A boron carbide reinforced iron-nickel-tungsten based lightweight alloy and a process for making the same

Abstract

The application relates to the technical field of metal alloys, and particularly discloses a boron carbide reinforced iron-nickel-tungsten-based light alloy and a preparation process thereof. The preparation process comprises the following steps: preparing a multilayer composite reinforced particle composed of an inner core boron carbide particle, a boron-carbon-nitrogen transition layer, a flaky hexagonal boron nitride outer layer and a nickel-tungsten-phosphorus alloy metal layer; mixing the multilayer composite reinforced particle with iron powder, nickel powder, tungsten powder, chromium powder, manganese powder, molybdenum powder and silicon powder, and performing ball milling, granulation, cold isostatic pressing forming, vacuum hot-pressing sintering, hot isostatic pressing treatment and stabilization treatment to obtain the light alloy. The application can improve the interface bonding between the boron carbide and the metal matrix, reduce particle agglomeration and interface debonding, and improve the hardness, tensile strength, wear resistance and high-temperature dimensional stability of the alloy.

Description

Technical Field

[0001] This invention relates to the field of metal alloy technology, specifically to a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy and its preparation process. Background Technology

[0002] Iron-nickel-tungsten based alloys combine the cost advantages of iron-based alloys, the toughness and corrosion resistance provided by nickel, and the high-temperature hardness and thermal stability provided by tungsten, making them promising for applications in wear-resistant structural components, high-temperature load-bearing components, and lightweight protective parts. To reduce alloy density and improve wear resistance, reinforcing components such as boron carbide, borides, carbides, or solid lubricating phases are often introduced into the metal matrix. However, ceramic reinforcing phases such as boron carbide suffer from poor wettability, thermal expansion mismatch, and insufficient interfacial bonding with the iron-nickel-tungsten matrix. Direct addition can easily lead to particle agglomeration, interfacial debonding, porosity residue, and localized enrichment of brittle phases, making it difficult to simultaneously improve hardness, tensile strength, wear resistance, and high-temperature dimensional stability.

[0003] Chinese invention patent CN104593700A discloses an in-situ synthesized boron carbide particle-reinforced steel-based wear-resistant composite material and its preparation method. This invention improves the hardness and wear resistance of steel-based materials by in-situ synthesizing boron carbide particles in the steel matrix. While this invention can improve the wear resistance of steel-based materials using hard boron carbide particles, its reinforcing phase mainly relies on in-situ reaction generation. It is difficult to finely control the interface to address issues such as insufficient wettability, interface debonding, and particle agglomeration between low-density boron carbide particles and the iron-nickel-tungsten matrix. Furthermore, it does not provide a multi-layered buffering, friction-reducing, and metallized bridging structure on the outer side of the boron carbide particles.

[0004] Chinese invention patent CN109852830A discloses an ultrafine carbide particle-reinforced metal matrix composite material and its preparation method. This invention uses a combination of ball milling and ultrasonic treatment of degummed carbon fibers to embed ultrafine carbon particles into metal powder, generating metal carbide particles in situ, thereby preparing the carbide particle-reinforced metal matrix composite material. This invention can improve the distribution of carbide particles in the metal matrix and enhance the overall performance of the composite material. However, its technical focus is on the in-situ generation of carbide reinforcing phases from ultrafine carbon particles. It does not involve multi-layered composite reinforcing particles with boron carbide as a low-density hard core and the construction of a boron-carbon-nitrogen transition layer, hexagonal boron nitride sheets, and a nickel-tungsten-phosphorus metallization layer on its surface. Therefore, it is still difficult to simultaneously achieve lightweighting, interface buffering, friction reduction and barrier properties, and metallurgical bonding reinforcement.

[0005] Chinese invention patent CN106623908B discloses a method for preparing nickel-coated hexagonal boron nitride composite powder. This invention forms a nickel coating layer on the surface of the hexagonal boron nitride powder through sensitization, activation, and electroless nickel plating to improve the wettability and interfacial bonding between the hexagonal boron nitride and the metal matrix. This invention can improve the dispersion and bonding effect of hexagonal boron nitride as a solid lubricating phase in metal-based or ceramic-based materials. However, its focus is on the nickel coating treatment of hexagonal boron nitride powder, primarily addressing the compatibility issue between the solid lubricating phase and the matrix. It does not anchor the hexagonal boron nitride sheets to the outside of the boron carbide hard core, nor does it further construct a boron-carbon-nitrogen transition layer and a nickel-tungsten-phosphorus alloy metallization layer to achieve a composite synergy of hard bearing, interfacial buffering, friction reduction, and metallurgical bridging.

[0006] While existing technologies improve the properties of metal matrix composites through in-situ generation of boron carbide particles, reinforcement with ultrafine carbide particles, and nickel-coated hexagonal boron nitride solid lubricating powder, they still have the following shortcomings: First, when directly introducing or generating hard ceramic phases in situ, it is difficult to solve the wettability and interfacial stress problems between the reinforcing phase and the iron-nickel-tungsten matrix; second, if friction-reducing components such as hexagonal boron nitride are added in the form of free powder, they are prone to agglomeration and the formation of weak interfaces; third, a single hard reinforcement or a single lubricating phase is difficult to simultaneously achieve low density, high strength, high hardness, wear resistance, and high-temperature deformation resistance. Therefore, it is necessary to provide a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy and its preparation process to achieve simultaneous improvement in lightweight, strong, tough, wear-resistant, and high-temperature dimensional stability. Summary of the Invention

[0007] To address the shortcomings of the existing technology, this invention provides a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy and its preparation process.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A preparation process for a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy includes the following steps:

[0010] (1) Weigh iron powder, nickel powder, tungsten powder, chromium powder, manganese powder, molybdenum powder, silicon powder and multilayer composite reinforcing particles according to the proportion; wherein, the multilayer composite reinforcing particles are multilayer interface composite structures with boron carbide particles as the core, and the surface of the boron carbide particles has a boron carbon nitrogen transition layer, a lamellar hexagonal boron nitride layer and a nickel tungsten phosphorus alloy metallization layer in sequence.

