CN103805949A - Molybdenum disulfide self-lubricating composite coating and piston ring coated with coating - Google Patents

Abstract

The invention discloses a molybdenum disulfide self-lubricating composite coating and a piston ring covered with the composite coating. Molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the molybdenum disulfide self-lubricating layer is a gradient layer with sulfur content continuously changing along the thickness direction, and the sulfur content of the contact surface between the gradient layer and the molybdenum nitride basic coating is the smallest . The molybdenum disulfide self-lubricating composite coating of the present invention has suitable hardness, low self-lubricating friction coefficient and strong adhesion, and the piston ring applied with the molybdenum disulfide self-lubricating composite coating shows great performance in surface wear resistance and self-lubricating Advantages, good wear resistance and self-lubrication, can effectively solve the problem of friction and wear between the piston ring and the cylinder.

Description

Molybdenum disulfide self-lubricating composite coating and piston ring covered with the composite coating

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technical field

The invention belongs to the technical field of thin film materials, and relates to a molybdenum disulfide self-lubricating composite coating and a piston ring covered with the composite coating.

Background technique

As a key component of a fuel engine, the piston ring constitutes a friction system together with the piston and cylinder. The friction between the piston ring and the cylinder wall is one of the main factors affecting the friction loss of the engine. Therefore, the wear resistance of the piston ring is relatively high. In particular, the new Euro IV emission standards put forward higher requirements on the wear resistance of piston rings.

At present, the wear resistance of the piston ring is generally improved by coating the wear-resistant layer on the piston ring. The traditional spraying process and electric brush plating are not suitable for piston ring coating, and the electrochrome plating treatment method has problems such as polluting the environment and the rubbing performance of the chrome plating layer cannot meet the new emission standards. Coating chromium nitride wear-resistant coating on the piston ring by physical vapor deposition (PVD) can effectively improve the wear resistance of the piston ring, but the friction coefficient of the PVD chromium nitride coating is relatively high, and the friction coefficient is greater than 0.4.

Molybdenum compound lubricating material is a kind of lubricating material with excellent tribological properties, which is widely used in aviation, aerospace, navigation, machinery and other fields. Molybdenum disulfide can significantly improve the bearing capacity and anti-wear performance of grease, especially under high load. In recent years, with the development of coating technology, researchers have developed molybdenum disulfide self-lubricating coatings. Molybdenum disulfide solid self-lubricating coatings have high load-bearing capacity and are suitable for low-speed and heavy-duty conditions under dry friction conditions. Under high temperature conditions, its performance index is better than solid lubricants such as graphite. Coating the molybdenum disulfide self-lubricating coating on the surface of the piston ring will greatly improve the wear resistance of the piston ring, thereby increasing the service life of the piston ring.

Contents of the invention

Aiming at the deficiencies in the prior art, the invention provides a molybdenum disulfide self-lubricating composite coating, a piston ring covered with the composite coating and a preparation method, so as to further improve the wear resistance of the piston ring.

A molybdenum disulfide self-lubricating composite coating provided by the present invention comprises a molybdenum nitride basic coating on the piston ring base and a molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating. The molybdenum self-lubricating layer is a gradient layer whose sulfur content changes continuously along the thickness direction, and the sulfur content of the contact surface between the gradient layer and the molybdenum nitride basic coating is the smallest. the

The molybdenum nitride basic coating has a thickness of 3-6 microns.

The molybdenum disulfide self-lubricating layer has a thickness of 0.3-4 microns.

Coating the molybdenum disulfide self-lubricating composite coating on the piston ring substrate can significantly improve the wear resistance of the piston ring. The piston ring matrix is a steel matrix or a cast iron matrix.

