Cast tungsten carbide composite material coated with multi-component carbide shell layer and preparation method of cast tungsten carbide composite material

Abstract

The invention belongs to the technical field of metal-based composite coating material preparation, and particularly relates to a cast tungsten carbide composite material coated with a multi-element carbide shell layer and a preparation method thereof.The composite material is of a core-shell double-layer structure, a core layer of the composite material is spherical cast tungsten carbide, the core layer is coated with the multi-element carbide shell layer, the multi-element carbide shell layer is a (W, Ti and X) C solid solution, and the diameter of the (W, Ti and X) C solid solution is larger than that of the spherical cast tungsten carbide. And X is selected from at least two elements of Ta, Nb, V, Zr, Mo and Hf. The surface of spherical cast tungsten carbide is coated with a multi-element carbide shell layer through the elemental metal powder raw material, non-crushing type precise mixing and push rod type hydrogen reduction furnace continuous treatment process, and the spherical cast tungsten carbide located in a core layer is greatly protected through coating of the multi-element carbide shell layer, so that when the spherical cast tungsten carbide is used as a coating, the surface of the spherical cast tungsten carbide is coated with the multi-element carbide shell layer; the coating has more excellent wear resistance, decomposition of a W2C phase in an instantaneous high-temperature melting environment is avoided, and the bonding strength and fatigue resistance of the coating and a matrix are improved.

Description

Technical Field

[0001] This invention belongs to the field of metal-based composite coating material preparation technology, specifically relating to a cast tungsten carbide composite material with a multi-component carbide shell and its preparation method. Background Technology

[0002] Spherical cast tungsten carbide (mainly W₂C and WC phases) is widely used as reinforcing particles in wear-resistant coatings for critical components in oil drilling tools and heavy machinery due to its excellent hardness and toughness. However, during coating preparation processes such as plasma cladding, laser cladding, and supersonic flame spraying, the spherical cast tungsten carbide reinforcing particles undergo instantaneous high-temperature melting. Under these conditions, the W₂C phase is thermodynamically unstable and readily decomposes into tungsten and carbon, diffusing into iron-based, nickel-based, or cobalt-based metal matrices. This decomposition not only leads to the failure of the reinforcing particles themselves but also forms a large number of brittle lamellar or network-like secondary carbides in the surrounding matrix, becoming the source of crack initiation and propagation. This severely degrades the coating's bonding strength, toughness, and fatigue resistance. Especially under impact-induced wear conditions, insufficient wear resistance becomes a key bottleneck restricting the coating's lifespan and reliability.

[0003] In the prior art, in order to improve the thermal stability of spherical cast tungsten carbide reinforcing particles, it is often necessary to optimize the coating preparation process and reduce heat input, but this approach is not conducive to the bonding between the reinforcing particles and the matrix.

[0004] In recent years, high-entropy ceramic materials, especially high-entropy carbides (HECs), have attracted widespread attention due to their four core effects: high-entropy effect, lattice distortion effect, hysteresis diffusion effect, and "cocktail" effect. Single-phase solid solution carbides formed by four or more principal elements (such as (Ti, Zr, Hf, Nb, Ta, W)C) exhibit high-temperature stability, hardness, and toughness far exceeding those of single carbides. If a metallurgically bonded, compositionally adjustable high-entropy or multi-component carbide shell can be constructed on the surface of spherically cast tungsten carbide particles, it is hoped that the problem of high-temperature decomposition can be solved.

[0005] Currently, there are no reports in publicly available technical documents on the in-situ, uniform, and non-damaging multi-element (high-entropy) carbide shell coating of spherical cast tungsten carbide powder using a one-step solid powder embedding and co-infiltration method, which uses elemental metal powder as raw material. Summary of the Invention

[0006] To address the above problems, this invention provides a cast tungsten carbide composite material with a multi-component carbide shell and its preparation method. Through a three-pronged process design—component elemental metal powder raw material, non-crushing precision mixing, and continuous processing in a pusher-type hydrogen reduction furnace—a multi-component carbide shell is coated onto the surface of spherical cast tungsten carbide, forming a composite material with a core-shell structure. This multi-component carbide shell coating significantly protects the spherical cast tungsten carbide within the core layer, improving its high-temperature resistance when used as a coating. It also avoids or greatly reduces the decomposition of the W2C phase under instantaneous high-temperature melting conditions, and enhances the bonding strength, wear resistance, and fatigue resistance of the coating to the substrate.

