Nickel-based coated tungsten carbide and preparation method and application thereof

Abstract

The application relates to the technical field of metal surface engineering, and particularly discloses a nickel-based coated tungsten carbide and a preparation method and application thereof, the nickel-based coated tungsten carbide is composed of the following components in percentage by weight: chromium 14.15-17.19%, molybdenum 1.68-1.89%, boron 1.23-1.5%, pretreated tungsten carbide 8-15%, yttrium oxide 0.5-1.5%, and the balance is nickel and inevitable impurities. The application optimizes the composition of the nickel-based alloy substrate by precisely controlling the contents of Cr, Mo, B and Y2O3; the high Cr and Mo contents provide a material basis for subsequent in-situ nitriding strengthening, and significantly improve the ability of the coating to resist pitting corrosion and uniform corrosion; the introduction of Y2O3 plays a role in refining grains and strengthening the structure; by introducing moderate WC content (8-15 wt%) and combining with the tough nickel base, the inherent defect of the traditional high WC content coating that is large in brittleness is overcome.

Description

Technical Field

[0001] This invention relates to the field of metal surface engineering technology, specifically to a nickel-based coated tungsten carbide, its preparation method, and its application. Background Technology

[0002] Oil plungers are core components of oil extraction equipment, operating under complex conditions of high pressure, high temperature, highly corrosive media (such as crude oil containing hydrogen sulfide and carbon dioxide), and mechanical wear. Traditional materials (such as carbon steel or ordinary stainless steel) are prone to corrosion, wear, and even breakage on the plunger surface due to insufficient corrosion resistance, low high-temperature strength, and poor wear resistance. This severely shortens equipment life, increases maintenance costs, and affects oil extraction efficiency.

[0003] Surface engineering technology is one of the main solutions to improve the service performance of oil plungers. Laser cladding technology, due to its advantages such as concentrated heat input, small heat-affected zone of the substrate, and strong metallurgical bond between the coating and the substrate, has been widely studied and used in the preparation of high-performance protective coatings. Nickel-based tungsten carbide (Ni-WC) composites, combining the good toughness and corrosion resistance of nickel-based alloys with the extremely high hardness and wear resistance of tungsten carbide, have become an ideal choice for preparing high-performance protective coatings.

[0004] However, existing methods for preparing Ni-WC composite powders mostly involve mechanical mixing or the use of pre-alloyed powders, where WC particles are physically mixed or randomly dispersed with the nickel-based alloy. During subsequent high-temperature, rapid melting processes such as laser cladding, WC particles directly exposed to the high-temperature molten pool are highly susceptible to decomposition and dissolution. This not only consumes the hard WC phase, which forms the main wear-resistant framework, but also creates brittle phases such as W2C in the coating, leading to increased coating brittleness, decreased wear resistance, and unstable performance.

[0005] To achieve high wear resistance, Chinese patent CN114672803A discloses a process for oil plungers based on laser cladding of a nickel-based tungsten carbide coating, which uses a high content (up to 43.94%) of WC. However, excessively high hard phase content significantly weakens the continuity of the nickel matrix, leading to a sharp decrease in coating toughness. Under impact or alternating loads, it is prone to crack initiation and brittle fracture. Furthermore, this patent fails to fundamentally solve the stability problem of WC during the cladding process. In addition, its coating is a single cladding layer, and its surface hardness and corrosion resistance are limited by the material itself, making it difficult to cope with combined failure modes under extreme working conditions. Based on the above, this invention proposes a nickel-based coated tungsten carbide, its preparation method, and its applications. Summary of the Invention

[0006] To address the technical problems in existing technologies, such as the easy decomposition and dissolution of tungsten carbide during high-temperature coating preparation, leading to increased coating brittleness and decreased toughness, as well as the difficulty in achieving both hardness and toughness and insufficient resistance to corrosion in complex media with traditional single coatings, this invention proposes a nickel-based coated tungsten carbide, its preparation method, and its application.

[0007] In a first aspect, the present invention provides a nickel-based coated tungsten carbide solution, employing the following technical solution:

[0008] A nickel-based coated tungsten carbide, by weight percentage, is composed of the following components: 14.15-17.19% chromium, 1.68-1.89% molybdenum, 1.23-1.5% boron, 8-15% pretreated tungsten carbide, 0.5-1.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0009] Preferably, the nickel-based coated tungsten carbide has a core-shell structure, with the core being pretreated tungsten carbide and the shell being a nickel-based alloy.

[0010] The core-shell structure design of this invention allows the outer nickel-based alloy shell to melt preferentially during high-energy beam processing such as laser cladding, providing physical shielding and thermal buffering for the pretreated tungsten carbide core inside, significantly inhibiting the decomposition and dissolution of WC in the high-temperature molten pool; thereby ensuring that the hard phase of WC can be uniformly distributed in the final coating in a complete morphology, thus significantly improving the toughness of the coating while ensuring high hardness.

