High-performance cermet composite grinding roller and preparation method thereof

Abstract

This invention belongs to the field of metal-ceramic composite materials technology, specifically relating to a high-performance metal-ceramic composite grinding roller and its preparation method. The grinding roller consists of a grinding surface layer, a pure metal transition layer, and a tough roller core, which are metallurgically integrated. The grinding surface layer is a composite of a multi-system ceramic reinforcing phase and a high-toughness, high-chromium cast iron matrix. The ceramic particles are treated with a NiP amorphous coating and optimized through a three-level particle size distribution and PSZ secondary reinforcing phase optimization. The roller core is made of medium-carbon alloy steel. The preparation method includes five steps: ceramic preform preparation, roller core pretreatment and assembly, centrifugal casting composite, vacuum sintering densification, and differential temperature heat treatment and finishing. This invention fundamentally solves the technical bottlenecks of weak bonding between ceramic and metal interfaces and uneven particle distribution through multiple technological couplings. The prepared grinding roller possesses both ultra-high wear resistance and excellent impact resistance (impact toughness AKU>30 J in the transition zone), with a uniform, dense, and defect-free microstructure, and a service life more than three times that of traditional high-chromium cast iron grinding rollers.

Description

A high-performance metal-ceramic composite grinding roller and its preparation method Technical Field

[0001] This invention belongs to the field of metal-ceramic composite materials technology, specifically relating to a high-performance metal-ceramic composite grinding roller and its preparation method. Background Technology

[0002] Vertical roller mills are the core grinding equipment in industries such as mining, cement, and power. Their core vulnerable parts—grinding rollers—work under harsh conditions of high temperature, high stress, and strong impact for a long time, resulting in extremely severe wear. Currently, high-chromium cast iron is the mainstream material for grinding rollers. It has high hardness but insufficient toughness, and is prone to breakage or surface peeling under impact load, resulting in a limited service life. To solve this problem, surface welding technology has emerged. However, the weld layer and the substrate are metallurgically bonded, which has problems such as high dilution rate and uneven distribution of hard phase, and the weld layer is prone to peeling. In recent years, some technologies have attempted to use metal-ceramic composite materials. Ceramic particle reinforced metal matrix composite grinding rollers are widely used due to their high wear resistance and good toughness. In the existing technology, although there is a scheme to prepare ceramic reinforced composite grinding rollers by casting composite method, the existing technology has the following problems: (1) Weak interface bonding: Due to the large difference in physical properties between ceramic and metal matrix, the bonding strength is low, and it is easy to crack and peel off from the interface during use. (2) Uneven ceramic distribution: During the casting process, ceramic particles are prone to floating or settling due to density differences, resulting in uneven hardness of the wear-resistant layer and premature failure in some areas. (3) Poor density of the composite layer: The presence of pores and other defects in the material becomes a source of cracks, affecting the overall wear resistance and fatigue strength. Therefore, developing a grinding roller and its preparation method that can achieve high-strength interfacial bonding, uniform distribution of ceramic particles, dense structure, and perfect synergy between wear resistance and toughness has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of existing technologies and provide a high-performance metal-ceramic composite grinding roller and its preparation method. Through precise control of multiple scales and multiple physical fields, it achieves synergistic optimization from the microscopic particle interface to the macroscopic roller structure, so as to solve the problems of weak interface bonding, uneven distribution of ceramic particles, poor density, and difficulty in achieving both wear resistance and toughness in existing grinding rollers.

[0004] This invention provides a high-performance metal-ceramic composite grinding roller. The grinding roller has an overall disc-shaped structure and includes, from the outside to the inside, a grinding surface layer, a pure metal transition layer, and an inner tough roller core. The three are combined into a whole by metallurgical bonding.

[0005] Specifically, the grinding surface layer is made of a metal-ceramic composite material, which consists of a multi-system ceramic reinforcing phase with a volume fraction of 40%-60% and the balance being a wear-resistant metal matrix. The surface hardness of the grinding surface layer is ≥ HRC65, and the thickness is 30-80 mm.

