Method for improving wear resistance of worn parts of steel and cast iron and for restoring such parts

FIELD: mechanical engineering, restoration of machine parts.

SUBSTANCE: method is realized by applying at least one coating by means of electric spark alloying. Wear resistance coating is applied with use of electrode of boron alloyed intermetallide Ni3Al containing, mass %: Al, 2 - 15; B, 0.02 - 02; Ni, the balance. In variants of invention electrode contains in addition dispersed particles of Si3 N4. Before applying on part layer of wear resistant coating, nickel layer with thickness 20 - 50 micrometers is applied as intermediate adhesion barrier. Coated parts are subjected to mechanical working. Restoration is realized for parts with wear degree up to 100 micrometers or with wear degree 100 - 300 micrometers.

EFFECT: possibility for restoring parts, improving their wear resistance and increasing adhesion strength of applied coating with base material of part.

6 cl, 3 tbl, 3 ex

 

The invention relates to machine building and repair of machine parts and can be used to restore worn parts made of steel or cast iron, for example seats under the bearings, bushings and bearings, slides, pulleys, drums, etc. and also to increase the life and reliability of the friction pairs by applying a coating of wear-resistant materials.

Known way to restore parts by means of electrolytic plating with subsequent machining of the coating (Bogoro L.Y. chrome Plating. - L.: Engineering. 1984. - 121 C.). However, using this method to restore the parts is limited by the fact that the obtained coatings are low adhesion with the material of the workpiece and insufficient wear resistance. In addition, the solutions that are used in electrolytic plating, are highly toxic.

There is a way to restore worn parts, including pre-machining the working surface of recoverable parts, installing it laying element with pre-applied wear-resistant material, welding and subsequent machining (RF patent 2206439, the IPC 23 R 6/02, 22.03.2001). The disadvantage of this method is that it is necessary to make the mortgage element and the wire is to be repeated mechanical processing.

The closest to the essential features of the claimed invention is a method of restoring the size of the holes in the parts made of cast iron, which consists in applying a wear-resistant anti-friction coatings and its subsequent mechanical processing (RF patent 2173731, IPC 23 4/12, 26/00, 24.04.2000). The coating of copper when worn holes to 140 microns provide the spark welding with pulse energy of 0.28-1,66 j, the specific time of deposition of 2.0 to 3.0 min/cm2when the frequency of vibration of the electrode 150-250 Hz. When worn holes 140-300 μm before coating of copper electrospark welding put a layer of the coating of steel with a specific time surfacing 2,5-4,0 min/cm2.

The disadvantage of this method is that as the wear-resistant coating is copper, the temperature coefficient of linear expansion (TCLE) which is equal to α=16,7·10-6To-1at T=300 K. At the same time cast iron SC-28, SC-32, SC-36, SC-40 temperature coefficient of linear expansion α=11,8·10-6To-1in the temperature range 293-473 To (Physical quantities. The Handbook. Appalaches, Nagbabasa, Amiradaki and others; Ed. by Isegoria, Esenaliev. - M.: Energoizdat, 1991. - 1232). The difference in coefficients of linear expansion may be in operation when a little heat is to cause cracking and delamination of the coating. In addition, copper has a relatively low wear resistance.

The objective of the invention is to develop methods for restoring and improving the durability of the wearing parts of steels and cast irons by applying a coating of the required thickness on the worn parts of the electrode from a material with high tribological properties. Restored the proposed method of covering the worn parts have high adhesion to the substrate.

This technical result is achieved by the fact that in the present method, comprising applying at least one coating spark doping and subsequent machining, wear resistant coating is applied by electrode made of intermetallic Ni3Al doped with boron, the following composition, wt.%: Al - 2÷15; B - 0.02÷0.2; Ni - rest or electrode made of intermetallic Ni3Al doped with boron, optionally containing dispersed particles of silicon nitride Si3N4following composition, wt.%: Al - 2÷15; 0.02÷0.2; Si3N4- up to 16; Ni - rest.

