A wc+tic particle reinforced high-entropy alloy coating and a preparation method thereof

Abstract

The application discloses a WC+TiC particle reinforced high-entropy alloy coating and a preparation method thereof, and belongs to the field of coating preparation. The coating comprises a bottom layer, and the chemical components and mass percentages of the bottom layer are as follows: carbon: 0.1-0.5%, boron: 1-1.3%, chromium: 19-21%, nickel: 21-24%, silicon: 1-1.5%, molybdenum: 8-10%, cobalt: 22-24%, sulfur: 0.005-0.015%, phosphorus: 0.015-0.045%, and the balance is iron and inevitable impurities; and a working layer, and the chemical components and mass percentages of the working layer are as follows: WC: 15-25%, X: 1.5-4.5%, and the balance of components and the proportion between the components are the same as those of the bottom layer, wherein the X is TiC particles coated with Ni on the surface. The method is used for preparing the coating, and compared with a conventional coating, can effectively improve the wear resistance and corrosion resistance of the coating, and prolong the service life of equipment.

Description

Technical Field

[0001] This invention belongs to the field of coating preparation technology, and more specifically, relates to a WC+TiC particle-reinforced high-entropy alloy coating and its preparation method. Background Technology

[0002] In fields such as machinery, aerospace, automotive, and offshore oil drilling, many workpieces experience friction and wear, thus demanding increasingly higher wear resistance from components. To improve the wear resistance of workpieces, surface modification or coating methods are commonly used.

[0003] Non-magnetic drill collars are drilling exploration equipment designed to provide a non-magnetic environment for magnetic measuring instruments during drilling, ensuring accurate measurement of the Earth's magnetic field. Because non-magnetic drill collars inevitably rub against the wellbore during drilling, they are more prone to wear than conventional drill collars, reducing their lifespan. Therefore, conventional surface modifications and coatings used for non-magnetic drill collars often fail to meet their operational requirements. To address this issue, existing technologies have focused on improving the performance of coatings.

[0004] For example, Chinese patent application number 201810009148.X, published on June 5, 2018, discloses a method for high-frequency induction cladding of a TiC-reinforced high-entropy alloy wear-resistant composite coating. The method involves heating and cladding a mixed powder composed of Ni-Cr-B-Si, Co-Cr-B-Si, Cu, Al, and TiC on a low-carbon steel surface under argon protection using an inductor. Since the constituent elements are more than five, the cladding process exhibits the hysteresis effect of a high-entropy alloy. The primary Cr7C3 has the characteristic of fine grains. Finally, an AlCoCrCuNi high-entropy alloy coating reinforced by TiC and Cr7C3 is formed on the steel substrate surface.

[0005] However, this method of direct induction cladding without flame spraying reduces the bonding strength between the coating and the substrate. This is because flame spraying typically creates a rough underlayer surface, which helps improve coating adhesion, while induction cladding, by fusing the coating on a rough surface, also allows the coating to adhere more firmly to the substrate. Secondly, particulate titanium carbide is not easily dispersed or dissolved, and it may precipitate at the bottom of the coating during the coating preparation process, thus affecting the bonding strength between the coating and the substrate. This problem is particularly pronounced under high-temperature conditions, making this coating unsuitable for high-temperature environments.

[0006] For example, Chinese patent application number CN202110916348.5, published on November 16, 2021, discloses a tungsten carbide / silicon carbide-based composite material, coating, and preparation method thereof suitable for short-distance spraying with oxy-propane supersonic flame. The composition and mass fraction of the composite powder are: nano-WC: 60-75 wt%, nano-SiC: 10-20 wt%, Co: 5-8 wt%, Cr: 6-10 wt%, Nb: 1-5 wt%, Al: 2-4 wt%, Re: 0.5-4 wt%. The coating preparation method is as follows: Using this formulation as the spraying material, it is sprayed onto the pretreated steel substrate surface through an oxy-propane supersonic flame 90° internal orifice spray gun, ultimately forming a coating with a thickness of 100–500 μm. This coating is uniform and dense, with a porosity of <0.5%; microhardness >1150HV0.2; coating-substrate bonding strength ≥72 MPa; and coating roughness <Ra 4 μm. The coating exhibits excellent corrosion resistance and resistance to erosion and wear from mud and sand, and can meet the requirements for spraying on the narrow inner surfaces of workpieces such as water turbines and water pumps.