[0006] Specifically, the multi-system ceramic reinforcing phase includes a primary reinforcing phase and a secondary reinforcing phase. The primary reinforcing phase is tungsten carbide (WC) particles, which are proportioned in a three-stage particle size distribution. The three-stage particle size distribution is as follows: coarse particles with a particle size of 1.0-1.6 mm account for 20% of the total WC, medium particles with a particle size of 0.4-0.8 mm account for 50%, and fine particles with a particle size of 0.1-0.3 mm account for 30%.

[0007] Specifically, the secondary reinforcing phase is partially stabilized zirconia (PSZ) particles with a particle size of 50-150 μm, and its volume accounts for 10%-15% of the total volume of the multi-system ceramic reinforcing phase.

[0008] The wear-resistant metal is a high-toughness, high-chromium cast iron alloy, with the following percentage content of alloying elements: Cr: 18-22%, C: 2.4-2.7%, Mo: 1.4-1.9%, Ni: 0.9-1.5%, Cu: 0.5-0.7%, Mn: 0.9-1.1%, Si≤0.8%, V: 0.4-0.5%, Nb: 0.2-0.3%, P≤0.03%, S≤0.03%, and the remainder is Fe.

[0009] This chemical composition can moderately reduce the Cr and C content while ensuring the formation of sufficient M7C3 carbides, and ensure air quenching penetration through Mo and Ni, refine the grains with V and Nb elements, and strictly limit harmful elements such as P and S, thus achieving a good combination of high toughness and high wear resistance.

[0010] Specifically, the WC particles and PSZ particles are coated with a nickel-phosphorus (Ni-P) alloy amorphous coating with a thickness of 5-15 μm.

[0011] Ni-P alloy amorphous coating can greatly improve its wettability with molten steel and reduce interfacial stress. Nickel-based alloy powder binder can form a liquid phase in the early stage of sintering, promoting densification and initial bonding.

[0012] Specifically, the material of the pure metal transition layer is the same as that of the wear-resistant metal matrix in the grinding surface layer, namely, a high-chromium cast iron alloy, which is used to achieve good stress transition and metallurgical bonding between the outer grinding surface layer and the inner tough roller core.

[0013] Specifically, the internal toughening roller core is selected from either 42CrMo or 35CrMo medium carbon alloy steel. The roller core undergoes quenching and tempering heat treatment to give it excellent comprehensive mechanical properties, with a tensile strength of not less than 700 MPa and an impact toughness (AKU) of not less than 25 J.

[0014] To further optimize the structure, the toughness roller core is provided with mounting and fixing holes that are evenly distributed in a ring. The fixing holes are machined with internal threads for mounting and fixing the grinding roller. At the same time, a circular weight-reducing through hole is also provided in the center of the toughness roller core to reduce the overall weight and balance the structure.

[0015] This invention also provides a method for preparing the above-mentioned high-performance metal-ceramic composite grinding roller, the method comprising the following steps:

[0016] S1. Preparation of ceramic preforms: The ceramic particle system containing the main reinforcing phase and the secondary reinforcing phase is ultrasonically cleaned to remove surface contaminants. A uniform Ni-P alloy amorphous coating is formed on the particle surface by ultrasonic-assisted chemical plating. The coated mixed ceramic particles are mixed with nickel-based alloy powder binder and the mixture is pressed into multiple preforms.

[0017] Preferably, in step S1, the pH value of the ultrasonic-assisted chemical plating solution is 5, the chemical plating temperature is 85~90℃, the applied ultrasonic power is 50-100W, the frequency is 25-40kHz, the plating time is 40~50min, and the chemical plating solution is composed of nickel sulfate 30g / L, sodium hypophosphite 30 g / L, lactic acid 20 ml / L, sodium citrate 12 g / L, sodium acetate 12 g / L, succinic acid 8 g / L and thiourea 2 mg / L.

[0018] Preferably, the nickel-based alloy powder binder in step S1 is a Ni-Cr-B-Si self-fluxing alloy powder. The powder is spherical with a particle size of 200-500 mesh. By weight percentage, it includes Cr: 10-15%, B: 2.0-3.5%, Si: 3.0-4.5%, Fe ≤5.0%, and the balance is Ni and unavoidable impurities.

[0019] Preferably, the mass ratio of the mixed ceramic particles to the nickel-based alloy powder binder is (85-95):(15-5).

