A large thickness wear-reducing and life-extending composite coating and a method of making the same

Abstract

The application discloses a large-thickness wear-reducing and life-extending composite coating and a preparation method thereof. The Cr layer and the WMoTaNbCr layer are prepared on the electroplated Cr coating by the magnetron sputtering method. The Cr target power is increased from 0 W to a first power threshold when the Cr layer is prepared by the magnetron sputtering method. The WMoTaNbCr target power is increased from 0 W to a second power threshold and the Cr target power is decreased from the first power threshold to 0 W when the WMoTaNbCr layer is prepared by the magnetron sputtering method. The power is kept at the second power threshold until the WMoTaNbCr layer reaches a predetermined thickness. The Cr layer and the WMoTaNbCr layer are prepared on the electroplated Cr coating by the magnetron sputtering method. The WMoTaNbCr layer can isolate external heat, inhibit heat transfer and relieve heat accumulation in the electroplated Cr coating, so that the problem of thermal stress cracks in the traditional electroplated Cr coating can be avoided.

Description

Technical Field

[0001] This invention belongs to the field of life-extending coating technology, and particularly relates to a thick friction-reducing and life-extending composite coating and its preparation method. Background Technology

[0002] Artillery plays an irreplaceable role as a suppressive weapon in conventional warfare. The barrel is the core component of an artillery system, determining its combat effectiveness. While achieving long range, high muzzle velocity, and high rate of fire, the high temperature, high pressure, and high propellant charge environment of the bore make barrel life an increasingly prominent issue. As the barrel gradually ablates and wears down, changes in its internal structure occur, altering the ballistic performance of the artillery. For example, a decrease in muzzle velocity forces a reduction in range, and may even result in the first shot being fired at close range. Currently, barrel life has become a crucial factor and key technology restricting the performance of artillery.

[0003] Compared to traditional life-extending technologies such as improving the internal structure design, manufacturing process, and material replacement, internal surface coating technology is an effective and economical means. Currently, electroplated Cr coating is commonly used for barrel life extension in China. However, as... Figure 2 As shown, electroplated Cr coatings are prone to thermal stress cracking. Summary of the Invention

[0004] The purpose of this invention is to provide a thick, friction-reducing, and life-extending composite coating and its preparation method, so as to mitigate heat accumulation in electroplated Cr coatings and avoid thermal stress cracking.

[0005] This invention adopts the following technical solution: a method for preparing a thick friction-reducing and life-extending composite coating, comprising the following steps:

[0006] A magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer were sequentially prepared on an electroplated Cr coating using a magnetron sputtering method.

[0007] Specifically, during magnetron sputtering of the Cr layer, the Cr target power is increased from 0W to a first power threshold; during magnetron sputtering of the WMoTaNbCr layer, the WMoTaNbCr target power is increased from 0W to a second power threshold while the Cr target power is reduced from the first power threshold to 0W, and the second power threshold is maintained until the magnetron sputtering of the WMoTaNbCr layer reaches a predetermined thickness.

[0008] Furthermore, the electroplated Cr layer is plasma cleaned before the magnetron sputtered Cr layer is prepared.

[0009] Furthermore, during the magnetron sputtering process, the Cr target is connected to a DC power supply, while the WMoTaNbCr target is connected to an RF power supply.

[0010] Another technical solution of the present invention: a thick friction-reducing and life-extending composite coating, prepared by the above method, comprising an electroplated Cr layer, wherein the surface of the electroplated Cr layer is sequentially covered with a magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer;

[0011] The thickness of the Cr layer sputtered by magnetron sputtering is 100–300 nm.

[0012] The thickness of the magnetron sputtered WMoTaNbCr layer is 5–10 μm;

[0013] The thickness of the electroplated Cr layer is greater than the sum of the thicknesses of the magnetron sputtered Cr layer and the magnetron sputtered WMoTaNbCr layer.

[0014] Furthermore, in the portion of the magnetron sputtered WMoTaNbCr layer adjacent to the magnetron sputtered Cr layer, the Cr content transitions gradually along a first direction, which points from the interface of the magnetron sputtered WMoTaNbCr layer to the outer surface.

