RU2765925C1 - Method for processing bronze inserts of sliding bearings (options) - Google Patents

Abstract

FIELD: electrical discharge alloying.

SUBSTANCE: invention relates to the field of electrophysical and electrochemical processing, in particular to electric spark alloying, and can be used to treat the surfaces of bronze inserts of sliding bearings. The method includes sulfidation and application to the working surfaces of inserts by the method for electrospray alloying of combined electrospray coatings (CESC) with tool electrodes with the formation of a sequence of layers: silver - soft metal in the form of lead or tin - silver. In this case, the treated surfaces are subjected to sulfidation before each application of a layer of silver. A layer of silver is applied at a pulse energy of Wu = 0.52-4.6 J, a layer of lead or tin is applied to a layer of silver at a pulse energy of Wu = 0.13-4.6 J or Wu = 0.36-4.6 J, respectively, another layer of silver is applied to a layer of lead or tin at a pulse energy of Wu = 0.05-0.36 J.

EFFECT: invention makes it possible to obtain a CESC with a thickness of 0.19-1.31 mm, which simplify further machining of the surfaces of bronze inserts of sliding bearings by improving the conditions of running-in of the inserts of sliding bearings, increasing their reliability and durability in operation.

6 cl, 22 dwg, 6 tbl

Description

The invention relates to the field of electrophysical and electrochemical processing, in particular to electroerosive (electrospark) alloying, and can be used for surface treatment of bearing shells.

There is a method of electrospark alloying (EIL) of the surface, that is, the process of transferring material to the surface to be treated by a spark electric discharge [Lazarenko NI Electrospark alloying of metal surfaces. - M.: Mashinostroenie, 1976].

The method is characterized by the following specific features:

- the anode material (doping material) can form on the cathode surface (doped surface) a coating layer that adheres extremely strongly 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 remaining surfaces of the part.

There is also known a method of processing bronze liners (BV) of plain bearings (PS), including applying to the liners by the method of electrospark alloying using an electrode-tool of an electrospark coating of silver at a pulse energy of 0.01-0.05 J, then an electrospark coating of copper at pulse energies of 0.01-0.5 J, after that - an electrospark coating of tin babbitt at pulse energies of 0.01-0.06 J to obtain a combined electrospark coating (CEIP) [RU No. 2299790 C1, IPC V23N 1/00. Processing method for bearing shells / B.C. Martsinkovsky, V.B. Tarelnik, V.A. Pchelintsev / Publ. May 27, 2007, Bull. No. 15].

Despite the possibility of manufacturing CEIPs obtained in the sequence silver → copper → babbit up to 250 µm thick, only a coating up to 25–30 µm thick can be recommended for practical use. A further increase in the thickness of the coating layer 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%. Thus, the use of bronze bearing shells processed in the above way does not always lead to the desired result due to the small thickness of the coating. Due to the need to compensate for bearing installation errors, under severe operating conditions (high number of revolutions and high specific pressure) during running-in, scuffing of the working surface of the bearing shell may occur due to insufficient thickness of the anti-friction layer.

The closest to the claimed technical solution is a method of processing bearing bushings, including applying combined electric spark coatings (CEIP) to the working surfaces of the bearings using the ESA method with tool electrodes with the formation of layers on the working surfaces in the sequence: silver - soft metal - silver. At the same time, a silver layer is first applied at a pulse energy Wu=0.1-0.3 J, then a lead coating layer is applied to the silver layer at a pulse energy Wu=0.3-0.4 J, after which another one silver layer at pulse energy Wu=0.04-0.10 J, moreover, the process productivity is 0.2-2.0 cm/min, the layer thickness is in the range of 80-120 μm, and the roughness (Rz), respectively , - 18-24 microns [UA No. 105965 C2, V23N 5/00. Cnoci6 forgings forging inserts / Martsinkovsky V.C., V.B. Tarelnik, O.V. Dzyuba / Publ. 02/15/2014, Bull. No. 13].

