A nanocomposite film and its preparation method and application

Abstract

The present invention belongs to the technical field of nanocomposite films and relates to a nanocomposite film, a preparation method thereof, and an application thereof. The nanocomposite film comprises a nickel layer, a copper layer, and a silver layer stacked in sequence; the nickel layer comprises n stacked nickel-tungsten alloy layers, where n is greater than or equal to 2, and at least two of the nickel-tungsten alloy layers have different tungsten contents; the nanocomposite film has less residual stress inside and a strong bonding force with a substrate; there is no debris peeling phenomenon in a wear test; the average friction coefficient is as low as below 0.20 after running a sliding wear test for 5 minutes; when a 120keV electron beam bombards a target disk and the bearing rotates at 6000rpm, the bearing noise is as low as below 65dB after running for 50,000 seconds; the nanocomposite film is widely used as a surface film layer of a bearing component to reduce friction and extend its service life; the preparation method is simple to operate, low in cost, and easy to mass-produce.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocomposite membranes, and in particular relates to a nanocomposite membrane and a preparation method and application thereof. Background Art

[0002] In an X-ray tube, X-rays are generated by a high-energy electron beam bombarding the anode target. A small number of high-energy electrons are converted into X-rays, while the majority are dissipated as heat. During normal operation, the anode target is bombarded by the high-energy electron beam, causing the anode rotating assembly to rotate at speeds of several thousand or even tens of thousands of revolutions. The bearing's service temperature can reach temperatures exceeding 400°C. In such high temperatures, the bearing's lubricant evaporates or loses its effectiveness, reducing its lubrication capacity. The friction pair formed by the steel balls and rail components fails due to fatigue and adhesive wear, accelerating the wear and failure rate of the bearing's steel balls. This can eventually cause the bearing to seize and lead to premature failure of the X-ray tube.

[0003] Currently, anode targets are lubricated during use through silver or lead plating. Lead plating, due to its low melting point, can volatilize at high temperatures, rendering the lubricant ineffective. Silver plating, however, can cause the silver film to flake off due to its weak bond with the substrate, squeezing out onto the outside of the track and rendering the silver film ineffective in its lubrication.

[0004] For example, CN115376871A discloses an X-ray tube and an X-ray generating device. The bearing assembly of the X-ray tube comprises a first rolling element having a first lubricating layer coated on its surface at a proximal end of a bearing anode target disk, and a plurality of second rolling elements having a second lubricating layer coated on its surface at a distal end of the bearing anode target disk. The first lubricating layer maintains a higher temperature at which it can maintain a solid state. The first lubricating layer is a silver-plated layer, and the second lubricating layer is a lead-plated layer or a molybdenum disulfide-plated layer. No disclosure is made regarding how to improve the bonding strength between the silver layer and the anode target disk.

[0005] For example, CN114540768A discloses a silver-plated and lead-plated composite coating process for solid lubrication of X-ray machine ball tube bearings. The process includes the following steps: cleaning the steel balls, silver-plating the steel balls, continuously performing work on the surface of the steel balls, lead-plating the steel balls, and continuously performing work on the surface of the steel balls. However, the process includes multiple vacuum treatments, high-pressure treatments, and impurity removal treatments, and the operation is highly complex. Moreover, the complex process may result in uneven coating thickness, affecting the lubrication effect and service life. In addition, lead has certain toxicity, and the operation risks and environmental pollution are relatively large.

[0006] In view of this, how to develop a nanocomposite film and its preparation method to ensure the bonding strength and stability of the nanocomposite film with the substrate under high temperature environment and give full play to the lubrication effect to effectively improve the friction performance of mechanical bearing components is an urgent problem to be solved in this field. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a nano-composite film and its preparation method and application. The bonding force between the nano-composite film and the substrate is strong, and the structure is thermally stable, which can effectively play a lubricating role, solving the problem of the existing lead or silver plating technology that the film layer is easy to fall off and the lubrication effect fails due to the low melting point or the weak bonding force between the film and the substrate after heating.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a nanocomposite film, which includes a nickel layer, a copper layer and a silver layer stacked in sequence; the nickel layer includes n layers of nickel-tungsten alloy layers stacked, n≥2 (for example, it can be 2, 3, 4, 5, 6, 7, 8, 9 or 10, etc.), and at least two layers (for example, it can be 2 layers, 3 layers, 4 layers, 5 layers or 6 layers, etc.) of the nickel-tungsten alloy layers have different tungsten contents.