[0020] Ni-Cr-B-Si alloy powder binder is a meticulously designed, multifunctional system that effectively improves a series of interconnected issues, such as preform strength, sintering densification, interfacial bonding strength, and end-use performance, by creatively introducing a high-performance liquid phase during sintering.

[0021] Preferably, in step S1, the process of pressing the preform from the mixture involves placing the mixture into an annular mold for cold isostatic pressing, with the pressure controlled at 150-250 MPa, and the porosity of the pressed material being 20%-25%, with the pores being interconnected.

[0022] The carefully calculated particle size distribution ensures that after pressing, the particles will inevitably accumulate through "point contact" or "small surface contact". The gaps left behind are interconnected, tortuous but continuous three-dimensional networks from macroscopic to microscopic. The role of cold isostatic pressing is to make this network denser and more stable, rather than destroy it. By applying pressure evenly from all sides, cold isostatic pressing causes the particles to rearrange and move closer together in all directions, which can minimize the "island"-like closed pores formed due to uneven pressing and better maintain the natural open pore structure determined by the particle size distribution.

[0023] S2. Roller Core Pretreatment and Assembly: The composite area on the outer surface of the tough roller core is rough-machined, leaving a machining allowance of 3-5mm on both sides. An annular anchoring groove with a depth of 1-2mm and a width of 2-3mm is machined in this area. The surface of the rough-machined roller core is subjected to wet sandblasting treatment driven by anhydrous ethanol to achieve a cleanliness level of Sa 3.0 and a surface roughness Ra of 12.5-25μm. A 100-200μm thick layer of ceramic flame retardant is uniformly sprayed onto the activated roller core surface. Multiple ceramic preforms are spliced ​​around the circumference and then precisely assembled with the sprayed roller core into a centrifugal casting mold.

[0024] Preferably, the ceramic flame retardant is 8% yttrium oxide stabilized zirconium oxide.

[0025] S3. Centrifugal casting composite: Melt high-chromium cast iron alloy steel, strictly follow the alloy element content ratio, and control its superheat to 150-200°C. Start the centrifuge and use a three-stage variable speed method for pouring and solidification.

[0026] Preferably, the three-stage variable speed method involves controlling the rotation speed at 200±50 rpm during the initial pouring stage until pouring is complete. After pouring, the rotation speed is rapidly increased to 600±50 rpm within 10 seconds and maintained for 1-2 minutes for pressure penetration. Then, during the stable solidification stage, the rotation speed is reduced to 400±50 rpm until the casting is completely solidified.

[0027] S4. Vacuum sintering densification: Transfer the centrifugal casting to a vacuum sintering furnace, adjust the vacuum level, perform pulse current-assisted sintering, hold for 1-3 hours, and then cool to room temperature with the furnace.

[0028] Preferably, the vacuum degree in step S4 is ≤1×10⁻⁶. -2Pa, the process parameters for pulsed current-assisted sintering are: heating to 1150-1200°C at a rate of 5-10°C / min, while simultaneously applying a low-voltage, high-current DC pulse. The parameters of the DC pulse are controlled as follows: pulse frequency 50-500 Hz, voltage ≤10 V, and 50-80 A / cm during the heating stage. 2 Once the target temperature is reached, the current density will be increased by 100-120 A / cm². 2 And keep warm in this state.

[0029] After centrifugal casting, what is obtained is only a "green" or "cast" composite material. The molten steel encapsulates the ceramic particles under the action of centrifugal force, but due to the short contact time and rapid cooling, the resulting interfacial bonding is mainly mechanical anchoring and limited physical wetting. The diffusion between ceramic and metal atoms is insufficient, and the interfacial bonding force has not reached the optimal level. The nickel-based alloy powder binder in the preform may not be completely melted or mixed unevenly with the molten steel. There may be micro-shrinkage and gas pores inside the composite layer due to solidification shrinkage.

[0030] During pulsed current-assisted sintering, under the drive of high temperature and pulsed current, atoms (especially Ni, Fe, C, etc.) gain enormous kinetic energy and diffuse violently across the interface. This transforms the interface from a clear "line" into a "region" with a certain thickness and a smooth transition of components, greatly alleviating the stress caused by the mismatch of thermal expansion coefficients. The energy provided by the pulsed current ensures that the nickel-based binder powder and molten steel completely form a liquid phase, better filling every tiny pore.