It should be noted that CEIP obtained in the sequence silver → lead → silver have surface roughness (Rz) in some areas - up to 24 µm, significant waviness - up to Wmax=70 µm, and continuity - up to 85%. Such anti-friction coatings, when applied to bronze PS liners, require further processing to improve the surface quality parameters and prevent the contact surfaces from setting. At the same time, a thickness of 120 microns is not enough for further processing by any known method: boring, milling, surface plastic deformation (SPD) processing, non-abrasive ultrasonic finishing (BUFO), etc. Thus, the process of forming running-in coatings on the working surfaces of bronze bearing shells requires further improvement.

The basis of the claimed invention is the task of improving the running-in conditions of bearing shells, increasing their reliability and durability in operation.

The problem is solved by the fact that in the method of processing bronze bushings of plain bearings, including sulfiding and applying on the working surfaces of the liners by the method of electrospark alloying of combined electrospark coatings with electrodes-tools with the formation of layers in the sequence: silver - soft metal - silver, according to the invention, a layer of silver is applied at pulse energy Wu=0.52-4.6 J, a layer of lead is applied to the silver layer at pulse energy Wu=0.13-4.6 J, another layer of silver is applied to the lead layer at pulse energy Wu=0.05 -0.36 J, while the treated surfaces are sulfided before each application of a layer of silver.

The problem is also solved by the fact that in the method of processing bronze bushings of plain bearings, including sulfiding and applying to the working surfaces of the liners by the method of electrospark alloying of combined electrospark coatings with electrodes-tools with the formation of layers on the working surfaces in the sequence: silver - soft metal - silver, according to the invention , a silver layer is applied at pulse energy Wu=0.52-4.6 J, a tin layer is applied to the silver layer at pulse energy Wu=0.36-4.6 J, another layer of silver is applied to the tin layer at pulse energy Wu = 0.05-0.36 J, while the treated surfaces are sulfided before each application of a layer of silver.

In both cases, sulfuric ointment with a sulfur concentration of 33.3% is used for sulfiding.

Also, in both versions, a coating thickness of 0.19-1.31 mm is provided.

The proposed technology for obtaining CEIP allows for a coating thickness of 0.19-1.31 mm, which simplifies further mechanical processing of surfaces. The problem of improving the running-in conditions of plain bearing shells, increasing their reliability and durability in operation has been solved.

The invention is illustrated by drawings.

On FIG. 1 shows a diagram of a friction pair of the T-01 M tribological tester: 1 - ball, 2 - disk;

in FIG. 2 - microstructure after etching in a hydrochloric acid solution of ferric chloride sample No. 1;

in FIG. 3-distribution of the microhardness of the surface layer after etching in a hydrochloric acid solution of ferric chloride sample No. 1;

in FIG. 4 - microstructure after etching in a hydrochloric acid solution of ferric chloride sample No. 2;

in FIG. 5 - microhardness distribution of the surface layer after etching in a hydrochloric acid solution of ferric chloride sample No. 2;

in FIG. 6 - microstructure after etching in a hydrochloric acid solution of ferric chloride sample No. 3;

in FIG. 7 - microhardness distribution of the surface layer after etching in a hydrochloric acid solution of ferric chloride sample No. 3;

in FIG. 8 - microstructure of sample No. 4 without etching;

in FIG. 9 - distribution of microhardness of the surface layer of sample No. 4 without etching;

in FIG. 10 - microstructure of sample No. 5 without etching;

in FIG. 11 - distribution of microhardness of the surface layer of sample No. 5 without etching;

in FIG. 12 - microstructure of sample No. 6 without etching;

in FIG. 13 - distribution of microhardness of the surface layer of sample No. 6 without etching;

in FIG. 14 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of an uncoated bronze disk sample No. 0;

in FIG. 15 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disk coated with S + Ag → Pb → S + Ag sample No. 1;

in FIG. 16 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disk coated with S + Ag → Pb → S + Ag sample No. 2;

in FIG. 17 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disk coated with S + Ag → Pb → S + Ag sample No. 3;

in FIG. 18 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disc coated with S+Ag→Sn→S+Ag sample No. 4;

in FIG. 19 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disk coated with S+Ag→Sn→S+Ag sample No. 5;

in FIG. 20 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disc coated with S+Ag→Sn→S+Ag sample No. 6;