The present invention also provides a method for depositing the molybdenum disulfide self-lubricating composite coating on the piston ring. Depositing the molybdenum disulfide self-lubricating composite coating in the vacuum deposition chamber includes: arc evaporating the molybdenum target in a nitrogen environment, and depositing the molybdenum disulfide self-lubricating composite coating on the piston ring. The molybdenum nitride basic coating is deposited on the ring substrate; the molybdenum target is arc evaporated in the hydrogen sulfide gas environment, and the molybdenum disulfide self-lubricating layer is deposited on the molybdenum nitride basic coating.

Preferably, before depositing the molybdenum nitride basic coating on the piston ring base, the piston ring base is subjected to plasma etching, so as to remove the surface pollutants of the piston ring base.

A kind of specific implementation manner of above-mentioned method is:

The molybdenum nitride basic coating and the molybdenum disulfide self-lubricating layer are deposited on the molybdenum nitride basic coating by arc evaporation. In the process of depositing the molybdenum nitride basic coating on the piston ring substrate, the vacuum degree of the deposition chamber is 0.5~3.0Pa, the deposition chamber temperature is 200~300℃, and the bias condition is -40~-400V; during the process of depositing molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the vacuum degree of the deposition chamber is 0.5~5.0 Pa, the temperature of the deposition chamber is 200~400°C, and the bias condition is -40~-200V.

During the process of depositing the molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the hydrogen sulfide gas flow rate is continuously increased to obtain the molybdenum disulfide self-lubricating layer whose sulfur content continuously changes along the thickness direction.

Preferably, during the process of depositing the molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the hydrogen sulfide gas introduced is ionized hydrogen sulfide. A specific method for obtaining ionized hydrogen sulfide is: introducing hydrogen sulfide into the vacuum chamber through a hollow cathode ion source to increase the ionization rate of hydrogen sulfide gas and obtain ionized hydrogen sulfide.

The method of the present invention obtains metal molybdenum by arc evaporating a molybdenum target, passes _N2 into the deposition chamber and ionizes _N2 to obtain nitrogen element; passes _H2S into the deposition chamber and ionizes _H2S to obtain sulfur element; And by gradually increasing the hydrogen sulfide gas flow rate, a gradient layer from a sulfur-deficient molybdenum disulfide layer to a pure molybdenum disulfide layer is deposited on the molybdenum nitride basic coating layer, realizing the continuous change of sulfur content with a gradient structure along the thickness direction Molybdenum disulfide self-lubricating layer.

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The present invention has following characteristics:

The molybdenum nitride basic coating can effectively improve the hardness of the piston ring substrate, and at the same time provide good support for the molybdenum disulfide self-lubricating layer; the gradient structure of the molybdenum disulfide self-lubricating layer solves the problem of excessive The abruptness avoids the stripping problem caused by excessive stress, has good adhesion, and effectively enhances the wear resistance of the piston ring.

Compared with prior art, the present invention can bring following beneficial effect:

1. The molybdenum disulfide self-lubricating composite coating of the present invention has a suitable hardness (hardness about 2000Hv), and will not cause unnecessary scratch damage to the cylinder due to excessive hardness; it has a low self-lubricating friction coefficient (about 0.3), Therefore, it can quickly adapt to the frictional conditions with the cylinder.

2. The piston ring coated with the molybdenum disulfide self-lubricating composite coating of the present invention has great advantages in surface wear resistance and self-lubrication, has good wear resistance and self-lubrication, and can effectively solve the problem of piston ring and cylinder The problem of friction and wear between them can significantly increase the service life of piston rings, reduce the incidence of engine failures, and improve engine performance, thereby bringing huge economic and social benefits.

Description of drawings

Fig. 1 is the optical microscope picture of the thickness test of molybdenum disulfide self-lubricating composite coating of the present invention;

Fig. 2 is the variation curve of the typical coefficient of friction of molybdenum disulfide self-lubricating composite coating of the present invention along with friction time;

Fig. 3 is the change graph of the nanohardness of molybdenum disulfide self-lubricating composite coating with the indentation depth of the present invention;

In the figure, 1-piston ring base; 2-molybdenum nitride basic coating; 3-molybdenum disulfide self-lubricating layer; 4-molybdenum disulfide self-lubricating composite coating surface.