[0031] The pulsed current electromigration effect can actively transport materials from enriched areas to pores or defects, thereby achieving extreme densification that is difficult to achieve with ordinary hot sintering. It also promotes the mutual solubility of elements between molten steel and nickel-based binders, forming a new alloy binder phase with more uniform composition and superior performance, rather than a simple mechanical mixture. At the same time, the current directly generates Joule heat through the material, and this uniform bulk heating method avoids the additional stress caused by temperature gradients in traditional external heating sintering.

[0032] With DC pulse assistance, rapid atomic diffusion and interfacial bonding can be achieved at temperatures far below conventional sintering temperatures, while avoiding local overheating or arc discharge.

[0033] S5. Differential Temperature Heat Treatment and Finishing: The sintered roller is heated to 850-900°C for austenitization and then subjected to differential temperature heat treatment. After heat treatment, a CNC vertical grinding machine equipped with CBN grinding wheels is used for finishing to ensure that the outer diameter tolerance of the grinding roller reaches IT7 grade and the cylindricity is ≤0.05 mm. Annularly distributed mounting holes are opened on the tough roller core of the grinding roller. Internal threads are machined in the mounting holes, and a circular weight-reducing through hole is opened in the center.

[0034] Preferably, in step S5, the differential temperature heat treatment involves holding at 850-900°C for 0.5-1h followed by cooling and quenching. During quenching, only the roller core is subjected to forced water cooling by spraying, while the composite wear-resistant layer area is kept warm and slowly cooled. Subsequently, the entire structure is tempered at 450-550°C for 4-6h.

[0035] Compared with the prior art, the significant advantages of the present invention are as follows:

[0036] (1) Significantly improved interface bonding strength: By improving wettability and suppressing the formation of brittle phases through “Ni-P amorphous coating”, combined with “three-dimensional anchoring of roller core surface” and “pulse current assisted sintering”, a strong metallurgical bond between ceramic and metal was achieved, fundamentally solving the problem of peeling.

[0037] (2) The composite layer has a highly uniform and dense structure: the "multi-element multi-grade" particle design and "cold isostatic pressing" ensure the uniformity and ideal porosity of the preform skeleton; the synergistic effect of "three-stage centrifugation" and "electric field assisted sintering" ensures the complete penetration of the metal melt and the extreme densification of the composite layer.

[0038] (3) Excellent overall performance: The "primary and secondary phase" ceramic system takes into account both ultra-high hardness and toughening effect; the "differential temperature heat treatment" precisely meets the requirements of high toughness of the roller core and low internal stress of the composite layer, so that the product has ultra-high wear resistance, the highest hardness of the grinding surface layer reaches HRC 70, and at the same time has excellent impact resistance. The impact toughness AKU at the metal connection between the transition layer and the roller core is greater than 30 J, and the service life is more than 3 times that of the original pure high chromium cast iron grinding roller.

[0039] (4) Advanced and controllable process: This method integrates multiple advanced manufacturing and control technologies, with a clear process, well-defined parameters, and good reproducibility, making it particularly suitable for the industrial and stable production of high-performance grinding rollers. Attached Figure Description

[0040] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 is a schematic diagram of the preparation method of the present invention.

[0042] Figure 2 is a schematic diagram of the grinding roller structure of the present invention. Detailed Implementation

[0043] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0044] Example 1

[0045] (1) Preparation of ceramic preforms:

[0046] WC coarse particles (1.0 mm in diameter, 20% by weight), WC medium particles (0.4 mm in diameter, 50% by weight), and WC fine particles (0.1 mm in diameter, 30% by weight) were selected to form a three-level particle size distribution of WC particles. Partially stabilized zirconia (PSZ) particles with a diameter of 50 μm were selected, accounting for 10% of the total volume of all reinforcing particles. The multi-element, multi-level ceramic particle system was ultrasonically cleaned to remove surface contaminants.

