Nickel-plated graphene reinforced NiFeCrSi gradient coating and preparation method thereof

Abstract

The invention discloses a nickel-plated graphene enhanced NiFeCrSi gradient coating and a preparation method of the nickel-plated graphene enhanced NiFeCrSi gradient coating. The gradient coating comprises the following components: (1) a base layer, namely a NiFeCrSi alloy coating; (2) a plurality of transition layer-NiFeCrSi alloy coatings are doped with nickel-plated graphene; (3) doping nickel-plated graphene into the wear-resistant layer, namely the NiFeCrSi alloy coating; the content of NiFeCrSi alloy in the transition layers and the wear-resistant layers is sequentially reduced from bottom to top, and the content of nickel-plated graphene in the transition layers and the wear-resistant layers is increased; the gradient coating is prepared on the surface of a metal matrix by adopting a laser cladding technology. According to the three-layer gradient structure coating, the coating has smooth physical and chemical property transition among different layers, interface stress and structural defects are reduced to the maximum extent, and the hardness and wear resistance of the coating are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface strengthening coatings, and specifically relates to a nickel-plated graphene-enhanced NiFeCrSi gradient coating and a preparation method thereof. Background Art

[0002] In the manufacture of hydraulic components, especially in key components such as the plunger of hydraulic motors, surface wear has always been the main problem affecting component performance and service life. Under low-speed and heavy-load conditions, the matching surfaces of the plunger and other components are often in a mixed lubrication state, which will lead to increased friction, and then cause abrasive wear and fatigue wear. The accumulation of these wears will not only lead to a decrease in the sealing and load-bearing capacity between the plunger and the cylinder body, but also significantly shorten the service life of the hydraulic motor. Therefore, improving the surface wear resistance and fatigue resistance of hydraulic components is a key measure to improve equipment reliability and extend service life.

[0003] As an advanced surface strengthening treatment method, laser cladding technology has been widely used in surface strengthening of hydraulic components due to its ability to precisely control the modification of the material surface with its high-energy laser beam. As a basic alloy material, NiFeCrSi alloy has excellent wear resistance and high hardness, but a single NiFeCrSi coating still has certain limitations under complex and harsh working conditions. In order to improve its performance under high load and harsh working conditions, a nanomaterial with excellent lubrication properties, graphene, can be added to the coating. However, the physical and chemical properties of NiFeCrSi alloy and graphene are quite different, which can easily lead to problems such as stress concentration, crack generation and coating shedding. In order to solve these problems, the use of laser cladding technology to prepare gradient coatings is an effective solution. The gradient coating can smoothly transition the performance difference between NiFeCrSi alloy and graphene, reduce the stress concentration between the two, and thus significantly reduce the risk of cracks and coating shedding. Therefore, it is of great practical significance to study the preparation of graphene gradient coatings by laser cladding. Summary of the invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and propose a nickel-plated graphene enhanced NiFeCrSi gradient coating and a preparation method thereof, so as to improve the wear resistance and achieve a balance between surface quality and wear resistance while ensuring good metallurgical bonding between the coating and the substrate and between the layers.

[0005] The objective of the present invention is achieved through the following technical scheme: a nickel-plated graphene-enhanced NiFeCrSi gradient coating, the gradient coating comprising: (1) a base layer - a NiFeCrSi alloy coating; (2) a plurality of transition layers - a NiFeCrSi alloy coating doped with nickel-plated graphene; (3) a wear-resistant layer - a NiFeCrSi alloy coating doped with nickel-plated graphene; the plurality of transition layers and the wear-resistant layers have a decreasing content of NiFeCrSi alloy and an increasing content of nickel-plated graphene from bottom to top; the gradient coating is prepared on the surface of a metal substrate.

[0006] Furthermore, the gradient structure enables the coatings between different levels to have a smooth transition of physical and chemical properties, minimizes interface stress and structural defects, and improves the hardness and wear resistance of the coating.

[0007] Furthermore, the content of nickel-plated graphene in the wear-resistant layer does not exceed 5wt%.

[0008] Furthermore, the gradient coating includes: (1) a base layer - a NiFeCrSi alloy coating; (2) a transition layer - a 97.5wt% NiFeCrSi alloy coating doped with 2.5wt% nickel-plated graphene; (3) a wear-resistant layer - a 95wt% NiFeCrSi alloy coating doped with 5wt% nickel-plated graphene.