[0007] The present invention is specifically achieved through the following technical solution: a cast tungsten carbide composite material with a multi-component carbide shell is proposed according to the present invention. The composite material has a core-shell double-layer structure, wherein the core layer is spherical cast tungsten carbide, and the core layer is covered with a multi-component carbide shell layer. The multi-component carbide shell layer is a (W, Ti, X)C solid solution, wherein X is selected from at least two elements selected from Ta, Nb, V, Zr, Mo, and Hf.

[0008] In the aforementioned cast tungsten carbide composite material coated with a multi-component carbide shell, the thickness of the multi-component carbide shell is preferably 2 to 15 μm. If the shell is too thin, the barrier effect will be insufficient; if it is too thick, it will easily crack due to internal stress. Furthermore, an excessively thick shell is prone to causing internal grain growth during the preparation process.

[0009] The aforementioned multi-component carbide-coated cast tungsten carbide composite material is prepared from raw materials including spherical cast tungsten carbide powder, metallic titanium powder, metallic X powder, and carbon black. The metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder. By weight, with 1000 parts of spherical cast tungsten carbide powder, the metallic titanium powder is 30-200 parts, the metallic X powder is 100-500 parts, and the carbon black is 30-100 parts. The weight parts of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively.

[0010] In the aforementioned cast tungsten carbide composite material with a multi-component carbide shell, the average particle size of the spherical cast tungsten carbide powder is preferably 20-150 μm, the average particle size of the titanium powder is preferably 0.5-2 μm, the average particle size of the Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is preferably 0.2-3 μm, and the average particle size of the carbon black is preferably 30-500 nm.

[0011] This invention also provides a method for preparing the above-mentioned cast tungsten carbide composite material coated with a multi-component carbide shell. The method employs a solid-state powder embedding and co-infiltration method based on elemental metal powders, and is carried out under specific equipment and mixing processes to ensure the sphericity of the core powder. Specifically, the method includes the following steps: (1) Weigh the raw materials according to the weight parts. The raw materials include: 1000 parts of spherical cast tungsten carbide powder, 30-200 parts of metallic titanium powder, 100-500 parts of metallic X powder, and 30-100 parts of carbon black; wherein, metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder, and the weight parts of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively. Weigh out spherical cast tungsten carbide powder, titanium powder, X powder, and carbon black according to the above weight ratio. Dry mix the titanium powder, X powder, and carbon black evenly beforehand to obtain a premixed powder. Add this premixed powder together with the spherical cast tungsten carbide powder into a three-dimensional motion mixer or a V-type mixer and mix under inert gas protection to obtain a mixed powder. This mixing process strictly avoids any form of ball milling, crushing, or high-energy mechanical alloying treatment. (2) The obtained mixed powder is placed in a high-temperature furnace and continuously heat-treated in a hydrogen-argon mixed atmosphere of pure hydrogen or hydrogen gas with a hydrogen gas integral of not less than 20%. First, it is kept at 800-1000℃ for 0.5-2h to allow highly active metals such as titanium to react with carbon and begin to diffuse to the WC surface. Then, it is kept at 1300-1600℃ for 1-6h. The powder after reaction is cooled to room temperature with the furnace. Then, the product is gently sieved to separate the very small amount of sintered agglomerates that may be generated, and a cast tungsten carbide composite material with a multi-component carbide shell is obtained.

[0012] In the aforementioned method for preparing cast tungsten carbide composite material with multi-component carbide shell coating, zinc stearate can be added as a temporary binder in step (1) to promote adhesion. Preferably, the weight of zinc stearate is 0.1-0.5% of the total weight of spherical cast tungsten carbide powder, titanium powder, X powder, and carbon black. Zinc stearate is added together with the premixed powder and spherical cast tungsten carbide powder into a three-dimensional motion mixer or a V-type mixer for mixing.

[0013] Preferably, in step (1), the mixing time between the premixed powder and the spherical cast tungsten carbide powder is 30~120 min.