[0007] However, supersonic flame spraying generates high-temperature flames, which may cause damage to temperature-sensitive substrates in some cases, and it is generally not suitable for preparing very thick coatings. Secondly, WC is relatively heavy and may settle directly at the interface between the coating and the substrate during actual spraying. This can affect the bonding strength between the coating and the substrate, making the coating prone to detachment, and since WC is not on the surface, it is difficult to improve the surface wear resistance. Summary of the Invention

[0008] 1. The problem to be solved

[0009] To address the problem that existing coatings are insufficient to meet the requirements of use in the harsh working environment of non-magnetic drill collars, this invention provides a WC+TiC particle-reinforced high-entropy alloy coating and its preparation method. Compared with conventional coatings, it can effectively improve the wear resistance and corrosion resistance of the coating and extend the service life of the equipment.

[0010] 2. Technical Solution

[0011] To solve the above problems, the present invention adopts the following technical solution.

[0012] A WC+TiC particle-reinforced high-entropy alloy coating, comprising:

[0013] The bottom layer, its chemical composition and mass percentage are as follows: carbon: 0.1-0.5%, boron: 1-1.3%, chromium: 19-21%, nickel: 21-24%, silicon: 1-1.5%, molybdenum: 8-10%, cobalt: 22-24%, sulfur: 0.005-0.015%, phosphorus: 0.015-0.045%, with the balance being iron and unavoidable impurities;

[0014] The working layer has the following chemical composition and mass percentage: WC: 15-25%, X: 1.5-4.5%, and the remaining components and the proportions between them are the same as those of the bottom layer. X is TiC particles coated with Ni powder.

[0015] As a further improvement to the technical solution, the thickness of the bottom layer is 0.2 to 0.3 mm.

[0016] As a further improvement to the technical solution, the thickness of the working layer is 0.6–0.8 mm.

[0017] As a further improvement to the technical solution, in X, the mass ratio of Ni to TiC is 1.5 to 4.

[0018] A method for preparing the above-mentioned WC+TiC particle-reinforced high-entropy alloy coating includes the following steps:

[0019] I. Surface pretreatment of the workpiece;

[0020] 2. Prepare the base material according to the set composition, and then flame spray it on the surface of the pretreated workpiece to form the base coating.

[0021] 3. The underlying coating is remelted using an induction remelting method;

[0022] IV. Pre-treat the bottom surface;

[0023] 5. Prepare the working layer raw materials according to the set composition, and then flame spray them on the pretreated bottom surface to form the working layer coating.

[0024] 6. The working layer coating is remelted using an induction remelting method to complete the coating preparation.

[0025] As a further improvement to the technical solution, in steps three and six, the bottom coating and the working layer coating need to be preheated before induction remelting, and the preheating temperature is 300℃.

[0026] As a further improvement to the technical solution, in step three, the induction remelting temperature of the bottom coating is 1000-1300℃.

[0027] As a further improvement to the technical solution, in step six, the induction remelting temperature of the working layer coating is 900–1000°C.

[0028] As a further improvement to the technical solution, in step six, after the working layer is remelted, it is cooled with nitrogen gas at a temperature of -50°C to -100°C and a flow rate of 10-15 L / min.

[0029] As a further improvement to the technical solution, in step five, when preparing the raw material for the working layer coating, the preparation process of X in the raw material is as follows:

[0030] (1) Clean the TiC powder;

[0031] (2) Pour the cleaned TiC powder into the roughening liquid for roughening treatment;

[0032] (3) Wash the roughened TiC powder, sensitize and activate it, and then clean the TiC powder.

[0033] (4) Prepare a plating solution in a container. The plating solution contains NiSO4·6H2O with a concentration of 65-70 g / L, N2H4·H2O with a concentration of 95-100 ml / L, disodium ethylenediaminetetraacetate with a concentration of 20-25 g / L, and lactic acid with a concentration of 45-50 ml / L. Use NaOH as a regulator to adjust the pH value of the plating solution to 8-10.

[0034] (5) Add the TiC powder cleaned in step (3) to the container. The powder loading amount is 15-20g per L of plating solution. Then, the container is placed in a constant temperature water bath at 65-70℃ for reaction. After the reaction is completed, the container is taken out and cooled and filtered in sequence. Then, the remaining solid particles after filtration are cleaned and dried to obtain TiC particles with Ni powder on the surface.

[0035] 3. Beneficial effects

[0036] Compared to existing technologies, this invention provides a WC+TiC particle-reinforced high-entropy alloy coating. It uses a FeCoNiCr series high-entropy alloy as the base coating and also employs this series of high-entropy alloys as the main raw material in the working layer coating. Benefiting from the high wear resistance and high corrosion resistance of this series of high-entropy alloys, the coating's performance is already guaranteed to a certain extent. Adding WC+TiC particles to the working layer coating further improves its wear resistance and corrosion resistance. Furthermore, WC and TiC have good thermal conductivity, which can disperse frictional heat during friction, reducing wear and thus extending the lifespan of both the coating and the substrate.