[0009] On the other hand, the present invention also provides a method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating, comprising the following steps: S1: preparing gradient wear-resistant coating powder, including: (1) base layer - NiFeCrSi alloy powder; (2) a plurality of transition layers - NiFeCrSi alloy powder doped with nickel-plated graphene; (3) wear-resistant layer - NiFeCrSi alloy powder doped with nickel-plated graphene, wherein the content of NiFeCrSi alloy in the plurality of transition layers and wear-resistant layers decreases from bottom to top, and the content of nickel-plated graphene increases; respectively uniformly mixing the powders used for the transition layer and the wear-resistant layer and drying them; S2: pre-treating the surface of the metal substrate, removing the oxide layer on the surface of the substrate, cleaning the surface of the metal substrate and preheating it; S3: Start the fiber laser, six-axis robot, synchronous powder feeder and argon gas cylinder; S4: Add NiFeCrSi alloy powder into the synchronous powder feeder to perform laser cladding on the base layer; S5: Laser cladding the transition layer on the base layer with the powder of the transition layer in the synchronous powder feeder; S6: replacing the powder in the synchronous powder feeder with the powder of the wear-resistant layer, and laser cladding the wear-resistant layer on the transition layer; S7: After the preparation of the gradient wear-resistant coating is completed, turn off the fiber laser, the six-axis robot, the argon gas cylinder and the synchronous powder feeder.

[0010] Furthermore, in step S1, the particle size of the NiFeCrSi alloy powder is 20-60 μm, and the chemical composition is: Cr: 14-17wt%, Si: 3-4.5wt%, Fe: ≤15wt%, C: 0.6-1.0wt%, B: 2.5-4.5wt%, and Ni as the remainder.

[0011] Furthermore, in step S1, the particle size of the added nickel-plated graphene powder is 20~60μm. In order to increase the wettability of graphene and the substrate coating, a nickel coating is plated on the graphene surface by chemical plating. The chemical composition of the core graphene of the nickel-plated graphene powder is: C: 99.75wt%, water: 0.2 wt%, S: 0.05wt%, and the chemical composition of the outer nickel-plated coating is: Ni: 85.56wt%, P: 0.21wt%; C balance.

[0012] Furthermore, in step S3, a coaxial powder feeding method is adopted, and the powder feeding gas and the protective gas are high-purity argon gas with a purity greater than 99.99%.

[0013] Furthermore, the flow rates of the powder feeding gas and the shielding gas are 20 L / min and 9 L / min, respectively.

[0014] Furthermore, in step S4 to step S6, the parameters for preparing the coating by laser cladding are as follows: laser power is 2500 W, spot diameter is 3 mm, scanning speed is 2 mm / s, powder disk speed is 1.5 r / min, and overlap rate is 50%.

[0015] The beneficial results of the present invention are: 1. The basic phase of the three-layer gradient structure coating is γ-Ni solid solution. The uniformly dispersed nickel-plated graphene phase is retained in the coating. Ni@Gr leads to significant grain refinement. Part of Ni@Gr decomposes to form hard carbides, which increases the carbide content in the coating. 2. The surface microhardness of the three-layer gradient structure coating can reach up to 1100.8 HV 0.2 ; 3. The three-layer gradient coating has good wear resistance. Under the reciprocating friction wear test conditions of 100N test load, 2mm stroke, 4Hz frequency and 20min duration, the wear volume is small, which is 1.95×10 -2 mm -3 . BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 Schematic diagram of the composition of the laser cladding coating samples prepared in Examples 1-6 of the present invention.

[0018] Figure 2 Microstructure diagram of the laser cladding coating samples prepared in Examples 1-6 of the present invention.

[0019] Figure 3 Microhardness of the laser cladding coating samples prepared in Examples 1-6 of the present invention.

[0020] Figure 4 The wear volume of the laser cladding coating samples prepared in Examples 1-6 of the present invention. DETAILED DESCRIPTION

[0021] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0022] The present invention provides a nickel-plated graphene-enhanced NiFeCrSi gradient coating, the gradient coating comprising: (1) a base layer-NiFeCrSi alloy coating; (2) a plurality of transition layers-NiFeCrSi alloy coatings doped with nickel-plated graphene; (3) a wear-resistant layer-NiFeCrSi alloy coatings doped with nickel-plated graphene; the plurality of transition layers and the wear-resistant layers have a decreasing content of NiFeCrSi alloy and an increasing content of nickel-plated graphene from bottom to top; the gradient coating is prepared on the surface of a metal substrate. The gradient structure enables the coatings between different layers to have a smooth transition of physical and chemical properties, minimizes interface stress and structural defects, and improves the hardness and wear resistance of the coating.

