Self-reaction lubricating coating for hydraulic element and preparation method of self-reaction lubricating coating

Abstract

The invention discloses a self-reaction lubricating coating for a hydraulic element and a preparation method of the self-reaction lubricating coating. The preparation method comprises the steps of substrate pretreatment, Cr bottoming, preparation of a gradient layer and a W-doped diamond-like layer and the like. The coating structure is composed of a Cr bottom layer, a Cr / C gradient layer, a W / C gradient layer and a W-DLC top layer, the mechanical property transition between a base body and the coating is uniform through the gradient polycrystalline layer structure design, and therefore the bonding strength between the coating and the base body is greatly improved. The W element doped in the coating can improve the microstructure integrity of the whole coating by forming WO3 and WC nanoclusters. Meanwhile, WO3 has very high catalytic activity, so that reactivity of the coating and a lubricant can be improved beneficially, and formation of a chemical reaction film on the surface of the coating is promoted. The chemical reaction film can continuously reduce the friction wear degree of direct contact between friction pairs at the local contact part in the mixed lubrication state and in the boundary lubrication state after the oil film is completely broken, and the service life of the hydraulic element is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of coating material preparation, and particularly to a self-reactive lubricating coating for hydraulic components and a preparation method thereof. Background Art

[0002] Hydraulic components are widely used in modern industry, and they play a role in transmission and control in various mechanical systems. Inside hydraulic components and between hydraulic components in the same system, there are many friction pairs, which refer to the surface pairs that are in contact with each other and move relatively. The lubricating oil film between the friction pairs can reduce the friction and wear of the contact surface, dissipate heat, absorb shock and vibration, thereby protecting the hydraulic components and extending their service life. However, when hydraulic components work under heavy loads, due to the increase in temperature, the decrease in oil viscosity, or heavy load shocks, the oil film is easily broken, resulting in direct contact between the friction pairs, causing severe wear and rapid failure.

[0003] Diamond-like coatings (DLC) are well-known for their excellent mechanical, chemical, and tribological properties and are widely used in the fields of machinery, chemistry, biology, vehicles, etc. The unique structure of diamond-like coatings is characterized by a mixture of sp 2 and sp 3 carbon bonds, providing the best balance of hardness and elasticity, and can effectively reduce friction and wear in moving mechanical components, thereby significantly extending the service life of components. Applying diamond-like coatings on hydraulic components can significantly improve the wear resistance of friction pairs in the case of oil film rupture, but there are also significant limitations, such as high residual stress, poor adhesion to iron substrates, and insufficient reactivity with hydraulic oil, which is not conducive to the lasting protection of friction pairs of hydraulic components.

[0004] Therefore, there is an urgent need for a coating that has strong adhesion to iron substrates, good reactivity with hydraulic oil, and can significantly and continuously reduce the friction and wear of the surface of friction pairs in the case of lubricating oil film rupture. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a coating that has strong adhesion to iron substrates, good reactivity with hydraulic oil, and can significantly and continuously reduce the friction and wear of the surface of friction pairs in the case of lubricating oil film rupture.

[0006] Another technical problem to be solved by the present invention is to provide a preparation method for the coating material.

[0007] The above technical object of the present invention is achieved through the following technical solutions: A preparation method for a self-reactive lubricating coating for hydraulic components, the method comprising the following steps:

[0008] S1, pre-treat the substrate;

[0009] S2. Under the conditions of a Cr target and an inert protective gas, a Cr bottom layer is deposited on the outer side of the substrate by magnetron sputtering.

[0010] S3. Under the conditions of a C target, a Cr target and an inert protective gas, a Cr / C gradient layer is deposited on the outer side of the Cr bottom layer by magnetron sputtering.

[0011] S4. Under the conditions of a C target, a Cr target, a W target and an inert protective gas, a W / C gradient layer is deposited on the outer side of the Cr / C gradient layer by magnetron sputtering.

[0012] S5. Under the conditions of a C target, a Cr target, a W target and an inert protective gas, a W-DLC top layer is deposited on the outer side of the W / C gradient layer by magnetron sputtering.