[0047] The electroless plating solution was prepared according to the following components: nickel sulfate 30 g / L, sodium hypophosphite 30 g / L, lactic acid 20 ml / L, sodium citrate 12 g / L, sodium acetate 12 g / L, succinic acid 8 g / L, and thiourea 2 mg / L. The pH of the plating solution was adjusted to 5.0 using ammonia. The pretreated mixed ceramic particles were immersed in the plating solution and plated at 85°C with ultrasonic waves of 50W and 25kHz for 40 minutes. After plating, the particles were rinsed with deionized water and vacuum dried at 110°C. Finally, a Ni-P amorphous alloy coating with a thickness of about 6 μm was obtained on the surface of the particles.

[0048] Ni-Cr-B-Si self-fluxing alloy powder with a particle size of 200 mesh was selected. The powder composition elements were Cr: 10-15%, B: 2.0-3.5%, Si: 3.0-4.5%, Fe ≤5.0%, and the balance being Ni and unavoidable impurities. The mixed ceramic particles and nickel-based alloy powder binder were mixed at a mass ratio of 85:15. The coated mixed ceramic particles and nickel-based alloy powder binder were mixed evenly, and the mixture was placed in a ring mold for cold isostatic pressing at a pressure of 150 MPa to form multiple interconnected preforms with a porosity of 25%.

[0049] (2) Roller core pretreatment and assembly:

[0050] The outer surface of the tough roller core is rough-machined in the composite area, leaving a 5mm machining allowance on both sides. An annular anchoring groove with a depth of 1mm and a width of 2mm is machined in this area. The rough-machined roller core surface is then subjected to wet sandblasting treatment driven by anhydrous ethanol to achieve a cleanliness level of Sa 3.0 and a surface roughness Ra of 12.5μm. A 100μm thick 8% yttrium oxide stabilized zirconia coating is uniformly sprayed onto the activated roller core surface. Multiple ceramic preforms are then spliced ​​together circumferentially and precisely assembled with the sprayed roller core into a centrifugal casting mold.

[0051] (3) Centrifugal casting composite:

[0052] High-chromium cast iron alloy steel was smelted, with the alloy element content controlled as follows: Cr: 18%, C: 2.4%, Mo: 1.4%, Ni: 0.9%, Cu: 0.5%, Mn: 0.9%, Si≤0.8%, V: 0.4%, Nb: 0.2%, P≤0.03%, S≤0.03%, with the remainder being Fe. The superheat of the molten steel was controlled at 150°C. The centrifuge was started, and during the initial pouring stage, the speed was controlled at 150 rpm and maintained until the pouring was completed. After the pouring was completed, the speed was rapidly increased to 550 rpm within 10 seconds and maintained for 2 minutes for pressure penetration. Then, during the stable solidification stage, the speed was reduced to 350 rpm until the casting was completely solidified.

[0053] (4) Vacuum sintering densification:

[0054] Transfer the centrifugal casting to a vacuum sintering furnace and adjust the vacuum level to ≤1×10⁻⁶. -2 Pa, heating to 1150°C at a rate of 5°C / min, while simultaneously applying a pulsed DC current of 8 V and 100 Hz, with a heating rate of 50 A / cm² during the heating phase. 2 Once the target temperature is reached, the current density will be increased by 100 A / cm². 2 The furnace is then held at this temperature for 1.2 hours for pulsed current-assisted sintering, and then cooled to room temperature with the furnace after sintering.

[0055] (5) Differential temperature heat treatment and finishing:

[0056] After the sintered roller is heated to 850°C for austenitization, it is held for 1 hour. Then the roller core is sprayed with forced water cooling, but at the same time the composite wear-resistant layer area is covered with a layer of heat-insulating cotton for heat preservation and slow cooling. Then the grinding roller is tempered at 450°C for 6 hours and air-cooled to room temperature.

[0057] After heat treatment, a CNC vertical grinding machine is used with CBN grinding wheels for precision machining to ensure that the outer diameter tolerance of the grinding roller reaches IT7 grade and the cylindricity is ≤0.05 mm. Annularly distributed mounting holes are opened on the tough roller core of the grinding roller, and internal threads are machined in the mounting holes. A circular weight-reducing through hole is opened in the center.