[0023] Embodiment 1: A method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating provided by the present invention is as follows: S1: Gradient wear-resistant coating powder was prepared, including: (1) base layer - NiFeCrSi alloy powder; (2) transition layer - 97.5wt% NiFeCrSi alloy powder doped with 2.5wt% nickel-plated graphene; (3) wear-resistant layer - 95wt% NiFeCrSi alloy powder doped with 5wt% nickel-plated graphene. The powders of the transition layer and the wear-resistant layer were mixed in a ball mill with a fixed rotation speed of 350 rpm for 0.5 h. The weight ratio of grinding balls to powder was 10:1. The powder mixture is then dried in a vacuum drying furnace at 55°C for 7 hours to remove water vapor in the powder; wherein the particle size of the NiFeCrSi alloy powder is 20-60 μm, and the chemical composition is: Cr: 14-17 wt%, Si: 3-4.5 wt%, Fe: ≤15 wt%, C: 0.6-1.0 wt%, B: 2.5-4.5 wt%, Ni balance; the particle size of the added nickel-plated graphene powder is 20-60 μm, and in order to increase the wettability of the graphene and the substrate coating, a nickel coating is plated on the graphene surface by chemical plating, and the chemical composition of the core graphene of the nickel-plated graphene powder is: C: 99.75 wt%, water: 0.2%, S: 0.05 wt%, and the chemical composition of the outer nickel-plated coating is: Ni: 85.56 wt%, P: 0.21 wt%; C balance; S2: A hydraulic motor plunger made of 42CrMo was selected as the cladding substrate. The QT600-3 substrate was processed into a size of 50×50×10mm using an electric spark wire cutting machine. After the surface was polished with an angle grinder, the surface was cleaned with acetone and ethanol to remove oil stains, and the substrate was preheated at a temperature of 500°C. S3: Start the fiber laser, six-axis robot, synchronous powder feeder and argon gas cylinder. Use coaxial powder feeding, with the flow rates of powder feeding gas and shielding gas being 20 L / min and 9 L / min respectively; S4: Add NiFeCrSi alloy powder into the synchronous powder feeder and perform laser cladding on the base layer with a thickness of 0.8 mm; S5: Replace the powder in the synchronous powder feeder and laser clad the transition layer on the base layer with a thickness of 0.8 mm; S6: Replace the powder in the synchronous powder feeder and laser clad the wear-resistant layer on the transition layer with a thickness of 0.9 mm; S7: After the preparation of the gradient wear-resistant coating is completed, turn off the fiber laser, the six-axis robot, the argon gas cylinder and the synchronous powder feeder; In steps S4-S6, the parameters for preparing the coating by laser cladding are as follows: laser power is 2500 W, spot diameter is 3 mm, scanning speed is 2 mm / s, powder disk speed is 1.5 r / min, and overlap rate is 50%.

[0024] Example 2: The preparation method of the double-layer coating as a comparison is as follows: The difference between this embodiment and embodiment 1 is that there is no step S6, and the first and second coating steps are the same as those in embodiment 1, and the second coating is 97.5wt% NiFeCrSi alloy powder doped with 2.5wt% nickel-plated graphene, which is a double-layer coating; Example 3: The method for preparing a single-layer primer coating as a comparison is as follows: The difference between this embodiment and embodiment 1 is that there are no steps S5 and S6, and only a bottom layer NiFeCrSi alloy coating is clad on the 42CrMo substrate, which is a single-layer coating; Example 4: The coating preparation method of a single-layer transition layer as a comparison is as follows: The difference between this embodiment and embodiment 1 is that there are no steps S4 and S6, and only a transition layer is clad on the 42CrMo substrate, and the transition layer is a 97.5wt% NiFeCrSi alloy doped with a 2.5wt% nickel-plated graphene coating, which is a single-layer coating; Example 5: The coating preparation method of the single-layer wear-resistant layer as a comparison is as follows: The difference between this embodiment and embodiment 1 is that there are no steps S4 and S5, and only a wear-resistant layer is clad on the 42CrMo substrate. The wear-resistant layer is a 95wt% NiFeCrSi alloy doped with a 5wt% nickel-plated graphene coating, which is a single-layer coating; Example 6: The preparation method of the four-layer coating as a comparison is as follows: The difference between this embodiment and embodiment 1 is that a step is added between step S6 and step S7: replacing the powder in the synchronous powder feeder, laser cladding another wear-resistant layer, the wear-resistant layer is a 92.5wt% NiFeCrSi alloy doped with 7.5wt% nickel-plated graphene coating, with a thickness of 0.85mm, which is a four-layer coating; The coating structure and mechanical properties in each embodiment are characterized as follows: For the samples prepared in Examples 1-6, the cross-sectional morphology of the cladding layer was observed and the organizational characteristics were analyzed using a scanning electron microscope, the hardness of the coating was measured using a Vickers hardness tester, and the friction and wear properties were measured by a wear test using a reciprocating friction and wear tester under the test conditions of a test load of 100N, a stroke of 2mm, a frequency of 4Hz, and a duration of 20min; the measurement results are shown in Figure 1-Figure 4 , the measurement results are shown.