[0013] Further, step S1 is specifically as follows: Under the condition of an inert protective gas, first use an anode layer ion source to bombard the substrate for cleaning, then evacuate to remove impurity ions, and then use the anode layer ion source to bombard the substrate again for re-cleaning.

[0014] Further, the step of evacuating to remove impurity ions is specifically as follows: Evacuate for 300 s to remove impurity ions, and finally increase the flow rate of the inert protective gas from 0 to 30 - 60 sccm in the last 60 s.

[0015] Further, in steps S1 - S5, the rotation speed of the substrate is maintained at 2 - 6 rpm.

[0016] Further, in steps S2 - S5, the 1st, 2nd, 3rd, and 4th target materials used in the magnetron sputtering method are a C target with a purity of 99%, a Cr target, a C target, and a W target, respectively.

[0017] Further, in step S1, the stable value of the bias voltage is 300 - 600 V, and the bias voltage adjustment time during cleaning is 40 - 80 s.

[0018] In step S2, the stable value of the bias voltage is 40 - 80 V, and the bias voltage adjustment time is 100 - 150 s.

[0019] In steps S3 - S5, the stable value of the bias voltage is maintained at 40 - 80 V.

[0020] Further, in step S1, the flow rate of the inert protective gas during cleaning is 30 - 60 sccm.

[0021] In steps S2 - S5, the flow rate of the inert protective gas is 20 - 40 sccm.

[0022] Further, in steps S1 - S5, the inert protective gas is selected from one or more of Ne, He, or Ar.

[0023] Further, in step S2, the power of the Cr target is increased to 2 - 4 kW;

[0024] In step S3, the power of the C target is increased to 2 - 3 kW, and the power of the Cr target is decreased to 0.1 kW;

[0025] In step S4, the power of the Cr target becomes 0.05 kW, and the power of the W target is increased to 0.5 - 1.5 kW.

[0026] Further, in step S1, both the cleaning time and the re - cleaning time are 750 - 1000 s;

[0027] In step S2, the deposition time is 200 - 300 s;

[0028] In step S3, the deposition time is 1500 - 2000 s;

[0029] In step S4, the deposition time is 80 - 150 s;

[0030] In step S5, the deposition time is 4800 - 6000 s.

[0031] As a general inventive concept, the present invention also provides a self - reactive lubricating coating for hydraulic components, which is prepared by the foregoing preparation method. The coating is obtained by sequentially depositing a Cr bottom layer, a Cr / C gradient layer, a W / C gradient layer, and a W - DLC top layer on the outer side of the substrate by magnetron sputtering.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] (1) The self - reactive lubricating coating for hydraulic components of the present invention is composed of a Cr bottom layer, a Cr / C gradient layer, a W / C gradient layer, and a W - DLC top layer. When preparing the Cr / C gradient layer, the gradient gradual transition of Cr and C elements is realized by gradually reducing the power of the Cr target and increasing the power of the C target. When preparing the W / C gradient layer, the gradient gradual transition of W and C elements is realized by gradually increasing the power of the W target. This gradient structure design makes the mechanical properties such as hardness and elastic modulus between the substrate and the coating transition evenly, improves the deformation coordination between the coating and the substrate under the loading condition, and avoids the phenomenon of delamination and peeling, thereby greatly enhancing the bonding strength between the coating and the substrate.

[0034] (2) The doped W element in the coating will form WC with C element when preparing the W / C transition layer and the W - DLC top layer, and will form WO3 with O element during the actual working process of the hydraulic component. The nanoclusters formed by WO3 and WC can improve the microstructure integrity of the overall coating. These clusters not only enhance the adhesion, but also help to improve the overall durability and performance of the coating under extreme conditions.