[0010] The nanocomposite film of the present invention improves the bonding force between the silver layer and the substrate by designing a multilayer film structure of a nickel layer, a copper layer and a silver layer stacked in sequence, and optimizing the elemental composition and structure of the nickel layer, thereby improving the wear resistance of the substrate. The n-layer nickel-tungsten alloy layer is designed to be stacked with n layers, n≥2, and at least two layers of the nickel-tungsten alloy layer have different tungsten contents. This not only improves the high temperature resistance of the nanocomposite film and the bonding force between the nickel layer and the substrate, but also reduces internal stress, avoiding cracks during the deposition process, thereby improving the adhesion of the silver layer to the substrate and preventing it from falling off and causing severe wear of the substrate.

[0011] Preferably, the hardness of the nickel layer is 3 GPa to 10 GPa, for example, 3 GPa, 5 GPa, 8 GPa or 10 GPa.

[0012] Preferably, the nickel layer includes 2 to 8 stacked nickel-tungsten alloy layers, for example, 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers or 8 layers.

[0013] Preferably, taking the atomic percentage of each nickel-tungsten alloy layer as 100%, the tungsten content of each nickel-tungsten alloy layer is independently 1% to 30%, for example, it can be 1%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%, etc.

[0014] Preferably, the tungsten content of each nickel-tungsten alloy layer increases gradually along the direction from the nickel layer to the copper layer.

[0015] The present invention further preferably increases the tungsten content gradient of each nickel-tungsten alloy layer along the direction from the nickel layer to the copper layer, that is, it is further preferred that the n-layer nickel-tungsten alloy layer is a single structure with a gradient increasing tungsten content. Compared with the traditional nickel layer without added tungsten content or the nickel-tungsten alloy layer with a single constant tungsten content, the present invention designs a single structure with a gradient increasing tungsten content, which reduces internal stress, avoids the generation of cracks, improves the bonding force between the nickel layer and the substrate, and then improves the adhesion of the silver layer on the substrate, thereby reducing wear.

[0016] Preferably, the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer that are periodically arranged, and the tungsten content of the first nickel-tungsten alloy layer is lower than the tungsten content of the second nickel-tungsten alloy layer.

[0017] Preferably, the number of cycles of the nickel layer is 2 to 4, for example, 2, 3 or 4.

[0018] That is, the nickel layer includes 4, 6 or 8 nickel-tungsten alloy layers that are periodically arranged.

[0019] Preferably, taking the atomic percentage of the first nickel-tungsten alloy layer as 100%, the tungsten content in the first nickel-tungsten alloy layer is 1% to 5%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0020] Preferably, taking the atomic percentage of the second nickel-tungsten alloy layer as 100%, the tungsten content in the second nickel-tungsten alloy layer is 10% to 30%, for example, it can be 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28% or 30%.

[0021] The present invention further prefers that the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer that are periodically arranged, and the tungsten content of the first nickel-tungsten alloy layer is lower than the tungsten content of the second nickel-tungsten alloy layer; that is, a repetitive structure with periodic changes in tungsten content is designed, and the tungsten content of the first nickel-tungsten alloy layer in direct contact with the substrate is low, and it is a soft nickel layer, so that the bonding force between it and the substrate is stronger and the internal stress is reduced more significantly, thereby further improving the adhesion of the silver layer to significantly improve wear.

[0022] Preferably, the thickness of the nickel layer is 50-500 nm, for example, it can be 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm.

[0023] Preferably, the copper layer has a thickness of 50-100 nm, for example, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0024] Preferably, the thickness of the silver layer is 100-1000 nm, for example, it can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1000 nm.