[0015] The beneficial effects of this invention are: by sequentially preparing a magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer on the surface of an electroplated Cr coating, the magnetron sputtered WMoTaNbCr layer can isolate external heat, suppress heat transfer, and mitigate heat accumulation in the electroplated Cr coating, thereby avoiding the problem of easy thermal stress cracking present in traditional electroplated Cr coatings. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the usage state of a thick friction-reducing and life-extending composite coating according to an embodiment of the present invention.

[0017] Figure 2 This is a schematic diagram of thermal stress cracks that occur in electroplated Cr coatings in existing technologies.

[0018] Figure 3 A schematic diagram of a complete electroplated Cr coating;

[0019] Figure 4 This is a schematic diagram of the magnetron sputtering of the Cr layer in an embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of a magnetron sputtered WMoTaNbCr layer in an embodiment of the present invention.

[0021] Wherein: 10. Substrate; 20. Electroplated Cr coating; 30. Magnetron sputtered Cr layer; 40. Magnetron sputtered WMoTaNbCr layer. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Researchers have been working to address the persistent problem of thermal stress cracking in electroplated Cr coatings, focusing on aspects such as equipment, process parameters, coating microstructure and properties, and crack control. However, the problem remains unsolved.

[0024] Refractory high-entropy alloys are high-entropy alloys containing three or more refractory metals. They have the characteristics of high hardness, wear resistance, high melting point, low thermal conductivity, and good thermal stability. The thermal conductivity and thermal diffusivity of high-entropy alloys are lower than those of pure metals. However, there is no mature plating solution formula for electroplating high-entropy alloy coatings, which makes it impossible to achieve the required performance indicators. Moreover, it is difficult to prepare large-volume refractory high-entropy alloy coatings to replace electroplated Cr coatings using traditional alloying techniques.

[0025] This invention discloses a method for preparing a thick, friction-reducing, and life-extending composite coating, comprising the following steps: sequentially preparing a magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer on an electroplated Cr coating using a magnetron sputtering method; wherein, during magnetron sputtering of the Cr layer, the Cr target power is increased from 0W to a first power threshold; during magnetron sputtering of the WMoTaNbCr layer, the WMoTaNbCr target power is increased from 0W to a second power threshold while the Cr target power is decreased from the first power threshold to 0W, and the second power threshold is maintained until the magnetron sputtered WMoTaNbCr layer reaches a predetermined thickness.

[0026] Regarding power adjustment, for example, when magnetron sputtering a Cr layer, the Cr target power is increased from 0W to a first power threshold. In this invention, the first power threshold is designed to be 150W, that is, the power increase threshold is set according to the coating thickness, such as 10W / min. Similarly, the second power threshold is designed to be 200W, and the power, time, and power increase rate can be set according to actual process requirements.

[0027] This invention, by sequentially preparing a magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer on the surface of an electroplated Cr coating, can isolate external heat, suppress heat transfer, and mitigate heat accumulation in the electroplated Cr coating, thereby avoiding the problem of easy thermal stress cracking present in traditional electroplated Cr coatings.

[0028] Since it is difficult to prepare coatings with large thicknesses (such as tens or even hundreds of micrometers) by magnetron sputtering, the large thickness characteristic of the coating can be retained by electroplating Cr coatings. By sputtering WMoTaNbCr layers, the refractory high-entropy alloy WMoTaNbCr layers have advantages such as dense structure, high hardness, wear resistance, high melting point, low thermal conductivity and good high temperature stability. Therefore, they can isolate external heat and reduce the heat accumulation of electroplated Cr coatings.

[0029] Furthermore, electroplating (Cr) and magnetron sputtering are two different coating preparation processes with different preparation principles, resulting in different microstructures and making it difficult for the layers to fuse together. Specifically, coatings prepared using electroplating and magnetron sputtering techniques, even with the same composition, will have significant differences in microstructure. Coatings prepared by different methods will have obvious interfaces between layers. This invention addresses this problem by employing the principle of "like dissolves like" and solving it through a gradient transition of coating composition and structure.