[0035] (3) The WO3 formed by the doped W element in the coating has strong catalytic activity because its partially filled d orbitals can participate in the electron transfer process, which can beneficially improve the reactivity between the coating and the lubricant and promote the formation of a chemical reaction film on the coating surface. The chemical reaction film can continuously reduce the friction and wear degree of direct contact between the friction pairs in the local contact part of the mixed lubrication state and the boundary lubrication state after the oil film is completely broken, and extend the service life of the hydraulic components. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of the self-reactive lubricating coating for hydraulic components of the present invention;

[0037] In the figure: 1. Substrate, 2. Cr bottom layer, 3. Cr / C gradient layer, 4. W / C gradient layer, 5. W-DLC top layer;

[0038] Figure 2 It is a Raman spectrogram of the self-reactive lubricating coating for hydraulic components in Example 1 of the present invention;

[0039] Figure 3 It is a comparative diagram of the Vickers hardness test results of the coatings in Example 1 and Comparative Example 1 of the present invention;

[0040] Figure 4 It is a comparative diagram of the change of the friction coefficient of the coatings in Examples 1 to 3 and Comparative Example 1 of the present invention with the rotation speed;

[0041] Figure 5 It is an XPS spectrogram of the self-reactive lubricating coating for hydraulic components in Example 1 of the present invention after the friction test;

[0042] Figure 6 It is a mass spectrogram of the coating surface in Example 1 of the present invention;

[0043] Figure 7 It is a diagram of the Vickers hardness test results of the self-reactive lubricating coating for hydraulic components in Example 1 of the present invention after the friction test. Detailed Embodiments

[0044] Next, the technical solutions in the embodiments of the present invention will be described in detail with reference to the accompanying drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0045] Example 1

[0046] In this example, the base material is gray cast iron, and a self-reactive lubricating coating for hydraulic components is prepared on the base material by magnetron sputtering technology, specifically as follows:

[0047] (1) Keep the substrate rotation speed at 4 rpm, increase the bias voltage from 100 V to 500 V over 60 s, and stabilize it at 500 V for 840 s. Introduce high-purity Ar gas with a flow rate of 40 sccm, and use the anode layer ion source to bombard the substrate for cleaning;

[0048] (2) After ion bombardment of the substrate, impurity ions will contaminate the cavity. Therefore, evacuate the vacuum for 300 s to remove the impurity ions, with a delay of 240 s, and finally increase the Ar gas flow rate from 0 to 40 sccm in the last 60 s;

[0049] (3) Keep the Ar gas flow rate at 40 sccm, increase the bias voltage from 100 V to 400 V over 60 s, and stabilize it at 400 V for 840 s. The ion source bombards the substrate again for cleaning;

[0050] (4) Reduce the Ar gas flow rate from 40 sccm to 30 sccm over 10 s, then stabilize it for 350 s. Reduce the bias voltage from 400 V to 60 V over 120 s, turn off targets 1, 3, and 4, and increase the power of the 2nd Cr target from 0.07 kW to 3 kW over 120 s, and then stabilize the deposition for 240 s;

[0051] (5) Keep the Ar gas flow rate at 30 sccm and the bias voltage at 60 V, and perform Cr / C gradient deposition for 1800 s. Increase the power of the two C targets of 1 and 3 from 0.1 kW to 2 kW, and reduce the power of the 2nd Cr target from 3 kW to 0.1 kW;

[0052] (6) Keep the Ar gas flow rate at 25 sccm, keep the Cr target power at 0.05 kW, keep the C target power at 2 kW unchanged, deposit the W / C gradient layer for 120 s, and increase the power of the 3rd W target from 0.1 kW to 1.0 kW;

[0053] (7) Keep the Ar gas flow rate at 25 sccm, keep the Cr target power at 0.05 kW, keep the C target power at 2 kW unchanged, and keep the W target power at 1.0 kW, and perform stable deposition for 5280 s.

[0054] The structure of the self-reactive lubricating coating for hydraulic components is as Figure 1 shown, including a substrate 1, a Cr bottom layer 2, a Cr / C gradient layer 3, a W / C gradient layer 4, and a W-DLC top layer 5.

[0055] The Raman spectrum of the self-reactive lubricating coating for hydraulic components is as Figure 2 shown. In the figure, the blue peak is the D peak and the green peak is the G peak. Among them, the area ratio of the D peak is 82.14%, the area ratio of the G peak is 17.86%, and the I D / I G value is 4.60.

