying, which would improve the quality of the shells, bearing and load capacity, reliability and durability of their work, reduce the complexity of manufacturing.

The problem is solved by the fact that in the method of processing liners of sliding bearings, including applying to the liners an erosion coating of soft material by electroerosion alloying with an electrode-tool at pulse energies of 0.01-0.5 J, according to the invention, the coating is made of copper or tin bronze, or tin is applied step by step with an electrode-tool, then an electroerosion coating of tin-antimony babbitt is applied to the formed electrode-tool coating, after which a stepwise electroerosive alloying of the obtained layer with a graphite electrode.

In this case, the electroerosive coating of copper, or tin bronze, or tin is applied using an electrode tool, at least in two stages: first, in modes at pulse energies of 0.1-0.5 J, then in modes at pulse energies of 0 , 01-0,05 J. Moreover, the electroerosive coating of tin-antimony babbitt is applied to the coating of copper or tin bronze, at least in two stages: first in the modes with pulse energies of 0.01-0.05 J, then modes at pulse energies of 0.1-0.4 J, and electroerosion coating of tin-antimony babbi and applied to the tin coating at modes with a pulse energy of 0.1-0.4 J. In addition, to improve the quality of the surface layer, the final electroerosive alloying with a graphite electrode is performed at least in two stages: first, at modes at pulse energies 0.2-0.4 J, then in modes at pulse energies of 0.05-0.15 J.

In order to obtain a thicker layer, the process of applying an erosion coating of tin-antimony babbitt followed by electroerosive alloying with a graphite electrode is repeated several times, starting with the operation of applying a coating of babbitt at modes with pulse energies of 0.1-0.4 J.

The material of the liners may be steel 20.

The hardness of steel 20 is 170-180 kgf / mm ² .

The microhardness of the structure after applying the erosion coating of copper is 75-85 kgf / mm ² .

The microhardness of the structure after applying the electroerosive coating of tin bronze is 75-90 kgf / mm ² .

The microhardness of the structure after applying the electroerosive coating of tin is 30-35 kgf / mm ² .

The microhardness of the structure after applying the erosion coating of tin-antimony babbit is 30-38 kgf / mm ² .

The resulting combined electroerosion coating has a maximum thickness of 1.0 mm after three times processing using an electrode-tool made of tin-antimony babbitt followed by treatment with a graphite electrode. A further increase in the thickness of the layer is possible, but not advisable due to the increase in processing time and decrease in the mechanical strength of babbitt.

An electroerosive coating takes up a large load within the boundaries of the allowable working clearance of a plain bearing - shaft when it is applied in a thin layer. A thin coating reduces the cost of the method. The resulting combined electrical discharge coating has a minimum thickness of 250 μm and a maximum thickness of 1.0 mm.

Inserts of plain bearings processed by the proposed method have high reliability and durability due to the fact that at all stages of the formation of the antifriction coating by electroerosive alloying, a strong metal bond is provided, both between the substrate and the intermediate layer of copper, tin bronze or tin, and with the subsequent layer from tin-antimony babbitt.

The method gives a full guarantee of high quality of the received liners.

In addition, the method is easier to implement in comparison with the method selected as a prototype.

The method can be used both in the manufacture of new liners of plain bearings, and for their repair.

The invention is described in detail in the examples with reference to illustrations, where:

In FIG. 1 shows flat samples of steel 20 for metallographic and durometric studies.

In FIG. 2 shows a flat sample of steel 20 to determine the most rational performance of the EEL process using various electrode materials.

In FIG. Figure 3 shows the profilogram of the surface roughness of the initial sample.

In FIG. 4 shows the installation with a manual vibrator model "Elitron - 22A."

In FIG. Figure 5 shows the profilogram of the surface roughness of the sample after EEL by copper at a pulse energy of W _p = 0.27 J.

In FIG. Figure 6 shows the profilogram of the surface roughness of the sample after EEL by copper at a pulse energy of W _p = 0.05 J.

In FIG. 7 shows a flat sample of steel 20 after EEL with copper.

In FIG. Figure 8 shows a flat sample of steel 20 after EEL with copper and tin-antimony babbit B88.

In FIG. Figure 9 shows the profilogram of sample roughness after doping with a graphite electrode at W _p = 0.13 J.

In FIG. 10 shows a flat sample with a copper sublayer and antifriction tin-antimony babbitt coating.

In FIG. 11 shows the surface of a flat sample with a copper sublayer and antifriction tin-antimony babbitt coating.

In FIG. 12 shows the structure of an antifriction tin-antimony babbitt coating with a copper sublayer.

In FIG. 13 schematically shows the distribution of microhardness over the depth of the formed layer.

In FIG. Figure 14 shows the profilogram of the surface roughness of the sample after EEL by tin bronze at a pulse energy of W _p = 0.13 J.