- in Fig. 21 - the nature of the change in the friction force Ft - in FIG. 1 steel ball on the surface of a bronze disc coated with Ag→Pb→Ag sample No. 7;

in FIG. 22 shows comparative diagrams of the change in friction forces for all series of samples at a load of 9.81 N.

To conduct metallographic and durometric studies of running-in coatings applied by the ESA method, samples of 15 × 15 × 6 mm in size were made from BrO10C10 bronze with a hardness of 1235 MPa. In this case, silver (Ср 999), lead (C1), and tin (O1) were used as the electrode material. In order to determine the effect of sulfiding on the quality parameters of the formed surface layer on bronze BrO10C10, three series of samples No. 1-6 were made, hardened according to Table 1:

The first series - without the use of sulfur;

The second series - sulfur in the form of a sulfur ointment with a sulfur concentration of 33.3% was applied to the treated surface before each application of silver: S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag;

The third series - sulfur in the form of a sulfuric ointment was applied to the treated surface before each stage of electrospark alloying: S+Ag→S+Pb→S+Ag and S+Ag→S+Sn→S+Ag.

The surface roughness after ESA was determined on a profilograph-profilometer mod. 201 plant "Caliber" by taking and processing profilograms. The metallographic analysis of the coatings was performed using an MIM-7 optical microscope; durametric studies were carried out on a PMT-3 instrument according to standard methods.

The tribological properties of the running-in coatings were determined on a T-01M tester according to the "ball-disk" scheme, Fig. 1. Rings 42 × 25 × 6 mm in size, made of bronze BrO10S10, were chosen as samples for research. Sulfuric ointment with a sulfur concentration of 33.3% was applied during the formation of CEIP, before each doping with silver in sequence and at the discharge energy, according to Table 1, for samples Nos. 1-6. In addition, we studied sample No. 0 - without coating and sample No. 7 with CEIP obtained by ESA in the sequence Ag→Pb→Ag at pulse energies, respectively: 0.9; 0.36 and 0.36 J.

Characteristics of the process of formation of running-in CEIPs on substrates made of bronze BrO10S10

When applying silver to sample No. 1, the surface roughness (Rz) is 8.5 μm, and the continuity is 60%. With further ESA with lead, the surface roughness increases to Rz=29 μm, and the continuity to 70%. The subsequent ESA with silver helps to reduce the surface roughness to 7.5 μm and increase the coating continuity to 100%, which is obviously associated with the secondary melting of lead due to its low melting point, its spreading over the surface and filling all the irregularities.

Microstructural analysis of the sample doped in the Ag→Pb→Ag sequence (sample No. 1) showed that the CEIP consists of 4 sections, Fig. 2, 3, namely: external - dark, uneven, about 100-150 microns thick, in some places - up to 170 microns, and microhardness 81-91 MPa; light - not uniform and not continuous layer, the thickness of which varies between 5-10 microns; a heat-affected zone (HAZ) with a thickness of ~100 µm and a microhardness of ~2200 MPa, as well as the base metal. The microstructure of the base metal, bronze BrO10C10, is a homogeneous grain of a-solid solution of tin in copper - dark component, eutectoid (α + Cu ₃₁ Sn ₈ ) - light component and lead inclusions [Kolachev B.A., Elagin V.I., Livanov V.A. Metal science and heat treatment of non-ferrous metals and alloys. Textbook for high schools. - 4th ed., revised. and additional - M.: MISIS, 2005. - 432 p.]. The microhardness of the base is 1235 MPa.