[0056] Example 2

[0057] In this embodiment, the substrate is gray cast iron, and a self-reactive lubricating coating for hydraulic components is prepared on the substrate by magnetron sputtering technology, specifically as follows:

[0058] (1) The substrate rotation speed is maintained at 4 rpm, the bias voltage is increased from 100 V to 500 V in 50 s and then stabilized for 900 s, high-purity Ar gas with a flow rate of 30 sccm is introduced, and the substrate is bombarded by the anode layer ion source for cleaning;

[0059] (2) Evacuate for 300 s to remove impurity ions, and finally increase the Ar gas flow rate from 0 to 40 sccm in 60 s;

[0060] (3) The Ar gas flow rate is maintained at 30 sccm, the bias voltage is increased from 100 V to 400 V in 50 s and stabilized at 400 V for 900 s, and the ion source bombards the substrate again for cleaning;

[0061] (4) The Ar gas flow rate is maintained at 30 sccm, the bias voltage is decreased from 400 V to 60 V in 120 s, targets 1, 3, and 4 are turned off, the power of target 2 (Cr target) is increased from 0.07 kW to 3 kW in 120 s, and then deposition is stabilized for 240 s;

[0062] (5) The Ar gas flow rate is maintained at 30 sccm, the bias voltage is maintained at 60 V, and Cr / C gradient deposition is carried out for 1800 s. The power of two C targets (targets 1 and 3) is increased from 0.1 kW to 2 kW, and the power of target 2 (Cr target) is decreased from 3 kW to 0.1 kW;

[0063] (6) The Ar gas flow rate is maintained at 25 sccm, the power of the Cr target is maintained at 0.05 kW, the power of the C target is maintained at 2 kW, a W / C gradient layer is deposited for 120 s, and the power of target 3 (W target) is increased from 0.1 kW to 0.5 kW;

[0064] (7) The Ar gas flow rate is maintained at 25 sccm, the power of the Cr target is maintained at 0.05 kW, the power of the C target is maintained at 2 kW, and the power of the W target is maintained at 0.5 kW, and stable deposition is carried out for 5280 s.

[0065] Example 3

[0066] In this embodiment, the substrate is gray cast iron, and a self-reactive lubricating coating for hydraulic components is prepared on the substrate by magnetron sputtering technology, specifically as follows:

[0067] (1) The substrate rotation speed is maintained at 4 rpm, the bias voltage is increased from 100 V to 500 V in 70 s and stabilized at 500 V for 800 s, high-purity Ar gas with a flow rate of 40 sccm is introduced, and the substrate is bombarded by the anode layer ion source for cleaning;

[0068] (2) Evacuate to vacuum for 300 s to remove impurity ions, and increase the Ar gas flow rate from 0 to 40 sccm in the last 60 s;

[0069] (3) Keep the Ar gas flow rate at 40 sccm, increase the bias voltage from 100 V to 400 V over 70 s, and stabilize at 400 V for 800 s. Then, bombard the substrate again with the ion source for cleaning;

[0070] (4) Reduce the Ar gas flow rate from 40 sccm to 30 sccm over 10 s, then stabilize for 350 s. Reduce the bias voltage from 400 V to 50 V over 120 s, turn off targets 1, 3, and 4, increase the power of target 2 (Cr target) from 0.07 kW to 3 kW over 120 s, and then deposit stably for 240 s;

[0071] (5) Keep the Ar gas flow rate at 30 sccm and the bias voltage at 50 V, and deposit the Cr / C gradient layer for 1800 s. Increase the power of the two C targets (targets 1 and 3) from 0.1 kW to 2 kW, and reduce the power of target 2 (Cr target) from 3 kW to 0.1 kW;

[0072] (6) Keep the Ar gas flow rate at 25 sccm, the power of the Cr target at 0.05 kW, and the power of the C target at 2 kW unchanged, deposit the W / C gradient layer for 120 s, and increase the power of target 3 (W target) from 0.1 kW to 1.5 kW;

[0073] (7) Keep the Ar gas flow rate at 25 sccm, the power of the Cr target at 0.05 kW, the power of the C target at 2 kW unchanged, and the power of the W target at 1.5 kW, and deposit stably for 5280 s.