[0058] Example 2

[0059] The difference compared to Example 1 is as follows:

[0060] (1) Preparation of ceramic preforms:

[0061] The selected particles were coarse WC with a diameter of 1.4 mm, medium WC with a diameter of 0.6 mm, fine WC with a diameter of 0.2 mm, and PSZ with a diameter of 100 μm, accounting for 12.5% ​​of the total volume of all reinforcing particles.

[0062] At a chemical plating temperature of 88℃, an ultrasonic wave with a power of 75W and a frequency of 35kHz was applied for 45 minutes, and the resulting Ni-P amorphous alloy coating was approximately 10μm thick.

[0063] The selected self-fluxing alloy powder has a particle size of 350 mesh, the mass ratio of mixed ceramic particles to nickel-based alloy powder binder is 90:10, the mixture is subjected to cold isostatic pressing in a ring mold at a pressure of 200 MPa, and the porosity of the pressed preform is 22.5%.

[0064] (2) Roller core pretreatment and assembly:

[0065] The annular anchoring groove machined on the outer surface composite area of ​​the tough roller core has a depth of 1.5 mm and a width of 2.5 mm. The surface roughness of the roller core after wet sandblasting is 18.5 μm. The ceramic flame retardant coating uniformly sprayed on the activated roller core surface has a thickness of 150 μm.

[0066] (3) Centrifugal casting composite:

[0067] The high-chromium cast iron alloy steel was smelted with the following alloy element contents controlled as follows: Cr: 20%, C: 2.6%, Mo: 1.7%, Ni: 1.2%, Cu: 0.6%, Mn: 1.0%, Si≤0.8%, V: 0.4%, Nb: 0.3%, P≤0.03%, S≤0.03%, with the remainder being Fe. The superheat of the molten steel was controlled at 175°C. The centrifugal casting speed was 200 rpm in the initial pouring stage, 600 rpm in the intermediate stage, and 400 rpm in the stable solidification stage.

[0068] (4) Vacuum sintering densification:

[0069] During vacuum sintering, the temperature was increased to 1175°C at a rate of 8°C / min, and a pulsed DC current of 8 V and 250 Hz was applied. The current density during the heating phase was 65 A / cm². 2 The current density is 110 A / cm² after reaching the target temperature. 2 The heat preservation time under this condition is 2 hours;

[0070] (5) Differential temperature heat treatment and finishing:

[0071] The sintered rollers were heated to 875°C and held for 0.75 hours. The grinding rollers were then tempered at 500°C for 5 hours.

[0072] Example 3

[0073] The difference compared to Example 1 is as follows:

[0074] (1) Preparation of ceramic preforms:

[0075] The following were selected: coarse WC particles with a diameter of 1.6 mm, medium WC particles with a diameter of 0.8 mm, fine WC particles with a diameter of 0.3 mm, and PSZ particles with a diameter of 150 μm, accounting for 15% of the total volume of all reinforcing particles.

[0076] At a chemical plating temperature of 90℃, an ultrasonic wave with a power of 100W and a frequency of 40kHz was applied for 50 minutes, and the resulting Ni-P amorphous alloy coating was approximately 15μm thick.

[0077] The selected self-fluxing alloy powder has a particle size of 500 mesh, the mass ratio of mixed ceramic particles to nickel-based alloy powder binder is 95:5, the mixture is subjected to cold isostatic pressing in a ring mold at a pressure of 250 MPa, and the porosity of the pressed preform is 20%.

[0078] (2) Roller core pretreatment and assembly:

[0079] The annular anchoring groove machined on the outer surface of the tough roller core has a depth of 2mm and a width of 3mm. The surface roughness of the roller core after wet sandblasting is 25μm. The ceramic flame retardant coating uniformly sprayed on the activated roller core surface has a thickness of 200μm.

[0080] (3) Centrifugal casting composite:

[0081] The high-chromium cast iron alloy steel was smelted with the following alloy element contents controlled as follows: Cr: 22%, C: 2.7%, Mo: 1.9%, Ni: 1.5%, Cu: 0.7%, Mn: 1.1%, Si≤0.8%, V: 0.5%, Nb: 0.2%, P≤0.03%, S≤0.03%, with the remainder being Fe. The superheat of the molten steel was controlled at 200°C. The centrifugal casting speed was 250 rpm during the initial pouring stage, 650 rpm during the intermediate stage, and 450 rpm during the stable solidification stage.