[0025] In a second aspect, the present invention provides a method for preparing the nanocomposite film according to the first aspect, the preparation method comprising the following steps:

[0026] First, n nickel-tungsten alloy layers are sequentially electrodeposited on a substrate to obtain a nickel layer, where n≥2 (for example, 2, 3, 4, 5, 6, 7, 8, 9, or 10); then, a copper layer and a silver layer are sequentially prepared on the nickel layer to obtain the nanocomposite film; wherein, at least two layers (for example, 2, 3, 4, 5, or 6 layers) of the nickel-tungsten alloy layers have different tungsten contents.

[0027] The preparation method of the present invention adopts the electrodeposition method to successfully prepare a nanocomposite film with stable structure and strong bonding with the substrate. It is simple to operate, low in cost, and easy to mass produce.

[0028] Preferably, the electroplating solution used in the electrodeposition comprises 20-100 g / L of nickel source, 30-300 g / L of tungsten source and 150-250 g / L of complexing agent.

[0029] Among them, 20~100g / L nickel source can be, for example, 20g / L, 30g / L, 40g / L, 50g / L, 60g / L, 70g / L, 80g / L, 90g / L or 100g / L; 30~300g / L tungsten source can be, for example, 30g / L, 50g / L, 80g / L, 100g / L, 150g / L, 200g / L, 250g / L or 300g / L; 150~250g / L complexing agent can be, for example, 150g / L, 180g / L, 200g / L, 220g / L or 250g / L.

[0030] Preferably, the nickel source comprises nickel sulfate hexahydrate.

[0031] Preferably, the tungsten source comprises sodium tungstate dihydrate.

[0032] Preferably, the complexing agent comprises sodium citrate dihydrate.

[0033] Preferably, the pH of the electroplating solution is 4-9, for example, 4, 5, 6, 7, 8 or 9.

[0034] Preferably, the electrodeposition temperature is 40-80°C, for example, 40°C, 50°C, 60°C, 70°C or 80°C.

[0035] Preferably, the average current density of the electrodeposition is 5-40 mA / cm 2 , for example, it can be 5mA / cm 2 , 8mA / cm 2 , 10mA / cm 2 , 15mA / cm 2 , 20mA / cm 2 , 25mA / cm 2 、30mA / cm 2 、35mA / cm 2 or 40mA / cm 2 wait.

[0036] Preferably, the preparation method further comprises degassing the nickel layer.

[0037] Preferably, the degassing treatment temperature is 50-200°C, for example, 50°C, 80°C, 100°C, 120°C, 150°C, 180°C or 200°C.

[0038] Preferably, the degassing treatment time is 1 to 24 hours, for example, it can be 1 hour, 2 hours, 4 hours, 8 hours, 16 hours or 24 hours.

[0039] Preferably, the method of preparing the copper layer and the silver layer independently includes any one of electroplating, thermal spraying, magnetron sputtering, ion-assisted deposition or chemical vapor deposition.

[0040] In a third aspect, the present invention provides an application of the nanocomposite film according to the first aspect, wherein the nanocomposite film is used as a surface film layer of a bearing component in an X-ray tube.

[0041] The nanocomposite film of the present invention has a stable structure and strong bonding strength with the substrate, and can be used as a surface film layer of a bearing assembly in an X-ray tube. It can ensure excellent bonding strength between the bearing assembly and the nanocomposite film under high-temperature environments, thereby fully utilizing the lubricating effect of the silver layer therein and extending the service life of the bearing assembly in the X-ray tube.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The nanocomposite film provided by the present invention optimizes the structure of the nickel layer and regulates its tungsten content to construct a gradient transition, reduce internal residual stress, and enhance the bonding force between the nanocomposite film and the substrate. After 5 minutes of sliding wear resistance test, the average friction coefficient is as low as below 0.20. When the target disk is bombarded by a 120keV electron beam and the bearing speed is 6000rpm, the bearing noise is as low as below 65dB after running for 50,000 seconds, and there is no debris peeling off the bearing, thereby effectively exerting the lubricating effect of the silver layer and reducing the friction of the bearing assembly during subsequent use in a high-temperature environment.