[0011] Preferably, the pretreated tungsten carbide is prepared by the following method:

[0012] Activated tungsten carbide is obtained by surface activation treatment of tungsten carbide, and then activated tungsten carbide is placed in a chemical nickel plating solution for chemical plating, followed by washing and drying to obtain pretreated tungsten carbide.

[0013] Preferably, the tungsten carbide has a particle size of 3-5 μm.

[0014] Preferably, in the electroless nickel plating solution, the concentration of nickel sulfate is 22-28 g / L, the concentration of sodium hypophosphite is 27-33 g / L, the concentration of sodium tungstate is 15-20 g / L, the concentration of sodium citrate is 30-40 g / L, the concentration of thiourea is 1-3 mg / L, the pH value is 4.5-5.5, and it is adjusted with dilute sulfuric acid.

[0015] Preferably, the mass ratio of the activated tungsten carbide to the electroless nickel plating solution is 1:5-7.

[0016] Preferably, the electroless plating temperature is 85-95℃ and the time is 40-50min.

[0017] This invention introduces sodium tungstate into the plating bath, synergistically using sodium hypophosphite as a reducing agent, to deposit a dense Ni-WP ternary alloy coating in situ on the surface of WC particles. This Ni-WP coating itself possesses high thermal stability and hardness. The introduction of tungsten (W) effectively increases the recrystallization temperature of the coating, further suppressing the thermal decomposition of WC in subsequent high-temperature processes. Simultaneously, this ternary alloy coating exhibits good interfacial compatibility with both the WC substrate and the outer nickel-based alloy layer, providing an excellent initial bonding interface for subsequent mechanical fusion coating, making the outer nickel-based alloy shell easier to form and resulting in a denser bond.

[0018] The functions of each chemical component in this invention are as follows:

[0019] Nickel (Ni): As the main base metal, it provides excellent toughness and good wettability to tungsten carbide (WC), ensuring a reliable metallurgical bond between the coating and the substrate. It also forms solid solutions with chromium (Cr), molybdenum (Mo), etc., enhancing the strength and corrosion resistance of the alloy matrix.

[0020] Chromium (Cr): High Cr content can significantly improve the coating's resistance to high-temperature oxidation and uniform corrosion. In subsequent nitriding treatment, it acts as the main reactant element, generating high-hardness and high-chemical-stability chromium nitride (CrN) in situ, giving the coating surface extremely high hardness and corrosion resistance.

[0021] Molybdenum (Mo): Significantly improves coating performance in applications involving chloride ions (Cl). - It enhances the resistance to pitting and crevice corrosion in complex media, and forms high-hardness molybdenum nitride (MoN) with nitrogen, which, in synergy with CrN, further enhances the surface's wear resistance and corrosion resistance.

[0022] Boron (B): As an excellent deoxidizer and melting point depressant, it can not only lower the melting point of alloys, improve melt flowability, and optimize the processability of laser cladding / plasma welding, but also form dispersed hard borides with Ni, Cr, etc., further improving the overall hardness of the coating.

[0023] Pre-treated tungsten carbide: WC with a moderate content (8-15%) and pre-coated with Ni-WP ternary alloy is used as a hard core to provide the coating with the main wear resistance properties; at the same time, by controlling the low WC content, the serious brittleness problem caused by traditional high WC content coatings is effectively avoided, ensuring that the coating has the necessary toughness.

[0024] Yttrium oxide (Y2O3): As a stable nanoscale dispersed strengthening phase and grain refiner, during the rapid solidification process of cladding, it acts as a heterogeneous nucleation core, increasing the nucleation rate, and hinders grain boundary migration through the pinning effect, effectively inhibiting grain growth and refining the coating microstructure. Thus, through the synergistic effect of grain refinement and dispersion strengthening, it improves the hardness, density, high-temperature strength and toughness of the coating.

[0025] Secondly, the present invention provides a method for preparing the above-mentioned nickel-based coated tungsten carbide, using the following technical solution:

[0026] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0027] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0028] S2. The pretreated tungsten carbide is mixed with nickel powder, chromium powder, molybdenum powder, boron powder and yttrium oxide powder, and placed in a high-energy ball mill for mechanical fusion treatment. Through repeated cold welding, fracture and re-welding between powder particles, the nickel-based alloy powder forms a coating shell on the surface of the pretreated tungsten carbide. After sieving, nickel-based coated tungsten carbide is obtained.

[0029] The Ni-WP ternary alloy coating formed by pre-coating the pretreated tungsten carbide of the present invention serves two purposes. First, it acts as a physical barrier to protect the WC core during the initial stage of mechanical fusion, preventing excessive breakage. Second, it acts as an excellent interface wetting layer and bonding substrate, significantly improving the adhesion of subsequent nickel-based alloy powders to its surface and the efficiency of cold welding. Third, the ternary alloy coating can also serve as a source of W and P elements for subsequent metallurgical fusion.