With an increase in the pulse energy (Table 1), when CEIP is applied to the surface of sample No. 2, the thickness of the dark layer in some areas reaches 250 μm, Fig. 4, 5, and the roughness is at the same level. The thickness of the light layer increases to 20 µm. Below the light layer there is a heat-affected zone (HAZ), the thickness of which reaches 150 µm with microhardness up to 2500 MPa.

With an increase in the discharge energy (sample No. 3), when applying the first layer (silver) and the second layer (lead), respectively, from 0.9 and 0.36 to 4.6 J, a rather massive (up to 830 μm) dark layer is formed roughness up to 10.0 microns, continuity up to 100% and microhardness 80-100 MPa, and in places adjacent to the light layer - up to 200 MPa. Below is a light layer 30–40 µm thick with a microhardness of 1150–858 MPa, Fig. 6, 7.

When replacing the electrode material (lead with tin), when obtaining CEIP (samples 4-6), in all cases the first layer (silver) was applied at Wp=4.6 J. When applying the second layer (tin), the pulse energy for samples No. 4, 5 and increased and amounted, respectively: 0.36; 0.9 and 4.6 J. The third layer (silver) was applied at Wp=4.6 J, it was used to increase the continuity of the coating and reduce the surface roughness. The performed metallographic analysis showed that all samples are characterized by 4 areas - the outer layer, the light sublayer, below - the diffusion zone (HAZ zone) and the base metal. As the discharge energy increases (0.36; 0.9 and 4.6 J), when applying tin by the ESA method, Fig. 8-13,

- the microhardness of the light sublayer increases and amounts to 1525, respectively; 1636 and 2383 MPa;

- the thickness of the dark layer with reduced microhardness increases to 0.67; 1.75 and 2.74 mm, respectively;

- in the HAZ, the depth of which reaches 1400, 2100 and 3100 µm, respectively, there is a layer whose microhardness is lower than the base microhardness and is: 800, 900 and 750 MPa.

The surface roughness for all samples remains practically unchanged and is in the range of 8.5–10.0 µm. The metallographic analysis of samples of the 2nd series, on the treated surface of which sulfur was applied before silver deposition (S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag), did not show significant differences in the structure of the formed ECIP. The difference is the reduction in the thickness of the coating, both when applying the second layer of lead or tin, and the entire CEIP, as well as reducing the roughness to Rz=5.5-7.5 μm. The results of the quality parameters of the CEIP of the 1st and 2nd series are shown in Table 2.

Summary table of quality parameters of the QEC for samples of the 1st and 2nd series

As a result of the analysis of the table, it was found that for samples without sulfiding, with an increase in the discharge energy, the layer thickness increases, the continuity is 100%, and the microhardness is in the range of 80-140 and 130-183 MPa, respectively, for CEIP with lead and tin. The thickness of the light sublayer varies insignificantly and is in the range of 10–40 and 10–25 µm, and the microhardness is 912–1150 and 1228–2383 MPa, respectively, for CEIP with lead and tin. The thickness of the hardened layer increases with increasing pulse energy and is in the range of 80–230 and 70–120 µm, respectively, for CEIP with lead and tin. The microhardness of the hardened layer of KEIP for all samples changes insignificantly and is in the range of 1313-2383 MPa.

In samples of the 2nd series, with increasing Wp, the layer thickness increases, the continuity is 100%, and the microhardness is in the range of 80-130 and 130-150 MPa, respectively, for CEIP with lead and tin. The thickness of the light sublayer varies slightly and is in the range of 10-40 and 10-30, and the microhardness is 900-1150 and 1150-2270, respectively, for CEIP with lead and tin. The thickness of the hardened layer increases with increasing discharge energy and is in the range of 60–130 and 60–110 µm, respectively, for CEIP with lead and tin. The microhardness of the hardened layer of KEIP for all samples varies insignificantly and is in the range of 1300-2410 MPa.

When coatings are applied to samples of the 3rd series, at all stages of the formation of the CEC, the layer is destroyed up to the base, for example, sample 1 ** (Table 3).