[0044] (2) The present invention provides a method for preparing a nanocomposite membrane. The method adopts an electroplating method to prepare a nanocomposite membrane with a stable structure by regulating parameters such as average current density, electroplating solution formula, and deposition time. The method is simple to operate, low in cost, and easy to scale up.

[0045] (3) The application of the nanocomposite film provided by the present invention is that the nanocomposite film has a strong bonding force with the substrate, is not easy to fall off, and is still effective in a high temperature environment, so that it has a wide range of applications, especially as a surface film layer of a bearing assembly in an X-ray tube. It can ensure an excellent bonding force between the bearing assembly and the nanocomposite film in a high temperature environment, thereby giving full play to the lubricating effect of the silver layer therein and extending the service life of the bearing assembly in the X-ray tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a schematic structural diagram of the nanocomposite film A deposited on the surface of the steel ball provided by the present invention.

[0047] Figure 2 Schematic diagram of the structure of the nickel layer in the nanocomposite film according to Example 1 of the present invention.

[0048] Figure 3 Schematic diagram of the structure of the nickel layer in the nanocomposite film described in Example 2 of the present invention.

[0049] Figure 4 Schematic diagram of the structure of the nickel layer in the nanocomposite film described in Example 6 of the present invention.

[0050] In the figure: 1, steel ball; 2, nickel layer; 21, first nickel-tungsten alloy layer; 22, second nickel-tungsten alloy layer; 23, third nickel-tungsten alloy layer; 3, copper layer; 4, silver layer. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0052] Example

[0053] Example 1

[0054] This embodiment provides a nanocomposite film, such as Figure 1 and Figure 2 As shown, the nanocomposite film includes a nickel layer 2, a copper layer 3 and a silver layer 4 stacked in sequence; the nickel layer 2 includes four stacked nickel-tungsten alloy layers; the nickel layer 2 includes a first nickel-tungsten alloy layer 21 and a second nickel-tungsten alloy layer 22 arranged periodically, the number of cycles is 2, the thickness of the first nickel-tungsten alloy layer 21 is 30nm, the tungsten content in the first nickel-tungsten alloy layer 21 is 5%, the thickness of the second nickel-tungsten alloy layer 22 is 25nm, the tungsten content in the second nickel-tungsten alloy layer 22 is 30%, the thickness of the copper layer 3 is 50nm, and the thickness of the silver layer 4 is 150nm.

[0055] This embodiment also provides a method for preparing the above-mentioned nanocomposite film, the preparation method comprising the following steps:

[0056] Prepare an electroplating solution containing 60 g / L NiSO4·6H2O, 150 g / L Na2WO4·2H2O, and 200 g / L C6H5Na3O7·2H2O. Adjust its pH to 6.5 and heat to 60°C. Using a pure nickel plate as a consumable anode and a steel ball 1 as a cathode (i.e., substrate), electrodeposit four nickel-tungsten alloy layers sequentially using a pulsed power supply to obtain a nickel layer 2.

[0057] The electrodeposition comprises: firstly, at an average current density of 40 mA / cm 2 The first nickel-tungsten alloy layer 21 was obtained by electro-deposition under the condition of a deposition time of 100 s, and then the average current density was 10 mA / cm 2 The second nickel-tungsten alloy layer 22 is obtained by electroplating under the condition of a deposition time of 250 s, and the nickel layer 2 is obtained by two cycles.

[0058] The nickel layer 2 was then subjected to a degassing treatment at 50° C. for 4 hours. Then, a 50 nm copper layer 3 and a 150 nm silver layer 4 were sequentially deposited on the nickel layer 2 by magnetron sputtering to obtain the nanocomposite film.