Detailed ways

The present invention will be further described below in conjunction with specific examples, but the protection content of the present invention is not limited to the following examples.

In the following embodiments, the arc ion plating equipment is used as the deposition equipment, supplemented by a hollow cathode ion source to ionize hydrogen sulfide gas, the target material is a molybdenum target, and the target material and the workpiece holder are arranged in the vacuum deposition chamber of the arc ion plating equipment .

Example 1

After the piston ring is cleaned, it is clamped on the workpiece frame, and the vacuum chamber is evacuated. When the vacuum degree is higher than 5×10 ^-3 Pa, start heating and degassing, and the temperature is controlled at 200°C. When the vacuum degree is 5×10 ^-3 Pa, Ar gas is introduced, the temperature is controlled at 200°C, and the bias voltage power supply is turned on to perform plasma etching on the piston ring substrate.

After the plasma etching is finished, adjust the bias voltage to -40V, close the Ar gas channel, feed _N2 gas, and adjust the vacuum degree of the deposition chamber to 0.5Pa, and the temperature is 200°C, and the arc evaporates the molybdenum target. Deposit a molybdenum nitride base coating with a thickness of 3 microns.

After the molybdenum nitride basic coating is deposited, close the N ₂ channel, feed H ₂ S through the hollow cathode ion source, gradually adjust the vacuum degree of the deposition chamber to 0.5Pa, keep the bias voltage -40V, and the temperature 200°C, continuously increase the input The flow of H ₂ S deposits a self-lubricating layer of molybdenum disulfide with a thickness of 0.3 microns on the molybdenum nitride basic coating. After the molybdenum disulfide self-lubricating layer is deposited, the piston ring is naturally cooled to room temperature and then the piston ring is taken out to obtain the piston ring deposited with the molybdenum disulfide self-lubricating composite coating.

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Example 2

After cleaning the piston ring, clamp it on the workpiece frame, and evacuate the vacuum chamber. When the vacuum degree is higher than 5×10 ^-3 Pa, start heating and degassing, and the temperature is controlled at 300°C. When the vacuum degree is 5×10 ^-3 Pa, Ar gas is introduced, the temperature is controlled at 300°C, and the bias voltage power supply is turned on to perform plasma etching on the piston ring base.

After the plasma etching is finished, adjust the bias voltage to -400V, close the Ar gas channel, feed _N2 gas, and adjust the vacuum degree of the deposition chamber to 3.0Pa, and the temperature is 300°C, and the arc evaporates the molybdenum target. A molybdenum nitride base coating with a thickness of 6 microns is deposited on it.

After the molybdenum nitride basic coating is deposited, the _N2 channel is closed, _H2S is introduced through the hollow cathode ion source, the vacuum degree of the deposition chamber is gradually adjusted to 5Pa, the bias voltage is kept at -200V, the temperature is 300°C, and the H2S is continuously increased. The flow rate of ₂ S was used to deposit a self-lubricating layer of molybdenum disulfide with a thickness of 4 microns on the molybdenum nitride basic coating. After the molybdenum disulfide self-lubricating layer is deposited, the piston ring is naturally cooled to room temperature and then the piston ring is taken out to obtain the piston ring deposited with the molybdenum disulfide self-lubricating composite coating.

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Example 3

After cleaning the piston ring, clamp it on the workpiece frame, and evacuate the vacuum chamber. When the vacuum degree is higher than 5×10 ^-3 Pa, start heating and degassing, and the temperature is controlled at 250°C. When the vacuum degree is 5×10 ^-3 Pa, Ar gas is introduced, the temperature is controlled at 250°C, and the bias voltage power supply is turned on to perform plasma etching on the piston ring substrate.

After the plasma etching is finished, adjust the bias voltage to -200V, close the Ar gas channel, pass in _N2 gas, and adjust the vacuum degree of the deposition chamber to 2Pa, and the temperature is 250°C, and the arc evaporates the molybdenum target on the piston ring substrate Deposit a base layer of molybdenum nitride to a thickness of 3 microns.