Table 3 shows the results of measuring the thickness of layers of soft antifriction metals: silver, lead, and tin, deposited at all stages of the formation of CEIP for all series of samples.

Summary table of quality parameters of CEIP samples of the 1st; 2nd and 3rd series

The analysis of Table 3 showed that during the formation of ECIP on samples of BrO10C10 without sulfiding, the thickness of the formed coating increases with an increase in doping modes. The deposition of sulfur (sulfiding) before deposition of silver slows down the increase in the thickness of the CEIP, and the use of sulfiding at all stages of formation almost completely destroys it.

In samples of the 2nd series, on the treated surface of which sulfuric ointment was applied before applying silver, with an increase in alloying modes, the thickness of the formed coating increases from 0.19 to 1.3 mm. In samples of the 3rd series, on the treated surface of which sulfuric ointment was applied before each stage of alloying, sulfur contributes to the destruction of the CEIP, and its final thickness does not exceed 0.12 and 0.11 mm, respectively, in the case of ESA with lead and tin.

Coatings of the 3rd series of samples are destroyed and are not recommended for use.

The tribological properties of the resulting coatings were determined on a T-01M tester manufactured by the Radom Institute of Technology (Poland) in accordance with the DIN-50324: 1992-07 Tribology standard according to the “ball-disk” scheme, Fig. one.

A 6.3 mm diameter ball made of 100Cr6 material (Table 4) was changed after each test.

Ball material composition

The following series of samples were tested (Table 5).

Modes and sequence of doping samples with KEIT for tribological tests

In order to ensure surface sulfiding, a sulfuric ointment with a sulfur concentration of 33.3% was applied to the treated areas before each application of a layer of silver (Table 2). In addition, sample No. 0 was tested - without coating and sample No. 7 with CEIP Ag→Pb→Ag.

The samples were lubricated with a drop of paraffin oil before each test. During the tests, the friction force Ft was recorded.

In the process of research, the following operating parameters of the tester were used: rotation speed ω=353 rpm; linear speed v=0.67 m/s; sliding distance (friction path) S=300 m; load Fn=1.0 kg (9.81 N); type of friction - dry friction (without lubrication).

in FIG. 14-21 shows the nature of the change in the friction force for all samples with KEIP when the steel ball passes the friction path S=300 m at a load Fn=9.81 N. For these friction pairs, Table 6 shows the average values of the friction force Ft and friction coefficients μ.

Friction force i coefficient of friction of a steel ball on the surface of a bronze disk with KEIP

Analyzing Fig. 14-21 and the data of Table 6, the following can be noted:

- for an uncoated sample (No. 0), the friction force from the moment the friction path begins to its completion increases smoothly;

- for sample No. 1 with a thickness of KEIP of 0.19 mm and a roughness of Rz = 7.5 μm, the friction force first gradually increases, and then, after passing the friction path of ~ 200 m, it stabilizes at the same level;

- an increase in the thickness of the CEIP in samples No. 2 and No. 3 to 0.26 and 1.01 mm, respectively, and the roughness (Rz), to 8.5 and 10.0 μm, respectively, is accompanied not only by an increase in the friction force, but also the appearance of vibration, which is displayed in the figure of the curve of the dependence of the friction force on the path in the form of oscillations. The friction force, as well as the amplitude of oscillations, decrease from the moment the friction path begins to its completion, which indicates a running-in period;

- samples No. 4 and No. 6 are characterized by a slight increase in the friction force at the beginning of the tests, then its decrease and stabilization, respectively, at the level of 0.9 and 2.2 N. For sample No. 5, the friction force along the entire friction path is at the level of ~ 2.0 N;

- the smallest friction coefficients are 0.095 and 0.148, respectively, for samples No. 4 and No. 1, and the largest - 0.259 and 0.219, respectively, for samples No. 3 and No. 6;

- the friction force of samples with KEIP, which include sulfur, is lower than without it (Sample No. 2 and No. 7).