[0037] Secondly, this invention employs a layered coating process, avoiding the direct sedimentation of WC and TiC at the coating-substrate interface, which could reduce the coating's wear resistance. By coating TiC with Ni, with each TiC particle as a core, Ni atoms are deposited on the TiC surface. Due to Ni's excellent wettability, TiC particles are uniformly dispersed within the coating during preparation. This helps ensure coating uniformity and consistency, reducing particle aggregation or voids. Furthermore, Ni adheres better to the substrate during coating, firmly fixing the TiC particles within the coating and reducing the risk of particle delamination. Moreover, coating TiC particles with Ni provides a protective layer, preventing oxidation reactions in high-temperature or oxidizing environments. Attached Figure Description

[0038] Figure 1 Here is a SEM image of the coating of this invention;

[0039] Figure 2 This is the XRD pattern of the coating of the present invention;

[0040] Figure 3 This is a hardness curve distribution diagram of the coating to the substrate according to the present invention;

[0041] Figure 4 This is a bar chart showing the wear amount after the friction and wear experiment;

[0042] Figure 5 Here is a SEM image of the TiC particles in Comparative Example 1;

[0043] Figure 6 A schematic diagram of the Ni-coating TiC plating apparatus. Detailed Implementation

[0044] Exemplary embodiments of the present invention are described in detail below. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from its spirit and scope. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice it. Therefore, the scope of the invention is defined only by the appended claims.

[0045] A WC+TiC particle-reinforced high-entropy alloy coating is used to improve the wear resistance and corrosion resistance of workpieces and is suitable for harsh working environments of non-magnetic drill collars. The alloy coating consists of an undercoat and a working layer.

[0046] The chemical composition and mass percentage of the undercoat are as follows: carbon: 0.1–0.5%, boron: 1–1.3%, chromium: 19–21%, nickel: 21–24%, silicon: 1–1.5%, molybdenum: 8–10%, cobalt: 22–24%, sulfur: 0.005–0.015%, phosphorus: 0.015–0.045%, with the balance being iron and unavoidable impurities. The undercoat is a layer that covers the substrate surface and bonds with it, with a thickness generally of 0.2–0.3 mm.

[0047] The chemical composition and mass percentage of the working layer coating are as follows: WC: 15–25%, X: 1.5–4.5%, with the balance being the same as that of the underlying layer, i.e., the balance being the underlying layer. X consists of TiC particles coated with Ni powder, wherein the mass ratio of Ni to TiC is 1.5–4. The working layer is a coating layer covering the surface of the underlying layer and in contact with the external environment, with a thickness typically of 0.6–0.8 mm.

[0048] The aforementioned coating uses a FeCoNiCr series high-entropy alloy as the base layer, and the working layer coating also uses this series of high-entropy alloys as the main raw material. Benefiting from the high wear resistance and high corrosion resistance of this series of high-entropy alloys, the performance of the coating itself is already guaranteed to a certain extent. WC and TiC are materials with very high hardness and excellent corrosion resistance. Adding WC+TiC particles to the working layer coating can further improve the wear resistance and corrosion resistance of the coating, thus making it suitable for the working environment of non-magnetic drill collars in seawater. At the same time, WC and TiC have good thermal conductivity, which can disperse frictional heat during friction, reduce wear, and thus extend the life of the coating and the substrate.

[0049] Furthermore, this invention employs a layered coating process. The bottom layer is a high-entropy alloy, and the working layer is a high-entropy alloy with WC+Ni coating on TiC. WC, being relatively heavy, may directly settle to the interface between the coating and the substrate without layering. This would negatively impact the bonding strength between the coating and the substrate, making the coating prone to detachment. Additionally, since WC is not on the surface, it is unlikely to improve surface wear resistance. Simultaneously, TiC also tends to settle to the surface of the coating and substrate at high temperatures. Therefore, without layered spraying, the non-magnetic drill collar coating is unlikely to provide wear resistance in high-temperature environments.