[0011] (2) After drying the weighed metal powder, it is placed under a protective atmosphere for the first ball milling and mixing to obtain premixed gold powder; then the multilayer composite reinforcing particles are added for the second ball milling and mixing, and after drying, the composite alloy mixed powder is obtained.

[0012] (3) Add a binder solution to the composite alloy mixed powder, mix and granulate, dry and sieve, and then cold isostatically press the obtained granulated powder to obtain an alloy compact;

[0013] (4) The alloy blank is placed in a vacuum hot pressing sintering furnace for sintering: first, it is heated to the first temperature under vacuum and held, then a protective gas is introduced and the temperature is raised to the second temperature and held; then axial pressure is applied and the temperature is raised to the third temperature for holding and sintering, and then the furnace is cooled to obtain the sintered alloy blank.

[0014] (5) The sintered alloy blank is subjected to hot isostatic pressing, then stabilization treatment, and cooled to obtain the final product.

[0015] To reduce density, traditional iron-nickel-tungsten-based lightweight alloys typically require increasing the proportion of low-density elements or lightweight phases, which can easily sacrifice hardness, wear resistance, and high-temperature dimensional stability. When reinforced solely with boron carbide, the wettability and interfacial bonding between boron carbide and the iron-nickel-tungsten matrix are insufficient, which can easily lead to particle agglomeration, interfacial debonding, and enrichment of pores and brittle phases, making it difficult to simultaneously improve tensile strength, wear resistance, and high-temperature deformation resistance.

[0016] Preferably, in step (1), the components are calculated based on 100 parts by mass of alloy billet, including 3-6 parts of multilayer composite reinforcing particles, 35-45 parts of iron powder, 12-18 parts of nickel powder, 4-8 parts of tungsten powder, 12-16 parts of chromium powder, 2-5 parts of manganese powder, 1-4 parts of molybdenum powder, and 12-18 parts of silicon powder.

[0017] The D50 particle size of the iron powder, nickel powder, chromium powder, manganese powder, molybdenum powder and silicon powder is 10-30 μm, and the D50 particle size of the tungsten powder is 2-8 μm.

[0018] Preferably, in step (2), the drying temperature is 80-120℃ and the time is 2-6h; the first ball milling and the second ball milling are both carried out under argon protection, anhydrous ethanol is used as the ball milling medium, and the ball-to-material mass ratio is (4-6):1; the rotation speed of the first ball milling is 180-250rpm and the time is 60-120min; the rotation speed of the second ball milling is 120-180rpm and the time is 30-90min.

[0019] Preferably, in step (3), the binder solution is a polyvinyl alcohol aqueous solution, wherein the amount of polyvinyl alcohol added is 0.3-1.0% of the mass of the composite alloy mixed powder; the granulation is passed through a 60-100 mesh sieve; the pressure of the cold isostatic pressing is 300-500 MPa, and the holding time is 2-5 min.

[0020] Preferably, in step (4), the vacuum level of the vacuum condition is not higher than 5 × 10⁻⁶.-2 Pa; the first temperature is 400-500℃, and the holding time is 60-120min; protective gas is introduced to make the furnace pressure 0.02-0.06MPa; the second temperature is 850-950℃, and the holding time is 20-40min; the applied axial pressure is 30-40MPa; the third temperature is 1200-1320℃, and the holding time is 2-3h.

[0021] Preferably, in step (5), the hot isostatic pressing treatment is performed at a temperature of 1100-1150℃, a pressure of 100-150MPa, and a holding time of 1-3h; the stabilization treatment is performed at a temperature of 600-650℃ and a holding time of 1-3h.

[0022] Preferably, the multilayer composite reinforcing particles are prepared by a method comprising the following steps:

[0023] S1. Add dopamine hydrochloride, boron source, nitrogen source and dispersant to ethanol-water mixture, adjust pH to alkaline to obtain composite modified dispersion; add boron carbide powder and hexagonal boron nitride nanosheets, stir and react, then separate, wash and dry to obtain boron carbide composite particles with precursor and hexagonal boron nitride nanosheets loaded on the surface.

[0024] S2. The boron carbide composite particles are heat-treated under a nitrogen atmosphere to obtain boron carbide-boron carbon nitride-hexagonal boron nitride composite particles.

[0025] S3. The boron carbide-boron carbon nitride-hexagonal boron nitride composite particles are sequentially subjected to catalytic activation and electroless nickel-tungsten-phosphorus plating to obtain the multilayer composite reinforced particles.

[0026] Furthermore, the preparation method of the multilayer composite reinforced particles is as follows:

[0027] S1. Add 0.02-0.12 parts by weight of dopamine hydrochloride, 0.1-0.2 parts by weight of boric acid, 0.4-0.7 parts by weight of melamine, and 0.01-0.1 parts by weight of polyvinylpyrrolidone to 20-60 parts by weight of a 40-55 wt% ethanol-water mixture. After stirring and dissolving, adjust the pH of the system to 8.5-9.0 with ammonia to obtain a composite modified dispersion. Add 2.8-4.0 parts by weight of boron carbide powder and 0.1-0.4 parts by weight of hexagonal boron nitride nanosheets. Stir at 400-800 rpm for 2-6 hours at 25-40℃. Filter, wash with deionized water and anhydrous ethanol in sequence, and vacuum dry to obtain boron carbide composite particles with boron carbon nitride precursor and hexagonal boron nitride nanosheets on the surface.