[0030] During the long-duration, high-energy mechanical fusion process of this invention, the pre-formed Ni-WP ternary alloy coating undergoes intense plastic deformation together with the nickel-based alloy powder. In this process, the ternary alloy coating undergoes in-situ metallurgical fusion with the continuously cold-welded and accumulated nickel-based alloy powder, and through atomic interdiffusion, ultimately forms a coating layer on the surface of the WC core.

[0031] Preferably, in step S2, the ball-to-material ratio for mechanical fusion treatment is 8-12:1, the rotation speed is 300-500 rpm, the treatment time is 6-10 hours, and inert gas protection is used during the treatment process.

[0032] This invention ensures sufficient impact energy for efficient coating (cold welding) by precisely controlling the mechanical fusion process parameters, while avoiding excessive energy that could lead to WC particle breakage or severe powder agglomeration. Inert gas protection effectively prevents powder oxidation during processing.

[0033] Preferably, the sieving in S2 specifically refers to sieving through a 500-600 mesh sieve.

[0034] In a third aspect, the present invention provides an application of the above-mentioned nickel-based coated tungsten carbide, employing the following technical solution:

[0035] Application of a nickel-based coated tungsten carbide in the preparation of a protective coating for the surface of an oil plunger.

[0036] Preferably, the surface protective coating is prepared by nickel-based coated tungsten carbide, and the surface protective coating has a composite gradient structure, including: a nickel-based tungsten carbide composite cladding layer that is metallurgically bonded to the substrate; and an in-situ generated nitride layer formed on the surface of the nickel-based tungsten carbide composite cladding layer.

[0037] Preferably, the nitride layer is mainly composed of chromium nitride (CrN) and / or molybdenum nitride (MoN).

[0038] Preferably, the surface protective coating is prepared by the following method:

[0039] A. Using laser cladding or plasma welding technology, nickel-based tungsten carbide is clad onto the surface of the oil plunger to form a nickel-based tungsten carbide composite cladding layer;

[0040] B. Nitriding treatment is performed on the oil plunger with the nickel-based tungsten carbide composite cladding layer to generate a nitride layer in situ on the surface of the composite cladding layer.

[0041] This invention prepares a composite gradient structure coating in which the nickel-based tungsten carbide composite cladding layer inside forms a strong metallurgical bond with the substrate, exhibiting good overall toughness and load-bearing capacity; while the in-situ generated nitride layer on the surface (mainly ultra-hard CrN and MoN) endows the coating with extremely high surface hardness, excellent wear resistance, erosion resistance, and extreme corrosion resistance in sulfur- and chlorine-containing media.

[0042] Preferably, the parameters for laser cladding in A are: laser power 3-5kW, scanning speed 8-12mm / s, spot diameter 3-5mm, and powder feeding rate 10-15g / min.

[0043] Preferably, the parameters for plasma cladding in step A are: plasma arc current 200-300A, and powder feeding rate 20-30g / min.

[0044] Preferably, the nitriding treatment temperature in step B is 550-650℃, and the holding time is 3-5h.

[0045] In step A of this invention, laser cladding / plasma welding technology ensures metallurgical bonding between the coating and the substrate, low dilution rate, and density. In step B, by precisely controlling the temperature and time of the nitriding treatment, the active elements Cr and Mo in the composite cladding layer react with the diffused nitrogen atoms to generate nitrides such as CrN and MoN with high hardness and high corrosion resistance in situ. This achieves secondary strengthening and functional gradient of the coating surface, significantly improving the overall performance of the coating.

[0046] In summary, the present invention has the following beneficial effects:

[0047] This invention employs a Ni-WP ternary alloy to pre-coat the WC core, fundamentally solving the technical challenge of easy decomposition and dissolution of the WC hard phase in high-temperature preparation processes such as laser cladding. This structure effectively ensures the integrity of the WC hard phase morphology and the uniformity of its distribution in the final coating, avoiding the formation of brittle phases. Thus, while maintaining high wear resistance, the toughness and impact resistance of the coating are significantly improved.

[0048] This invention optimizes the composition of the nickel-based alloy matrix by precisely controlling the contents of Cr, Mo, B, and Y2O3. The high Cr and Mo contents provide a material basis for subsequent in-situ nitriding strengthening and significantly improve the coating's resistance to pitting and uniform corrosion. The introduction of Y2O3 plays a role in refining the grains and strengthening the microstructure. By introducing a moderate WC content (8-15wt%) and combining it with the tough nickel matrix, the inherent defect of high WC content coatings being brittle is overcome.

