RU2524467C1 - Method of treating friction bearing liners - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes depositing a composite electrospark coating on a liner by electrospark doping using a tool electrode. A layer of silver is first deposited on the working surface of the liner with pulse energy W_u=0.1-0.3 J, a layer of lead is then deposited on the layer of silver with pulse energy W_u=0.3-0.4 J and another layer of silver is then deposited on the layer of lead with pulse energy W_u=0.04-0.10 J.

EFFECT: improved conformability of friction bearing liners, high reliability and longevity thereof.

11 dwg, 3 tbl

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 bearing shells.

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

The method is characterized by 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 a method of pouring in 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 the plastic matrix and called babbit [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 liners of plain bearings, comprising sequentially depositing liners on the working surfaces by electroerosive alloying with an electrode-tool of an erosion coating of silver at pulse energies of 0.01-0.5 J, an erosion coating of copper at pulse energies 0.01-0.5 J, erosion coating of tin babbit at pulse energies of 0.01-0.06 J to obtain a combined erosion coating [RU No. 2299790 C1, B 23H 1/00, 2007].

Despite the possibility of manufacturing combined electroerosion coatings (CEP), formed in the sequence silver + copper + babbitt up to 250 microns thick, only coatings up to 25-30 microns thick can be recommended for practical use. A further increase in the layer thickness leads to a sharp increase in surface roughness from Ra = 0.8-1.0 μm to Ra = 11.0-12.0 μm and a decrease in continuity from 95-100% to 40-50%.

Therefore, the use of bearing shells treated with the above method does not always lead to the desired result due to the small thickness of the coating. Due to the need to compensate for mounting errors in bearings, in toughened operating conditions (high speed and high specific pressures) during running-in, the working surface of the bearing shell may seize due to insufficient thickness of the antifriction layer.

The basis of the invention is the task of improving the working conditions of the bearings of the bearings, increasing the reliability and durability.

The problem is solved in that in the method of processing the bearings of the bearings, including applying to the liners of a comprehensive electrical discharge coating containing a layer of silver, by electroerosive alloying with an electrode tool, according to the invention, a layer of electrical discharge coating is applied to the working surfaces of the inserts with an electrode tool silver at a pulse energy of W _u = 0.1-0.3 J, then a coating layer of lead is applied to the silver layer by the same method at a pulse energy of W _u = 0.3-0.4 J, after which, in the same manner, another silver coating layer is applied to the lead layer at a pulse energy of W _u = 0.04-0.10 J.

The technical result of the use of the present invention is to increase the thickness of the running-in coating of soft metals, which provides an improvement in the working conditions of the liners.

The bearing shells processed by the proposed method have higher reliability and durability.

The invention is illustrated by illustrative material.

Figure 1 shows the topography of the surface area of the sample from bronze with a CEC made of soft metals (copper, silver, tin, lead, babbit grade B83), on which three characteristic points are selected: 1 - protrusion (smooth surface), 2 - cavity (rough surface), 3 - time;

figure 2 shows the spectrum of the surface at a characteristic point of the protrusion in figure 1;

figure 3 - surface spectrum at a characteristic point of the depression in figure 1;

figure 4 is a spectrum at a characteristic pore point in figure 1;

figure 5 is a spectrum from the entire surface of figure 1;

Fig. 6 shows a topography of a surface portion of a bronze sample with a silver and lead CEC according to the invention, on which three characteristic points are selected: 1 — protrusion (smooth surface), 2 — depression (rough surface), 3 — pore;

in Fig.7 shows the spectrum of the surface at a characteristic point 1 in Fig.6 is a ledge;

on Fig - surface spectrum at characteristic point 2 in Fig.6 - depression;

figure 9 is a spectrum at a characteristic point 3 in figure 6 - time;

figure 10 presents the scan points of the element-by-layer composition of the coating along the depth of the layer;

11 shows the microstructure of the surface layer of bronze bearing shells with a combined coating of silver and lead.

The present invention was the result of research aimed at increasing the thickness of the running-in coating of soft metals (copper, silver, tin, lead, babbit brand B83).

To further study the topography and composition of the surface layers of bronze bearing shells coated with silver + copper + babbit coated, research was conducted on a scanning electron microscope REMMA-102 manufactured by OJSC “SELMI” in Sumy, equipped with an X-ray spectrometer based on a silicon lithium semiconductor detector.

Microphotographs of the surface areas of the samples under study were obtained in the imaging mode by the current of secondary electrons at an accelerating voltage on the electron gun of the microscope of 20 kV and a probe current (beam) of 200 pA.

The spectrum of the surface and the element-by-element composition both at characteristic points and from the entire investigated surface are shown in FIG. 2, FIG. 3, FIG. 4, FIG. 5 and Table 1, respectively. In accordance with the images in the above illustrations and data listed in Table 1, at all characteristic points there are elements that are part of the CEP.