[0028] S2. The obtained boron carbide composite particles are placed in a tube furnace and heated to 800-900℃ at 2-8℃ / min under a nitrogen atmosphere, and held at the temperature for 1-4h. Then, the temperature is cooled to room temperature with the furnace, washed with deionized water, and vacuum dried to obtain boron carbide-boron carbon nitride-hexagonal boron nitride composite particles.

[0029] S3. The obtained boron carbide-boron carbon nitride-hexagonal boron nitride composite particles are subjected to catalytic activation treatment; the activated composite particles are added to a chemical nickel-tungsten-phosphorus plating solution for metallization coating. The pH of the plating solution is adjusted to 8.5-9.0 with ammonia water, the plating temperature is 78-88℃, the solid-liquid ratio is 35-45g / L, and the reaction is carried out under stirring at 200-400rpm for 30-90min; after the plating is completed, the particles are filtered, washed sequentially with deionized water and anhydrous ethanol, and vacuum dried to obtain multilayer composite reinforced particles.

[0030] Preferably, in step S3, the catalytic activation treatment includes: first treating the composite particles in a sensitizing solution, washing them with water, and then treating them in an activation solution; the electroless nickel-tungsten-phosphorus plating solution includes: nickel salt, tungstate, reducing agent, complexing agent, buffer, and stabilizer, with a plating temperature of 75-90℃ and a pH of 8.2-9.0.

[0031] Preferably, the electroless nickel-tungsten-phosphorus plating solution comprises: 25-32 g / L nickel sulfate hexahydrate, 5-8 g / L sodium tungstate dihydrate, 20-25 g / L sodium hypophosphite monohydrate, 25-35 g / L sodium citrate, 10-15 g / L ammonium chloride, and 8-12 mL / L lactic acid.

[0032] A boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy is prepared using the aforementioned preparation process.

[0033] To address the aforementioned problems, this invention does not simply add boron carbide and boron nitride to an iron-nickel-tungsten matrix. Instead, it first constructs multi-layered composite reinforcing particles with boron carbide as the core, a boron-carbon-nitride transition layer and lamellar hexagonal boron nitride as interface control layers, and a nickel-tungsten-phosphorus alloy layer as the outer metallization layer. The boron carbide core has low density and high hardness, serving as the main hard load-bearing phase to improve the alloy's hardness, resistance to abrasive cutting, and resistance to load deformation. The outer boron-carbon-nitride transition layer alleviates the differences in elastic modulus and thermal expansion between the boron carbide hard phase, the hexagonal boron nitride lamellars, and the metal matrix, reducing interfacial stress concentration during sintering and service.

[0034] The hexagonal boron nitride lamellars are not dispersed in the matrix as free powder, but are anchored on the boron-carbon-nitrogen transition layer outside the boron carbide particles. This structure avoids the agglomeration of ordinary hexagonal boron nitride in the metal matrix and the formation of weak interfaces. On the other hand, it utilizes the low shear properties of its lamellars to form local friction-reducing interfaces during friction, reducing wear heat and abrasive plowing. At the same time, its lamellar barrier structure can prolong the diffusion path of corrosive media such as oxygen, chloride ions, and moisture along the reinforcing phase / matrix interface, thereby improving the corrosion resistance of the alloy.

[0035] The nickel-tungsten-phosphorus metallization layer is located on the outermost side of the multilayer composite reinforcing particles. During vacuum hot pressing sintering, it can diffusely bond with the iron-nickel-tungsten-chromium-molybdenum-silicon matrix, improving the wettability and metallurgical bonding strength between the reinforcing particles and the metal matrix. This reduces interfacial porosity, debonding, and coarse, brittle reaction phases caused by boron carbide particles being directly exposed to the iron-based components. Simultaneously, nickel helps improve the matrix's toughness and corrosion resistance, tungsten and molybdenum enhance high-temperature hardness and thermal stability, chromium and silicon improve oxidation and corrosion resistance, and manganese improves powder sintering activity and microstructure uniformity.

[0036] A multi-layered composite reinforced particle structure is used to form a multi-layered synergistic reinforcement system, consisting of boron carbide hard load-bearing, boron-carbon-nitrogen interface buffer, hexagonal boron nitride friction-reducing barrier, nickel-tungsten-phosphorus metallurgical bridging, and iron-nickel-tungsten-chromium-molybdenum-silicon matrix load-bearing. This system can improve alloy hardness and tensile strength while maintaining low density, reduce wear, minimize dimensional changes and deformation after high-temperature holding at 800℃, and improve interface stability under corrosive media, thereby achieving simultaneous improvement in lightweight, high strength, high hardness, wear resistance, corrosion resistance, and high-temperature deformation resistance.

[0037] The beneficial effects of this invention are:

[0038] 1. This invention provides a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy and its preparation process. Multilayer composite reinforcing particles are used as the reinforcing phase, with boron carbide particles at the core serving as the main hard load-bearing phase. Boron carbide has low density and high hardness, which can improve the alloy's hardness, resistance to abrasive cutting, and resistance to load deformation without significantly increasing the alloy's density, thus enabling the iron-nickel-tungsten-based alloy to achieve lightweight and wear-resistant strengthening effects.