[0014] Preferably, the average particle size of the spherical cast tungsten carbide powder is 20~150μm, the average particle size of the titanium powder is 0.5~2μm, the average particle size of the Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is 0.2~3μm, and the average particle size of the carbon black is 30~500nm.

[0015] Preferably, the high-temperature furnace is a push-boat type hydrogen reduction furnace to ensure continuous production.

[0016] Further, in step (2), the obtained mixed powder is evenly spread in an alumina pusher boat, and then loaded into a pusher boat-type hydrogen reduction furnace, and the continuous heat treatment is carried out in a hydrogen-argon mixed atmosphere of pure hydrogen or hydrogen gas with a hydrogen gas integral of not less than 20%.

[0017] Compared with the prior art, the present invention has significant advantages and beneficial effects, achieving considerable technological progress and practicality, and has broad application value. It possesses at least the following advantages: (1) This invention uses a three-in-one process design of elemental metal powder raw material + non-crushing precision mixing + pusher-type hydrogen reduction furnace to coat the surface of spherical cast tungsten carbide with a (W,Ti,X)C multi-element carbide shell (X is selected from at least two elements among Ta, Nb, V, Zr, Mo, and Hf), forming a cast tungsten carbide composite material with a core-shell structure. The coating of the multi-element carbide shell greatly protects the spherical cast tungsten carbide in the core layer, making it more wear-resistant when used as a coating, and avoiding or greatly reducing the decomposition of the W2C phase under instantaneous high temperature melting environment, thereby improving the bonding strength and fatigue resistance of the coating to the substrate.

[0018] (2) This invention avoids mechanical damage to the spherical cast tungsten carbide during the entire preparation process. The sphericity retention rate (roundness > 0.9) of the cast tungsten carbide composite material coated with the multi-component carbide shell is greater than 95%, ensuring its excellent flowability in the thermal spray powder feeding system. The in-situ formed multi-component carbide shell has extremely high mixing entropy and lattice distortion energy, forming a strong diffusion barrier. This makes the core decomposition region area of ​​the cast tungsten carbide composite material coated with the multi-component carbide shell reduced by more than 85% compared with the tungsten carbide powder without the multi-component carbide shell during the coating preparation process, thus solving the problem of core instability.

[0019] (3) The multi-component carbide shell of the cast tungsten carbide composite material prepared by the present invention not only has high hardness (microhardness can reach 28-35 GPa), but also has a thermal expansion coefficient and chemical affinity that are more compatible with nickel-based / cobalt-based coating materials. It can significantly enhance the interfacial bonding strength with nickel-based / cobalt-based materials, and improve the wear resistance life of the coating by 1-3 times in the friction and wear test.

[0020] (4) The raw material cost of the present invention is controllable, the process flow is simple, and it is especially suitable for mature pusher-type hydrogen reduction furnace. It can be continuously and mass-produced, and it is easy to realize the transformation from laboratory to industry. It has extremely high economic efficiency and practical value. Attached Figure Description

[0021] Figure 1 This is a SEM image of the spherical cast tungsten carbide composite material coated with (W, Ti, Ta, Nb)C quaternary carbide prepared in Example 1.

[0022] Figure 2 yes Figure 1 Cross-sectional SEM image of a single spherical particle.

[0023] Figure 3 yes Figure 2 A magnified view of a portion of the image.

[0024] Figure 4 This is a cross-sectional SEM image of the original spherical tungsten carbide powder particles.

[0025] Figure 5 This is a SEM image of a nickel-based tungsten carbide coating prepared using the (W, Ti, Ta, Nb)C quaternary carbide-coated spherical cast tungsten carbide composite material of Example 1.

[0026] Figure 6 The image shows a SEM image of a nickel-based tungsten carbide coating prepared using raw tungsten carbide powder in a comparative manner. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] The present invention provides a cast tungsten carbide composite material with a multi-component carbide shell, which has a core-shell double-layer structure. The core layer is a spherical cast tungsten carbide, and the core layer is covered with a continuous and dense multi-component carbide shell. The multi-component carbide shell is a (W, Ti, X)C solid solution, wherein X is selected from at least two elements selected from Ta, Nb, V, Zr, Mo and Hf. The shell and the core layer are densely and uniformly bonded.