On FIG. 22 shows a diagram that allows you to compare the values of the friction force of all series of samples at a load of 9.81 N.

As a result of experimental studies, it was established:

During the formation of KEIP on samples of BrO10C10 without sulfiding, with an increase in alloying modes, the thickness of the formed coating increases from 0.27 to 2.9 mm, while the microhardness is in the range of 80-140 and 130-183 MPa, respectively, for coatings with lead and tin , and the roughness Rz=8.5-10.0 µm. The continuity of the CEC for all samples is 100%.

In samples, on the treated surface of which sulfuric ointment was applied before applying silver (S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag), with an increase in doping modes, the thickness of the formed coating increases from 0.19 to 1, 3 mm, microhardness is in the range of 80-180 MPa, with a smaller value closer to the surface, and roughness Rz=5.5-7.5 µm. Continuity for all samples is 100%.

In samples of the 3rd series, on the treated surface of which sulfuric ointment was applied before each stage of alloying, sulfur contributes to the destruction of the CEIP, and its final thickness does not exceed 0.12 and 0.11 mm, respectively, in the case of ESA with lead and tin.

As a result of the conducted experimental studies, the technology of deposition of running-in CEIPs on bronze BrO10C10, obtained in the sequence S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag, has been improved. It is shown that the presence of sulfur in the coating helps to reduce the setting of the contacting surfaces. The proposed technology for obtaining CEIP allows for a coating thickness of 0.19-1.31 mm, which simplifies further mechanical processing of surfaces.

Tribological studies on the T-01M tester according to the “ball-disk” scheme have established that with an increase in the thickness of the KEIP, the friction force increases. In samples S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag, the thickness of which, depending on the discharge energy, is 0.19, respectively; 0.26; 1.01 mm and 0.89; 1.05; 1.31 mm, the friction force is, respectively, 1.454; 1.762; 2.098 N and 0.934; 1.904 and 2.152 N.

Sulfur in KEIP (sample No. 2) reduces the friction force of a steel ball on the surface of bronze samples (sample No. 7) by 1.44 times. For practical application, we can recommend CEIP: S+Ag→Pb→S+Ag and S+Ag→Sn→S+Ag, obtained at pulse energy, respectively 0.52→0.13→0.05 and 4.6→0 ,36→0.36 J, providing a reduction in the friction force compared to uncoated samples, respectively, by 1.22 and 1.90 times.

Claims (6)

1. A method for processing bronze bushings of a plain bearing, including sulfiding and applying combined spark coatings with electrodes-tools to the working surfaces of the bearings by the method of electrospark alloying with the formation of a sequence of layers: silver - soft metal - silver, characterized in that the silver layer is applied at pulse energy Wu= 0.52-4.6 J, a lead layer is applied to the silver layer at pulse energy Wu=0.13-4.6 J, another layer of silver is applied to the lead layer at pulse energy Wu=0.05-0.36 J , while the treated surfaces are sulfided before each application of a layer of silver. 2. The method according to p. 1, characterized in that sulfuric ointment with a sulfur concentration of 33.3% is used during sulfiding. 3. Method according to claim 1 or 2, characterized in that the coating thickness is 0.19-1.31 mm. 4. A method for processing bronze bushings of a plain bearing, including sulfiding and applying combined spark coatings with electrodes-tools to the working surfaces of the bearings by the method of electrospark alloying with the formation of a sequence of layers on the working surfaces: silver - soft metal - silver, characterized in that the silver layer is applied with energy pulse Wu=0.52-4.6 J, a tin layer is applied to the silver layer at pulse energy Wu=0.36-4.6 J, another layer of silver is applied to the tin layer at pulse energy Wu=0.05-0 .36 J, while the treated surfaces are sulfided before each application of a layer of silver. 5. The method according to p. 4, characterized in that sulfuric ointment with a sulfur concentration of 33.3% is used during sulfiding. 6. Method according to claim 4 or 5, characterized in that the coating thickness is 0.19-1.31 mm.

Images