[0039] 2. The present invention constructs a boron-carbon-nitrogen transition layer on the surface of boron carbide particles, which can alleviate the differences in elastic modulus and thermal expansion between the boron carbide hard phase, the hexagonal boron nitride lamellar layer and the iron-nickel-tungsten matrix, reduce the interfacial stress concentration during sintering and high-temperature service, reduce interfacial debonding, porosity and brittle phase enrichment, thereby improving the load-bearing stability of the reinforced particles in the matrix.

[0040] 3. This invention anchors lamellar hexagonal boron nitride to the outside of boron carbide particles, rather than adding it directly to the metal matrix as a free powder. This structure avoids the agglomeration of hexagonal boron nitride in the matrix, forming a weak interface. At the same time, it utilizes the low-shear properties of the lamellar boron nitride to form a local friction-reducing interface during friction, reducing the friction coefficient and wear, and extending the diffusion path of corrosive media along the interface through the lamellar barrier effect.

[0041] 4. The present invention provides a nickel-tungsten-phosphorus alloy metallization layer on the outermost side of the multi-layer composite reinforcing particles. During the sintering process, the metallization layer can diffuse and bond with the iron-nickel-tungsten matrix, improving the wettability and metallurgical bonding strength between the reinforcing particles and the metal matrix, and reducing the interfacial porosity, debonding and coarse brittle reaction phase caused by the direct contact of boron carbide particles with iron-based components. At the same time, tungsten and phosphorus elements participate in the regulation of the metallization layer, which is beneficial to improving the interfacial thermal stability and wear resistance.

[0042] 5. This invention employs a combined process of stepwise ball milling, cold isostatic pressing, vacuum hot pressing sintering, hot isostatic pressing treatment, and stabilization treatment. Stepwise ball milling avoids the breakage of multi-layer composite reinforcing particles during high-energy mixing, while ensuring their uniform distribution in the metal powder; vacuum hot pressing sintering and hot isostatic pressing treatment can improve the alloy density and reduce residual porosity; stabilization treatment can reduce residual stress and stabilize the microstructure, thereby achieving a simultaneous improvement in low density, high hardness, high strength, wear resistance, and high-temperature deformation resistance. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 The image shows a SEM image of the boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy prepared in Example 1. Detailed Implementation

[0045] The invention will now be described in further detail with reference to specific embodiments, but it should not be construed as limiting the scope of the invention to the following embodiments.

[0046] The raw materials described in this application are partially described; all other raw materials not described are commercially available.

[0047] Boron carbide powder was purchased from Qinghe County Ruijiang Metal Materials Co., Ltd., with an effective component content of 99.9% and a particle size of 50nm.

[0048] The hexagonal boron nitride nanosheets were purchased from Ningbo Luofei Nanotechnology Co., Ltd., item number: LF-BN-Y100, with an average particle size of 100 nm and a purity of 99.9%.

[0049] Example 1

[0050] A preparation process for a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy includes the following steps:

[0051] (1) Based on the preparation of 100 parts by weight of alloy billet, weigh the following components: 4.00 parts by weight of multilayer composite reinforcing particles, 39.50 parts by weight of iron powder, 15.00 parts by weight of nickel powder, 5.50 parts by weight of tungsten powder, 14.00 parts by weight of chromium powder, 3.50 parts by weight of manganese powder, 2.50 parts by weight of molybdenum powder, and 16.00 parts by weight of silicon powder;

[0052] Among them, the purity of iron powder, nickel powder, tungsten powder, chromium powder, manganese powder, molybdenum powder and silicon powder is not less than 99.5%, and the oxygen content is not higher than 0.15%; the D50 particle size of iron powder, nickel powder, chromium powder, manganese powder, molybdenum powder and silicon powder is 10-30μm, and the D50 particle size of tungsten powder is 2-8μm.

[0053] (2) Place the weighed metal powders into a vacuum drying oven and dry at 100°C for 4 hours; after drying, place the metal powders into a ball mill jar under argon protection, use anhydrous ethanol as the wet ball milling medium, and the ball-to-powder mass ratio is 5:1. Ball mill at 220 rpm for 90 min to obtain premixed gold powder; add multilayer composite reinforcing particles to the premixed gold powder, continue ball milling at 160 rpm for 60 min under argon protection, and vacuum dry to obtain composite alloy mixed powder;

[0054] (3) Spray 3wt% polyvinyl alcohol aqueous solution into the composite alloy mixed powder obtained in step (2). The amount of polyvinyl alcohol added is 0.6% of the mass of the composite alloy mixed powder. After mixing evenly, granulate through an 80-mesh sieve and dry at 60℃ for 5h. Load the dried granulated powder into a mold and cold isostatically press it under a pressure of 450MPa for 3min to obtain the alloy compact.

[0055] (4) Place the alloy compact obtained in step (3) in a vacuum hot pressing sintering furnace, first at a vacuum degree not exceeding 5×10 -3 Under the condition of Pa, the temperature was increased to 450℃ at 3℃ / min and held for 90min; then high-purity argon was introduced to maintain the pressure inside the furnace at 0.04MPa, and the temperature was increased to 900℃ at 5℃ / min and held for 30min; then axial pressure of 35MPa was applied to the compact and the temperature was increased to 1280℃ and held for 2.5h. The compact was then cooled to below 600℃ in the furnace, and then the pressure was released and the compact was cooled to room temperature to obtain the sintered alloy compact.