[0029] Preferably, the thickness of the multi-component carbide shell is 2 to 15 μm. If the shell is too thin, the barrier effect will be insufficient, and if it is too thick, it will easily crack due to internal stress. In addition, an excessively thick shell is prone to causing internal grain growth during the preparation process.

[0030] Preferably, the raw materials for the cast tungsten carbide composite material coated with a multi-component carbide shell include spherical cast tungsten carbide powder, metallic titanium powder, metallic X powder, and carbon black. The metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder. According to the weight parts, with 1000 parts of spherical cast tungsten carbide powder, the metallic titanium powder is 30-200 parts, the metallic X powder is 100-500 parts, and the carbon black is 30-100 parts. Among them, the weight parts of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively.

[0031] The average particle size of the spherical cast tungsten carbide powder is preferably 20-150 μm, the average particle size of the titanium powder is preferably 0.5-2 μm, the average particle size of the Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is preferably 0.2-3 μm, and the average particle size of the carbon black is preferably 30-500 nm.

[0032] Preferably, the metal X powder is selected from two or three of Ta powder, Nb powder, and V powder.

[0033] More preferably, the multi-component carbide shell is a (W, Ti, Ta, Nb)C quaternary solid solution or a (W, Ti, Nb, V)C quaternary solid solution.

[0034] The preparation method of the aforementioned cast tungsten carbide composite material with a multi-component carbide shell includes: (1) Weigh the raw materials according to the following weight parts: 1000 parts of spherical cast tungsten carbide powder, 30-200 parts of metallic titanium powder, 100-500 parts of metallic X powder, and 30-100 parts of carbon black; wherein, metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder, and the weight parts of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively; Weigh out spherical cast tungsten carbide powder, titanium powder, X powder, and carbon black according to the above weight ratio. Dry mix the titanium powder, X powder, and carbon black evenly beforehand to obtain a premixed powder. Add this premixed powder and spherical cast tungsten carbide powder together into a three-dimensional motion mixer or a V-type mixer and mix under the protection of an inert gas (nitrogen or argon) until the premixed powder is evenly adhered to the surface of the spherical cast tungsten carbide to obtain a mixed powder. (2) The obtained mixed powder is evenly spread in an alumina pusher boat and then loaded into a high-temperature furnace. The high-temperature furnace is a pusher boat type hydrogen reduction furnace, and continuous heat treatment is carried out in a hydrogen-argon mixed atmosphere with pure hydrogen or a hydrogen gas integral of not less than 20%. The high-temperature furnace is equipped with at least two temperature zones: first, it is kept at a preheating temperature zone of 800-1000℃ for 0.5-2h, so that highly active metals such as titanium react with carbon initially and begin to diffuse to the WC surface; then it is advanced to the high-temperature reaction zone of 1300-1600℃ and kept for 1-6h. In this stage, the metal elements are fully miscible through solid-phase diffusion and react with carbon, forming a uniform (W, Ti, X)C multi-element carbide solid solution shell layer on the surface of spherical cast tungsten carbide particles through in-situ epitaxial growth. Hydrogen not only acts as a reducing atmosphere to prevent oxidation, but also acts as a carrier gas and activator to promote the transport and reaction of reactants. (3) After the continuous heat treatment in step (2) is completed, the alumina pusher boat is pushed to the cooling section, and the powder after reaction is cooled to room temperature with the furnace. Then the product is gently sieved to separate the very small amount of sintered agglomerates that may be generated, and finally a cast tungsten carbide composite material with a free-flowing multi-component carbide shell is obtained.

[0035] In step (1) of the aforementioned preparation method, the process of mixing the premixed powder with the spherical cast tungsten carbide strictly avoids any form of ball milling, crushing or high-energy mechanical alloying treatment. The mixing time is preferably 30~120min until the premixed powder is uniformly adhered to the surface of the spherical cast tungsten carbide particles.

[0036] Furthermore, in step (1), a trace amount of zinc stearate may be added as a temporary binder to promote adhesion. Preferably, the weight of zinc stearate added accounts for 0.1-0.5% of the total weight of the spherical cast tungsten carbide powder, titanium powder, X powder, and carbon black. Zinc stearate is added together with the premixed powder and the spherical cast tungsten carbide powder into a three-dimensional motion mixer or a V-type mixer for mixing.