[0049] This invention employs a two-step process of laser cladding / plasma welding followed by in-situ nitriding to form a composite gradient structure coating on the workpiece surface: the inner layer is a Ni-WC composite layer with high toughness that is metallurgically bonded to the substrate, and the outer layer is a CrN / MoN nitride layer generated in situ with ultra-high hardness and excellent corrosion resistance. This effectively solves the contradiction between hardness and toughness that is difficult to achieve with traditional single coatings, and can better adapt to the complex working conditions of wear-corrosion coupling in oil extraction.

[0050] The surface protective coating prepared by the technology of this invention has excellent comprehensive performance, and its surface microhardness can reach 1418 HV. 0.2 The volumetric wear rate is as low as 1.21 × 10⁻⁶. -6 mm 3 With a corrosion rate as low as 0.016 mm / a in simulated oilfield water medium, and a bending crack angle reaching 102°, this coating exhibits excellent toughness. When applied to critical components such as oil plungers, this coating can significantly extend their service life and reduce equipment failure rates, demonstrating significant industrial application value. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to the embodiments.

[0052] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0053] Tungsten carbide powder: 99% purity, 3μm particle size, spherical shape, purchased from Hebei Yinbai Alloy Welding Materials Co., Ltd.

[0054] Chromium powder: 99.9% purity, 350 mesh, purchased from Hebei Yirui Alloy Welding Materials Co., Ltd.

[0055] Molybdenum powder: 99.9% purity, 400 mesh, purchased from Hebei Yirui Alloy Welding Materials Co., Ltd.

[0056] Boron powder: 99.5% purity, 5μm particle size, purchased from Kairui New Materials (Beijing) Technology Co., Ltd.;

[0057] Yttrium oxide powder: purity 99.99%, particle size 50nm, purchased from Ganzhou Xiyou New Materials Co., Ltd.

[0058] Nickel powder: 99.9% purity, 5μm particle size, purchased from Kairui New Materials (Beijing) Technology Co., Ltd.

[0059] Preparation Examples 1-3 and Comparative Preparation Example 1 provide pretreated tungsten carbide.

[0060] Preparation Example 1

[0061] Pretreated tungsten carbide is prepared by the following method:

[0062] Tungsten carbide powder was added to an 8% hydrochloric acid solution at a mass ratio of 1:5. The solution was magnetically stirred at 200 rpm for 40 minutes at 45°C to remove surface oxides and activate the surface. The solution was then repeatedly filtered and washed with deionized water until the pH of the filtrate was 7. The solution was then vacuum dried at 60°C for 4 hours to obtain activated tungsten carbide.

[0063] Activated tungsten carbide was added to a chemical nickel plating solution and chemically plated at 85°C with stirring at 250 rpm for 50 min. After the reaction was completed, the solution was filtered, washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 70°C for 6 h to obtain pretreated tungsten carbide.

[0064] In the electroless nickel plating solution, the concentrations of nickel sulfate (22 g / L), sodium hypophosphite (27 g / L), sodium tungstate (15 g / L), sodium citrate (30 g / L), thiourea (1 mg / L), and pH (4.5) were adjusted using 30% dilute sulfuric acid.

[0065] Preparation Example 2

[0066] Pretreated tungsten carbide is prepared by the following method:

[0067] Tungsten carbide powder was added to a 10% hydrochloric acid solution at a material-to-liquid mass ratio of 1:6. The solution was magnetically stirred at 250 rpm for 30 min at 50 °C to remove surface oxides and activate the surface. The solution was then repeatedly filtered and washed with deionized water until the pH of the filtrate was 7. The solution was then vacuum dried at 70 °C for 3.5 h to obtain activated tungsten carbide.

[0068] Activated tungsten carbide was added to a chemical nickel plating solution and chemically plated at 90°C with stirring at 300 rpm for 45 min. After the reaction was completed, the solution was filtered, washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 75°C for 5 h to obtain pretreated tungsten carbide.

[0069] In the electroless nickel plating solution, the concentration of nickel sulfate is 25 g / L, the concentration of sodium hypophosphite is 30 g / L, the concentration of sodium tungstate is 18 g / L, the concentration of sodium citrate is 35 g / L, the concentration of thiourea is 2 mg / L, the pH value is 5, and it is adjusted with 30% dilute sulfuric acid.

[0070] Preparation Example 3

[0071] Pretreated tungsten carbide is prepared by the following method:

[0072] Tungsten carbide powder was added to a 12% hydrochloric acid solution at a material-to-liquid mass ratio of 1:7. The solution was then magnetically stirred at 300 rpm for 20 minutes at 55°C to remove surface oxides and activate the surface. The solution was then repeatedly filtered and washed with deionized water until the pH of the filtrate was 7. Finally, the solution was vacuum dried at 80°C for 3 hours to obtain activated tungsten carbide.

[0073] Activated tungsten carbide was added to a chemical nickel plating solution and chemically plated at 95°C with stirring at 350 rpm for 40 min. After the reaction was completed, the solution was filtered, washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 80°C for 4 h to obtain pretreated tungsten carbide.

