Sliding element, namely, piston ring with coating

FIELD: machine building.

SUBSTANCE: invention relates to sliding element, particularly, to piston ring with coating on at least one sliding surface which in the direction from inside to outside consists of an adhesive layer (10), a metal-containing (preferably tungsten-containing) DLC-layer (12) and a DLC-layer containing no metal (14). The relation of the width of the DLC-layer containing no metal to the width of metal-containing DLC-layer is from 0.7 to 1.5 and/or the relation to the total coating width is from 0.4 to 0.6, while the total coating width amounts to from 5 mcm to 40 mcm.

EFFECT: better sliding element in relation to the combination of friction factor and wear characteristics.

8 cl, 3 dwg, 3 ex

 

The technical field to which the invention relates

The invention relates to a sliding element, in particular porshneva ring coated at least on one surface of the slip.

Moving elements such as, for example, piston rings, pistons or cylinder liner in internal combustion engines must operate for a long period of service as at as low friction and low abrasion. However, the friction in internal combustion engines directly accompanied fuel consumption can be kept low due to the coating of DLC (diamond-like carbon - diamond-like carbon). Moreover, in principle it is possible to achieve layer thicknesses of up to 40 μm. However, when the layer thickness exceeds 5 μm, there is a problem changing layer properties, for example, in relation to the structure and composition of the layer, so that the required durability is not achieved. This is true equally for the layer thickness of less than 5 microns.

The level of technology

In this regard, well-known, in addition, PVD coatings (applied by physical vapour deposition) on the basis of solid materials, which often contain chromium nitride. However, although such layers have the desired wear resistance, they do not have the required low coefficient of friction.

From DE 102005063123 B3 known sliding element with a DLC-coating with what Orosei pererabatyvaemogo. However, in General, the duration of low coefficients of friction can be enhanced.

Document DE 102008016864 relates to a rolling element with a coating that is from the inside outwards contains an adhesion layer, a metal-containing DLC layer and not containing metal DLC-layer.

In DE 19735962 Al disclosed a guide sleeve and a method of forming hard carbon film on the inner surface of the guide sleeve, where a CVD method (chemical vapour deposition with the support of the plasma on the inner surface formed of hard carbon film of hydrogenated amorphous carbon.

Finally, in document WO 2006/125683 A1 shows a piston ring, which from the inside outwards contains a layer with an element of group IVB, VB or VIB, an intermediate layer of diamond-like nanocomposite composition and DLC-layer.

The invention

Against this background, the basis of the invention the task is to develop a sliding element, which is even more improved in relation to the combination of friction and wear characteristics.

This problem is solved sliding element described in item 1 of the claims.

In accordance with this, the element has at least one sliding surface coating, which from the inside outwards contains adhesive layer, a metallic, in which lastnosti, containing tungsten DLC-layer and not containing metal DLC layer, and the ratio of thickness not containing metal and metal-containing DLC layer is from 0.7 to 1.5, and/or the ratio of the thickness does not contain metal DLC layer to the total thickness of the coating ranges from 0.4 to 0.6. The adhesive layer is preferably chromium adhesion layer. Metal-containing DLC layer includes amorphous carbon, and can be designated as a-C:H:Me, and the DLC layer, preferably containing tungsten may be designated as a-C:H:W Outer or upper layer also contains amorphous carbon and can be specified as a-C:H. In the described values are particularly good properties in respect to friction and abrasion. These tribological properties in order to increase the service life can be affected by a thicker top layer. However, if it becomes too thick in comparison with the middle layer, deteriorating the durability. Especially good wear resistance cannot be set when the middle and top layer have almost the same thickness, that is, there is preferred ratio of the thickness of about 1.0, in particular from 0.9 to 1.1, or the ratio of the thickness of the top layer to the total thickness of approximately 0.5, in particular from 0.45 to 0.55. As for friction, coatings within these ranges was able to set the coefficients of friction, which Ho is Osho comply with the requirements established for internal combustion engine, and which, in particular, essentially do not change. On the contrary, outside of these ranges already after a short time are the high peaks of the friction coefficient and variable characteristics of friction.

As explanation for this behavior, although the invention is not limited to the currently accepted that do not contain metal DLC-layer initially has a very high internal pressure in the whole system, i.e. all the coverages that when the thickness of the metal-containing DLC layer, which is close to the thickness of the outer layer, can be compensated so that the coating was formed optimally in relation to the combination of strength and toughness. Thus, the sliding element with this coating, in particular a piston ring, has good resistance to wear. When the ratio of thickness not containing metal and metal-containing DLC-layers <0.7 and/or with respect to the thickness of the top layer to the total thickness of <0.4 to sliding element has a very low life, as external, do not contain metal DLC layer although it has high wear resistance, but has a very low layer thickness. On the contrary, when the ratio of thickness not containing metal and metal-containing DLC layer >1.5 and/or with respect to the thickness of the top layer to the thickness of the entire layer >0.6 thickness of the metal is terasawa DLC layer is not enough, to compensate for the internal voltage. This leads to premature wear of the DLC layer in General, despite the greater thickness of the outer layer, or peeling of the DLC-layer due to the high loads during operation.