[0037] Preferably, the average particle size of the spherical cast tungsten carbide powder is 20~150μm, the average particle size of the titanium powder is preferably 0.5~2μm, the average particle size of the Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is 0.2~3μm, and the average particle size of the carbon black is 30~500nm.

[0038] The present invention will be described in detail below with reference to specific embodiments. Unless otherwise specified, all conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Raw materials and reagents whose manufacturers are not specified are all commercially available products.

[0039] Example 1: Raw materials: 1000g of spherical cast tungsten carbide powder with an average particle size of 100μm, 50g of metallic titanium powder with an average particle size of 2μm, 150g of metallic tantalum powder with an average particle size of 2μm, 80g of metallic niobium powder with an average particle size of 2μm, 50g of carbon black with an average particle size of 50nm, and 4.5g of zinc stearate.

[0040] Preparation method: (1) Weigh each raw material according to the above weight ratio, premix titanium powder, tantalum powder, niobium powder and carbon black in a small three-dimensional motion mixer for 30 min to obtain premixed powder; add this premixed powder together with spherical cast tungsten carbide powder and zinc stearate into a large three-dimensional motion mixer (volume 20L), fill the large three-dimensional motion mixer with argon to replace the air, and run at a speed of 20 rpm for 60 min after the replacement is completed to obtain mixed powder; (2) The obtained mixed powder was loaded into multiple alumina pusher boats with a layer thickness of about 15 mm. The pusher boats were pushed into a pusher-type hydrogen reduction furnace with 5 temperature zones in sequence. The atmosphere inside the furnace was pure hydrogen with a flow rate of 5 L / min. The first and second temperature zones were preheating temperature zones with a set temperature of 950 °C and a total residence time of 1.5 h. The third, fourth and fifth temperature zones were high-temperature reaction temperature zones with a set temperature of 1500 °C and a total residence time of 2 h. After the reaction was completed, the powder was cooled with the furnace and then gently sieved through a 40-mesh sieve to obtain about 1200 g of spherical cast tungsten carbide composite material coated with (W, Ti, Ta, Nb)C quaternary carbide, which was designated as "Tungsten Carbide Composite Material I".

[0041] Figure 1 This is a SEM image of the (W, Ti, Ta, Nb)C quaternary carbide-coated spherical cast tungsten carbide composite material prepared in this embodiment. It can be seen that the composite material maintains a well-preserved and regular spherical structure, and the particle size of the spherical particles is approximately 100-200 μm, indicating that the spherical structure of tungsten carbide was not destroyed during the preparation process.

[0042] Figure 2 yes Figure 1 Cross-sectional SEM image of a single spherical particle. Figure 3 yes Figure 2 A magnified view of a portion of the image, by Figure 2 and Figure 3 It can be clearly seen that the spherical particles of the composite material have a clear core-shell double-layer structure. The core layer is spherical cast tungsten carbide, which clearly shows the eutectoid W2C+WC structure. The shell layer is a (W, Ti, Ta, Nb)C quaternary carbide. The thickness of the (W, Ti, Ta, Nb)C quaternary carbide shell layer is about 10 μm. The shell layer and the core layer are densely and uniformly bonded.

[0043] Example 2: Raw materials: 1000g of spherical cast tungsten carbide powder with an average particle size of 75μm, 80g of metallic titanium powder with an average particle size of 1μm, 60g of metallic niobium powder with an average particle size of 1μm, 80g of metallic vanadium powder with an average particle size of 1μm, and 40g of carbon black with an average particle size of 60nm.