[0074] In the electroless nickel plating solution, the concentration of nickel sulfate is 28 g / L, the concentration of sodium hypophosphite is 33 g / L, the concentration of sodium tungstate is 20 g / L, the concentration of sodium citrate is 40 g / L, the concentration of thiourea is 3 mg / L, the pH value is 5.5, and it is adjusted with 30% dilute sulfuric acid.

[0075] Comparative Preparation Example 1

[0076] Compared to Preparation Example 1, this preparation is identical to Preparation Example 1, except that the electroless nickel plating solution does not contain sodium tungstate. Details are as follows:

[0077] Pretreated tungsten carbide is prepared by the following method:

[0078] Tungsten carbide powder was added to an 8% hydrochloric acid solution at a mass ratio of 1:5. The solution was magnetically stirred at 200 rpm for 40 minutes at 45°C to remove surface oxides and activate the surface. The solution was then repeatedly filtered and washed with deionized water until the pH of the filtrate was 7. The solution was then vacuum dried at 60°C for 4 hours to obtain activated tungsten carbide.

[0079] Activated tungsten carbide was added to a chemical nickel plating solution and chemically plated at 85°C with stirring at 250 rpm for 50 min. After the reaction was completed, the solution was filtered, washed three times alternately with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 70°C for 6 h to obtain pretreated tungsten carbide.

[0080] In the electroless nickel plating solution, the concentration of nickel sulfate is 22 g / L, the concentration of sodium hypophosphite is 27 g / L, the concentration of sodium citrate is 30 g / L, the concentration of thiourea is 1 mg / L, the pH value is 4.5, and it is adjusted with 30% dilute sulfuric acid.

[0081] Preparation Examples 4-6 and Comparative Preparation Examples 2-5 provide a nickel-based coated tungsten carbide, its preparation method, and its application.

[0082] Preparation Example 4

[0083] A nickel-based coated tungsten carbide comprises, by weight percentage, 14.15% chromium, 1.68% molybdenum, 1.23% boron, 8% pretreated tungsten carbide of Preparation Example 1, 0.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0084] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0085] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0086] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 30 rpm for 20 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder ratio of 1:1. The ball-to-powder ratio is controlled at 8:1, the rotation speed is 300 rpm, and mechanical fusion is performed for 10 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 500-mesh sieve.

[0087] Preparation Example 5

[0088] A nickel-based coated tungsten carbide comprises, by weight percentage, 15.65% chromium, 1.78% molybdenum, 1.37% boron, 11.5% pretreated tungsten carbide from Preparation Example 2, 1% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0089] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0090] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0091] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 25 rpm for 25 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder ratio of 1:1. The ball-to-powder ratio is controlled at 10:1, the rotation speed is 400 rpm, and mechanical fusion is performed for 8 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 550-mesh sieve.

[0092] Preparation Example 6

[0093] A nickel-based coated tungsten carbide comprises, by weight percentage, 17.19% chromium, 1.89% molybdenum, 1.5% boron, 15% pretreated tungsten carbide of Preparation Example 3, 1.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0094] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0095] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0096] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 20 rpm for 30 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6mm and φ10mm and a ball-to-powder mass ratio of 1:1. The ball-to-powder ratio is controlled at 12:1, the rotation speed is 500 rpm, and mechanical fusion treatment is performed for 6 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 600-mesh sieve.

[0097] Comparative Preparation Example 2

[0098] Comparative Preparation Example 2 is the same as Preparation Example 4, except that the pretreated tungsten carbide in Preparation Example 1 is replaced with the pretreated tungsten carbide in Comparative Preparation Example 1.

[0099] Specifically as follows:

[0100] A nickel-based coated tungsten carbide comprises, by weight percentage, 14.15% chromium, 1.68% molybdenum, 1.23% boron, 8% pretreated tungsten carbide from Comparative Preparation Example 1, 0.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0101] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0102] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0103] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 30 rpm for 20 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder ratio of 1:1. The ball-to-powder ratio is controlled at 8:1, the rotation speed is 300 rpm, and mechanical fusion is performed for 10 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 500-mesh sieve.

[0104] Comparative preparation example 3

[0105] Compared with Preparation Example 3, the only difference from Preparation Example 4 is that the pretreated tungsten carbide in Preparation Example 1 was replaced with tungsten carbide, and the tungsten carbide content was 40%.

[0106] Specifically as follows:

[0107] A nickel-based coated tungsten carbide comprises, by weight percentage: 14.15% chromium, 1.68% molybdenum, 1.23% boron, 40% tungsten carbide, 0.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0108] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0109] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0110] S2. Tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 30 rpm for 20 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder ratio of 1:1. The ball-to-powder ratio is controlled at 8:1, the rotation speed is 300 rpm, and mechanical fusion is performed for 10 hours under argon protection to form a coating layer on the surface of the tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 500-mesh sieve.