[0030] The gradient transition of coating composition refers to: 1) preparing coatings with the same composition using different coating preparation methods (i.e., preparing a magnetron sputtered Cr layer on the surface of an electroplated Cr coating); 2) preparing coatings with similar compositions using the same preparation method (i.e., preparing a magnetron sputtered WMoTaNbCr layer on the surface of a magnetron sputtered Cr layer).

[0031] The gradient transition of microstructure refers to: 1) the transition of spherical cluster particles on the surface of electroplated Cr coating and magnetron sputtered Cr layer; 2) the transition of columnar crystal structure between magnetron sputtered Cr layer and magnetron sputtered WMoTaNbCr layer.

[0032] The bonding strength between the electroplated Cr coating and the magnetron sputtered WMoTaNbCr layer can be achieved by magnetron sputtering a Cr layer.

[0033] In one embodiment, the electroplated Cr layer is plasma-cleaned before the magnetron sputtered Cr layer is prepared. Additionally, during magnetron sputtering, the Cr target is connected to a DC power supply, and the WMoTaNbCr target is connected to an RF power supply.

[0034] The friction-reducing and life-extending composite coating prepared by the method of this invention can solve the disadvantage of traditional electroplated Cr layers being prone to thermal stress cracking, and can also solve the problem of low coating thickness prepared by magnetron sputtering technology. The method is simple to operate, low in cost, and easy to promote and apply.

[0035] Example 1:

[0036] The specific preparation method is as follows:

[0037] (1) Thin film deposition preparation: A 45# steel substrate with an electroplated Cr coating (thickness: 100μm) is placed into a vacuum chamber containing a Cr target and a WMoTaNbCr target. The Cr target is connected to a DC power supply, and the WMoTaNbCr target is connected to an RF power supply. The target-substrate distance is 60mm. The vacuum is evacuated to 3×10 -3 After Pa, 60 sccm of argon gas was introduced to maintain the pressure inside the vacuum chamber at approximately 0.74 Pa. Then, plasma cleaning was performed for 10 minutes under a sample bias voltage of -400 V. Electroplated Cr coating, such as... Figure 3 As shown, Figure 3 (a) shows the surface morphology of the electroplated Cr coating. Figure 3(b) is a cross-sectional morphology diagram of the electroplated Cr coating.

[0038] (2) Magnetron sputtering of Cr layer: A pure metallic Cr layer was deposited for 10 min under the conditions of sample bias voltage of -200V and argon flow rate of 20 sccm. During the deposition process, the Cr target power was increased from 0W to 150W. The prepared magnetron sputtered Cr layer is shown in the figure. Figure 4 As shown, Figure 4 (a) is a surface morphology diagram of the magnetron sputtered Cr layer. Figure 4 (b) is a cross-sectional topography of the magnetron sputtered Cr layer.

[0039] (3) Magnetron sputtering preparation of WMoTaNbCr layer: Within 10 min, the Cr target power was reduced from 150 W to 0 W, and the WMoTaNbCr target power was increased from 0 W to 200 W. A WMoTaNbCr layer was deposited for 360 min while maintaining a sample bias voltage of -200 V and an argon flow rate of 20 sccm. The prepared magnetron sputtered WMoTaNbCr layer is shown below. Figure 5 As shown, Figure 5 (a) is a surface morphology diagram of the magnetron sputtered WMoTaNbCr layer. Figure 5 (b) is a cross-sectional topography of the magnetron sputtered WMoTaNbCr layer.

[0040] During the deposition process, the gas pressure in the vacuum chamber in steps (2) and (3) is kept at 0.54 Pa and the workpiece rack rotation speed is kept at 5 r / min.

[0041] In this embodiment, the thickness of the magnetron sputtered Cr layer is 100 nm, and the thickness of the magnetron sputtered WMoTaNbCr layer is 5 μm.