[0059] Example 2

[0060] This embodiment provides a nanocomposite film, such as Figure 1 and Figure 3As shown, the nanocomposite film includes a nickel layer 2, a copper layer 3 and a silver layer 4 stacked in sequence; the nickel layer 2 includes 6 nickel-tungsten alloy layers stacked; the nickel layer 2 includes a first nickel-tungsten alloy layer 21 and a second nickel-tungsten alloy layer 22 periodically arranged, the number of cycles is 3, the thickness of the first nickel-tungsten alloy layer 21 is 20 nm, the tungsten content in the first nickel-tungsten alloy layer 21 is 5%, the thickness of the second nickel-tungsten alloy layer 22 is 20 nm, the tungsten content in the second nickel-tungsten alloy layer 22 is 20%, the thickness of the copper layer 3 is 50 nm, and the thickness of the silver layer 4 is 500 nm.

[0061] This embodiment also provides a method for preparing the above-mentioned nanocomposite film, the preparation method comprising the following steps:

[0062] Prepare an electroplating solution containing 60 g / L NiSO4·6H2O, 100 g / L Na2WO4·2H2O, and 200 g / L C6H5Na3O7·2H2O. Adjust its pH to 6 and heat to 40°C. Using a pure nickel plate as a consumable anode and a steel ball 1 as a cathode (i.e., substrate), electrodeposit six nickel-tungsten alloy layers sequentially using a pulsed power supply to obtain a nickel layer 2.

[0063] The electrodeposition comprises: firstly, at an average current density of 40 mA / cm 2 The first nickel-tungsten alloy layer 21 was obtained by electro-deposition under the condition of a deposition time of 50 s, and then the average current density was 10 mA / cm 2 The second nickel-tungsten alloy layer 22 is obtained by electroplating under the condition of a deposition time of 120 s, and the nickel layer 2 is obtained by three cycles.

[0064] The nickel layer 2 was then subjected to a degassing treatment at 100° C. for 2 h. Then, a 50 nm copper layer 3 and a 500 nm silver layer 4 were sequentially deposited on the nickel layer 2 by magnetron sputtering to obtain the nanocomposite film.

[0065] Example 3

[0066] This embodiment provides a nano-composite film, which includes a nickel layer, a copper layer and a silver layer stacked in sequence; the nickel layer includes four nickel-tungsten alloy layers stacked in sequence; the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer arranged periodically, the number of cycles is 2, the thickness of the first nickel-tungsten alloy layer is 25 nm, and the tungsten content in the first nickel-tungsten alloy layer is 3%, the thickness of the second nickel-tungsten alloy layer is 25 nm, and the tungsten content in the second nickel-tungsten alloy layer is 20%, the thickness of the copper layer is 50 nm, and the thickness of the silver layer is 200 nm.

[0067] This embodiment also provides a method for preparing the above-mentioned nanocomposite film, the preparation method comprising the following steps:

[0068] Prepare an electroplating solution containing 20 g / L NiSO4·6H2O, 30 g / L Na2WO4·2H2O, and 150 g / L C6H5Na3O7·2H2O. Adjust its pH to 8 and heat to 80°C. Use a pure nickel plate as a consumable anode and a steel ball as a cathode (i.e., substrate) to sequentially electrodeposit four nickel-tungsten alloy layers using a pulsed power supply to obtain a nickel layer.

[0069] The electrodeposition comprises: firstly, at an average current density of 8 mA / cm 2 The first nickel-tungsten alloy layer was obtained by electrodeposition at an average current density of 20 mA / cm 2 The second nickel-tungsten alloy layer is obtained by electroplating under the condition of a deposition time of 20 s, and the nickel layer is obtained by two cycles.

[0070] The nickel layer was then subjected to a degassing treatment at 50° C. for 4 hours; and then a 50 nm copper layer and a 200 nm silver layer were sequentially deposited on the nickel layer using a magnetron sputtering method to obtain the nanocomposite film.

[0071] Example 4

[0072] This embodiment provides a nanocomposite film, which is the same as Example 1 except that the nickel layer includes 8 stacked nickel-tungsten alloy layers and the number of cycles is 4, that is, the nickel layer includes 4 cycles of a first nickel-tungsten alloy layer (tungsten content of 5%) and a second nickel-tungsten alloy layer (tungsten content of 30%).