[0025] exist Figure 1In the figure: (1) is a cladding base NiFeCrSi alloy coating, the transition layer is a 97.5wt% NiFeCrSi alloy doped with 2.5wt% nickel-plated graphene coating, and the wear-resistant layer is a 95wt% NiFeCrSi alloy doped with 5wt% nickel-plated graphene coating; (2) is a cladding base NiFeCrSi alloy coating, the transition layer is a 97.5wt% NiFeCrSi alloy doped with 2.5wt% nickel-plated graphene coating; (3) is a cladding base NiFeCrSi alloy coating; (4) is a cladding transition layer of 97.5wt% NiFeCrSi alloy doped with 2.5wt% nickel-plated graphene coating; (5) is a cladding wear-resistant layer of 95wt% NiFeCrSi alloy doped with 5wt% nickel-plated graphene coating; (6) is a cladding base NiFeCrSi alloy coating, the transition layer is a 97.5wt% NiFeCrSi alloy doped with 2.5wt% nickel-plated graphene coating, and the wear-resistant layer is a 95wt% The fourth layer is a 92.5wt% NiFeCrSi alloy doped with a 7.5wt% nickel-plated graphene coating; pass Figure 2 , Examples 1-6, the coating surface quality of the six coatings is good, without obvious cracks and pores, the nickel-plated graphene in the coating appears as a black nearly circular shape, evenly distributed and relatively intact, with the increase of the amount of graphene added, the black nearly circular shape in the coating also increases, the gray-white phase in the coating is the basic phase γ-Ni, the gray-black phase is the second phase, including carbides, borides, etc., among which the graphene and the second phase in Example 1 are most evenly distributed, and the size of the second phase is small, and the organization performance is good; pass Figure 3 The surface hardness of the gradient three-layer coating in Example 1 is the highest, which is 1100.8HV 0.2 The microhardness of the double-layer coating in Example 2 is 895.1 HV 0.2 The single-layer coating in Example 3 has the lowest hardness, with a surface hardness of 668.6 HV. 0.2 The microhardness of the single-layer coating in Example 4 is 750.4 HV 0.2 The microhardness of the single-layer coating in Example 5 is 850.5 HV 0.2 The microhardness of the single-layer coating in Example 6 is 950.2 HV 0.2In summary, the number of gradient coatings in Example 3, Example 2, Example 1, and Example 6 gradually increases, the hardness of the three-layer gradient coating in Example 1 is the highest, and the hardness of the four-layer gradient coating in Example 6 is less than that of the three-layer gradient coating in Example 1, which proves that the three-layer gradient coating in Example 1 is the optimal gradient structure, and continuing to increase the number of coating layers will instead reduce the microhardness; comparing Example 1 and Example 5, the composition of the top coating in Example 1 is consistent with the composition of the single-layer coating in Example 5, and the microhardness of the coating in Example 1 is about 30% higher than that of the coating in Example 5; comparing Example 2 and Example 4, the composition of the top coating in Example 2 is consistent with the composition of the single-layer coating in Example 4, and the microhardness of the coating in Example 2 is about 19% higher than that of the coating in Example 4, which proves that the gradient structure coating has excellent microhardness through the gradually changing structure inside the coating.

[0026] pass Figure 4 The wear volume of the gradient three-layer coating in Example 1 is the smallest, which is 1.95×10 -2 mm -3 The wear volume of the double-layer coating in Example 2 is 2.54×10 -2 mm -3 The wear volume of the single-layer coating in Example 3 is the largest, which is 3.57×10 -2 mm -3 The wear volume of the single-layer coating in Example 4 is 3.25×10 -2 mm -3 The wear volume of the single-layer coating in Example 5 is 2.9×10 -2 mm -3 The wear volume of the single-layer coating in Example 6 is 2.34×10 -2 mm -3 In summary, the number of gradient coatings in Example 3, Example 2, Example 1, and Example 6 gradually increases, the wear volume of the three-layer gradient coating in Example 1 is the smallest, and the wear volume of the four-layer gradient coating in Example 6 is 1.2 times that of the three-layer gradient coating in Example 1, which proves that the three-layer gradient coating in Example 1 is the optimal gradient structure, and continuing to increase the number of coating layers will reduce its wear resistance; comparing Example 1 and Example 5, the composition of the top coating in Example 1 is consistent with the composition of the single-layer coating in Example 5, and the wear volume of the coating in Example 5 is about 49% higher than that of the coating in Example 1; comparing Example 2 and Example 4, the composition of the top coating in Example 2 is consistent with the composition of the single-layer coating in Example 4, and the microhardness of the coating in Example 4 is about 28% higher than that of the coating in Example 2, which proves that the gradient structure coating has excellent wear resistance through the gradually changing structure inside the coating.