[0042] Example 2:

[0043] The specific preparation method is as follows:

[0044] (1) Thin film deposition preparation: A 45# steel substrate with an electroplated Cr layer (thickness: 100μm) is placed into a vacuum chamber containing a Cr target and a WMoTaNbCr target. The Cr target is connected to a DC power supply, and the WMoTaNbCr target is connected to an RF power supply. The target-substrate distance is 60mm. The vacuum is evacuated to 3×10 -3 After Pa, 60 sccm of argon gas is introduced to maintain the gas pressure in the vacuum chamber at about 0.74 Pa. Then, plasma cleaning is performed for 10 min under the condition of sample bias voltage of -400 V.

[0045] (2) Preparation of Cr layer by magnetron sputtering: a pure metal Cr layer was deposited for 35 min under the conditions of sample bias voltage of -200V and argon flow rate of 20sccm. During the deposition process, the Cr target power was increased from 0W to 150W.

[0046] (3) Preparation of WMoTaNbCr layer by magnetron sputtering: The Cr target power was reduced from 150W to 0W within 30 minutes, and the WMoTaNbCr target power was increased from 0W to 200W. The WMoTaNbCr layer was deposited for 780 minutes while maintaining the sample bias voltage at -200V and the argon flow rate at 20sccm.

[0047] During the deposition process, the gas pressure in the vacuum chamber in steps (2) and (3) is kept at 0.54 Pa and the workpiece rack rotation speed is kept at 5 r / min.

[0048] In this embodiment, the thickness of the magnetron sputtered Cr layer is 300 nm, and the thickness of the magnetron sputtered WMoTaNbCr layer is 10 μm.

[0049] Example 3:

[0050] The specific preparation method is as follows:

[0051] (1) Thin film deposition preparation: A 45# steel substrate with an electroplated Cr layer (thickness: 100μm) is placed into a vacuum chamber containing a Cr target and a WMoTaNbCr target. The Cr target is connected to a DC power supply, and the WMoTaNbCr target is connected to an RF power supply. The target-substrate distance is 60mm. The vacuum is evacuated to 3×10 -3 After Pa, 60 sccm of argon gas is introduced to maintain the gas pressure in the vacuum chamber at about 0.74 Pa. Then, plasma cleaning is performed for 10 min under the condition of sample bias voltage of -400 V.

[0052] (2) Preparation of Cr layer by magnetron sputtering: a pure metal Cr layer was deposited for 25 min under the conditions of sample bias voltage of -200V and argon flow rate of 20sccm. During the deposition process, the Cr target power was increased from 0W to 150W.

[0053] (3) Preparation of WMoTaNbCr layer by magnetron sputtering: The Cr target power was reduced from 150W to 0W within 20 minutes, and the WMoTaNbCr target power was increased from 0W to 200W. The WMoTaNbCr layer was deposited for 600 minutes while maintaining the sample bias voltage at -200V and the argon flow rate at 20sccm.

[0054] During the deposition process, the gas pressure in the vacuum chamber in steps (2) and (3) is kept at 0.54 Pa and the workpiece rack rotation speed is kept at 5 r / min.

[0055] In this embodiment, the thickness of the magnetron sputtered Cr layer is 200 nm, and the thickness of the refractory high-entropy alloy WMoTaNbCr layer is 8 μm.

[0056] Example 4:

[0057] The specific preparation method is as follows:

[0058] (1) Thin film deposition preparation: A 45# steel substrate with an electroplated Cr layer (thickness: 100μm) is sent into a vacuum chamber containing a Cr target and a WMoTaNbCr target. The Cr target is connected to a DC power supply, and the WMoTaNbCr target is connected to an RF power supply. The target-substrate distance is 60mm. After evacuating to 3×10-3Pa, 60sccm of argon gas is introduced to maintain the gas pressure in the vacuum chamber at about 0.74Pa. Then, plasma cleaning is performed for 10min under the condition of sample bias voltage of -400V.

[0059] (2) Preparation of Cr layer by magnetron sputtering: A pure metal Cr layer was deposited for 18 min under the conditions of sample bias voltage of -200V and argon flow rate of 20sccm. During the deposition process, the Cr target power was increased from 0W to 150W.