[0074] Comparative Example 1

[0075] This example is a comparative example of Example 1. The substrate is gray cast iron, and a self-reactive lubricating coating for hydraulic components is prepared on the substrate by magnetron sputtering technology, as follows:

[0076] (1) Keep the substrate rotation speed at 4 rpm, increase the bias voltage from 100 V to 500 V over 60 s, and stabilize at 500 V for 840 s. Introduce high-purity Ar gas with a flow rate of 40 sccm, and bombard the substrate with the anode layer ion source for cleaning;

[0077] (2) Evacuate to vacuum for 300 s to remove impurity ions, and increase the Ar gas flow rate from 0 to 40 sccm in the last 60 s;

[0078] (3) Keep the Ar gas flow rate at 40 sccm, increase the bias voltage from 100 V to 400 V over 60 s, and stabilize at 400 V for 840 s. Then, bombard the substrate again with the ion source for cleaning.

[0079] (4) The Ar gas flow rate decreased from 40 sccm to 30 sccm over 10 s and then stabilized for 350 s. The bias voltage decreased from 400 V to 60 V over 120 s, and targets 1, 3, and 4 were turned off. The power of target 2 (Cr target) increased from 0.07 kW to 3 kW over 120 s and then deposited stably for 240 s;

[0080] (5) The Ar gas flow rate was maintained at 30 sccm and the bias voltage at 60 V, and Cr / C gradient deposition was carried out for 1800 s. The power of two C targets (targets 1 and 3) increased from 0.1 kW to 2 kW, and the power of target 2 (Cr target) decreased from 3 kW to 0.1 kW.

[0081] (6) The Ar gas flow rate was maintained at 25 sccm, the power of the Cr target was maintained at 0.05 kW, the power of the C target was maintained at 2 kW without turning on the W target, and stable deposition was carried out for 5400 s.

[0082] The fracture toughness of the coatings in Example 1 and Comparative Example 1 was tested using an American Wilson Tukon 2500 full-automatic Vickers hardness tester. The experimental parameters were set as follows: the load was 1 kgf, the holding time was 10 s, and the indenter of the hardness tester was a diamond regular square pyramid with a vertex angle of 136°.

[0083] The experimental results are as Figure 3 shown. It can be observed that the length of the prefabricated crack on the coating in Example 1 was very short and almost undetectable, while obvious prefabricated cracks could be observed on the coating in Comparative Example 1. This proves that the fracture toughness of the coating in Example 1 is more excellent than that in Comparative Example 1, and further proves that the bonding strength of the coating in Example 1 is higher than that in Comparative Example 1.

[0084] The tribological behavior of the coatings in Examples 1 - 3 and Comparative Example 1 in a hydraulic oil environment was tested using an MRH-3 Jinan Yihua high-speed ring-block wear tester. A GCr15 steel ring with an outer diameter of 40 mm and an inner diameter of 16 mm was used as the counter-pair. The friction experimental parameters were set as follows: ring-block friction experiment, lubricating medium was 46# anti-wear hydraulic oil, test temperature was 30 - 35 °C, test time was 1 h, load was 250 N, and rotation speeds were 92, 184, 276, and 369 rpm.

[0085] The results of the friction experiment are as Figure 4 shown. Under different rotation speed conditions, the friction coefficients of the coatings obtained in Example 1, Example 2, and Example 3 were all less than those of the coating obtained in Comparative Example 1, and the friction performance was more excellent than that in Comparative Example 1.

[0086] After the friction experiment, the XPS spectrum of the self-reactive lubricating coating for hydraulic components prepared in Example 1 is as Figure 5As shown, the blue peak and red peak are W peaks, the purple peak and orange peak are WO3 peaks, and the yellow peak and green peak are WC peaks, indicating that the W element in the coating exists in three forms: W element, WC, and WO3.