[0050] The particle size distribution of spherical WC powder is generally more uniform, which helps to achieve material homogeneity and stability, thereby reducing variability. Coating TiC with Ni, with each TiC particle as the core, allows Ni atoms to be deposited on the TiC surface. Because Ni has good wettability, it can uniformly disperse TiC particles in the coating during the coating process, which helps to ensure the uniformity and consistency of the coating and reduces particle aggregation or voids in the coating. Secondly, Ni can better bond with the substrate during the coating process, thus firmly fixing the TiC particles in the coating and reducing the risk of particle delamination. Furthermore, coating TiC particles with Ni provides a protective layer, preventing oxidation reactions of the particles in high-temperature or oxidizing environments.

[0051] The preparation method of the above-mentioned WC+TiC particle-reinforced high-entropy alloy coating includes the following steps:

[0052] 1. Prepare a workpiece as the coating substrate, and perform sandblasting to clean and roughen the surface of the workpiece, removing oil and rust and roughening it.

[0053] 2. Prepare the base material according to the set composition, and then flame spray it on the surface of the pretreated workpiece to form the base coating.

[0054] 3. Preheat the base coat to 300℃, and then remelt the base coat at 1000-1300℃ using induction remelting.

[0055] Fourth, the bottom surface is sandblasted to clean and roughen it, removing oil and rust and roughening it.

[0056] 5. Prepare the working layer raw material according to the set composition, and then flame-spray it onto the pretreated bottom layer surface to form the working layer coating. In this step, the preparation process of X in the raw material for preparing the working layer coating is as follows: Figure 6 As shown, it includes the following steps:

[0057] (1) Pretreatment of TiC particles was carried out before plating. The TiC particles were washed in HCl solution and NaON solution in sequence, and then washed with deionized water. Ultrasonic waves were applied to the solution during the cleaning process.

[0058] (2) Pour the cleaned TiC particles into a roughening solution (HF 45-50ml / L, HNO3 75-80ml / L) for 15-20 minutes to roughen the surface and facilitate plating.

[0059] (3) The coarsened TiC powder particles were washed with deionized water, and then sensitized and activated in a sensitizing solution (SnCl2 7-10g / L, HCl 35-40ml / L) and an activating solution (aqua regia) for 20 minutes each. The powder particles were then rinsed three times with deionized water. The pretreated powder was then poured into the plating solution and prepared for plating.

[0060] (4) Prepare the plating solution in a beaker. The plating solution includes: NiSO4·6H2O as the main salt with a concentration of 65-70 g / L; N2H4·H2O as a reducing agent with a concentration of 95-100 ml / L; disodium ethylenediaminetetraacetate as a complexing agent with a concentration of 20-25 g / L; and lactic acid with a concentration of 45-50 ml / L. Lactic acid also acts as a pH-releasing agent. Furthermore, NaOH is used as a regulator to adjust the pH of the plating solution to 8-10.

[0061] (5) Add the cleaned TiC powder from step (3) to a beaker at a rate of 15-20 g per L of plating solution. Then, place the beaker in a constant-temperature water bath at 65-70℃ for reaction, continuously stirring electromagnetically throughout the reaction. During the 0-5 min coating stage, metallic Ni first deposits on the highly active fresh steps on the surface of the TiC particles and forms nuclei. The new nuclei have extremely high activity, further promoting and accelerating the deposition of new Ni atoms on their surface, causing Ni to agglomerate and grow in local areas, eventually completely coating the entire surface of the TiC particles. After 1 h of reaction, the plating is complete. Remove the beaker and cool it rapidly, then allow it to stand and filter, washing it 2-3 times with deionized water. Finally, dry the remaining powder in a constant-temperature drying oven to obtain TiC particles coated with Ni powder.

[0062] 6. Preheat the working layer coating to 300℃, and then remelt the working layer coating at 900-1000℃ using induction remelting. After remelting, cool with nitrogen at -50℃ to -100℃ and a nitrogen flow rate of 10-15L / min to complete the coating preparation.

[0063] During the preparation process, the induction remelting process was carried out in an atmospheric environment.

[0064] Flame spraying, compared to supersonic flame spraying, eliminates the need for high-speed gas flow and specialized equipment, allowing for large-area spraying. It is simpler, less expensive, and suitable for large-scale spraying, and can be performed on-site. Furthermore, flame spraying typically uses lower temperatures, thus avoiding thermal damage to the material.

[0065] Compared to directly induction remelting the coating, first applying flame spraying to create a rough underlayer surface, and then induction remelting the coating on this rough surface, allows the coating to adhere more firmly to the substrate, significantly improving the bond strength between the substrate and the coating. Furthermore, flame spraying first allows for precise control of the coating thickness, enabling the production of coatings with the desired thickness.