In FIG. Figure 15 shows the profilogram of the surface roughness of the sample after EEL by tin bronze at a pulse energy of W _p = 0.05 J.

In FIG. 16 shows a sample of steel 20 after EEL with tin bronze.

In FIG. 17 shows a sample of steel 20 after EEL with tin bronze, tin-antimony babbitt and a graphite electrode at W _p = 0.13 J.

In FIG. 18 is a profilogram of the surface of the sample in FIG. 17 after EEL with a graphite electrode at W _p = 0.13 J.

In FIG. 19 shows the structure of antifriction tin-antimony babbitt coating on a sample of steel 20 with a tin bronze sublayer.

In FIG. 20 shows a graph of the distribution of microhardness over the depth of the formed layer on a sample of steel 20 with a tin bronze sublayer.

In FIG. Figure 21 shows the profilogram of the surface roughness of the sample after EEL with tin at a pulse energy of W _p = 0.13 J.

In FIG. 22 shows a profilogram of the surface roughness of the sample after EEL with tin at a pulse energy of W _p = 0.05 J.

In FIG. 23 shows a sample of steel 20 after EEL tin.

In FIG. 24 shows a sample of steel 20 after EEL with tin, tin-antimony babbitt and a graphite electrode at W _p = 0.39 J.

In FIG. 25 shows a sample of steel 20 after EEL with tin, tin-antimony babbitt and a graphite electrode at W _p = 0.13 J.

In FIG. 26 is a profilogram of the sample in FIG. 25 after alloying with a graphite electrode at W _p = 0.13 J.

In FIG. 27 shows the structure of antifriction tin-antimony babbitt coating with a transitional tin sublayer on a flat sample of steel 20, X 200.

In FIG. Figure 28 shows a graph of the distribution of microhardness over the depth of a tin-antimony babbitt coating with a tin sublayer on a steel substrate 20.

For metallographic and durometric studies, flat samples of steel 20 with a size of 15 × 15 × 6 mm were used (Fig. 1). To determine the most rational performance of the EEL process using various electrode materials, a flat sample of steel 20 with a size of 50 × 20 × 5 mm was used (Fig. 2). The surface of the samples was ground to Ra = 0.5 μm (Fig. 3). In FIG. Figure 3 shows the profilogram of the roughness of the initial sample.

EEL samples were produced on the installation with a manual vibrator model "Elitron - 22A" (Fig. 4). The main modes of its operation are given in table. one.

The following materials were used as electrodes: copper, tin bronze of grade BrOF10-1, tin, tin-antimony babbit B88 and graphite of grade EG-4 OST 229-83.

After manufacturing, the sections were examined with a Neofot-2 optical microscope, where the quality of the layer, its continuity, thickness and structure of the sublayer zones — the diffusion zone and the heat-affected zone — were evaluated. At the same time, a durometric analysis was carried out on the distribution of microhardness in the surface layer and along the depth of the thin section from the surface. Microhardness was measured on a PMT-3 microhardness meter by indentation of the diamond pyramid under various loads.

The thickness of the coating layer was measured with a micrometer, and the surface roughness was measured using a profilograph — mode profilometer. 250 factory "Caliber" by removing and processing profilograms. The continuity of the coating was evaluated visually.

To improve the quality of the formed coatings, after each stage of EEL, the surface was treated with a wire brush.

An example embodiment of the invention is the formation of coatings St20 + Cu + B88.

Initially, copper was applied to the surface of the sample. In order to form a coating with maximum continuity and minimum roughness, alloying was carried out in stages, first at a pulse energy of W _p = 0.27 J, then at W _P = 0.05 J (respectively, Fig. 5 and Fig. 6). In this case, the layer thickness decreased from 0.08 to 0.05 mm, and the roughness (Ra) from 10.4 to 6.2 μm. The continuity of the layer was 100% (Fig. 7).

It should be noted that when applying copper at the 2nd stage using a lower alloying mode, electric discharges occur along the protrusions of the roughness of the previously deposited layer, as a result of which they partially collapse and deform, which leads to a decrease in surface roughness and an increase in its continuity.

After each doping step, the formed coating was carefully inspected using a six-fold magnifier to assess the continuity of the applied layer. In the case of identifying untreated areas, the EEL process was repeated.

Copper electrodes are periodically oxidized, which significantly affects the quality of the formed coatings. With prolonged alloying, burns appear, the electrodes are mechanically destroyed and individual particles up to 0.2 mm in size are welded to the alloyed surface. Subsequent treatment with a metal brush eliminates possible disadvantages and, thus, significantly improves the quality of the formed surface.

Next, tin-antimony babbit B88 was applied to the copper coating.

Given the specific features of doping with tin-antimony babbitt and in order to form layers with maximum continuity, the process of forming a babbitt layer was carried out in stages.