[0111] Comparative preparation example 4

[0112] Compared to Preparation Example 4, this preparation is identical to Preparation Example 4 except that it does not contain yttrium oxide. Details are as follows:

[0113] A nickel-based coated tungsten carbide comprises, by weight percentage, 14.15% chromium, 1.68% molybdenum, 1.23% boron, 8% pretreated tungsten carbide from Preparation Example 1, with the balance being nickel and unavoidable impurities.

[0114] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0115] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide and nickel powder by weight percentage for later use;

[0116] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, and boron powder are placed in a three-dimensional motion mixer and stirred at 30 rpm for 20 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder mass ratio of 1:1. The ball-to-powder ratio is controlled at 8:1, the rotation speed is 300 rpm, and mechanical fusion is performed for 10 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-based coated tungsten carbide is obtained by sieving through a 500-mesh sieve.

[0117] Comparative preparation example 5

[0118] Compared to Preparation Example 4, Preparation Example 5 is identical, except that the chromium content in the component is reduced to 10 wt%. Details are as follows:

[0119] A nickel-based coated tungsten carbide comprises, by weight percentage: 10% chromium, 1.68% molybdenum, 1.23% boron, 8% pretreated tungsten carbide of Preparation Example 1, 0.5% yttrium oxide, with the balance being nickel and unavoidable impurities.

[0120] A method for preparing nickel-based coated tungsten carbide includes the following steps:

[0121] S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use;

[0122] S2. Pretreated tungsten carbide, nickel powder, chromium powder, molybdenum powder, boron powder, and yttrium oxide powder are placed in a three-dimensional motion mixer and stirred at 30 rpm for 20 minutes to obtain a mixed powder. The mixed powder is then transferred to a high-energy planetary ball mill using a stainless steel grinding jar and cemented carbide grinding balls (YG6) with diameters of φ6 mm and φ10 mm and a ball-to-powder ratio of 1:1. The ball-to-powder ratio is controlled at 8:1, the rotation speed is 300 rpm, and mechanical fusion is performed for 10 hours under argon protection to form a coating layer on the surface of the pretreated tungsten carbide. The resulting nickel-coated tungsten carbide is obtained by sieving through a 500-mesh sieve.

[0123] Examples 1-3 provide a method for preparing a protective coating on the surface of an oil plunger.

[0124] Example 1

[0125] The surface protective coating is prepared by the following method:

[0126] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide from Preparation Example 4 was clad onto the sample surface, ultimately forming a 2mm thick nickel-based tungsten carbide composite cladding layer.

[0127] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 550°C for 5 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0128] Example 2

[0129] The surface protective coating is prepared by the following method:

[0130] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 4kW, scanning speed 10mm / s, spot diameter 4mm, powder feed rate 12.5g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide from Preparation Example 5 was clad onto the sample surface, ultimately forming a 1.5mm thick nickel-based tungsten carbide composite cladding layer.

[0131] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 600℃ for 4 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0132] Example 3

[0133] The surface protective coating is prepared by the following method:

[0134] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 5kW, scanning speed 12mm / s, spot diameter 5mm, powder feed rate 10g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide of Preparation Example 6 was clad onto the sample surface, ultimately forming a nickel-based tungsten carbide composite cladding layer with a thickness of 1mm.

[0135] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 650°C for 3 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0136] To verify the comprehensive performance of the surface protective coatings obtained in Examples 1-3 of this invention, Comparative Examples 1-5 were set up, wherein:

[0137] Comparative Example 1

[0138] Comparative Example 1 is the same as Example 1, except that the nickel-based coated tungsten carbide of Preparation Example 4 is replaced by the nickel-based coated tungsten carbide of Comparative Preparation Example 2 by the same mass. Details are as follows:

[0139] The surface protective coating is prepared by the following method:

[0140] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide of Comparative Preparation Example 2 was clad onto the sample surface, ultimately forming a nickel-based tungsten carbide composite cladding layer with a thickness of 2mm.

[0141] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 550°C for 5 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0142] Comparative Example 2

[0143] Comparative Example 2 is the same as Example 1, except that the nickel-based coated tungsten carbide of Preparation Example 4 is replaced by the nickel-based coated tungsten carbide of Comparative Preparation Example 3 by the same mass. Details are as follows:

[0144] The surface protective coating is prepared by the following method:

[0145] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide of Comparative Preparation Example 3 was clad onto the sample surface, ultimately forming a nickel-based tungsten carbide composite cladding layer with a thickness of 2mm.

[0146] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 550°C for 5 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0147] Comparative Example 3

[0148] Comparative Example 3 is the same as Example 1, except that the nickel-based coated tungsten carbide of Preparation Example 4 is replaced with the nickel-based coated tungsten carbide of Comparative Example 4 by the same mass. Details are as follows:

[0149] The surface protective coating is prepared by the following method:

[0150] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide of Comparative Preparation Example 4 was clad onto the sample surface, ultimately forming a nickel-based tungsten carbide composite cladding layer with a thickness of 2mm.