Table 1 The element composition of the coating at characteristic points and from the entire investigated surface Investigated point, surface area (Σ) Elements,% Cu Zn Ag Sn Pb one 32.857 1.262 23.939 38,673 3.269 2 25.391 1.448 20.984 49.606 2.571 3 27.97 3.441 15.291 50.094 3.201 Σ 26.854 2.920 16.939 50.347 2.940

The distribution of elements as the surface layer deepens, with a scan step of 5 μm, is presented in Table 2.

table 2 The element composition of the coating by the depth of the surface layer The investigated point of the surface Elements,% Cu Zn Ag Sn Pb one 61.832 1.909 6.070 27,247 2.942 2 73.057 3.679 3.070 18,269 1.924 3 55.913 2.288 7.430 28.903 5.466 four 63.844 2.828 0.892 26,344 6,092 5 78.721 5.618 0.000 13.13 2.531 6 84.492 5.244 0.737 7.169 1.303 7 86.832 6.084 0,000 5,355 1.729

As can be seen from Figures 2-5 and Tables 1 and 2, the surface layer formed by the EEL consists of elements of alloying electrodes and a substrate. The running-in coating thickness is 30 μm.

Figure 6-9 shows, respectively, the topography and the spectrum of characteristic points of the surface area of the bronze samples with CEC containing silver and lead.

The element composition of the coating at characteristic points on the surface of the bronze sample with a CEP containing silver and lead is presented in Table 3.

The distribution of elements as the surface layer deepens during scanning, according to FIG. 10, is also presented in Table 3.

Table 3 The element composition of the coating by the depth of the surface layer Surface point Elements,% Cu Zn Ag Sn Pb one 22.284 0.000 45.894 0.000 31.822 2 52.032 0.000 24.064 0.000 23.904 3 48.569 0.000 24.318 0.000 27.113 four 44.892 0.000 37.820 0.000 17.288 5 60.235 2.011 17.760 0.000 19.993 6 69.678 2.273 9.035 3.384 15.630 7 50.181 1.739 28.917 1.584 17.578 8 83.297 3.998 1.909 2.652 8.144 9 87.348 3.726 0.603 6.749 1.572 10 90.937 3.579 0.166 4.777 0.542

The best results were obtained when forming a running-in coating using silver and lead electrodes. The method of applying CEC of the present invention was carried out as follows.

First, silver was erosion-coated at a pulse energy W _u = 0.1-0.3 J on the working surfaces of bronze bearing shells using a tool electrode. After that, a lead coating was applied onto a silver coating by the same method at a pulse energy W _u = 0.3-0.4 J. The third layer was applied electrical discharge coating also of silver at a pulse energy of W _u = 0.04-0.10 J.

The first layer of silver was applied at a pulse energy of W _u = 0.1-0.3 J, while the productivity of the process was in the range 1.0–2.0 cm ² / min, the layer thickness was in the range 30–35 μm, and roughness (Rz), respectively, is 3.6-4.0 microns. The decrease in pulse energy entails an increase in the process productivity, a decrease in the layer thickness and a slight decrease in surface roughness. An increase in the pulse energy does not lead to an increase in the layer thickness, but only to an increase in the surface roughness.

The second layer of lead was applied at a pulse energy of Wu = 0.3-0.4 J, while the process productivity was in the range of 2.0-3.0 cm ² / min, the layer thickness was in the range of 80-130 μm, and the roughness (Rz), respectively, 26-32 microns. The decrease in pulse energy entails an increase in the process productivity, a decrease in the layer thickness and a slight decrease in surface roughness. An increase in the pulse energy leads to a slight increase in the layer thickness and to a sharp increase in the surface roughness.

The third layer of silver was applied at a pulse energy of W _u = 0.04-0.1 J, while the productivity of the process was in the range 0.2–2.0 cm ² / min, the layer thickness was in the range 80–120 μm, and roughness (Rz), respectively, is 3.6-4.0 microns. The decrease in pulse energy leads to an increase in process productivity and a slight decrease in surface roughness. An increase in the pulse energy leads to a sharp increase in surface roughness.

To prevent deformation of the lead electrode, it was periodically (~ 30 s) cooled in water.

Received CEC with a maximum thickness of 120 microns.

As a result of metallographic studies, it was found that when a silver and lead CEC is applied to a bronze substrate, the surface layer consists of three zones (Fig. 11).

The upper layer (a layer of reduced hardness) with a microhardness of 600 MPa extends to a depth of 70 ... 80 microns.

Below is a transition zone (zone of increased hardness) with a microhardness of 1270 ... 1400 MPa and a depth of 50 ... 60 microns. The microhardness in the transition zone increases due to quenching processes occurring as a result of EEL. As deepening, the microhardness in the transition zone decreases and passes into the microhardness of the base (1050 ... 1100 MPa).

As an example of the implementation of the method according to the invention, a method for processing liners of bronze was used, however, experience shows that the proposed method can be used for the manufacture of liners of bearings made of other metals, for example, steel 20 or antifriction cast iron (grades AChTs-1, AChTs-2 and etc.).

Compared with the prototype, the plain bearing shells processed by the proposed method have higher reliability and durability due to the fact that with the achieved thickness of the CEC, providing compensation for the installation errors of the bearing, the plain bearing will remain operational even if the coating is destroyed.

Claims (1)

A method of processing liners of sliding bearings, comprising applying to the liner a comprehensive electroerosive coating containing a layer of silver by electroerosive alloying with an electrode tool, characterized in that a layer of an erosion coating of silver is applied to the working surface of the liner with an electrode tool at a pulse energy W _u = 0.1-0.3 J, then a coating layer of lead is applied to the silver layer in the same manner at a pulse energy of W _u = 0.3-0.4 J, after which a layer of lead is applied one more layer of silver erosion coating at a pulse energy of W _u = 0.04-0.10 J.

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