[0082] (4) Vacuum sintering densification:

[0083] During vacuum sintering, the temperature was increased to 1200°C at a rate of 8°C / min, and a pulsed DC current of 8 V and 500 Hz was applied. The current density during the heating phase was 80 A / cm². 2 The current density is 120 A / cm² after reaching the target temperature. 2 The heat preservation time under this condition is 3 hours;

[0084] (5) Differential temperature heat treatment and finishing:

[0085] The sintered rollers were heated to 900°C and held for 1 hour. The grinding rollers were then tempered at 550°C for 4 hours.

[0086] Comparative Example 1

[0087] The difference between this comparative example and Example 2 is that:

[0088] The chemical plating step for ceramic particles was omitted, and the preform is a single-size WC particle with a particle size of 0.6 mm.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 2 is that:

[0091] The pulsed current assistance in vacuum sintering was eliminated, and conventional vacuum sintering was adopted. The specific parameters were adjusted so that the vacuum degree was ≤1×10⁻⁶. -2 Pa, heated to 1250°C at 5°C / min, held for 4 hours, and after sintering, the rollers were heat-treated and held for heat treatment before being water-quenched as a whole.

[0092] The grinding roller samples prepared in the examples and comparative examples were subjected to relevant performance tests, and the test results are shown in Table 1.

[0093] Table 1 Performance test results of the examples and comparative examples

[0094]

[0095] As shown in Table 1, the grinding roller samples of Examples 1-3 all exhibited excellent performance. The surface hardness of the grinding layer was greater than 65, the bench impact toughness (AKU) was greater than 30J, no defects were found in the interface, and the average service life was more than three times that of high-chromium cast iron grinding rollers. In Comparative Example 1, after centrifugal casting, UT testing revealed multiple poor bonding signals at the interface, small-scale peeling occurred during machining, and large-area peeling failure occurred in less than 100 hours of machine testing. Comparative Example 2 achieved a surface hardness of HRC 65 or higher in the grinding layer, but metallographic examination revealed a small amount of brittle η phase at the interface. Macroscopic cracks appeared in the composite layer during the bench impact test, which may be due to excessive internal stress in the composite layer caused by overall quenching.

[0096] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A high-performance metal-ceramic composite grinding roller, characterized in that, The grinding roller has a disc-shaped structure, comprising, from the outside to the inside, a grinding surface layer, a pure metal transition layer, and an inner toughening roller core, which are metallurgically bonded together to form a whole. The grinding surface layer is made of a metal-ceramic composite material, which consists of a multi-system ceramic reinforcing phase with a volume fraction of 40%-60% and the remainder being a wear-resistant metal matrix. The surface hardness of the grinding surface layer is ≥ HRC 65, and the thickness is 30-80. The multi-system ceramic reinforcing phase is a preform structure comprising a primary reinforcing phase and a secondary reinforcing phase. The primary reinforcing phase is tungsten carbide particles, proportioned in a three-stage particle size distribution: 20% coarse particles (1.0-1.6 mm), 50% medium particles (0.4-0.8 mm), and 30% fine particles (0.1-0.3 mm). The preform structure is prepared by a method comprising the following steps: ultrasonically cleaning the ceramic particle system containing the primary and secondary reinforcing phases to remove surface contaminants; forming a uniform nickel-phosphorus alloy amorphous coating on the particle surface using ultrasonic-assisted chemical plating; mixing the coated ceramic particles with a nickel-based alloy powder binder; placing the mixture into a ring mold for cold isostatic pressing to form multiple preforms at a pressure of 150-250 MPa, with a porosity of 20%-25%; the secondary reinforcing phase is partially stabilized zirconia particles with a particle size of 50-150 mm. μm, accounting for 10%-15% of the total volume of the multi-system ceramic reinforcing phase; the tungsten carbide particles and some stable zirconium oxide particles are coated with a nickel-phosphorus alloy amorphous coating with a thickness of 5-15 μm; the wear-resistant metal is a high-toughness high-chromium cast iron alloy, the material of the pure metal transition layer is the same as the wear-resistant metal matrix in the grinding surface layer, and the internal toughness roller core is selected from 42CrMo or 35CrMo medium carbon alloy steel.