[0073] This embodiment also provides a method for preparing the above-mentioned nanocomposite film. The preparation method is the same as Example 1, except that the electrodeposition process is repeated 4 times, and the deposition time of the first nickel-tungsten alloy layer is adjusted to 50 seconds, and the deposition time of the second nickel-tungsten alloy layer is adjusted to 125 seconds.

[0074] Example 5

[0075] This embodiment provides a nanocomposite film, which is the same as Example 1 except that the nickel layer only includes two stacked nickel-tungsten alloy layers, that is, the nickel layer only includes one period of a first nickel-tungsten alloy layer (tungsten content of 5%) and a second nickel-tungsten alloy layer (tungsten content of 30%).

[0076] This embodiment also provides a method for preparing the above-mentioned nanocomposite film. The preparation method is the same as that of Example 1 except that the second cycle is not repeated during the electrodeposition process, that is, only one cycle of electrodeposition is performed.

[0077] Example 6

[0078] This embodiment provides a nanocomposite film, such as Figure 1 and Figure 4 As shown, the nanocomposite film includes a nickel layer 2, a copper layer 3 and a silver layer 4 stacked in sequence; the nickel layer 2 includes three stacked nickel-tungsten alloy layers; along the direction from the nickel layer 2 to the copper layer 3, the tungsten content of each nickel-tungsten alloy layer increases gradiently, and the three nickel-tungsten alloy layers are respectively a first nickel-tungsten alloy layer 21, a second nickel-tungsten alloy layer 22 and a third nickel-tungsten alloy layer 23, with tungsten contents of 1%, 3% and 20% respectively, and the thicknesses of the three nickel-tungsten alloy layers are respectively 25nm, 25nm and 50nm, the thickness of the copper layer 3 is 100nm, and the thickness of the silver layer 4 is 800nm.

[0079] This embodiment also provides a method for preparing the above-mentioned nanocomposite film, the preparation method comprising the following steps:

[0080] Prepare an electroplating solution comprising 20 g / L NiSO4·6H2O, 60 g / L Na2WO4·2H2O, and 150 g / L C6H5Na3O7·2H2O, adjust its pH to 9, and heat to 60°C. Using a pure nickel plate as a consumable anode and a steel ball 1 as a cathode (i.e., a substrate), a pulsed power supply is used to sequentially electrodeposit a first nickel-tungsten alloy layer 21, a second nickel-tungsten alloy layer 22, and a third nickel-tungsten alloy layer 23 to obtain a nickel layer 2.

[0081] The electrodeposition comprises: firstly, at an average current density of 10 mA / cm 2 The first nickel-tungsten alloy layer 21 was obtained by electro-deposition at an average current density of 15 mA / cm 2 The second nickel-tungsten alloy layer 22 was obtained by electro-deposition under the condition of a deposition time of 50 s, and finally the average current density was 25 mA / cm 2 The third nickel-tungsten alloy layer 23 is obtained by electroplating under the condition of a deposition time of 30 seconds.

[0082] The nickel layer 2 was then subjected to a degassing treatment at 80° C. for 4 hours. Then, a 100 nm copper layer 3 and an 800 nm silver layer 4 were sequentially deposited on the nickel layer 2 by magnetron sputtering to obtain the nanocomposite film.

[0083] Example 7

[0084] This embodiment provides a nanocomposite film. The nanocomposite film is the same as that of embodiment 1 except that the tungsten content in the first nickel-tungsten alloy layer is 10%.

[0085] This embodiment also provides a method for preparing the above-mentioned nanocomposite film. The preparation method is the same as that of Example 1, except that the concentration of Na2WO4·2H2O in the electroplating solution used for electrodeposition is adjusted to 200 g / L, the concentration of C6H5Na3O7·2H2O is adjusted to 250 g / L, and the pH value of the electroplating solution is adjusted to 6.

[0086] Example 8

[0087] This embodiment provides a nanocomposite film. The nanocomposite film is the same as that of embodiment 3 except that the tungsten content in the second nickel-tungsten alloy layer is 8%.