First, in order to obtain 100% continuity of the coating and subsequent deposition of tin-antimony babbitt with a lower surface roughness, a regime with a pulse energy of W _p = 0.05 J and then with W _p = 0.27 J was used.

It should be noted that when tin-antimony babbitt is applied to a copper substrate with a pulse energy of more than 0.05 J, the quality of the coating sharply decreases (the continuity decreases and the roughness increases). Tin-antimony babbitt is transferred in the form of separate drops, and the greater the pulse energy, the larger the size of the drops and the lower the continuity of the coating.

The initially deposited tin-antimony babbitt layer at a pulse energy of W _p = 0.05 J accumulates heat and increases the spreading time of the drop when a subsequent layer of babbitt is deposited at higher doping conditions.

In FIG. Figure 8 shows the surface of the sample after EEL with B88 babbit at a pulse energy of W _p = 0.05 J, and then with W _p = 0.27 J.

The surface roughness with an increase in pulse energy from 0.05 to 0.27 J increased from 6.5 to 23 μm, and the thickness of the applied layer was 0.08 to 0.42 mm.

Further, in order to reduce surface roughness, an EEL was coated with a graphite electrode at W _p = 0.39 J, and then at W _p = 0.13 J. Before each treatment with graphite, the coating surface was brushed.

With an EEL with a graphite electrode, electric discharges flow along the protrusions of the microroughnesses of the surface of the previously deposited coating. At the same time, they melt, reduce the height of the microroughness and spread the coating material over a large area, thereby increasing the continuity of the tin-antimony babbitt coating. The total coating thickness after doping with B88 babbit and subsequent processing with a graphite electrode was 0.35 mm, and the roughness (Ra) was 8.6 μm (Fig. 9).

To obtain a thicker layer, electroerosive alloying with a tin-antimony babbitt electrode-tool followed by treatment with a graphite electrode can be repeated several times, starting from processing at pulse energies of 0.27 J. The total coating thickness can be obtained up to 1.0 mm In FIG. 10, FIG. 11 shows a flat sample with a copper sublayer and an antifriction tin-antimony babbitt coating 1.0 mm thick.

In FIG. 12 shows the structure of an antifriction tin-antimony babbitt coating with a copper sublayer on a sample of steel 20, X 400, and FIG. 13 shows a graph of the distribution of microhardness over the depth of the formed antifriction layer on a steel substrate 20.

Analysis of the structure of the tin-antimony babbitt coating with a copper sublayer (Fig. 12) showed that the formed layer consists of 4 zones. The uppermost layer with a thickness of up to 300 μm and a microhardness of N _µ = 24-36 kgf / mm ² of babbitt, below is a layer of copper, the depth of which is within 50 μm, and a microhardness of N _µ = 75-85 kgf / mm ² . Even lower, between copper and steel 20, there is a transition zone with a depth of 10-20 microns and N _µ = 95-120 kgf / mm ² . Further, as it deepens, the microhardness gradually increases to the microhardness of the heat affected zone (220-240 kgf / mm ² ) and then goes into the microhardness of the base metal N _µ = 175-180 kgf / mm ² .

The next example embodiment of the invention is the formation of coatings St20 + BrOF10-1 + B88

Initially, tin bronze of the BrOF10-1 brand was applied to the surface of the sample. In order to form a coating with maximum continuity and minimum roughness, alloying was carried out in stages, first at a discharge energy of W _p = 0.13 J, then at W _p = 0.05 J, respectively, FIG. 14a and FIG. 15. The thickness of the layer decreased from 0.10 to 0.05 mm, and the roughness (Ra) from 30.2 to 7.3 microns. The continuity of the layer was 100% (Fig. 16).

It should be noted that when applying tin bronze at the 2nd stage using a lower alloying mode, electric discharges occur along the protrusions of the roughness of the previously deposited layer, as a result of which they partially collapse and deform, which leads to a decrease in surface roughness and an increase in its continuity.

The tin bronze electrodes are periodically oxidized, which significantly affects the quality of the formed coatings. Subsequent treatment with a metal brush eliminates possible disadvantages and thus significantly improves the quality of the formed surface.

Further, B88 babbitt was gradually applied to the bronze coating, followed by graphite treatment, and the babbitt and graphite were applied in the same modes and in the same sequence as on the sample with a copper sublayer. In FIG. 17 shows a sample of steel 20 after EEL with tin bronze, B88 babbitt and a graphite electrode at W _p = 0.13 J.

The total coating thickness after alloying with B88 babbit and subsequent processing with a graphite electrode was 0.40 mm, and the roughness (Ra) was 8.6 μm in accordance with the profilogram of the sample surface after alloying with a graphite electrode at W _p = 0.13 J (Fig. 18) .

To obtain a thicker layer, electroerosive alloying with a tin babbitt tool electrode followed by treatment with a graphite electrode can be repeated several times, starting from processing at pulse energies of 0.27 J. After three such procedures, a total coating thickness of up to 1 mm can be obtained.