2. The high-performance metal-ceramic composite grinding roller according to claim 1, characterized in that, The toughness roller core has uniformly distributed mounting holes in a ring, and internal threads are machined in the mounting holes. At the same time, a circular weight-reducing through hole is also opened in the center of the toughness roller core.

3. A method for preparing a high-performance metal-ceramic composite grinding roller as described in any one of claims 1-2, characterized in that, The preparation method includes the following steps: S1, Roller core pretreatment and assembly: The composite area on the outer surface of the tough roller core is rough machined, and an annular anchoring groove is machined in the area. The surface of the rough-machined roller core is subjected to wet sandblasting treatment driven by anhydrous ethanol to achieve a cleanliness level of Sa 3.0 and a surface roughness Ra of 12.5-25μm. A 100-200μm thick layer of ceramic flame retardant is uniformly sprayed on the activated roller core surface. Multiple preforms as described in claim 1 are spliced ​​together circumferentially and assembled with the sprayed roller core in a centrifugal casting mold; S2, Centrifugal melting and casting composite: High-chromium cast iron alloy molten steel is melted, and the alloy element content is proportioned according to the ratio. The superheat is controlled at 150-200°C. The centrifuge is started, and a three-stage variable speed method is used for casting and solidification; S3. Vacuum sintering densification: Transfer the centrifugal casting to a vacuum sintering furnace, adjust the vacuum level, perform pulse current-assisted sintering, hold for 1-3 hours, and then cool to room temperature with the furnace; S4. Differential temperature heat treatment and finishing: Heat the sintered roller to 850-900°C for austenitization and then perform differential temperature heat treatment. After heat treatment, perform finishing and open a ring-shaped uniformly distributed mounting and fixing holes on the tough roller core of the grinding roller. The fixing holes are machined with internal threads, and a circular weight-reducing through hole is opened in the center.

4. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In the preparation step of the preform in step S1, the pH value of the plating solution for the ultrasonic-assisted chemical plating is 5, the chemical plating temperature is 85~90℃, the applied ultrasonic power is 50-100W, the frequency is 25-40kHz, and the plating time is 40~50min.

5. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In the preparation step of the preform in step S1, the nickel-based alloy powder binder is a Ni-Cr-B-Si self-fluxing alloy powder. The powder is spherical with a particle size of 200-500 mesh. By weight percentage, it includes Cr: 10-15%, B: 2.0-3.5%, Si: 3.0-4.5%, Fe ≤5.0%, and the balance is Ni and unavoidable impurities. The mass ratio of the mixed ceramic particles to the nickel-based alloy powder binder is (85-95):(15-5).

6. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In step S1, the ceramic flame retardant is 8% yttrium oxide stabilized zirconium oxide.

7. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In step S2, the three-stage variable speed method involves controlling the rotation speed at 200±50 rpm during the initial pouring stage until the pouring is completed. After the pouring is completed, the rotation speed is rapidly increased to 600±50 rpm within 10 seconds and maintained for 1-2 minutes to allow for pressure penetration. Then, in the stable solidification stage, the rotation speed is reduced to 400±50 rpm until the casting is completely solidified.

8. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In step S3, the vacuum degree is ≤1×10⁻² Pa. The process parameters for pulsed current assisted sintering are: heating to 1150-1200°C at a rate of 5-10°C / min, while applying a low-voltage, high-current DC pulse. The parameters of the DC pulse are controlled as follows: pulse frequency 50-500 Hz, voltage ≤10 V, current density of 50-80 A / cm² during the heating stage, and after reaching the target temperature, the current density is increased to 100-120 A / cm², and the temperature is maintained under this condition.

9. The method for preparing the high-performance metal-ceramic composite grinding roller according to claim 3, characterized in that, In step S4, the differential temperature heat treatment involves holding the temperature at 850-900°C for 0.5-1h and then cooling and quenching. During quenching, only the roller core is subjected to forced water cooling by spraying, while the composite wear-resistant layer area is kept warm and slowly cooled. Subsequently, the entire structure is tempered at 450-550°C for 4-6h.

Images