[0088] This embodiment also provides a method for preparing the above-mentioned nanocomposite film. In the preparation method, the average current density of the first nickel-tungsten alloy layer deposited is adjusted to 12 mA / cm2 except that the pH value is 9. 2 The average current density of the second nickel-tungsten alloy layer electrodeposited is 15 mA / cm 2 , the rest are the same as in Example 3.

[0089] 2. Comparative Example

[0090] Comparative Example 1

[0091] This comparative example provides a nanocomposite film, which is the same as Example 1 except that the nickel layer is a tungsten-nickel alloy layer with a tungsten content of 30% and a thickness of 110 nm.

[0092] This comparative example provides a method for preparing the above-mentioned nanocomposite film. The preparation method is as follows: except that the electrodeposition process is performed only when the average current density is 10 mA / cm 2 Except that the nickel layer was obtained by electrodeposition under the condition of a deposition time of 1100 s, the rest were the same as in Example 1.

[0093] Comparative Example 2

[0094] This comparative example provides a nanocomposite film, which is the same as Example 1 except that the nickel layer is a tungsten-nickel alloy layer with a tungsten content of 5% and a thickness of 110 nm.

[0095] This comparative example provides a method for preparing the above-mentioned nanocomposite film. The preparation method is as follows: 2 Except that the nickel layer was obtained by electrodeposition under the condition of a deposition time of 380 s, the rest were the same as in Example 1.

[0096] 3. Test and its results

[0097] The nanocomposite film obtained in the above embodiment or comparative example, i.e., the nanocomposite film deposited on the steel ball, i.e., the coated steel ball, was subjected to a sliding wear resistance test. The coated steel ball was subjected to a friction test with a load of 3N, circular motion, a rotation speed of 100rpm, and a grinding medium of bearing steel. After 5 minutes of circulation, the change in the average friction coefficient was recorded. The bearing was then installed in a test tube, and the target disk was bombarded by an electron beam to evaluate the structural thermal stability of the coated steel ball. The binding force of the lubricating film was evaluated by noise (noise after operation). The test conditions were a vacuum degree of less than 10 -4 Pa, the rotation speed was 6000 rpm, the applied load was 50N, the electron beam energy was 120 KeV, and the test time was 50000s; the results are shown in Table 1.

[0098] Table 1

[0099] From the data in Table 1 we can see that:

[0100] (1) It can be seen from Examples 1 to 4 that the present invention enhances the bonding strength between the nanocomposite film and the substrate by designing the structure of the nanocomposite film, optimizing the structure of the nickel-tungsten alloy layer and regulating the tungsten content, and can effectively control the residual stress of the coating, thereby preventing debris from peeling off during the wear test, thereby effectively exerting the lubricating effect of the silver layer and reducing the friction during the subsequent use of the bearing assembly. The average friction coefficient in the wear test is as low as below 0.20. At the same time, the high percentage of Ni-W (10%-30%) in the layered structure can effectively reduce and extend the service life, maintain the thermal stability of the structure, and reduce the bearing noise to below 65dB.

[0101] (2) Combining Example 1 with Example 5 and Example 6, it can be seen that the nickel layer in Example 5 only includes two stacked nickel-tungsten alloy layers, and the nickel layer in Example 6 includes three stacked nickel-tungsten alloy layers, both of which lead to an increase in the average friction coefficient in the wear test and an increase in noise after operation. This shows that the present invention further improves the performance of the obtained nanocomposite film by further optimizing the nanocomposite film to include a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer that are periodically arranged, and further optimizing the number of cycles of the nickel layer to be 2 to 4.