[0044] Preparation method: (1) Weigh each raw material according to the above weight ratio, premix titanium powder, niobium powder, vanadium powder and carbon black in a small three-dimensional motion mixer for 30 min to obtain premixed powder; add this premixed powder together with spherical cast tungsten carbide powder into a large three-dimensional motion mixer (volume 20L), fill the large three-dimensional motion mixer with argon to replace the air, and run at a speed of 25 rpm for 60 min after the replacement is completed to obtain mixed powder; (2) The obtained mixed powder was loaded into multiple alumina pusher boats with a layer thickness of about 15 mm. The pusher boats were pushed into a pusher-type hydrogen reduction furnace with 5 temperature zones in sequence. The atmosphere inside the furnace was a hydrogen-argon mixture, in which the volume percentage of hydrogen was 30% and the volume percentage of argon was 70%, and the flow rate of the mixture was 6 L / min. The first and second temperature zones were preheating temperature zones, with a set temperature of 900℃ and a total residence time of 1 h in the first and second temperature zones. The third, fourth, and fifth temperature zones were high-temperature reaction temperature zones, with a set temperature of 1450℃ and a total residence time of 3 h in the third, fourth, and fifth temperature zones. After the reaction was completed, the powder was cooled with the furnace and then gently sieved through a 40-mesh sieve to obtain about 1200 g of spherical cast tungsten carbide composite material coated with (W, Ti, Nb, V)C quaternary carbide, which was designated as "Tungsten Carbide Composite Material II".

[0045] The spherical cast tungsten carbide composite material with (W, Ti, Nb, V)C quaternary carbide coating prepared in this embodiment was characterized by SEM. The thickness of the (W, Ti, Nb, V)C quaternary carbide shell was approximately 12 μm.

[0046] Comparative Example The same batch of spherical cast tungsten carbide powder, without any coating treatment, is used directly. hereinafter referred to as "raw tungsten carbide powder".

[0047] Figure 4 The image is a cross-sectional SEM image of the original spherical tungsten carbide powder particles. It can be seen that the sphericity is intact and the eutectoid W2C+WC structure is clearly displayed, but there is no encapsulating shell.

[0048] Performance comparison test: The tungsten carbide composite material I obtained in Example 1, the tungsten carbide composite material II obtained in Example 2, and the original tungsten carbide powder of the comparative example were combined with nickel-based powder and nickel-based tungsten carbide coatings were prepared on 45# steel substrates by plasma cladding process.

[0049] Figure 5 , Figure 6 The images show SEM images of the tungsten carbide composite material I obtained in Example 1, the nickel-based tungsten carbide coating prepared from the original tungsten carbide powder and nickel-based powder in the comparative example. Figure 5 In the image, the light gray spherical particles are spherical particles of spherical cast tungsten carbide composite material coated with (W, Ti, Ta, Nb)C quaternary carbides, while the dark areas are nickel-based. It can be clearly seen that the spherical particles have clear and complete outlines, clean interfaces, and no signs of decomposition. Figure 6 In the image, the dark area is nickel-based, and the light gray nearly circular area is the original tungsten carbide spherical particles. It can be seen that the edges of the original tungsten carbide particles, which have not undergone any coating treatment, have decomposed, and there are a large number of secondary precipitates around them.

[0050] Wear resistance was tested using an impact abrasive wear testing machine. The impact abrasive wear specimens were 10 mm × 10 mm × 30 mm in size. The grinding ring was made of GCr15 bearing steel, and the abrasive was quartz sand with an average particle size of 4-6 mm. The flow rate was set to 48 kg / h. The impact abrasive wear specimen was fixed on the upper hammer and subjected to vertical reciprocating motion. The impact shaft rotated at a speed of 200 r / min, the impact frequency was 200 times / min, the impact energy was 3 J, and the impact abrasive wear time was 1 hour. Test results: The average wear amount of the nickel-based tungsten carbide coating made from tungsten carbide composite material I obtained in Example 1 and nickel-based powder was about 0.5g, the average wear amount of the nickel-based tungsten carbide coating made from tungsten carbide composite material II obtained in Example 2 and nickel-based powder was about 0.4g, and the average wear amount of the nickel-based tungsten carbide coating made from the original tungsten carbide powder and nickel-based powder in the comparative example was about 0.9g. It can be seen that the wear resistance of the nickel-based tungsten carbide coating made from tungsten carbide composite material and nickel-based powder obtained in Examples 1 and 2 is 1.8 to 2.25 times that of the comparative example.

[0051] This invention coats the surface of spherical cast tungsten carbide with a multi-component carbide shell, forming a cast tungsten carbide composite material with a core-shell structure. The coating of the multi-component carbide shell greatly protects the spherical cast tungsten carbide in the core layer, giving it superior wear resistance when used as a coating.