[0066] Preheating to 300℃ before induction remelting reduces the temperature gradient, minimizes the risk of thermal stress, and helps prevent cracking. Induction remelting achieves a metallurgical bond between the coating and the substrate, further improving interfacial bonding strength. Sandblasting after the underlayer remelting ensures a perfect bond between the underlayer and the working layer, preventing delamination. Furthermore, the underlayer induction remelting temperature is 1000-1300℃, while the working layer's induction remelting temperature is 900-1000℃. Since the substrate typically absorbs heat more readily than the coating, this higher underlayer temperature helps improve adhesion between the coating and the substrate, allowing for better contact and adhesion, reducing the risk of peeling. During induction remelting, electromagnetic induction conducts electricity through the coating and generates a magnetic field, causing eddy currents in the substrate and increasing its temperature. Therefore, the induction remelting temperature of the coating surface is relatively low, while the underlayer's induction remelting temperature is higher.

[0067] Rapid cooling with nitrogen after induction remelting helps reduce thermal stress and deformation during curing, improves the dimensional stability of the coating and workpiece, limits grain growth, maintains a fine grain structure, and enhances the material's mechanical properties and wear resistance. Furthermore, rapid cooling shortens the preparation cycle and increases production efficiency, making it particularly suitable for mass production and industrial applications. Finally, this invention, through the design of materials and methods, enables preparation in an atmospheric environment, significantly reducing production costs compared to traditional methods that require a helium atmosphere.

[0068] The present invention will be further illustrated below through specific embodiments.

[0069] Example 1

[0070] Step 1: Prepare a high-nitrogen stainless steel austenitic non-magnetic drill collar substrate. Perform sandblasting cleaning and roughening treatment on the outer surface of the non-magnetic drill collar substrate to remove oil and rust and roughen it.

[0071] Step 2: Prepare the base powder. Its chemical composition and mass percentage are as follows: carbon 0.1%, boron 1%, chromium 19%, nickel 21%, silicon 1%, molybdenum 8%, cobalt 22%, sulfur 0.005%, phosphorus 0.015%, and the balance is iron. High-entropy alloy powder is sprayed onto the outer surface of the non-magnetic drill collar substrate with a 0.2mm layer using a high-energy flame spraying process. The spraying process gas source pressure is set to: oxygen 0.35MPa, acetylene 0.05MPa; gas source flow rate is set to: oxygen 15L / min, acetylene 10L / min; spraying distance is set to 180mm; powder feed rate is set to 90g / min; and the coating thickness is 0.2mm.

[0072] Step 3: Under atmospheric conditions, using a loop coil vacuum induction heating device, the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer is heated to 1000℃, causing partial remelting of the high-entropy alloy coating. A metallurgical reaction occurs between the outer surface of the non-magnetic drill collar substrate and the high-entropy alloy layer, forming a strongly bonded interface layer. Simultaneously with the induction coil remelting the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 6 r / min, and the induction heating coil moves relative to the workpiece at a speed of 50 mm / min.

[0073] Step 4: The outer surface of the bottom layer is sandblasted to clean and roughen it, removing oil and rust and roughening it.

[0074] Step 5: Prepare the working layer powder. Its chemical composition and mass percentage are as follows: WC 15%, Ni-coated TiC (Ni:TiC = 6:4) 1.5%, and the balance is a high-entropy alloy with the same composition as the base layer. Using a high-energy flame spraying process, the WC+TiC-doped high-entropy alloy powder is sprayed 1 mm thick onto the outer surface of the non-magnetic drill collar substrate. The spraying process gas source pressure is set to: oxygen 0.35 MPa, acetylene 0.05 MPa; gas source flow rate is set to: oxygen 15 L / min, acetylene 10 L / min; spraying distance is set to 180 mm; powder feed rate is set to 90 g / min; and the coating thickness is 0.6 mm.

[0075] Step Six: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, heat the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer to 900℃. This causes partial remelting of the high-entropy alloy coating, and a metallurgical reaction occurs between the outer surface of the bottom layer and the working layer, forming a strong bonding interface layer. Simultaneously, while the induction coil remelts the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 6 r / min, and the induction heating coil moves relative to the workpiece at a speed of 50 mm / min. The coating preparation is complete, and the coating is numbered as follows: Figure 4 #1 in the list.

[0076] The prepared coating was found to be crack-free, with a thickness of 850 μm and a microhardness of 320 HV.0.2 The bonding strength between the coating and the substrate is 61 MPa. In the ring-block friction and wear test, #1, under a load of 200 N and 2 hours of dry friction, showed a wear amount of 134.1 mg, while the wear amount of the P550 steel substrate (#0) was 266.2 mg, which is 1.98 times the wear resistance of the P550 steel substrate.