[0102] (3) Combining Example 1 with Example 7 and Example 8, it can be seen that the tungsten content in the first nickel-tungsten alloy layer in Example 7 is relatively high, which makes it easy to generate cracks during the coating preparation process, and the film-base bonding strength becomes poor, resulting in an increase in the average friction coefficient in the wear test and an increase in noise after subsequent operation. The tungsten content in the second nickel-tungsten alloy layer in Example 8 is relatively low, which causes the nickel layer to soften and grow grains to grow during high-temperature rotation, resulting in an increase in the wear test in the friction experiment and an increase in noise after subsequent operation. This shows that the present invention further prefers that the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer that are periodically arranged, and further prefers that the tungsten content in the first nickel-tungsten alloy layer is 1%~5%, and the tungsten content in the second nickel-tungsten alloy layer is 10%~30%, which further improves the bonding strength and structural thermal stability of the nanocomposite film to the substrate.

[0103] (4) From Example 1, Comparative Examples 1 and 2, it can be seen that since the nanocomposite film in Comparative Example 1 only has one tungsten-nickel alloy layer with a tungsten content of 30%, its hardness is too high and its internal stress is large, so that the whole film is easily peeled off; since the nanocomposite film in Comparative Example 2 only has one tungsten-nickel alloy layer with a tungsten content of 5%, its hardness is too low and the bonding strength of the film under high load and high heat environment cannot be guaranteed; this shows that the nickel layer selected by the present invention includes n layers of nickel-tungsten alloy layers stacked, n≥2, and at least two layers of the nickel-tungsten alloy layers have different tungsten contents, so as to construct a gradient transition of tungsten content, reduce residual stress, and enhance the bonding strength of the nanocomposite film to the substrate and the structural thermal stability.

[0104] In summary, the nanocomposite film provided by the present invention, as well as its preparation method and application, successfully obtains a nanocomposite film with a thermally stable structure and strong bonding with the substrate by optimizing the structure and tungsten content of the nickel layer in the nanocomposite film. This solves the problem in the prior art that the single nickel structure layer is easily deformed and detached, resulting in the silver layer being unable to fully exert its lubricating effect, and provides a high-quality surface film layer structure for bearing components.

[0105] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A nanocomposite film, characterized in that: The nanocomposite film comprises a nickel layer, a copper layer and a silver layer stacked in sequence; The nickel layer includes n stacked nickel-tungsten alloy layers, where n is greater than or equal to 2, and the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer that are periodically arranged; Based on the atomic percentage of the first nickel-tungsten alloy layer being 100%, the tungsten content in the first nickel-tungsten alloy layer is 1% to 5%; based on the atomic percentage of the second nickel-tungsten alloy layer being 100%, the tungsten content in the second nickel-tungsten alloy layer is 10% to 30%.

2. The nanocomposite film according to claim 1, characterized in that The number of cycles of the nickel layer is 2 to 4.

3. The nanocomposite film according to claim 1, characterized in that The thickness of the nickel layer is 50-500 nm; The thickness of the copper layer is 50-100 nm; The thickness of the silver layer is 100-1000 nm.

4. A method for preparing a nanocomposite film according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: First, n nickel-tungsten alloy layers are sequentially electrodeposited on a substrate to obtain a nickel layer, where n is greater than or equal to 2; and then a copper layer and a silver layer are sequentially prepared on the nickel layer to obtain the nanocomposite film; Wherein, the nickel layer includes a first nickel-tungsten alloy layer and a second nickel-tungsten alloy layer arranged periodically; Based on the atomic percentage of the first nickel-tungsten alloy layer being 100%, the tungsten content in the first nickel-tungsten alloy layer is 1% to 5%; based on the atomic percentage of the second nickel-tungsten alloy layer being 100%, the tungsten content in the second nickel-tungsten alloy layer is 10% to 30%.

5. The preparation method according to claim 4, characterized in that The electroplating solution used in the electroplating comprises 20-100 g / L nickel source, 30-300 g / L tungsten source and 150-250 g / L complexing agent; The pH of the electroplating solution is 4-9.

6. The preparation method according to claim 4, characterized in that The temperature of the electrodeposition is 40-80°C; The average current density of the electrodeposition is 5-40 mA / cm 2 .

7. A use of the nanocomposite film according to any one of claims 1 to 3, characterized in that: The nanocomposite film is used as a surface film layer of a bearing component in an X-ray tube.

Images