[0056] (5) The sintered alloy blank obtained in step (4) is subjected to hot isostatic pressing under an argon atmosphere at a temperature of 1120℃ and a pressure of 120MPa for 2 hours; then it is subjected to stabilization treatment at 620℃ for 2 hours and cooled to obtain boron carbide reinforced iron-nickel-tungsten-based lightweight alloy.

[0057] The preparation method of the multilayer composite reinforced particles is as follows:

[0058] S1. Add 0.08 parts by weight of dopamine hydrochloride, 0.16 parts by weight of boric acid, 0.48 parts by weight of melamine and 0.02 parts by weight of polyvinylpyrrolidone to 30 parts by weight of 45 wt% ethanol-water mixture, stir to dissolve, and adjust the pH of the system to 8.7 with ammonia to obtain a composite modified dispersion; add 3.20 parts by weight of boron carbide powder and 0.20 parts by weight of hexagonal boron nitride nanosheets, stir at 600 rpm for 4 h at 40 °C; filter, wash with deionized water and anhydrous ethanol in sequence, and vacuum dry to obtain boron carbide composite particles with boron carbon nitride precursor and hexagonal boron nitride nanosheets on the surface;

[0059] S2. The obtained boron carbide composite particles were placed in a tube furnace and heated to 850°C at 5°C / min under a nitrogen atmosphere. The temperature was maintained for 2 hours, and then cooled to room temperature with the furnace. The particles were washed with deionized water and dried under vacuum to obtain boron carbide-boron carbon nitride-hexagonal boron nitride composite particles.

[0060] S3. The obtained boron carbide-boron carbon nitride-hexagonal boron nitride composite particles were subjected to catalytic activation treatment; the activated composite particles were added to a chemical nickel-tungsten-phosphorus plating solution for metallization coating. The pH of the plating solution was adjusted to 8.7 with ammonia water, the plating temperature was 82℃, the solid-liquid ratio was 40g / L, and the reaction was carried out under stirring at 300rpm for 60min; after the plating was completed, the particles were filtered, washed sequentially with deionized water and anhydrous ethanol, and vacuum dried to obtain multilayer composite reinforced particles.

[0061] The catalytic activation treatment step in S3 is as follows: the obtained boron carbide-boron carbon nitride-hexagonal boron nitride composite particles are first placed in a sensitizing solution of 10 g / L stannous chloride and 40 mL / L hydrochloric acid for 8 min, and then washed with water until neutral; then placed in an activation solution of 0.25 g / L palladium chloride and 5 mL / L hydrochloric acid for 6 min, and then washed with water until neutral.

[0062] The electroless nickel-tungsten-phosphorus plating solution in S3 includes: 28 g / L nickel sulfate hexahydrate, 6 g / L sodium tungstate dihydrate, 22 g / L sodium hypophosphite monohydrate, 30 g / L sodium citrate, 12 g / L ammonium chloride, and 10 mL / L lactic acid.

[0063] Example 2

[0064] The preparation process is basically the same as in Example 1, except that: based on the preparation of 100 parts by weight of alloy billet, 5.50 parts by weight of multilayer composite reinforcing particles, 37.00 parts by weight of iron powder, 14.00 parts by weight of nickel powder, 6.00 parts by weight of tungsten powder, 14.50 parts by weight of chromium powder, 3.00 parts by weight of manganese powder, 2.00 parts by weight of molybdenum powder, and 18.00 parts by weight of silicon powder are weighed; the remaining raw materials and preparation process are the same as in Example 1.

[0065] Example 3

[0066] The preparation process is basically the same as in Example 1, except that: based on the preparation of 100 parts by weight of alloy billet, 3.50 parts by weight of multilayer composite reinforcing particles, 42.50 parts by weight of iron powder, 16.00 parts by weight of nickel powder, 7.00 parts by weight of tungsten powder, 13.00 parts by weight of chromium powder, 2.50 parts by weight of manganese powder, 3.50 parts by weight of molybdenum powder, and 12.00 parts by weight of silicon powder are weighed; the remaining raw materials and preparation process are the same as in Example 1.

[0067] Example 4

[0068] The preparation process is basically the same as in Example 1, except that: based on the preparation of 100 parts by weight of alloy billet, 4.00 parts by weight of multilayer composite reinforcing particles, 38.00 parts by weight of iron powder, 17.00 parts by weight of nickel powder, 4.50 parts by weight of tungsten powder, 16.00 parts by weight of chromium powder, 3.00 parts by weight of manganese powder, 2.50 parts by weight of molybdenum powder, and 15.00 parts by weight of silicon powder are weighed; the remaining raw materials and preparation process are the same as in Example 1.

[0069] Example 5

[0070] The preparation process is basically the same as in Example 1, except that: based on the preparation of 100 parts by weight of alloy billet, 3.00 parts by weight of multilayer composite reinforcing particles, 45.00 parts by weight of iron powder, 12.00 parts by weight of nickel powder, 4.00 parts by weight of tungsten powder, 12.00 parts by weight of chromium powder, 2.00 parts by weight of manganese powder, 4.00 parts by weight of molybdenum powder, and 18.00 parts by weight of silicon powder are weighed; the remaining raw materials and preparation process are the same as in Example 1.

[0071] Comparative Example 1

[0072] The process is basically the same as in Example 1, except that: multi-layer composite reinforcing particles are not added, and the amount of iron powder is adjusted to 43.50 parts by weight to keep the total amount of alloy billet at 100 parts by weight; the other raw materials and preparation process are the same as in Example 1.