[0060] (3) Preparation of WMoTaNbCr layer by magnetron sputtering: The Cr target power was reduced from 150W to 0W within 15min, and the WMoTaNbCr target power was increased from 0W to 200W. The WMoTaNbCr layer was deposited for 360min while keeping the sample bias voltage at -200V and the argon flow rate at 20sccm.

[0061] During the deposition process, the gas pressure in the vacuum chamber in steps (2) and (3) is kept at 0.54 Pa and the workpiece rack rotation speed is kept at 5 r / min.

[0062] In this embodiment, the thickness of the magnetron sputtered Cr layer is 150 nm, and the thickness of the refractory high-entropy alloy WMoTaNbCr layer is 5 μm.

[0063] This invention also discloses a thick, friction-reducing, and life-extending composite coating, prepared using the method described above, such as... Figure 1 As shown, the substrate includes a substrate 10, the surface of which has an electroplated Cr layer 20. The surface of the electroplated Cr layer 20 has a magnetron sputtered Cr layer 30 and a magnetron sputtered WMoTaNbCr layer 40 in sequence. The thickness of the magnetron sputtered Cr layer 30 is 100-300 nm. The thickness of the magnetron sputtered WMoTaNbCr layer 40 is 5-10 μm. The thickness of the electroplated Cr layer 20 is greater than the sum of the thicknesses of the magnetron sputtered Cr layer 30 and the magnetron sputtered WMoTaNbCr layer 40.

[0064] Specifically, in the portion of the magnetron sputtered WMoTaNbCr layer 40 adjacent to the magnetron sputtered Cr layer 30, the Cr content transitions gradually along a first direction, which points from the interface of the magnetron sputtered WMoTaNbCr layer to the outer surface.

[0065] Therefore, the friction-reducing and life-extending composite coating prepared by this invention can not only solve the disadvantage of traditional electroplated Cr coatings being prone to thermal stress cracking, but also solve the problem of low coating thickness prepared by single magnetron sputtering technology, and has broad application prospects in the field of tube friction reduction and life extension.

Claims

1. A method for preparing a thick, friction-reducing, and life-extending composite coating, characterized in that, Includes the following steps: A magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer were sequentially prepared on an electroplated Cr layer using a magnetron sputtering method. Specifically, during magnetron sputtering of the Cr layer, the Cr target power is increased from 0 W to a first power threshold; during magnetron sputtering of the WMoTaNbCr layer, the WMoTaNbCr target power is increased from 0 W to a second power threshold while the Cr target power is reduced from the first power threshold to 0 W, and the second power threshold is maintained until the magnetron sputtering of the WMoTaNbCr layer reaches a predetermined thickness.

2. The method for preparing a thick, friction-reducing, and life-extending composite coating as described in claim 1, characterized in that, The electroplated Cr layer was plasma cleaned before the magnetron sputtered Cr layer was prepared.

3. The method for preparing a thick, friction-reducing, and life-extending composite coating as described in claim 2, characterized in that, During magnetron sputtering, the Cr target is connected to a DC power supply, while the WMoTaNbCr target is connected to an RF power supply.

4. A thick, friction-reducing, and life-extending composite coating, characterized in that: The preparation is carried out by the method according to any one of claims 1-3, including an electroplated Cr layer, wherein the surface of the electroplated Cr layer is sequentially covered with a magnetron sputtered Cr layer and a magnetron sputtered WMoTaNbCr layer; The thickness of the magnetron sputtered Cr layer is 100~300nm; The thickness of the magnetron sputtered WMoTaNbCr layer is 5~10μm; The thickness of the electroplated Cr layer is greater than the sum of the thicknesses of the magnetron sputtered Cr layer and the magnetron sputtered WMoTaNbCr layer.

5. The thick, friction-reducing, and life-extending composite coating as described in claim 4, characterized in that, In the magnetron sputtered WMoTaNbCr layer, the portion adjacent to the magnetron sputtered Cr layer exhibits a gradient change in Cr content along a first direction, which is the direction from the connecting surface of the magnetron sputtered WMoTaNbCr layer to the outer surface.

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