[0151] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 550°C for 5 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0152] Comparative Example 4

[0153] Comparative Example 4 is the same as Example 1, except that the nickel-based coated tungsten carbide of Preparation Example 4 is replaced by the nickel-based coated tungsten carbide of Comparative Preparation Example 5 by the same mass. Details are as follows:

[0154] The surface protective coating is prepared by the following method:

[0155] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide of Comparative Preparation Example 5 was clad onto the sample surface, ultimately forming a nickel-based tungsten carbide composite cladding layer with a thickness of 2mm.

[0156] B. The sample with the nickel-based tungsten carbide composite cladding layer is placed in a pit-type gas nitriding furnace, and ammonia is introduced as the nitrogen source. The sample is held at 550°C for 5 hours for nitriding treatment. Then the furnace is cooled to room temperature, and a nitride layer is generated in situ on the surface of the composite cladding layer to obtain a surface protective coating.

[0157] Comparative Example 5

[0158] Comparative Example 5 is the same as Example 1, except that it did not undergo nitriding treatment. Details are as follows:

[0159] The surface protective coating is prepared by the following method:

[0160] A. 45# steel was selected as the oil plunger sample (100mm×50mm×10mm), and pre-blasted to remove rust. An IPGYLS-6000 fiber laser was used for cladding, with the following parameters: laser power 3kW, scanning speed 8mm / s, spot diameter 3mm, powder feed rate 15g / min, and argon as the protective gas and powder feed gas. The nickel-based coated tungsten carbide from Preparation Example 4 was clad onto the sample surface, ultimately forming a 2mm thick nickel-based tungsten carbide composite cladding layer.

[0161] The overall performance of the surface protective coatings in Examples 1-3 and Comparative Examples 1-5 of the present invention was tested respectively.

[0162] 1. Surface Hardness: The microhardness of the outermost layer of the coating (20μm from the surface) was tested using an HVS-1000 digital display micro Vickers hardness tester (load 200gf, hold for 15s, i.e., HV). 0.2 The Rockwell hardness (HRC) of the coating was tested using an HR-150A Rockwell hardness tester. Five points were taken at different locations for each sample, and the average value was taken.

[0163] 2. Wear Resistance: Following ASTM G133-22 standard, a reciprocating wear test was conducted using an MFT-5000 multi-functional friction and wear testing machine under room temperature and dry friction conditions. The mating part was a Φ6mm Si3N4 ceramic ball, with a normal load of 20N, a reciprocating frequency of 10Hz, a stroke of 5mm, and a test time of 30min. After the test, the volume of the wear track was measured using a white light interferometer to calculate the volumetric wear rate (unit: 10). -6 mm 3 / N·m). The smaller the value, the better the wear resistance.

[0164] 3. Corrosion resistance: Referencing ASTM G59-97 standard, under simulated conditions containing H2S (saturated) and Cl... - Potentiodynamic polarization curves were measured using a CHI660E electrochemical workstation in an oilfield aqueous solution (pH 4.0, temperature 80℃) containing 3.5 wt% NaCl. A three-electrode system was employed, with the working electrode being the coated sample (exposed area 1 cm²). 2 The auxiliary electrode was a platinum sheet, and the reference electrode was a saturated calomel electrode (SCE). The scan rate was 0.5 mV / s. The self-corrosion current density Icorr was calculated using the Tafel extrapolation method, and then the annual corrosion rate (unit: mm / a) was calculated according to Faraday's law. The smaller the value, the better the corrosion resistance.

[0165] 4. Bond Strength: Following ASTM C633-13 standard, the tensile bond strength of the coating / substrate interface was tested using a WDW-100 electronic universal testing machine. The coated sample was bonded to a tensile butt bar of the same material using E-7 epoxy adhesive. After curing at 180℃ for 2 hours, the test was conducted at a tensile rate of 1 mm / min until separation occurred at the coating-substrate interface. The maximum tensile stress value was recorded. Each group of samples was tested three times, and the average value was taken.

[0166] 5. Toughness (Bending Test): The toughness of the coating was evaluated using the three-point bending method. The coated specimen (10mm × 50mm × 5mm, with the coating on the tension side) was placed on the bending fixture of a universal testing machine with a support span of 30mm, and loaded at an indenter indentation speed of 0.5mm / min. Crack initiation on the coating surface was monitored in real time using an acoustic emission sensor and a high-magnification camera. The indenter displacement at the first appearance of a macroscopic crack (length > 0.1mm) was recorded and converted into a bending crack angle based on geometric relationships. A larger bending crack angle indicates a stronger resistance to cracking under plastic deformation and better toughness.