[0073] Comparative Example 2

[0074] The process is basically the same as in Example 1, except that 4.00 parts by weight of multilayer composite reinforcing particles are replaced with 4.00 parts by weight of unmodified boron carbide powder; the other raw materials and preparation process are the same as in Example 1.

[0075] Comparative Example 3

[0076] The process is basically the same as in Example 1, except that 4.00 parts by weight of multilayer composite reinforcing particles are replaced with a mechanical mixture of 3.80 parts by weight of unmodified boron carbide powder and 0.20 parts by weight of hexagonal boron nitride nanosheets; the remaining raw materials and preparation process are the same as in Example 1.

[0077] Comparative Example 4

[0078] The process is basically the same as in Example 1, except that the added reinforcing particles are boron carbide-boron carbon nitride-hexagonal boron nitride composite particles, without electroless nickel-tungsten-phosphorus plating. The boron carbide-boron carbon nitride-hexagonal boron nitride composite particles are prepared according to steps S1-S2 of the multilayer composite reinforcing particle preparation method in Example 1, without S3 catalytic activation and electroless nickel-tungsten-phosphorus plating. The remaining raw materials and preparation process are the same as in Example 1.

[0079] Comparative Example 5

[0080] The process is basically the same as in Example 1, except that the added reinforcing particles are boron carbide-nickel tungsten phosphorus composite particles, without the boron-carbon-nitrogen transition layer and hexagonal boron nitride nanosheet layer. The preparation method of the boron carbide-nickel tungsten phosphorus composite particles is as follows: boric acid, melamine and hexagonal boron nitride nanosheets are not added, and the boron carbide powder is directly catalytically activated and chemically plated with nickel tungsten phosphorus according to S3 of Example 1; the remaining raw materials and preparation process are the same as in Example 1.

[0081] Comparative Example 6

[0082] The process is basically the same as in Example 1, except that: the outermost layer of the multilayer composite reinforcing particles is a nickel-phosphorus metallization layer and does not contain tungsten; sodium tungstate dihydrate is not added to the chemical plating solution, and the remaining chemical plating components and plating conditions are the same as in Example 1; the remaining raw materials and preparation process are the same as in Example 1.

[0083] Comparative Example 7

[0084] The process is basically the same as in Example 1, except that the amount of multilayer composite reinforcing particles added is adjusted to 8.00 parts by weight, and the amount of iron powder is adjusted to 35.50 parts by weight, so as to keep the total amount of alloy billet at 100 parts by weight; the other raw materials and preparation process are the same as in Example 1.

[0085] Comparative Example 8

[0086] The process is basically the same as in Example 1, except that step (4) does not involve vacuum hot pressing sintering, but instead uses ordinary vacuum pressureless sintering; specifically, the alloy blank is placed in a vacuum furnace, and the vacuum degree is not higher than 5×10 -3The temperature was raised to 1280℃ under Pa conditions and held for 2.5h, then cooled to room temperature in the furnace; step (5) was not hot isostatic pressing, but only stabilization treatment was carried out by holding at 620℃ for 2h; the other raw materials and preparation process were the same as in Example 1.

[0087] Test Example 1

[0088] 1. Density test

[0089] Density testing was performed according to GB / T 3850-2015 "Dense Sintered Metallic Materials and Hard Alloys - Determination of Density". The samples were machined into 10mm × 10mm × 10mm block samples, and the Archimedes' displacement method was used to determine the sample density.

[0090] 2. Hardness test

[0091] Rockwell hardness testing was conducted according to GB / T 230.1-2018 "Metallic materials - Rockwell hardness test - Part 1: Test method", using the HRC scale. Five test points were randomly selected on the surface of each sample, and the distance between any two adjacent indentation centers was not less than four times the indentation diameter. The average value was taken as the hardness of that group of samples.

[0092] 3. Tensile strength test

[0093] The room temperature tensile test was conducted according to GB / T 228.1-2021 "Metallic materials, tensile testing - Part 1: Test at room temperature". The sample was processed into a round bar tensile specimen with a parallel section diameter of 5 mm and an original gauge length of 25 mm. The tensile rate was 1 mm / min. The tensile strength was tested, and each group was tested 4 times, and the average value was taken.

[0094] 4. Wear resistance test

[0095] Sliding wear tests were conducted according to GB / T 12444-2006 "Test Methods for Wear of Metallic Materials - Test Ring-Block Sliding Wear Test". Samples were machined into 10mm × 10mm × 15mm test blocks. The grinding ring material was GCr15 bearing steel, and the hardness of the grinding ring was HRC60±2. The test load was 100N, the rotational speed was 200r / min, and the test was conducted for 60min under dry friction conditions. The mass of the test blocks was weighed before and after the test, and the volumetric wear was calculated based on the measured density of each group of samples. The average friction coefficient during the steady-state phase was recorded during the test. Each group was tested four times, and the average value was taken.

[0096] 5. High-temperature dimensional stability test

[0097] The sample was processed into a strip-shaped specimen measuring 50mm × 10mm × 5mm. The initial length L0 of the specimen was measured using vernier calipers, and the initial surface flatness was checked. The specimen was then placed in an air-atmosphere box furnace and heated to 800℃ at a rate of 5℃ / min, held at that temperature for 24 hours, and cooled to room temperature with the furnace. The specimen length L1 and maximum warpage height were then measured. The dimensional change rate was calculated using the following formula: Dimensional Change Rate = |L1 - L0| / L0 × 100%.

[0098] When the maximum warpage height is less than 0.05 mm and no obvious bending, bulging or cracks are visible to the naked eye, it is recorded as "no obvious deformation"; when the maximum warpage height is 0.05-0.20 mm, it is recorded as "slight deformation"; when the maximum warpage height is greater than 0.20 mm or visible cracks or bulges appear, it is recorded as "obvious deformation".