[0077] Example 2

[0078] Step 1: Prepare a high-nitrogen stainless steel austenitic non-magnetic drill collar substrate. Perform sandblasting cleaning and roughening treatment on the outer surface of the non-magnetic drill collar substrate to remove oil and rust and roughen it.

[0079] Step 2: Prepare the base powder. Its chemical composition and mass percentage are as follows: carbon 0.25%, boron 1.2%, chromium 20%, nickel 22%, silicon 1.25%, molybdenum 9%, cobalt 23%, sulfur 0.007%, phosphorus 0.030%, with the balance being iron. High-entropy alloy powder is then sprayed onto the outer surface of the non-magnetic drill collar substrate to a thickness of 0.3 mm using a high-energy flame spraying process. The spraying process gas source pressure is set to: oxygen 0.40 MPa, acetylene 0.06 MPa; gas source flow rate is set to: oxygen 17 L / min, acetylene 13 L / min; spraying distance is set to 180 mm; powder feed rate is set to 95 g / min; and the coating thickness is 0.3 mm.

[0080] Step 3: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer is heated to 1300℃. This causes partial remelting of the high-entropy alloy coating, resulting in a metallurgical reaction between the outer surface of the non-magnetic drill collar substrate and the high-entropy alloy layer, forming a strongly bonded interface layer. Simultaneously with the induction coil remelting the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 7 r / min, and the induction heating coil moves relative to the workpiece at a speed of 65 mm / min.

[0081] Step 4: The outer surface of the bottom layer is sandblasted to clean and roughen it, removing oil and rust and roughening it.

[0082] Step 5: Prepare the working layer powder. Its chemical composition and mass percentage are as follows: WC 20%, Ni-coated TiC (Ni:TiC = 7:3) 3%, and the balance is a high-entropy alloy with the same composition as the base layer. Using a high-energy flame spraying process, the WC+TiC-doped high-entropy alloy powder is sprayed onto the outer surface of the non-magnetic drill collar substrate to a thickness of 0.6 mm. The spraying process gas source pressure is set to: oxygen 0.40 MPa, acetylene 0.06 MPa; gas source flow rate is set to: oxygen 17 L / min, acetylene 13 L / min; spraying distance is set to 180 mm; powder feed rate is set to 95 g / min; and the coating thickness is 0.6 mm.

[0083] Step Six: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, heat the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer to 1000℃. This causes partial remelting of the high-entropy alloy coating, and a metallurgical reaction occurs between the outer surface of the bottom layer and the working layer, forming a strong bonding interface layer. Simultaneously, while the induction coil remelts the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 7 r / min, and the induction heating coil moves relative to the workpiece at a speed of 65 mm / min. The coating preparation is complete, and the coating is numbered as follows: Figure 4 #2 in the list.

[0084] The prepared coating was found to be crack-free, with a thickness of 930 μm and a microhardness of 348 HV. 0.2 The coating bond strength to the substrate is 71 MPa. In the ring-block friction and wear test, #2, under a 200 N load and 2 hours of dry friction, showed a wear of 113.7 mg, while the wear of the P550 steel substrate (#0) was 266.2 mg, making #2 2.34 times the wear resistance of the P550 steel substrate.

[0085] Example 3

[0086] Step 1: Prepare a high-nitrogen stainless steel austenitic non-magnetic drill collar substrate. Perform sandblasting cleaning and roughening treatment on the outer surface of the non-magnetic drill collar substrate to remove oil and rust and roughen it.

[0087] Step 2: Prepare the base powder. Its chemical composition and mass percentage are as follows: carbon 0.5%, boron 1.3%, chromium 21%, nickel 24%, silicon 1.5%, molybdenum 10%, cobalt 24%, sulfur 0.015%, phosphorus 0.045%, and the balance is iron. High-entropy alloy powder is sprayed onto the outer surface of the non-magnetic drill collar substrate with a 0.2mm layer using a high-energy flame spraying process. The spraying process gas source pressure is set to: oxygen 0.45MPa, acetylene 0.08MPa; gas source flow rate is set to: oxygen 20L / min, acetylene 15L / min; spraying distance is set to 180mm; powder feed rate is set to 100g / min; and the coating thickness is 0.2mm.

[0088] Step 3: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer is heated to 1300℃. This causes partial remelting of the high-entropy alloy coating, and a metallurgical reaction occurs between the outer surface of the non-magnetic drill collar substrate and the high-entropy alloy layer, forming a strongly bonded interface layer. Simultaneously with the induction coil remelting the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 9 r / min, and the induction heating coil moves relative to the workpiece at a speed of 70 mm / min.