[0052] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. The present invention can also have other embodiments based on the above structure and function, which will not be listed hereafter. Therefore, any simple modifications, equivalent changes, and alterations made by those skilled in the art to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A cast tungsten carbide composite material with a multi-component carbide shell coating, characterized in that, The composite material has a core-shell double-layer structure, with the core layer being spherical cast tungsten carbide and the core layer being covered by a multi-element carbide shell layer, which is a (W, Ti, X)C solid solution, wherein X is selected from at least two elements selected from Ta, Nb, V, Zr, Mo, and Hf.

2. The cast tungsten carbide composite material with a multi-component carbide shell as described in claim 1, characterized in that, The thickness of the multi-component carbide shell is 2–15 μm.

3. The cast tungsten carbide composite material with a multi-component carbide shell as described in claim 1, characterized in that, The raw materials for preparing the composite material include spherical cast tungsten carbide powder, metallic titanium powder, metallic X powder and carbon black, wherein the metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder and Hf powder.

4. The cast tungsten carbide composite material with a multi-component carbide shell as described in claim 3, characterized in that, Based on the weight percentages, for 1000 parts of spherical cast tungsten carbide powder, the weight percentages are as follows: titanium metal powder 30-200 parts, X metal powder 100-500 parts, and carbon black 30-100 parts; among which, the weight percentages of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively.

5. The cast tungsten carbide composite material with a multi-component carbide shell as described in claim 3, characterized in that, The particle size of spherical cast tungsten carbide powder is 20~150μm, the particle size of metallic titanium powder is 0.5~2μm, the particle size of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is 0.2~3μm, and the particle size of carbon black is 30~500nm.

6. A method for preparing a cast tungsten carbide composite material coated with a multi-component carbide shell, characterized in that, Includes the following steps: (1) Weigh the raw materials according to the following weight parts: 1000 parts of spherical cast tungsten carbide powder, 30-200 parts of metallic titanium powder, 100-500 parts of metallic X powder, and 30-100 parts of carbon black; wherein, metallic X powder is selected from at least two of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder, and the weight parts of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder are 0-400 parts, 0-200 parts, 0-150 parts, 0-200 parts, 0-300 parts, and 0-400 parts, respectively; Weigh out spherical cast tungsten carbide powder, metallic titanium powder, metallic X powder and carbon black according to the above weight ratio. Dry mix the metallic titanium powder, metallic X powder and carbon black evenly in advance to obtain premixed powder. Add this premixed powder together with the spherical cast tungsten carbide powder into a three-dimensional motion mixer or a V-type mixer and mix under inert gas protection to obtain mixed powder. (2) The obtained mixed powder is placed in a high-temperature furnace and continuously heat-treated in a hydrogen-argon mixed atmosphere with pure hydrogen or hydrogen gas fraction not less than 20%. First, it is kept at 800-1000℃ for 0.5-2h, and then kept at 1300-1600℃ for 1-6h. The powder after reaction is cooled to room temperature with the furnace, and then the product is gently sieved to obtain a cast tungsten carbide composite material with a multi-component carbide shell.

7. The method for preparing the cast tungsten carbide composite material with a multi-component carbide shell as described in claim 6, characterized in that, In step (1), the mixing time between the premixed powder and the spherical cast tungsten carbide powder is 30~120 min.

8. The method for preparing the cast tungsten carbide composite material with a multi-component carbide shell as described in claim 6, characterized in that, In step (1), zinc stearate is added as a temporary binder. The weight of zinc stearate is 0.1-0.5% of the total weight of spherical cast tungsten carbide powder, titanium powder, X powder and carbon black. Zinc stearate is added together with the premixed powder and spherical cast tungsten carbide powder into a three-dimensional motion mixer or a V-type mixer for mixing.

9. The method for preparing the cast tungsten carbide composite material with a multi-component carbide shell as described in claim 6, characterized in that, The particle size of spherical cast tungsten carbide powder is 20~150μm, the particle size of metallic titanium powder is 0.5~2μm, the particle size of Ta powder, Nb powder, V powder, Zr powder, Mo powder, and Hf powder is 0.2~3μm, and the particle size of carbon black is 30~500nm.

10. The method for preparing the cast tungsten carbide composite material with a multi-component carbide shell as described in claim 6, characterized in that, The high-temperature furnace is a pushboat-type hydrogen reduction furnace.

Images