After the molybdenum nitride basic coating is deposited, close the N ₂ channel, feed H ₂ S through the hollow cathode ion source, gradually adjust the vacuum degree of the deposition chamber to 2.0Pa, keep the bias voltage -200V, and the temperature 250°C, continuously increase the input The flow of H ₂ S deposits a self-lubricating layer of molybdenum disulfide with a gradient structure of 2 microns in thickness on the molybdenum nitride basic coating. After the molybdenum disulfide self-lubricating layer is deposited, the piston ring is naturally cooled to room temperature and then the piston ring is taken out to obtain the piston ring deposited with the molybdenum disulfide self-lubricating composite coating.

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The friction coefficient of the molybdenum disulfide self-lubricating composite coating and its variation curve with friction time are tested by a pin-on-disk friction and wear testing machine, as shown in Figure 2. It can be seen from the figure that the friction coefficient of the molybdenum disulfide self-lubricating composite coating is about 0.3. The nanohardness of the molybdenum disulfide self-lubricating composite coating and its change curve with the indentation depth were measured by a nanohardness meter, as shown in Figure 3. It can be seen from the figure that the nanohardness of the molybdenum disulfide self-lubricating composite coating is about 22GPa.

Claims (10)

1. A molybdenum disulfide self-lubricating composite coating, characterized in that: It includes a molybdenum nitride basic coating on the piston ring base and a molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating. The molybdenum disulfide self-lubricating layer is a gradient layer with sulfur content continuously changing along the thickness direction , and the sulfur content of the interface between the gradient layer and the molybdenum nitride base coating is the smallest. 2. Molybdenum disulfide self-lubricating composite coating as claimed in claim 1, is characterized in that: The thickness of the molybdenum nitride basic coating is 3-6 microns. 3. Molybdenum disulfide self-lubricating composite coating as claimed in claim 1, is characterized in that: The thickness of the molybdenum disulfide self-lubricating layer is 0.3-4 microns. 4. A piston ring, characterized in that: Coated with the molybdenum disulfide self-lubricating composite coating according to claim 1. 5. A piston ring according to claim 4, characterized in that: The piston ring matrix is a steel matrix or a cast iron matrix. 6. The method for depositing a molybdenum disulfide self-lubricating composite coating on a piston ring is characterized in that, depositing a molybdenum disulfide self-lubricating composite coating in a vacuum deposition chamber, comprising: The molybdenum target is arc-evaporated in a nitrogen environment, and the molybdenum nitride basic coating is deposited on the piston ring substrate; the molybdenum target is arc-evaporated in a hydrogen sulfide gas environment, and a molybdenum disulfide self-lubricating layer is deposited on the molybdenum nitride basic coating. 7. The method of claim 6, wherein: Before depositing the molybdenum nitride basic coating on the piston ring base, the piston ring base is plasma etched. 8. The method of claim 6, wherein: The molybdenum nitride basic coating and the molybdenum disulfide self-lubricating layer are deposited on the molybdenum nitride basic coating by arc evaporation. In the process of depositing the molybdenum nitride basic coating on the piston ring substrate, the vacuum degree of the deposition chamber is 0.5~3.0Pa, the deposition chamber temperature is 200~300℃, and the bias condition is -40~-400V; during the process of depositing molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the vacuum degree of the deposition chamber is 0.5~5.0 Pa, the temperature of the deposition chamber is 200~400°C, and the bias condition is -40~-200V. 9. The method of claim 6, wherein: In the process of depositing molybdenum disulfide self-lubricating layer on the molybdenum nitride basic coating, the hydrogen sulfide gas flow rate is continuously increased. 10. The method of claim 6, wherein: The hydrogen sulfide is fed into the inner body of the vacuum deposition chamber through the hollow cathode ion source.

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