In FIG. 19 shows the structure of antifriction tin-antimony babbitt coating on a sample of steel 20 (X 200), with a tin bronze sublayer. Analysis of this structure (Fig. 19) showed that the formed layer consists of 4 zones. The uppermost layer with a thickness of up to 350 μm and a microhardness of N _µ = 24-36 kgf / mm ^{2 is} made of B88 babbitt, a layer of tin bronze is located below, the depth of which is in the range of 50-80 μm, and the microhardness of N _µ = 75-90 kgf / mm ² . Even lower, between tin bronze and steel 20, there is a transition zone up to 10 μm deep, in which, as it deepens, the microhardness smoothly increases to the microhardness of the heat-affected zone (250-300 kgf / mm ² ), and then, decreasing, passes into the microhardness of the main metal N _µ = 175-180 kgf / mm ² . The microhardness distribution diagram over the depth of the above-formed layer on a steel substrate 20 is shown in FIG. twenty.

Another example embodiment of the invention is the formation of coatings St20 + Sn + B88

Initially, tin was deposited on the surface of the sample. In order to form a coating with maximum continuity and minimum roughness, alloying was carried out in stages, first at a discharge energy of W _p = 0.13 J, then at W _p = 0.05 J (respectively, FIG. 21 and FIG. 22). In this case, the layer thickness decreased from 0.10 to 0.07 mm, and the roughness (Ra) from 32.7 to 14.8 μm. The continuity of the layer was 100% (Fig. 23).

It should be noted that when tin is deposited at the 2nd stage using a lower alloying mode, electric discharges occur along the protrusions of the roughness of the previously deposited layer, as a result of which they partially collapse and deform, which leads to a decrease in the surface roughness and an increase in its continuity. B88 babbitt was applied to the tin coating at W _p = 0.27 J.

Further, in order to reduce surface roughness, an EEL was coated with a graphite electrode at W _p = 0.39 J, and then at W _p = 0.13 J (respectively, Fig. 24 and Fig. 25). Before each graphite treatment, the coating surface was brushed.

The total coating thickness after doping with B88 babbit and subsequent processing with a graphite electrode was 0.35 mm, and the roughness (Ra) was 8 μm (Fig. 26).

To obtain a thicker layer, electroerosive alloying with a tin-antimony babbitt electrode-tool followed by treatment with a graphite electrode can be repeated several times, starting from processing at pulse energies of 0.27 J. After three such procedures, the total coating thickness was 0.9 mm.

In FIG. 27 shows the structure of the antifriction coating after three steps of applying tin-antimony babbitt on a steel sample 20 with a transition layer of tin, and in FIG. Figure 28 shows the microhardness distribution curve over the depth of the formed layer with a tin sublayer on a steel substrate 20.

Analysis of the structure of the tin-antimony babbitt coating with a tin sublayer (Fig. 27) showed that the formed layer consists of 3 zones. The uppermost layer with a thickness of up to 900 μm and a microhardness of N _µ = 24-36 kgf / mm ² consists of B88 babbitt and tin, below which is a transition zone up to 10 μm deep, in which, as it deepens, the microhardness gradually increases to the microhardness of the heat affected zone (200- 220 kgf / mm ² ) and then goes into the microhardness of the base metal N _µ = 175-180 kgf / mm ² .

In the table. Figure 2 shows the regimes of the phased deposition of antifriction coatings of tin-antimony babbitt with a sublayer of copper, tin bronze and tin, as well as the layer thickness and surface roughness at each stage of EEL.

Claims (4)

1. A method of processing liners of sliding bearings, comprising applying to the surface of the liners an erosion coating of soft material, characterized in that the surface of the liners is coated with a soft material in the form of copper, or tin bronze, or tin by EDM, which is carried out first with energies a pulse of 0.1-0.5 J, and then with a pulse energy of 0.01-0.05 J, and an erosion coating of tin-antimony babbitt is applied to the resulting coating, after which electroerosion is performed first alloying with a graphite electrode, first with a pulse energy of 0.2-0.4 J, and then with a pulse energy of 0.05-0.15 J. 2. The method according to p. 1, characterized in that the erosion coating of tin-antimony babbitt on a coating of copper or tin bronze is applied in two stages, first with a pulse energy of 0.01-0.05 J, then with a pulse energy of 0 , 1-0.4 J. 3. The method according to p. 1, characterized in that the erosion coating of tin-antimony babbitt on the coating of tin is applied with a pulse energy of 0.1-0.4 J. 4. The method according to p. 1, characterized in that the deposition of an erosion coating of tin-antimony babbitt followed by electroerosive alloying with a graphite electrode is repeated several times, starting with the operation of coating from babbitt with a pulse energy of 0.1-0.4 J.

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