[0089] Step 4: The outer surface of the bottom layer is sandblasted to clean and roughen it, removing oil and rust and roughening it.

[0090] Step 5: Prepare the working layer powder. Its chemical composition and mass percentage are as follows: WC 25%, Ni-coated TiC (Ni:TiC = 8:2) 4.5%, and the balance is a high-entropy alloy with the same composition as the base layer. Using a high-energy flame spraying process, the WC+TiC-doped high-entropy alloy powder is sprayed 0.9 mm thick onto the outer surface of the non-magnetic drill collar substrate. The spraying process gas source pressure is set to: oxygen 0.45 MPa, acetylene 0.08 MPa; gas source flow rate is set to: oxygen 20 L / min, acetylene 15 L / min; spraying distance is set to 180 mm; powder feed rate is set to 100 g / min; and the coating thickness is 0.9 mm.

[0091] Step Six: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, heat the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer to 1000℃. This causes partial remelting of the high-entropy alloy coating layer, and a metallurgical reaction occurs between the outer surface of the bottom layer and the working layer, forming a strong bonding interface layer. Simultaneously, while the induction coil remelts the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 9 r / min, and the induction heating coil moves relative to the workpiece at a speed of 70 mm / min. The coating preparation is complete, and the coating is numbered as follows: Figure 4 #3 in the list.

[0092] The prepared coating was found to be crack-free, with a thickness of 1050 μm and a microhardness of 381 HV. 0.2 The bonding strength between the coating and the substrate is 59 MPa. In the ring-block friction and wear test, #3, under a load of 200 N and 2 hours of dry friction, showed a wear amount of 145.5 mg, while the wear amount of the P550 steel substrate (#0) was 266.2 mg, making #3 1.82 times more wear-resistant than the P550 steel substrate.

[0093] Comparative Example 1

[0094] Step 1: Prepare a high-nitrogen stainless steel austenitic non-magnetic drill collar substrate. Perform sandblasting cleaning and roughening treatment on the outer surface of the non-magnetic drill collar substrate to remove oil and rust and roughen it.

[0095] Step 2: Prepare the base powder. Its chemical composition and mass percentage are as follows: carbon 0.25%, boron 1.2%, chromium 20%, nickel 22%, silicon 1.25%, molybdenum 9%, cobalt 23%, sulfur 0.007%, phosphorus 0.030%, with the balance being iron. High-entropy alloy powder is then sprayed onto the outer surface of the non-magnetic drill collar substrate to a thickness of 0.3 mm using a high-energy flame spraying process. The spraying process gas source pressure is set to: oxygen 0.40 MPa, acetylene 0.06 MPa; gas source flow rate is set to: oxygen 17 L / min, acetylene 13 L / min; spraying distance is set to 180 mm; powder feed rate is set to 95 g / min; and the coating thickness is 0.3 mm.

[0096] Step 3: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer is heated to 1300℃. This causes partial remelting of the high-entropy alloy coating, resulting in a metallurgical reaction between the outer surface of the non-magnetic drill collar substrate and the high-entropy alloy layer, forming a strongly bonded interface layer. Simultaneously with the induction coil remelting the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 7 r / min, and the induction heating coil moves relative to the workpiece at a speed of 65 mm / min.

[0097] Step 4: The outer surface of the bottom layer is sandblasted to clean and roughen it, removing oil and rust and roughening it.

[0098] Step 5: Prepare the working layer powder. Its chemical composition and mass percentage are as follows: WC 20%, Ni-coated TiC (Ni:TiC = 4:5) 3%, and the balance is a high-entropy alloy with the same composition as the base layer. Using a high-energy flame spraying process, the WC+TiC-doped high-entropy alloy powder is sprayed onto the outer surface of the non-magnetic drill collar substrate to a thickness of 0.6 mm. The spraying process gas source pressure is set to: oxygen 0.40 MPa, acetylene 0.06 MPa; gas source flow rate is set to: oxygen 17 L / min, acetylene 13 L / min; spraying distance is set to 180 mm; powder feed rate is set to 95 g / min; and the coating thickness is 0.6 mm.