[0087] The Tof-SIM detection was performed on the scratch surface of the coating of Example 1 after the friction test in an area with a side length of 100 μm using a time-of-flight secondary ion mass spectrometer. The detection mode was negative ion mode. The mass spectrum obtained was as follows: Figure 6 As shown, it can be seen that the coating plays a certain role as a chemical catalyst for the hydraulic oil, helping to form a stable chemical reaction film, thereby reducing the friction and wear of direct contact between the friction pairs.

[0088] The fracture toughness of the coating of Example 1 after the friction test was tested using a Wilson Tukon 2500 fully automatic Vickers hardness tester from the United States. The experimental parameters were set as follows: load of 1 kgf, holding time of 10 seconds, and the indenter of the hardness tester was a diamond regular quadrangular pyramid with a vertex angle of 136°.

[0089] The experimental results are as follows Figure 7 As shown, it can be observed that the length of the prefabricated cracks on the coating of Example 1 has increased to a certain extent compared with that before the friction test, but still shows relatively good fracture toughness. This proves that the overall durability and performance of the coating under extreme conditions have been significantly improved, and it can continuously reduce the degree of friction and wear after direct contact between friction pairs, thereby extending the service life of hydraulic components.

[0090] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a self-reactive lubricating coating for a hydraulic component, characterized in that: The method comprises the following steps: S1, pre-treating the substrate; S2, depositing a Cr bottom layer on the outside of the substrate by magnetron sputtering under the conditions of Cr target and inert protective gas; S3, depositing a Cr / C gradient layer by magnetron sputtering under the conditions of a C target, a Cr target and an inert protective gas; S4, depositing a W / C gradient layer by magnetron sputtering under the conditions of C target, Cr target, W target and inert protective gas; S5, depositing the W-DLC top layer by magnetron sputtering under the conditions of C target, Cr target, W target and inert protective gas.

2. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: The step S1 specifically includes: under the condition of inert protective gas, firstly bombarding the substrate with the anode layer ion source for cleaning, then evacuating to remove the impurity ions, and then bombarding the substrate with the anode layer ion source again for re-cleaning.

3. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: In the steps S1-S5, the rotation speed of the substrate is maintained at 2-6 rpm.

4. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: In step S1, the bias voltage stabilization value is 300-600V, and the bias voltage adjustment time during cleaning is 40-80s; In step S2, the bias voltage stabilization value is 40-80V, and the bias voltage adjustment time is 100-150s; In step S3, step S4 and step S5, the bias voltage stability value is maintained at 40-80V.

5. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 2, characterized in that: The specific steps of evacuating to remove impurity ions are as follows: evacuating for 300 seconds to remove impurity ions, and increasing the flow rate of the inert protective gas from 0 to 30-60 sccm in the last 60 seconds.

6. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: In step S1, the flow rate of the inert protective gas during cleaning is 30-60 sccm; In step S2, step S3, step S4 and step S5, the flow rate of the inert protective gas is 20-40 sccm.

7. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 5 or 6, characterized in that: The inert protective gas is selected from at least one of Ne, He or Ar.

8. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: In step S2, the Cr target power is increased to 2-4 kW; In step S3, the C target power is increased to 2-3 kW, and the Cr target power is reduced to 0.1 kW; In step S4, the Cr target power is changed to 0.05 kW, and the W target power is increased to 0.5-1.5 kW.

9. The method for preparing the self-reactive lubricating coating for hydraulic components according to claim 1, characterized in that: In step S1, the cleaning and re-cleaning time are both 750-1000s; In step S2, the deposition time is 200-300 s; In step S3, the deposition time is 1500-2000s; In step S4, the deposition time is 80-150 s; In step S5, the deposition time is 4800-6000 s.

10. A self-reactive lubricating coating for hydraulic components, characterized in that: The coating comprises a Cr bottom layer, a Cr / C gradient layer, a W / C gradient layer and a W-DLC top layer which are deposited in sequence on the outer side of a substrate by a magnetron sputtering method.

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