[0099] Table 1 Performance Test Results

[0100]

[0101] The results above show that the boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy prepared by this invention improves hardness, tensile strength, wear resistance, and high-temperature dimensional stability while maintaining a low density. Examples 1-5 all use multilayer composite reinforcing particles as the reinforcing phase. These multilayer composite reinforcing particles have boron carbide particles as the core, and a boron-carbon-nitrogen transition layer, a lamellar hexagonal boron nitride outer layer, and a nickel-tungsten-phosphorus alloy metallization layer are sequentially constructed on their surface. Their overall effect is generally better than that of the comparative examples.

[0102] Comparative Example 1 did not include multilayer composite reinforcing particles. The boron carbide core introduced in this example can serve as a low-density, high-hardness load-bearing reinforcing phase, improving the alloy's resistance to abrasive cutting and its ability to resist deformation under external loads. The nickel-tungsten-phosphorus metallization layer can improve the wettability and metallurgical bonding strength between the reinforcing particles and the iron-nickel-tungsten matrix. Therefore, this example is superior to Comparative Example 1 without reinforcing particles in terms of hardness, tensile strength, wear resistance, and high-temperature dimensional stability, indicating that the addition of reinforcing particles is the basis for improving overall performance. Comparative Example 2 directly added unmodified boron carbide powder. In this example, the boron carbide is not directly dispersed in the metal matrix in the form of bare particles, but is modified through a multilayer interface structure. Unmodified boron carbide has poor wettability with the iron-nickel-tungsten matrix, and agglomeration, interface porosity, and local debonding are prone to occur during sintering, resulting in insufficient reinforcement. However, the boron-carbon-nitrogen transition layer and the nickel-tungsten-phosphorus metallization layer in this example can buffer interface stress and improve interface bonding, allowing the reinforcing particles to be embedded more uniformly and stably in the matrix, thereby improving the alloy's strength and wear resistance. Comparative Example 3 uses unmodified boron carbide powder and hexagonal boron nitride nanosheets for mechanical mixing. In this example, the hexagonal boron nitride sheets are anchored on the outside of the boron carbide particles, making them part of the reinforcing particle interface layer, rather than existing as free powder. Under mechanical mixing, hexagonal boron nitride tends to agglomerate in the metal matrix and form a weak interface. Although this can reduce the friction coefficient to some extent, it weakens the matrix continuity and interface strength. Comparative Example 4 omits the nickel-tungsten-phosphorus metallization layer. In this example, a nickel-tungsten-phosphorus alloy metallization layer is further formed on the outside of the reinforcing particles. This metallization layer can diffuse and bond with the iron-nickel-tungsten matrix during vacuum hot pressing sintering, reducing the interfacial porosity and debonding defects between the reinforcing phase and the matrix. Although Comparative Example 4 has a structure of boron carbide, boron-carbon-nitrogen transition layer, and hexagonal boron nitride sheets, it lacks an outer metallization bridging layer. The bonding between the reinforcing particles and the metal matrix is ​​still insufficient. Therefore, its tensile strength, high-temperature dimensional stability, and wear resistance are all inferior to those of the examples. Comparative Example 5 only included boron carbide-nickel-tungsten-phosphorus composite particles. The embodiments further incorporated a boron-carbon-nitrogen transition layer and a lamellar hexagonal boron nitride outer layer between the boron carbide and nickel-tungsten-phosphorus metallization layers. While Comparative Example 5 improved the wettability between boron carbide and the metal matrix, it lacked a buffer layer and a friction-reducing barrier layer, leading to more concentrated interfacial thermal stress and a lack of stable lamellar friction-reducing structures during friction. In the embodiments, the boron-carbon-nitrogen transition layer alleviated the differences in elastic modulus and thermal expansion between different phases, and the hexagonal boron nitride lamellars reduced friction and extended the diffusion path of corrosive media along the interface, resulting in a more balanced alloy performance in terms of strength, wear resistance, and high-temperature dimensional stability.

[0103] Comparative Example 6 replaced the nickel-tungsten-phosphorus metallization layer with a tungsten-free nickel-phosphorus metallization layer. The tungsten element in this example can participate in forming a more heat-resistant and stable metallization interface, which helps improve high-temperature hardness, wear resistance, and thermal stability. Although Comparative Example 6 still has a metallization layer and exhibits some interface improvement, it lacks the strengthening and thermal stability contribution of tungsten, therefore it is inferior to the examples in terms of high-temperature dimensional stability, hardness, and wear resistance. Comparative Example 7 excessively added multilayer composite reinforcing particles, while the examples controlled the reinforcing particle content within an appropriate range. When the reinforcing particle content is too high, although the amount of hard phase increases, it easily causes interparticle contact, local agglomeration, and a decrease in matrix continuity, resulting in a reduction in the alloy's tensile strength and high-temperature dimensional stability. Comparative Example 8 used ordinary vacuum pressureless sintering without hot isostatic pressing, while the examples used a combination of vacuum hot pressing sintering, hot isostatic pressing, and stabilization treatment. Vacuum hot pressing sintering can promote powder particle contact, diffusion, and densification. Hot isostatic pressing can further eliminate residual porosity and improve the interfacial bonding around the reinforcing particles. Stabilization treatment helps to reduce sintering residual stress and stabilize the microstructure. Comparative Example 8, due to insufficient densification and numerous interfacial defects, showed a significant decrease in strength, wear resistance, and high-temperature deformation resistance.