[0099] Step Six: Under atmospheric conditions, using a toroidal coil vacuum induction heating device, heat the outer surface of the non-magnetic drill collar substrate coated with a high-entropy alloy powder layer to 1000℃. This causes partial remelting of the high-entropy alloy coating, and a metallurgical reaction occurs between the outer surface of the bottom layer and the working layer, forming a strong bonding interface layer. Simultaneously, while the induction coil remelts the high-entropy alloy layer on the outer surface, the non-magnetic drill collar substrate rotates at 7 r / min, and the induction heating coil moves relative to the workpiece at a speed of 65 mm / min. The coating preparation is complete, and the coating is numbered as follows: Figure 4 #4 in the list.

[0100] The prepared coating was found to be crack-free, with a thickness of 950 μm and a microhardness of 359 HV. 0.2 The coating's bond strength to the substrate is 67 MPa. In a ring-block friction and wear test, #4, under a 200 N load and 2 hours of dry friction, showed a wear of 170 mg, while the P550 steel substrate (#0) showed a wear of 266.2 mg, 1.56 times the wear resistance of the P550 steel substrate. However, if... Figure 5 As shown, the bonding between TiC and the high-entropy alloy matrix is ​​not ideal. Pores and oxides appear at the interface between TiC and the high-entropy alloy, leading to a decrease in wear resistance.

[0101] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A WC+TiC particle-reinforced high-entropy alloy coating, characterized in that: include: The bottom layer has a thickness of 0.2–0.3 mm, and its chemical composition and mass percentage are as follows: Carbon: 0.1-0.5%, Boron: 1-1.3%, Chromium: 19-21%, Nickel: 21-24%, Silicon: 1-1.5%, Molybdenum: 8-10%, Cobalt: 22-24%, Sulfur: 0.005-0.015%, Phosphorus: 0.015-0.045%, Balance: Iron and unavoidable impurities; The working layer has a thickness of 0.6 to 0.8 mm and its chemical composition and mass percentage are as follows: WC: 15 to 25%, X: 1.5 to 4.5%, and the remaining components and the proportions between the components are the same as those of the bottom layer. X is TiC particles coated with Ni powder, and the mass ratio of Ni to TiC in X is 1.5 to 4.

2. A method for preparing the WC+TiC particle-reinforced high-entropy alloy coating as described in claim 1, characterized in that: Includes the following steps: I. Surface pretreatment of the workpiece; 2. Prepare the base material according to the set composition, and then flame spray it on the surface of the pretreated workpiece to form the base coating.

3. The underlying coating is remelted using an induction remelting method; IV. Pre-treat the bottom surface; 5. Prepare the working layer raw materials according to the set composition, and then flame spray them on the pretreated bottom surface to form the working layer coating.

6. The working layer coating is remelted using an induction remelting method to complete the coating preparation.

3. The method for preparing a WC+TiC particle-reinforced high-entropy alloy coating according to claim 2, characterized in that: In steps three and six, the bottom coating and working layer coating need to be preheated before induction remelting, and the preheating temperature is 300°C.

4. The method for preparing a WC+TiC particle-reinforced high-entropy alloy coating according to claim 2, characterized in that: In step three, the induction remelting temperature of the bottom coating is 1000–1300°C.

5. The method for preparing a WC+TiC particle-reinforced high-entropy alloy coating according to claim 2, characterized in that: In step six, the induction remelting temperature of the working layer coating is 900–1000°C.

6. The method for preparing a WC+TiC particle-reinforced high-entropy alloy coating according to claim 2, characterized in that: In step six, after the working layer is remelted, it is cooled with nitrogen gas at a temperature of -50°C to -100°C and a flow rate of 10-15 L / min.

7. The method for preparing a WC+TiC particle-reinforced high-entropy alloy coating according to claim 2, characterized in that: In step five, when preparing the raw material for the working layer coating, the preparation process of X in the raw material is as follows: (1) Clean the TiC powder; (2) Pour the cleaned TiC powder into the roughening solution for roughening treatment; (3) Wash the roughened TiC powder, sensitize and activate it, and then clean the TiC powder; (4) Prepare a plating solution in a container. The plating solution contains NiSO4·6H2O with a concentration of 65-70 g / L, N2H4·H2O with a concentration of 95-100 ml / L, disodium ethylenediaminetetraacetate with a concentration of 20-25 g / L, and lactic acid with a concentration of 45-50 ml / L. Use NaOH as a regulator to adjust the pH value of the plating solution to 8-10. (5) Add the TiC powder cleaned in step (3) to the container. The powder loading amount is 15-20g per L of plating solution. Then, the container is placed in a constant temperature water bath at 65-70℃ for reaction. After the reaction is completed, the container is taken out and cooled and filtered in sequence. Then, the remaining solid particles after filtration are cleaned and dried to obtain TiC particles with Ni powder on the surface.

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