Although the coating is formed by at least one sliding surface of a sliding element, at least partially, it could spread across the sliding surface and, in particular, can be formed also on the surfaces of all or part of that border with the sliding surface, as, for example, the lateral surface of the piston ring and/or at the transition from the sliding surface to the adjacent surfaces.

A preferred improvement of the sliding element according to the invention are described in the following claims.

As the base material of the sliding element, in particular a piston ring, in the currently preferred cast iron or steel. For these materials it is possible to achieve particularly good properties.

As for the hardness of the layer, the preferred values from 1700 to 2900 HV0.02 for not containing a metal (a-C:H, top) DLC-layer and/or from 800 to 1600 HV0.02 for metal containing (a-C:H:Me-) DLC-layer, since these values were able to achieve good compliance.

Both metal-containing and not containing metal DLC layer is activated hydrogen, favorably proved itself in tests.

In addition to containing tungsten DLC layer is preferable to contain nanocrystalline inclusions of tungsten carbide, which also has a beneficial effect on the properties.

For the thickness of the adhesive layer, which, in particular, is a chromium adhesion layer is preferably at most 1 μm.

So it is especially good to achieve the described balance between friction coefficient and characteristics abrasion, the preferred total thickness of the coating is from 5 μm to 40 μm.

For the efficient formation of the coating at the present time for the adhesive layer, it is preferable that it be formed by deposition of metal by evaporation.

In addition, favorable from the point of view of metal-containing and/or not containing metal DLC-receiving layer coating according to the invention is guaranteed, if these layers are formed by a method of PA-CVD (chemical vapor deposition, activated plasma).

Brief description of drawings

Next, with reference to the drawings and more explains the preferred embodiments of the invention. Shown:

Figure 1: schematic structure of the coating according to the invention.

Figure 2: illustration of the relative wear for the two examples according to the invention and one comparative example.

Fig.: illustration of the relative coefficients of friction for the two examples according to the invention and one comparative example.

Detailed description of preferred embodiments of the invention

As shown schematically in figure 1, the coating according to the invention contains in the direction from the inside to the outside of the adhesive layer 10, the intermediate layer 12 and top layer 14, the thickness and the relationship of the thicknesses lie in the above range.

Examples

Properties of the coating according to the invention were tested on two examples and one comparative example. The experiments were conducted with the following coatings:

Example123
The ratio of the middle layer/top layer0,712,401,08
The share of the top layer from the layer0,420,710,52

Thus, referring to examples 1 and 3, we are talking about the examples according to the invention, and example 2 is a comparative example. The studies were carried out for the system "piston ring/greased kuninganna the cylinder liner made of cast iron". Figure 2 shows the relative ratios of wear of piston rings. As you can see in figure 2, note the measures according to the invention find significantly lower wear, than comparative example 2, in particular, a gap of only about 20% or less from wear and tear that occurred in comparative example 2.

In addition, as figure 3 shows, the coefficient of friction in the examples according to the invention essentially does not change with time, whereas for the comparative example, the friction coefficient has a higher value during the whole process and contains a very high highs. Secondly, the coefficient of friction has a strong fluctuations. You can also talk about the failure of the coating corresponding to this comparative example, before the end of the test period.

1. Piston ring coated with at least one sliding surface, which from the inside outwards contains adhesion layer (10), a metallic, preferably containing tungsten DLC layer (12) and containing no metal DLC layer (14), characterized in that the thickness does not contain metal DLC layer has a ratio of from 0.7 to 1.5 to the thickness of the metal-containing DLC layer and/or the ratio from 0.4 to 0.6 for the full thickness of the coating, the complete thickness of the coating is from 5 μm to 40 μm.

2. Piston ring according to claim 1, characterized in that it as the base material contains iron or steel.

3. Piston ring according to claims 1 or 2, characterized in that it contains no metal DLC layer has a hardness of from 1700 to 2900 HV002 and/or metal-containing DLC layer has a hardness of from 800 to 1600 HV0.02.

4. Piston ring according to claims 1 or 2, characterized in that the metal-containing and/or not containing metal DLC layer contains hydrogen.

5. Piston ring according to claims 1 or 2, characterized in that the containing tungsten DLC layer contains precipitation of nanocrystalline tungsten carbide.

6. Piston ring according to claim 1, characterized in that the adhesion layer, in particular chromium adhesion layer, has a thickness of at most 1 μm.

7. Piston ring according to claim 1, characterized in that the adhesive layer is obtained by deposition of metal by evaporation.

8. Piston ring according to claims 1 or 2, characterized in that the metal-containing and/or not containing metal DLC layer is formed by chemical vapor deposition from the vapor phase, activated plasma (PA-CVD).



 

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