In addition, when the wear of parts and 100 ám wear resistant coating is applied by electrode made of intermetallic Ni3Al doped with boron, the following composition, wt.%: Al - 2÷15; 0.02÷0.2; Ni - else, and when you wear 100-300 μm iznosostoyki the e coating is applied by electrode made of intermetallic Ni 3Al doped with boron, optionally containing dispersed particles of silicon nitride Si3N4following composition, wt.%: Al - 2÷15; 0.02÷0.2; Si3N4- up to 16; Ni - rest.

In addition, the part before applying the wear-resistant coating as an intermediate adhesion-barrier coatings put a layer of Nickel with a thickness of 20-50 μm.

In addition, for details at planting are required tightness, mechanical processing is not performed.

The intermetallic Ni3Al doped with boron and has sufficient elasticity and high yield. Its linear thermal expansion coefficient close to thermal expansion of iron and steel (see tables 1 and 2) and is equal to α=12,8·10-6To-1at room temperature (Ox AU Structure and properties of dual-metal systems. M: Fizmatgiz, 1959, volume I, 755 S.). In addition, this intermetallide has a high resistance to wear.

Use in the composition of the electrode dispersed particles of silicon nitride allows, on the one hand, due to variations in the content of particles of Si3N4to provide a coating of the desired value of thermal expansion (see table 3), and on the other hand, the particles of Si3N4reduces the level of residual stresses in the coating process, thereby making it possible to apply coating of greater thickness.

On some brands of steels and cast irons not UDA is conducted directly apply high-quality wear-resistant coating of these compounds or due to insufficient adhesion, or because of the formation in a diffusive layer of fragile aluminides (FeNi)3Al and (FeNi)Al. In these cases, in the present method as an intermediate adhesion-barrier coatings put a layer of Nickel, which provides good adhesion and preventing the interaction of Ni3Al material recovered parts. Linear thermal expansion coefficient of Nickel is close to thermal expansion of steel and cast iron and is equal to α=11,4·10-6To-1at T=200 K and α=13,4·10-6To-1at T=300 K.

The content of Nickel and aluminum in the specified interval of the electrodes is determined by the region of existence of intermetallic Ni3Al on the phase diagram of the state. When changing the concentration of Nickel and aluminum outside the specified limits material has a different phase composition with the appropriate properties. The lower the value of the boron concentration in the electrodes is a minimum to achieve the necessary technological ductility of intermetallic Ni3Al, exceeding the upper specified limit concentration of boron leads to embrittlement of intermetallic Ni3Al. The maximum number of particles of silicon nitride in the electrode is determined by the fact that in a larger content of the material becomes brittle, resulting in reduced strength and durability. Electrodes with a complete absence of particles of silicon nitride can be used for some mothers the fishing hardened parts, for example, when you need a small thickness and thermal expansion of the coating and material hardening details close.

The proposed method is as follows.

When worn steel parts not exceeding 100 microns, a layer of intermetallic Ni3Al doped with boron, without particles of silicon nitride. If necessary, depending on the component material may be applied as an intermediate adhesion-barrier coating layer of Nickel. When you wear 100-300 μm on the surface of the worn parts cause adhesion-barrier layer of Ni with a thickness of 20-50 μm, and then wear resistant coating of the required thickness of the intermetallic Ni3Al doped with boron and containing dispersed particles of silicon nitride Si3N4. The coating is carried out by the electric-spark alloying (ESA) on the installation of the ES-4M electrodes from a material of the above composition. The electrodes are made of a powder mixture by the method of self-propagating high temperature synthesis (SHS) or by pressing followed by sintering. The modes of the coating are selected based on the required thickness of layer applied. When the wear of the mating parts of 150-300 μm, the desired coating thickness receive several passes, the corresponding electrode. Modes ESA pick so total that the woman cover 50-70 microns exceeded the wear parts. The required size of the receive subsequent machining - grinding or polishing using priter that provides the necessary technological gap in the mating parts.

For details, at planting are required tightness, subsequent machining do not spend, and make landing in hot or through the press. When landing, the driving protrusions of the surface resulting from ESA, prevent turning of the coupling parts relative to each other.

Example 1.

Wear seat under the bearing on the shaft does not exceed 0.2 mm Coating is applied by the method of electric-spark alloying (ESA) electrode of intermetallic Ni3Al doped with boron. Make one or more passes until the desired thickness of the coating.

Example 2.