Claims

1. A preparation process for a boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy, characterized in that, Includes the following steps: (1) Weigh iron powder, nickel powder, tungsten powder, chromium powder, manganese powder, molybdenum powder, silicon powder and multilayer composite reinforcing particles according to the proportion; wherein, the multilayer composite reinforcing particles are multilayer interface composite structures with boron carbide particles as the core, and the surface of the boron carbide particles has a boron carbon nitrogen transition layer, a lamellar hexagonal boron nitride layer and a nickel tungsten phosphorus alloy metallization layer in sequence. (2) After drying the weighed metal powder, it is placed under a protective atmosphere for the first ball milling and mixing to obtain premixed gold powder; then the multilayer composite reinforcing particles are added for the second ball milling and mixing, and after drying, the composite alloy mixed powder is obtained. (3) Add a binder solution to the composite alloy mixed powder, mix and granulate, dry and sieve, and then cold isostatically press the obtained granulated powder to obtain an alloy compact; (4) The alloy blank is placed in a vacuum hot pressing sintering furnace for sintering: first, it is heated to the first temperature under vacuum and held, then a protective gas is introduced and the temperature is raised to the second temperature and held; then axial pressure is applied and the temperature is raised to the third temperature for holding and sintering, and then the furnace is cooled to obtain the sintered alloy blank. (5) The sintered alloy blank is subjected to hot isostatic pressing, then stabilization treatment, and cooled to obtain the final product.

2. The preparation process according to claim 1, characterized in that, In step (1), each component, based on the preparation of 100 parts by mass of alloy billet, consists of 3-6 parts of multilayer composite reinforcing particles, 35-45 parts of iron powder, 12-18 parts of nickel powder, 4-8 parts of tungsten powder, 12-16 parts of chromium powder, 2-5 parts of manganese powder, 1-4 parts of molybdenum powder, and 12-18 parts of silicon powder; the D50 particle size of the iron powder, nickel powder, chromium powder, manganese powder, molybdenum powder, and silicon powder is 10-30 μm, and the D50 particle size of the tungsten powder is 2-8 μm.

3. The preparation process according to claim 1, characterized in that, In step (2), the drying temperature is 80-120℃ and the time is 2-6h; the first ball milling and the second ball milling are both carried out under argon protection, anhydrous ethanol is used as the ball milling medium, and the ball-to-material mass ratio is (4-6):1; the rotation speed of the first ball milling is 180-250rpm and the time is 60-120min; the rotation speed of the second ball milling is 120-180rpm and the time is 30-90min.

4. The preparation process according to claim 1, characterized in that, In step (3), the binder solution is a polyvinyl alcohol aqueous solution, wherein the amount of polyvinyl alcohol added is 0.3-1.0% of the mass of the composite alloy mixed powder; the granulation is passed through a 60-100 mesh sieve; the pressure of the cold isostatic pressing is 300-500 MPa, and the holding time is 2-5 min.

5. The preparation process according to claim 1, characterized in that, In step (4), the vacuum level of the vacuum condition is not higher than 5 × 10⁻⁶. -2 Pa; the first temperature is 400-500℃, and the holding time is 60-120min; protective gas is introduced to make the furnace pressure 0.02-0.06MPa; the second temperature is 850-950℃, and the holding time is 20-40min; the applied axial pressure is 30-40MPa; the third temperature is 1200-1320℃, and the holding time is 2-3h.

6. The preparation process according to claim 1, characterized in that, In step (5), the hot isostatic pressing treatment is performed at a temperature of 1100-1150℃, a pressure of 100-150MPa, and a holding time of 1-3h; the stabilization treatment is performed at a temperature of 600-650℃ and a holding time of 1-3h.

7. The preparation process according to claim 1, characterized in that, The multilayer composite reinforced particles are prepared by a method including the following steps: S1. Add dopamine hydrochloride, boron source, nitrogen source and dispersant to ethanol-water mixture, adjust pH to alkaline to obtain composite modified dispersion; add boron carbide powder and hexagonal boron nitride nanosheets, stir and react, then separate, wash and dry to obtain boron carbide composite particles with precursor and hexagonal boron nitride nanosheets loaded on the surface. S2. The boron carbide composite particles are heat-treated under a nitrogen atmosphere to obtain boron carbide-boron carbon nitride-hexagonal boron nitride composite particles. S3. The boron carbide-boron carbon nitride-hexagonal boron nitride composite particles are sequentially subjected to catalytic activation and electroless nickel-tungsten-phosphorus plating to obtain the multilayer composite reinforced particles.

8. The preparation process according to claim 7, characterized in that, In step S3, the catalytic activation treatment includes: first treating the composite particles in a sensitizing solution, washing them with water, and then treating them in an activation solution; the electroless nickel-tungsten-phosphorus plating solution includes: nickel salt, tungstate, reducing agent, complexing agent, buffer and stabilizer, with a plating temperature of 75-90℃ and a pH of 8.2-9.

0.

9. The preparation process according to claim 8, characterized in that, The electroless nickel-tungsten-phosphorus plating solution comprises: 25-32 g / L nickel sulfate hexahydrate, 5-8 g / L sodium tungstate dihydrate, 20-25 g / L sodium hypophosphite monohydrate, 25-35 g / L sodium citrate, 10-15 g / L ammonium chloride, and 8-12 mL / L lactic acid.

10. A boron carbide-reinforced iron-nickel-tungsten-based lightweight alloy, characterized in that, It is prepared using the preparation process described in any one of claims 1-9.

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