[0027] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A nickel-plated graphene-enhanced NiFeCrSi gradient coating, characterized in that: The gradient coating comprises: (1) a base layer - a NiFeCrSi alloy coating; (2) a plurality of transition layers - a NiFeCrSi alloy coating doped with nickel-plated graphene; (3) a wear-resistant layer - a NiFeCrSi alloy coating doped with nickel-plated graphene; the NiFeCrSi alloy content of the plurality of transition layers and the wear-resistant layers decreases from bottom to top, while the nickel-plated graphene content increases; the gradient coating is prepared on the surface of a metal substrate.

2. A nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 1, characterized in that: The gradient structure enables the coatings between different layers to have a smooth transition of physical and chemical properties, minimizes interface stress and structural defects, and improves the hardness and wear resistance of the coating.

3. The nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 1, characterized in that: The content of nickel-plated graphene in the wear-resistant layer does not exceed 5wt%.

4. The nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 1, characterized in that: The gradient coating includes: (1) a base layer - a NiFeCrSi alloy coating; (2) a transition layer - a 97.5wt% NiFeCrSi alloy coating doped with 2.5wt% nickel-plated graphene; (3) a wear-resistant layer - a 95wt% NiFeCrSi alloy coating doped with 5wt% nickel-plated graphene.

5. A method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: preparing gradient wear-resistant coating powder, including: (1) base layer - NiFeCrSi alloy powder; (2) a plurality of transition layers - NiFeCrSi alloy powder doped with nickel-plated graphene; (3) wear-resistant layer - NiFeCrSi alloy powder doped with nickel-plated graphene, wherein the content of NiFeCrSi alloy in the plurality of transition layers and wear-resistant layers decreases from bottom to top, and the content of nickel-plated graphene increases; respectively uniformly mixing the powders used for the transition layer and the wear-resistant layer and drying them; S2: pretreating the surface of the metal substrate, removing the oxide layer on the substrate surface, cleaning the surface of the metal substrate and preheating it; S3: Start the fiber laser, six-axis robot, synchronous powder feeder and argon gas cylinder; S4: Add NiFeCrSi alloy powder into the synchronous powder feeder to perform laser cladding on the base layer; S5: Laser cladding the transition layer on the base layer with the powder of the transition layer in the synchronous powder feeder; S6: replacing the powder in the synchronous powder feeder with the powder of the wear-resistant layer, and laser cladding the wear-resistant layer on the transition layer; S7: After the preparation of the gradient wear-resistant coating is completed, turn off the fiber laser, the six-axis robot, the argon gas cylinder and the synchronous powder feeder.

6. The method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 5, characterized in that: In step S1, the particle size of the NiFeCrSi alloy powder is 20-60 μm, and the chemical composition is: Cr: 14-17 wt%, Si: 3-4.5 wt%, Fe: ≤15 wt%, C: 0.6-1.0 wt%, B: 2.5-4.5 wt%, and Ni as the remainder.

7. The method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 5, characterized in that: In step S1, the particle size of the added nickel-plated graphene powder is 20~60μm. In order to increase the wettability of graphene and the substrate coating, a nickel coating is plated on the graphene surface by chemical plating. The chemical composition of the core graphene of the nickel-plated graphene powder is: C: 99.75wt%, water: 0.2 wt%, S: 0.05wt%, and the chemical composition of the outer nickel-plated coating is: Ni: 85.56wt%, P: 0.21wt%; C balance.

8. The method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 5, characterized in that: In step S3, a coaxial powder feeding method is adopted, and the powder feeding gas and the protective gas are high-purity argon gas with a purity greater than 99.99%.

9. The method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 8, characterized in that: The flow rates of powder feeding gas and shielding gas are 20 L / min and 9 L / min respectively.

10. The method for preparing a nickel-plated graphene-enhanced NiFeCrSi gradient coating according to claim 5, characterized in that: In step S4 to step S6, the parameters for preparing the coating by laser cladding are as follows: laser power is 2500 W, spot diameter is 3 mm, scanning speed is 2 mm / s, powder disk speed is 1.5 r / min, and overlap rate is 50%.

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