Wear holes in the outer ring of the bearing is ˜0,2 mm Coating is applied by a method of the ESA of intermetallic Ni3Al doped with boron.

Example 3.

The restoration of the seats for the bearings when you wear ˜0.2 mm is produced as follows. Degrease the wear surface of the gasoline nefras C2-80/120 TU 38.401-67-108-92), put a method of electric-spark alloying of the adhesion-barrier layer of Nickel of a thickness of ˜40 μm, then applied the same method, the desired coating thickness of intermetallic Ni 3Al doped with boron and containing dispersed particles of silicon nitride. The appropriate degree determined by the field of tolerance to the desired number of bearing according to GOST 25346-82.

The application of the ESA method using electrodes of the proposed structures allows to recover details from steel and cast iron with a large enough wear while improving tribological properties of products. Depending on the wear resistance of the source material recovered items increase the wear resistance of the details of the applied coating may be from 1.5 to 5 times. Using the ESA method in combination with the application of adhesive-protective coating provides the bonding strength between the base material and a wear resistant coating, exceeding the cohesive strength of the base material.

Table 1

Temperature coefficient of linear expansion of iron. The values true TCLE α (at a given temperature T) or the average linear thermal expansion coefficient(interval ΔT)
Brand or nameΔT T °α,, 10-6To-1
Midrange 00, SC2010,0
MF 12-28, MF 15-32, MF 18-36, MF 21-40 20-20011,8
MF 32-52-7711,2
AVC-1, ABC-12011,0
FM 1,3, FM 1,820-100to 12.0
FC, PCI LAN card, HTV, CNV20-60013,6
Cast iron: white20

20-100
7-11

10
grey2011
ferritic malleable20-10011
20-30012,3
20-50013,6
20-70014,7

Table 2

Temperature coefficient of linear expansion of some steels. The values of the average linear thermal expansion coefficient(interval ΔT)
Steel gradeΔT, °, 10-6To-1
1020-100012,6
2520-1000the 13.4
5520-100014.4V
6520-100014,8
30X20-100013,8
40X20-800to 12.0
30HGSA20-70014,3
GM20-800the 13.4
NA20-70013,9
20HN3A20-70013,6
NM20-70014,6
12H1320-80013,0
30CH1320-80012,6

Table 3

Temperature coefficient of linear expansion of intermetallic Ni3Al doped with boron, depending on the content of the silicon nitride Si3N4. The values of the average linear thermal expansion coefficient α (in the range of ΔT=295-1275 K)
Material composition (wt.%)α·10-6To-1
The intermetallic Ni3Al doped with boron16,3
The intermetallic Ni3Al, SHS16,3
The intermetallic Ni3Al doped with boron at 99.1

The silicon nitride Si3N4- 0,9
the 15.6
Ni3Al doped with boron - 97,7

Si3N4at 2.3
15,0
Ni3Al doped with boron - 96,3

Si3N4- 3,7
14,2
Ni3Al doped with boron - 95,4

Si3N4- 4,6
13,3
Ni3Al doped with boron - 94,4

Si3N4- 5,6
13,3
Ni3Al doped with boron - 90,1

Si3N4- 9,9
13,3
Ni3Al doped with boron - 84,2

Si3N4with 15.8
12,6

1. The method of restoring worn parts made of steel or cast iron, including the application of spark doping at least one coating, wherein the wear resistant coating is applied by electrode made of intermetallic Ni3Al doped with boron, the following composition, wt.%: Al 2÷15, 0.02÷0,2, Ni else.

2. The method according to claim 1, characterized in that the restore items to wear to 100 microns.

3. The method according to claim 1, wherein the wear resistant coating is applied by electrode made of intermetallic Ni3Al doped with boron, optionally containing dispersed particles of silicon nitride Si3N4following composition, wt.%: Al 2÷15, 0.02÷0,2, Si3N416, Ni else.

4. The method of claim 3, wherein the restore parts wear 100-300 microns.

5. The method according to any one of claims 1 to 4, characterized in that the part before applying the wear-resistant coating as about itocnode adhesion-barrier coatings put a layer of Nickel with a thickness of 20-50 μm.

6. The method according to claim 1, wherein after coating spend machining parts.



 

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