[0167] The test results are shown in Table 1:

[0168] Table 1: Comprehensive performance test data of surface protective coatings in Examples 1-3 and Comparative Examples 1-5

[0169]

[0170] As shown in Table 1, the surface protective coatings prepared in Examples 1-3 of the present invention exhibit excellent and balanced comprehensive performance in terms of surface hardness, wear resistance, corrosion resistance, bonding strength and toughness, which are significantly better than those in Comparative Examples 1-5.

[0171] As can be seen from Example 1 and Comparative Example 1, the coating strength and toughness of WC pre-coated with Ni-P in Comparative Example 1 are significantly lower than those in Example 1, and the wear resistance is also poor.

[0172] As can be seen from Example 1 and Comparative Example 2, Comparative Example 2 uses high content (40%) WC without pretreatment. Its coating exhibits extremely high brittleness (bending crack angle <30°) and low bonding strength. It is prone to peeling of hard phase during wear. Although the hardness is high, the wear resistance is far inferior to that of Example 1.

[0173] As can be seen from Example 1 and Comparative Example 3, the formulation of Comparative Example 3 does not contain Y2O3, and its bonding strength and toughness are lower than those of Example 1.

[0174] As can be seen from Example 1 and Comparative Example 4, the Cr content in the formulation of Comparative Example 4 is low (10%), which results in insufficient elements available for the reaction to generate CrN in the subsequent nitriding treatment. Therefore, the surface hardness and wear resistance are significantly lower than those of Example 1. Moreover, the low Cr content severely weakens the corrosion resistance of the coating, and its corrosion rate is much higher than that of Example 1.

[0175] As can be seen from Example 1 and Comparative Example 5: Comparative Example 5 only underwent laser cladding without nitriding treatment, and its coating surface did not form a high-hardness nitride layer. Therefore, its surface hardness and wear resistance were the worst among all samples. Although its toughness was good, it could not provide effective protection in abrasive and corrosive environments.

[0176] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A nickel-based coated tungsten carbide, characterized in that, By weight percentage, it consists of the following components: 14.15-17.19% chromium, 1.68-1.89% molybdenum, 1.23-1.5% boron, 8-15% pretreated tungsten carbide, 0.5-1.5% yttrium oxide, with the balance being nickel and unavoidable impurities; The nickel-based coated tungsten carbide has a core-shell structure, with the core being pretreated tungsten carbide and the shell being a nickel-based alloy; The pretreated tungsten carbide is prepared by the following method: Activated tungsten carbide is obtained by surface activation treatment of tungsten carbide, and then activated tungsten carbide is placed in a chemical nickel plating solution for chemical plating, followed by washing and drying to obtain pretreated tungsten carbide. The electroless nickel plating solution contains nickel sulfate at a concentration of 22-28 g / L, sodium hypophosphite at a concentration of 27-33 g / L, sodium tungstate at a concentration of 15-20 g / L, sodium citrate at a concentration of 30-40 g / L, thiourea at a concentration of 1-3 mg / L, and a pH of 4.5-5.5, adjusted with dilute sulfuric acid.

2. The nickel-based coated tungsten carbide according to claim 1, characterized in that, The electroless plating temperature is 85-95℃, and the time is 40-50 minutes.

3. A method for preparing nickel-based coated tungsten carbide as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Weigh out the raw materials chromium powder, molybdenum powder, boron powder, pretreated tungsten carbide, yttrium oxide powder and nickel powder by weight percentage for later use; S2. The pretreated tungsten carbide is mixed with nickel powder, chromium powder, molybdenum powder, boron powder and yttrium oxide powder, and placed in a high-energy ball mill for mechanical fusion treatment. Through repeated cold welding, fracture and re-welding between powder particles, the nickel-based alloy powder forms a coating shell on the surface of the pretreated tungsten carbide. After sieving, nickel-based coated tungsten carbide is obtained.

4. The method for preparing nickel-based coated tungsten carbide according to claim 3, characterized in that, In the S2 process, the ball-to-material ratio for mechanical fusion is 8-12:1, the rotation speed is 300-500 rpm, the processing time is 6-10 hours, and inert gas protection is used during the process.

5. The application of the nickel-based coated tungsten carbide as described in claim 1 or 2 in the preparation of a protective coating for the surface of an oil plunger; The surface protective coating is prepared by the following method: A. Using laser cladding or plasma welding technology, nickel-based tungsten carbide is clad onto the surface of the oil plunger to form a nickel-based tungsten carbide composite cladding layer; B. Nitriding treatment is performed on the oil plunger with the nickel-based tungsten carbide composite cladding layer to generate a nitride layer in situ on the surface of the composite cladding layer.

6. The application of the nickel-based coated tungsten carbide according to claim 5 in the preparation of a protective coating for the surface of an oil plunger, characterized in that, The nitriding treatment in section B is carried out at a temperature of 550-650℃ for 3-5 hours.

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